Apenas leia:
A mesma companhia que silenciosamente instalou rootkits junto com seus softwares revelou algumas semanas atrás ter deliberadamente desabilitado a função de virtualização de seus notebooks por “motivos de segurança”.
Mais irônico impossível.
O resultado? Ninguém conseguirá aproveitar o novo “XP Mode” que acompanha o Windows Seven. Agora acredite quando digo que a Sony é simplesmente uma porcaria.
Be who you are and say what you feel; ’cause people who mind don’t matter, and people who matter don’t mind.
– Dr. Seuss (1904-1991)
Este post é uma tradução do post original anterior, Converting Audio Bit Depths in C#, em inglês
Sinais de áudio digitais podem ser armazenados em muitos tipos de formatos diferentes. Por exemplo, um sinal de áudio poderia ser armazenado como um sinal PCM de 16-bits dentro de um arquivo WAVE ou codificado em um formato com perdas como o MP3. Mas em todos os casos, todos sinais digitais são representados como uma sequência de valores, denominadas amostras, as quais são resultado da mensuração de uma determinada característica do som em função do tempo, para que possam ser manipuladas digitalmente.
Amostras (ou samples) formam um sinal discreto (digital) tipicamente originado de um sinal contínuo (analógico, como as ondas sonoras), obtido através de algum tipo de procedimento ou algorítmo de conversão (de amostragem). Assim existem, portanto, muitas maneiras de se representar uma amostra, como com bytes de 8-bits, inteiros de 32-bits ou números de ponto flutuante (floats) de 32-bits. E, por vezes, a conversão entre estes vários tipos de representações são um requerimento inicial em diversas aplicações.
Convertendo entre diferentes representações de amostras de áudio em C#
Para converter entre diferentes representações de amostras, além de modificar o tipo de dado (sua profundidade em bits) ainda é preciso adequar nossas amostras em uma nova escala. Por exemplo, para converter de um float de 32-bits para um unsigned byte de 8-bits, nós temos que transportar a amostra original de seu intervalo de [-1;1] para seu novo intervalo de [0;255].
Para realizar este processo, a classe a seguir contém um único (exaustivamente sobrecarregado) método que permite converter, por exemplo, amostras de 16-bit para 8-bit, 16-bit para float, float para 16-bit, entre outros. De fato, são possíveis conversões entre quaisquer um dos seguintes tipos: unsigned 8-bit bytes, signed 16-bit integers, signed 32-bit integers e 32-bit floating point single precision numbers. Espero que o código seguinte seja útil a alguem que esteja interessado!
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<span>namespace</span> cSouza.Audio { <span>using</span> System; <span>/// <summary></span> <span>/// Static methods to convert between different sample formats.</span> <span>/// </summary></span> <span>/// <remarks></span> <span>/// <para></span> <span>/// Code is mainly based on information available on the original</span> <span>/// C source code pa_converters.c from Portable Audio I/O Library.</span> <span>/// </para></span> <span>/// <para></span> <span>/// This class try to be as fast as possible without using unsafe code.</span> <span>/// </para></span> <span>/// <para></span> <span>/// Dither isn't currently supported. Currently supported conversions</span> <span>/// are 'to' and 'from' conversions between the following value types:</span> <span>/// </para></span> <span>/// <para></span> <span>/// Integer 8-bit (byte), </span> <span>/// Integer 16-bit (Int16), </span> <span>/// Integer 32-bit (Int32), </span> <span>/// Single precision 32-bit floating point (float).</span> <span>/// </para></span> <span>/// <para></span> <span>/// Which are the most common PCM formats.</span> <span>/// </para></span> <span>/// <example></span> <span>/// To use it, just call Convert. The compiler will automatically detect</span> <span>/// which method to call based on your data types. Couldn't be simplier.</span> <span>/// <code></span> <span>/// int[] srcPcm16samples = new int[] { 1, 2, 3};</span> <span>/// float[] destIeeeFloat32samples = new float[3];</span> <span>/// </span> <span>/// SampleConverter.Convert(srcPcm16samples, destIeeeFloat32samples);</span> <span>/// </span> <span>/// // destIeeeFloat32samples now contains the converted samples.</span> <span>/// </code></span> <span>/// </example></span> <span>/// </remarks></span> <span>public</span> <span>static</span> <span>class</span> SampleConverter { <span>#region</span> Consts: Standard values used <span>in</span> almost all conversions. <span>private</span> <span>const</span> <span>float</span> const_1_div_128_ = 1.0f / 128.0f; <span>// 8 bit multiplier</span> <span>private</span> <span>const</span> <span>float</span> const_1_div_32768_ = 1.0f / 32768.0f; <span>// 16 bit multiplier</span> <span>private</span> <span>const</span> <span>double</span> const_1_div_2147483648_ = 1.0 / 2147483648.0; <span>// 32 bit</span> <span>#endregion</span> <span>#region</span> From UInt8 (<span>byte</span>) <span>#region</span> From UInt8 (<span>byte</span>) to Int16 (<span>short</span>) <span>/// <summary></span> <span>/// Converts a array of signed 8-bit int samples</span> <span>/// into a array of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span>[][] from, Int16[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[0].Length; i++) to[i][j] = (Int16)((from[i][j] - 128) << 8); } <span>/// <summary></span> <span>/// Converts a array of signed 8-bit int samples</span> <span>/// into a array of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span>[] from, Int16[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (Int16)((from[i] - 128) << 8); } <span>/// <summary></span> <span>/// Converts a signed 8-bit int sample</span> <span>/// into a 32-bit float-point sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span> from, <span>out</span> Int16 to) { to = (Int16)((from - 128) << 8); } <span>#endregion</span> <span>#region</span> From UInt8 (<span>byte</span>) to Int32 (<span>int</span>) <span>/// <summary></span> <span>/// Converts a matrix of unsigned 8-bit int samples</span> <span>/// into a matrix of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span>[][] from, <span>int</span>[][] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) <span>for</span> (<span>int</span> j = 0; j < from[0].Length; j++) to[i][j] = ((from[i][j] - 128) << 24); } <span>/// <summary></span> <span>/// Converts a array of unsigned 8-bit int samples</span> <span>/// into a array of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span>[] from, <span>int</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = ((from[i] - 128) << 24); } <span>/// <summary></span> <span>/// Converts a unsigned 8-bit int sample</span> <span>/// into a 32-bit float-point sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span> from, <span>out</span> <span>int</span> to) { to = ((from - 128) << 24); } <span>#endregion</span> <span>#region</span> From UInt8 (<span>byte</span>) to Single (<span>float</span>) <span>/// <summary></span> <span>/// Converts a matrix of unsigned 8-bit int samples</span> <span>/// into a matrix of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span>[][] from, <span>float</span>[][] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) <span>for</span> (<span>int</span> j = 0; j < from[0].Length; j++) to[i][j] = (from[i][j] - 128) * const_1_div_128_; } <span>/// <summary></span> <span>/// Converts a array of unsigned 8-bit int samples</span> <span>/// into a array of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span>[] from, <span>float</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (from[i] - 128) * const_1_div_128_; } <span>/// <summary></span> <span>/// Converts a unsigned 8-bit int sample</span> <span>/// into a 32-bit float-point sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span> from, <span>out</span> <span>float</span> to) { to = (from - 128) * const_1_div_128_; } <span>#endregion</span> <span>#endregion</span> <span>#region</span> From Int16 (<span>short</span>) <span>#region</span> From Int16 (<span>short</span>) to UInt8 (<span>byte</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 16-bit int samples</span> <span>/// into a matrix of 8-bit unsigned byte samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16[][] from, <span>byte</span>[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>byte</span>)(((from[i][j]) >> 8) + 128); } <span>/// <summary></span> <span>/// Converts a array of signed 16-bit int samples</span> <span>/// into a array of 8-bit unsigned byte samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16[] from, <span>byte</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>byte</span>)(((from[i]) >> 8) + 128); } <span>/// <summary></span> <span>/// Converts a signed 16-bit int sample</span> <span>/// into a 8-bit unsigned byte sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16 from, <span>out</span> <span>byte</span> to) { to = (<span>byte</span>)(((from) >> 8) + 128); } <span>#endregion</span> <span>#region</span> From Int16 (<span>short</span>) to Int32 (<span>int</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 16-bit int samples</span> <span>/// into a matrix of 32-bit signed integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16[][] from, Int32[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>byte</span>)(((from[i][j]) >> 8) + 128); } <span>/// <summary></span> <span>/// Converts a array of signed 16-bit int samples</span> <span>/// into a array of 32-bit signed integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16[] from, Int32[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>byte</span>)(((from[i]) >> 8) + 128); } <span>/// <summary></span> <span>/// Converts a signed 16-bit int sample</span> <span>/// into a 32-bit signed integer sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16 from, <span>out</span> Int32 to) { to = (<span>byte</span>)(((from) >> 8) + 128); } <span>#endregion</span> <span>#region</span> From Int16 (<span>short</span>) to Single (<span>float</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 16-bit int samples</span> <span>/// into a matrix of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16[][] from, <span>float</span>[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>float</span>)(from[i][j]*const_1_div_32768_); } <span>/// <summary></span> <span>/// Converts a array of signed 16-bit int samples</span> <span>/// into a array of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16[] from, <span>float</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>float</span>)(from[i]*const_1_div_32768_); } <span>/// <summary></span> <span>/// Converts a signed 16-bit int sample</span> <span>/// into a 32-bit float-point sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16 from, <span>out</span> <span>float</span> to) { to = (<span>float</span>)(from*const_1_div_32768_); } <span>#endregion</span> <span>#endregion</span> <span>#region</span> From Int32 (<span>int</span>) <span>#region</span> From Int32 (<span>int</span>) To UInt8 (<span>byte</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 32-bit int samples</span> <span>/// into a matrix of 8-bit unsigned byte samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32[][] from, <span>byte</span>[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>byte</span>)(((from[i][j]) >> 24) + 128); } <span>/// <summary></span> <span>/// Converts a array of signed 32-bit int samples</span> <span>/// into a array of 8-bit unsigned byte samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32[] from, <span>byte</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>byte</span>)(((from[i]) >> 24) + 128); } <span>/// <summary></span> <span>/// Converts a signed 32-bit int sample</span> <span>/// into a 8-bit unsigned byte sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32 from, <span>out</span> <span>byte</span> to) { to = (<span>byte</span>)((from >> 24) + 128); } <span>#endregion</span> <span>#region</span> From Int32 (<span>int</span>) to Int16 (<span>short</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 32-bit int samples</span> <span>/// into a matrix of 16-bit signed integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32[][] from, Int16[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (Int16)(from[i][j] >> 16); } <span>/// <summary></span> <span>/// Converts a array of signed 32-bit int samples</span> <span>/// into a array of 16-bit signed integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32[] from, Int16[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (Int16)(from[i] >> 16); } <span>/// <summary></span> <span>/// Converts a signed 32-bit int sample</span> <span>/// into a 16-bit signed integer sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32 from, <span>out</span> Int16 to) { to = (Int16)(from >> 16); } <span>#endregion</span> <span>#region</span> From Int32 (<span>int</span>) to Single (<span>float</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 32-bit int samples</span> <span>/// into a matrix of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32[][] from, <span>float</span>[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>float</span>)(from[i][j]*const_1_div_2147483648_); } <span>/// <summary></span> <span>/// Converts a array of signed 32-bit int samples</span> <span>/// into a array of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32[] from, <span>float</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>float</span>)((<span>double</span>)from[i]*const_1_div_2147483648_); } <span>/// <summary></span> <span>/// Converts a signed 32-bit int sample</span> <span>/// into a 32-bit float-point sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32 from, <span>out</span> <span>float</span> to) { to = (<span>float</span>)((<span>double</span>)from*const_1_div_2147483648_); } <span>#endregion</span> <span>#endregion</span> <span>#region</span> From Single (<span>float</span>) <span>#region</span> From Single (<span>float</span>) to UInt8 (<span>byte</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 32-bit float samples</span> <span>/// into a matrix of 8-bit unsigned byte samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span>[][] from, <span>byte</span>[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>byte</span>)(128 + ((<span>byte</span>)(to[i][j]*(127.0f)))); } <span>/// <summary></span> <span>/// Converts a array of signed 32-bit float samples</span> <span>/// into a array of 8-bit unsigned byte samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span>[] from, <span>byte</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>byte</span>)(128 + ((<span>byte</span>)(to[i]*(127.0f)))); } <span>/// <summary></span> <span>/// Converts a signed 32-bit float sample</span> <span>/// into a 8-bit unsigned byte sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span> from, <span>out</span> <span>byte</span> to) { to = (<span>byte</span>)(128 + ((<span>byte</span>)(from*(127.0f)))); } <span>#endregion</span> <span>#region</span> From Single (<span>float</span>) to Int16 (<span>short</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 32-bit float samples</span> <span>/// into a matrix of signed 16-bit integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span>[][] from, <span>short</span>[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>short</span>) (from[i][j] * (32767.0f)); } <span>/// <summary></span> <span>/// Converts a array of signed 32-bit float samples</span> <span>/// into a array of signed 16-bit integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span>[] from, <span>short</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>short</span>) (from[i] * (32767.0f)); } <span>/// <summary></span> <span>/// Converts a signed 32-bit float sample</span> <span>/// into a signed 16-bit integer sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span> from, <span>out</span> <span>short</span> to) { to = (<span>short</span>) (from * (32767.0f)); } <span>#endregion</span> <span>#region</span> From Single (<span>float</span>) to Int32 (<span>int</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 32-bit float samples</span> <span>/// into a matrix of signed 32-bit integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span>[][] from, Int32[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>int</span>)((<span>double</span>)from[i][j] * 0x7FFFFFFF); } <span>/// <summary></span> <span>/// Converts a array of signed 32-bit float samples</span> <span>/// into a array of signed 32-bit integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span>[] from, Int32[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>int</span>)((<span>double</span>)from[i] * 0x7FFFFFFF); } <span>/// <summary></span> <span>/// Converts a signed 32-bit floating-point sample</span> <span>/// into a signed 32-bit integer sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span> from, <span>out</span> Int32 to) { to = (<span>int</span>)((<span>double</span>)from * 0x7FFFFFFF); } <span>#endregion</span> <span>#endregion</span> } } |
Note, porém, que conversões raramente são perfeitas. Isto é verdade para quase tudo, especialmente para sinais digitais. Converter de uma codifiação para outra pode introduzir erros de conversão nos dados. Para ajudar nesta questão, foi inventada a técnica conhecida como dithering. Dithering é o mesmo que propositalmente adicionar ruído num sinal.
Ruído? Sim, ruído. Ruído não é sempre uma coisa ruim. Basta dar uma olhada nos exemplos de imagens na Wikipedia e você logo entenderá isto. Infelizmente, esta classe ainda não suporta dithering, poderá suportar no futuro caso surja necessidade.
Até mais!
Você se considera um bom programador? Se respondeu sim a esta pergunta, então aposto que não vai deixar este bug passar despercebido:
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1 |
1: <strong>public</strong> <strong>static</strong> <strong>int</strong> binarySearch(int[] a, int key) {<br />2: <strong>int</strong> low = 0;<br />3: <strong>int</strong> high = a.length - 1;<br />4:<br />5: <strong>while</strong> (low <= high) {<br />6: <strong>int</strong> mid = (low + high) / 2;<br />7: <strong>int</strong> midVal = a[mid];<br />8:<br />9: <strong>if</strong> (midVal < key)<br />10: low = mid + 1<br />11: <strong>else if</strong> (midVal > key)<br />12: high = mid - 1;<br />13: <strong>else</strong><br />14: return mid; // key found<br />15: }<br />16: <strong>return</strong> -(low + 1); // key not found.<br />17: }<br /> |
E ai, vê alguma coisa?
Óbvio não?
Dica: olhe atentamente para a linha 6:
Ainda não percebeu? Então digamos, o que acontece, se, por acaso, low valer 10 e high valer 2.147.483.647 (ou seja, 2^31-1, o valor máximo que um inteiro de 32 bits pode possuir)?
Sim, de fato, a maioria das implementações de busca binária possui este erro. Não apenas livros, apostilas e materiais didáticos, mas sistemas críticos de produção também. Mas ai você fala: Ahh mas eu nunca vou empregar este tipo de busca em algo tão grande! – Bom, talvez não, mas não se esqueça que este é o mecanismo chave de muitos outros algoritmos de divisão-e-conquista, como, por exemplo, o mergesort.
Mais do que isto, esta observação serve para elucidar o quão é difícil garantir a corretude de um software. Demoraram 16 anos para detectar um erro no algoritmo que é, provavelmente, o mais popular de toda computação, presente em virtualmente todos os livros da área. Pois é: Planejamento cuidadoso é uma bênção, testar é uma maravilha. Utilizar métodos formais, melhor ainda. Revisão de código e análise estatística? Impossível ainda restar algum bug! Errado! Nenhuma destas coisas são suficientes para eliminarmos todos os bugs de um software. A verdade é: Eles sempre vão estar presentes e nos acompanhar por toda nossa vida :~
Ah, a correção? Simplesmente mude a linha 6 para:
[Fonte: Official Google Research Blog]
Para a versão em português deste post, clique aqui.
Digital audio signals can be stored in a myriad of different formats. For example, digital audio could be stored as a raw 16-bit PCM signal buried inside a WAVE file or as an encoded lossy format such as MP3. But invariably most digital signals are represented by a sequence of values, called samples, which are the measurement of a choosen sound characteristic over time, so they can be manipulated digitally.
Samples are a discrete-time (digital) signal tipically originated from a continous (analog, such as sound waves) signal through some kind of conversion procedure or algorithm. There is, however, many ways to represent a sample, such as a 8-bit byte, a 32-bit integer or a 32-bit float. And sometimes converting between those different representations (performing some kind of resampling) is an requirement in many applications.
To convert between different sample representations, besides changing the data type we also have to rescale our samples. To convert from 32-bit float to 8-bit unsigned byte, for example, we have to rescale the original sample from its [-1;1] interval to a unsigned, [0;255] interval. The class below has a single (heavily overloaded) method suitable to convert, for example, 16-bit to 8-bit, 16-bit to float, float to 16-bit, and so on. In fact, it can convert in between unsigned 8-bit bytes, signed 16-bit integers, signed 32-bit integers and 32-bit floating point single precision numbers. I hope someone finds it useful!
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<span>namespace</span> cSouza.Audio { <span>using</span> System; <span>/// <summary></span> <span>/// Static methods to convert between different sample formats.</span> <span>/// </summary></span> <span>/// <remarks></span> <span>/// <para></span> <span>/// Code is mainly based on information available on the original</span> <span>/// C source code pa_converters.c from Portable Audio I/O Library.</span> <span>/// </para></span> <span>/// <para></span> <span>/// This class try to be as fast as possible without using unsafe code.</span> <span>/// </para></span> <span>/// <para></span> <span>/// Dither isn't currently supported. Currently supported conversions</span> <span>/// are 'to' and 'from' conversions between the following value types:</span> <span>/// </para></span> <span>/// <para></span> <span>/// Integer 8-bit (byte), </span> <span>/// Integer 16-bit (Int16), </span> <span>/// Integer 32-bit (Int32), </span> <span>/// Single precision 32-bit floating point (float).</span> <span>/// </para></span> <span>/// <para></span> <span>/// Which are the most common PCM formats.</span> <span>/// </para></span> <span>/// <example></span> <span>/// To use it, just call Convert. The compiler will automatically detect</span> <span>/// which method to call based on your data types. Couldn't be simplier.</span> <span>/// <code></span> <span>/// int[] srcPcm16samples = new int[] { 1, 2, 3};</span> <span>/// float[] destIeeeFloat32samples = new float[3];</span> <span>/// </span> <span>/// SampleConverter.Convert(srcPcm16samples, destIeeeFloat32samples);</span> <span>/// </span> <span>/// // destIeeeFloat32samples now contains the converted samples.</span> <span>/// </code></span> <span>/// </example></span> <span>/// </remarks></span> <span>public</span> <span>static</span> <span>class</span> SampleConverter { <span>#region</span> Consts: Standard values used <span>in</span> almost all conversions. <span>private</span> <span>const</span> <span>float</span> const_1_div_128_ = 1.0f / 128.0f; <span>// 8 bit multiplier</span> <span>private</span> <span>const</span> <span>float</span> const_1_div_32768_ = 1.0f / 32768.0f; <span>// 16 bit multiplier</span> <span>private</span> <span>const</span> <span>double</span> const_1_div_2147483648_ = 1.0 / 2147483648.0; <span>// 32 bit</span> <span>#endregion</span> <span>#region</span> From UInt8 (<span>byte</span>) <span>#region</span> From UInt8 (<span>byte</span>) to Int16 (<span>short</span>) <span>/// <summary></span> <span>/// Converts a array of signed 8-bit int samples</span> <span>/// into a array of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span>[][] from, Int16[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[0].Length; i++) to[i][j] = (Int16)((from[i][j] - 128) << 8); } <span>/// <summary></span> <span>/// Converts a array of signed 8-bit int samples</span> <span>/// into a array of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span>[] from, Int16[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (Int16)((from[i] - 128) << 8); } <span>/// <summary></span> <span>/// Converts a signed 8-bit int sample</span> <span>/// into a 32-bit float-point sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span> from, <span>out</span> Int16 to) { to = (Int16)((from - 128) << 8); } <span>#endregion</span> <span>#region</span> From UInt8 (<span>byte</span>) to Int32 (<span>int</span>) <span>/// <summary></span> <span>/// Converts a matrix of unsigned 8-bit int samples</span> <span>/// into a matrix of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span>[][] from, <span>int</span>[][] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) <span>for</span> (<span>int</span> j = 0; j < from[0].Length; j++) to[i][j] = ((from[i][j] - 128) << 24); } <span>/// <summary></span> <span>/// Converts a array of unsigned 8-bit int samples</span> <span>/// into a array of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span>[] from, <span>int</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = ((from[i] - 128) << 24); } <span>/// <summary></span> <span>/// Converts a unsigned 8-bit int sample</span> <span>/// into a 32-bit float-point sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span> from, <span>out</span> <span>int</span> to) { to = ((from - 128) << 24); } <span>#endregion</span> <span>#region</span> From UInt8 (<span>byte</span>) to Single (<span>float</span>) <span>/// <summary></span> <span>/// Converts a matrix of unsigned 8-bit int samples</span> <span>/// into a matrix of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span>[][] from, <span>float</span>[][] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) <span>for</span> (<span>int</span> j = 0; j < from[0].Length; j++) to[i][j] = (from[i][j] - 128) * const_1_div_128_; } <span>/// <summary></span> <span>/// Converts a array of unsigned 8-bit int samples</span> <span>/// into a array of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span>[] from, <span>float</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (from[i] - 128) * const_1_div_128_; } <span>/// <summary></span> <span>/// Converts a unsigned 8-bit int sample</span> <span>/// into a 32-bit float-point sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span> from, <span>out</span> <span>float</span> to) { to = (from - 128) * const_1_div_128_; } <span>#endregion</span> <span>#endregion</span> <span>#region</span> From Int16 (<span>short</span>) <span>#region</span> From Int16 (<span>short</span>) to UInt8 (<span>byte</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 16-bit int samples</span> <span>/// into a matrix of 8-bit unsigned byte samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16[][] from, <span>byte</span>[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>byte</span>)(((from[i][j]) >> 8) + 128); } <span>/// <summary></span> <span>/// Converts a array of signed 16-bit int samples</span> <span>/// into a array of 8-bit unsigned byte samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16[] from, <span>byte</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>byte</span>)(((from[i]) >> 8) + 128); } <span>/// <summary></span> <span>/// Converts a signed 16-bit int sample</span> <span>/// into a 8-bit unsigned byte sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16 from, <span>out</span> <span>byte</span> to) { to = (<span>byte</span>)(((from) >> 8) + 128); } <span>#endregion</span> <span>#region</span> From Int16 (<span>short</span>) to Int32 (<span>int</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 16-bit int samples</span> <span>/// into a matrix of 32-bit signed integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16[][] from, Int32[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>byte</span>)(((from[i][j]) >> 8) + 128); } <span>/// <summary></span> <span>/// Converts a array of signed 16-bit int samples</span> <span>/// into a array of 32-bit signed integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16[] from, Int32[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>byte</span>)(((from[i]) >> 8) + 128); } <span>/// <summary></span> <span>/// Converts a signed 16-bit int sample</span> <span>/// into a 32-bit signed integer sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16 from, <span>out</span> Int32 to) { to = (<span>byte</span>)(((from) >> 8) + 128); } <span>#endregion</span> <span>#region</span> From Int16 (<span>short</span>) to Single (<span>float</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 16-bit int samples</span> <span>/// into a matrix of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16[][] from, <span>float</span>[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>float</span>)(from[i][j]*const_1_div_32768_); } <span>/// <summary></span> <span>/// Converts a array of signed 16-bit int samples</span> <span>/// into a array of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16[] from, <span>float</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>float</span>)(from[i]*const_1_div_32768_); } <span>/// <summary></span> <span>/// Converts a signed 16-bit int sample</span> <span>/// into a 32-bit float-point sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int16 from, <span>out</span> <span>float</span> to) { to = (<span>float</span>)(from*const_1_div_32768_); } <span>#endregion</span> <span>#endregion</span> <span>#region</span> From Int32 (<span>int</span>) <span>#region</span> From Int32 (<span>int</span>) To UInt8 (<span>byte</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 32-bit int samples</span> <span>/// into a matrix of 8-bit unsigned byte samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32[][] from, <span>byte</span>[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>byte</span>)(((from[i][j]) >> 24) + 128); } <span>/// <summary></span> <span>/// Converts a array of signed 32-bit int samples</span> <span>/// into a array of 8-bit unsigned byte samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32[] from, <span>byte</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>byte</span>)(((from[i]) >> 24) + 128); } <span>/// <summary></span> <span>/// Converts a signed 32-bit int sample</span> <span>/// into a 8-bit unsigned byte sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32 from, <span>out</span> <span>byte</span> to) { to = (<span>byte</span>)((from >> 24) + 128); } <span>#endregion</span> <span>#region</span> From Int32 (<span>int</span>) to Int16 (<span>short</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 32-bit int samples</span> <span>/// into a matrix of 16-bit signed integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32[][] from, Int16[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (Int16)(from[i][j] >> 16); } <span>/// <summary></span> <span>/// Converts a array of signed 32-bit int samples</span> <span>/// into a array of 16-bit signed integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32[] from, Int16[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (Int16)(from[i] >> 16); } <span>/// <summary></span> <span>/// Converts a signed 32-bit int sample</span> <span>/// into a 16-bit signed integer sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32 from, <span>out</span> Int16 to) { to = (Int16)(from >> 16); } <span>#endregion</span> <span>#region</span> From Int32 (<span>int</span>) to Single (<span>float</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 32-bit int samples</span> <span>/// into a matrix of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32[][] from, <span>float</span>[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>float</span>)(from[i][j]*const_1_div_2147483648_); } <span>/// <summary></span> <span>/// Converts a array of signed 32-bit int samples</span> <span>/// into a array of 32-bit float-point samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32[] from, <span>float</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>float</span>)((<span>double</span>)from[i]*const_1_div_2147483648_); } <span>/// <summary></span> <span>/// Converts a signed 32-bit int sample</span> <span>/// into a 32-bit float-point sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(Int32 from, <span>out</span> <span>float</span> to) { to = (<span>float</span>)((<span>double</span>)from*const_1_div_2147483648_); } <span>#endregion</span> <span>#endregion</span> <span>#region</span> From Single (<span>float</span>) <span>#region</span> From Single (<span>float</span>) to UInt8 (<span>byte</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 32-bit float samples</span> <span>/// into a matrix of 8-bit unsigned byte samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span>[][] from, <span>byte</span>[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>byte</span>)(128 + ((<span>byte</span>)(to[i][j]*(127.0f)))); } <span>/// <summary></span> <span>/// Converts a array of signed 32-bit float samples</span> <span>/// into a array of 8-bit unsigned byte samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span>[] from, <span>byte</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>byte</span>)(128 + ((<span>byte</span>)(to[i]*(127.0f)))); } <span>/// <summary></span> <span>/// Converts a signed 32-bit float sample</span> <span>/// into a 8-bit unsigned byte sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span> from, <span>out</span> <span>byte</span> to) { to = (<span>byte</span>)(128 + ((<span>byte</span>)(from*(127.0f)))); } <span>#endregion</span> <span>#region</span> From Single (<span>float</span>) to Int16 (<span>short</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 32-bit float samples</span> <span>/// into a matrix of signed 16-bit integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span>[][] from, <span>short</span>[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>short</span>) (from[i][j] * (32767.0f)); } <span>/// <summary></span> <span>/// Converts a array of signed 32-bit float samples</span> <span>/// into a array of signed 16-bit integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span>[] from, <span>short</span>[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>short</span>) (from[i] * (32767.0f)); } <span>/// <summary></span> <span>/// Converts a signed 32-bit float sample</span> <span>/// into a signed 16-bit integer sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span> from, <span>out</span> <span>short</span> to) { to = (<span>short</span>) (from * (32767.0f)); } <span>#endregion</span> <span>#region</span> From Single (<span>float</span>) to Int32 (<span>int</span>) <span>/// <summary></span> <span>/// Converts a matrix of signed 32-bit float samples</span> <span>/// into a matrix of signed 32-bit integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span>[][] from, Int32[][] to) { <span>for</span> (<span>int</span> j = 0; j < from.Length; j++) <span>for</span> (<span>int</span> i = 0; i < from[i].Length; i++) to[i][j] = (<span>int</span>)((<span>double</span>)from[i][j] * 0x7FFFFFFF); } <span>/// <summary></span> <span>/// Converts a array of signed 32-bit float samples</span> <span>/// into a array of signed 32-bit integer samples.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span>[] from, Int32[] to) { <span>for</span> (<span>int</span> i = 0; i < from.Length; i++) to[i] = (<span>int</span>)((<span>double</span>)from[i] * 0x7FFFFFFF); } <span>/// <summary></span> <span>/// Converts a signed 32-bit floating-point sample</span> <span>/// into a signed 32-bit integer sample.</span> <span>/// </summary></span> <span>/// <param name="from">The original sample.</param></span> <span>/// <param name="to">The resulting sample.</param></span> <span>public</span> <span>static</span> <span>void</span> Convert(<span>float</span> from, <span>out</span> Int32 to) { to = (<span>int</span>)((<span>double</span>)from * 0x7FFFFFFF); } <span>#endregion</span> <span>#endregion</span> } } |
Please note, however, that conversion isn’t always perfect. This is true for almost everything, specially for digital signals. Converting from one encoding to another may introduce conversion errors in the data. To help with this, God invented a technique known as dithering. Dithering is the same as pourposely introducing noise in a signal.
Noise? Yes, noise. Noise isn’t always bad. Just take a look at the image examples in Wikipedia and you will understand that. Unfortunately, this class doesn’t support dithering (yet), but may support in the future, if there is need.
SlimDX is an open source library which allows .NET 2.0+ applications (including C#, VB.NET, IronPython, and F#) to use Microsoft’s DirectX APIs, as well as several related Microsoft multimedia APIs.
SlimDX is a direct replacement (albeit not exactly API compatible) for the now-defunct Microsoft’s Managed DirectX (MDX) wrappers.
However, not everything is perfect. The main issue with SlimDX is the current lack of documentation. Sure they do have a lot of examples, but unfortunately, only a few of them deal with DirectSound. And most of them assumes you already have experience with standard DirectSound (and DirectX itself) to understand them.
So to help completely newcomers to the DirectX world, here is a extremely simple example on how to read data from the microphone using SlimDX just to get you started.
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<span> 1: </span><span>// We'll use fully qualified names only to show</span> |
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<span> 2: </span><span>// from where each class come from. We start by</span> |
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<span> 3: </span><span>// instantiating our directsound capture device.</span> |
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<span> 4: </span>SlimDX.DirectSound.DirectSoundCapture captureDevice = |
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<span> 5: </span> <span>new</span> SlimDX.DirectSound.DirectSoundCapture(); |
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<span> 6: </span> |
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<span> 7: </span> |
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<span> 8: </span><span>// Here we set up the wave format. I've choosen to use</span> |
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<span> 9: </span><span>// 32-bit floats, but you may use others, like signed 16-bit integer</span> |
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<span> 10: </span>SlimDX.Multimedia.WaveFormat waveFormat = <span>new</span> SlimDX.Multimedia.WaveFormat(); |
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<span> 11: </span>waveFormat.FormatTag=SlimDX.WaveFormatTag.IeeeFloat; <span>// For Int16, change to Pcm</span> |
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<span> 12: </span>waveFormat.BitsPerSample = 32; <span>// Floats are 32 bits</span> |
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<span> 13: </span>waveFormat.BlockAlignment = (<span>short</span>)(waveFormat.BitsPerSample/8); |
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<span> 14: </span>waveFormat.Channels = 1; |
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<span> 15: </span>waveFormat.SamplesPerSecond = 44100; |
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<span> 16: </span>waveFormat.AverageBytesPerSecond = |
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<span> 17: </span> waveFormat.SamplesPerSecond*waveFormat.BlockAlignment*waveFormat.Channels; |
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<span> 18: </span> |
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<span> 19: </span><span>// Here we set up the capture buffer which will receive data</span> |
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<span> 20: </span><span>// from our capturing device.</span> |
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<span> 21: </span>SlimDX.DirectSound.CaptureBufferDescription bufferDescription = |
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<span> 22: </span> <span>new</span> SlimDX.DirectSound.CaptureBufferDescription(); |
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<span> 23: </span>bufferDescription.BufferBytes=8192; |
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<span> 24: </span>bufferDescription.Format=waveFormat; |
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<span> 25: </span>bufferDescription.WaveMapped=<span>false</span>; |
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<span> 26: </span> |
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<span> 27: </span><span>// Finally, we create the buffer using the device and the buffer description</span> |
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<span> 28: </span>SlimDX.DirectSound.CaptureBuffer buffer = |
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<span> 29: </span> <span>new</span> SlimDX.DirectSound.CaptureBuffer(captureDevice,bufferDescription); |
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<span> 30: </span>buffer.Start(<span>true</span>); |
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<span> 31: </span> |
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<span> 32: </span> |
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<span> 33: </span><span>// Now we just have to read it!</span> |
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<span> 34: </span><span>float</span>[] sample = <span>new</span> <span>float</span>[8192/<span>sizeof</span>(<span>float</span>)]; |
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<span> 35: </span> |
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<span> 36: </span><span>while</span> (!stop) <span>// define this variable as a simple stop flag</span> |
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<span> 37: </span>{ |
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<span> 38: </span> buffer.Read(sample, 0, <span>true</span>); |
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<span> 39: </span> |
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<span> 40: </span> <span>// Now you can do whatever you want with the samples here!</span> |
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<span> 41: </span> |
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<span> 42: </span> <span>// PS: This is a utterly simplified usage. Depending on what</span> |
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<span> 43: </span> <span>// you want to achieve, its better to use Notifiers instead.</span> |
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<span> 44: </span>} |
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<span> 45: </span> |
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<span> 46: </span><span>// Before exiting, we release resources</span> |
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<span> 47: </span><span>// explicitely by disposing everything.</span> |
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<span> 48: </span>buffer.Stop(); |
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<span> 49: </span>buffer.Dispose(); |
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<span> 50: </span>captureDevice.Dispose(); |
Tipically you would run this code in a separate thread so it doesn’t block the main application. I hope someone finds it useful! If you have questions please leave a comment.
I’ve spent about half an hour googling for something that could act as key-value Dictionary class, but which, at the same time, could allow access by index. There is, in fact, a misleading-named OrderedDictionary class in the framework (that isn’t sorted, but ordered – in the sense that positioning does matter) that allows access by key and index, but it doesn’t use generics, so it isn’t that powerful.
After browsing some blogs and seeing some implementations I finally found about KeyedCollection. With some effort, it solves my problem, albeit a bit harder than what it could be if we had an OrderedDictionary<TKey, TItem> class. To use it, you need to inherit from it and then implement an abstract method to tell which property of your values is going to be the key.
I was almost going to do that, but then I found this:
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<span> 1: </span><span>public</span> <span>class</span> GenericKeyedCollection<TKey, TItem> : KeyedCollection<TKey, TItem> |
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<span> 2: </span>{ |
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<span> 3: </span> <span>private</span> Func<TKey, TItem> getKeyMethod; |
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<span> 4: </span> |
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<span> 5: </span> <span>protected</span> <span>override</span> TKey GetKeyForItem(TItem item) |
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<span> 6: </span> { |
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<span> 7: </span> <span>return</span> getKeyMethod(item); |
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<span> 8: </span> } |
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<span> 9: </span> |
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<span> 10: </span> <span>public</span> GenericKeyedCollection(Func<TKey, TItem> getKeyMethod) |
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<span> 11: </span> { |