Converting audio bit depths in C#

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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.

Converting between different sample bit depths in C#

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!

<span>namespace</span> cSouza.Audio
{
    <span>using</span> System;
    
    <span>/// &lt;summary&gt;</span>
    <span>///   Static methods to convert between different sample formats.</span>
    <span>/// &lt;/summary&gt;</span>
    <span>/// &lt;remarks&gt;</span>
    <span>/// &lt;para&gt;</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>/// &lt;/para&gt;</span>
    <span>/// &lt;para&gt;</span>
    <span>///   This class try to be as fast as possible without using unsafe code.</span>
    <span>/// &lt;/para&gt;</span>
    <span>/// &lt;para&gt;</span>
    <span>///   Dither isn't currently supported. Currently supported conversions</span>
    <span>///   are 'to' and 'from' conversions between the following value types:</span>
    <span>/// &lt;/para&gt;</span>
    <span>/// &lt;para&gt;</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>/// &lt;/para&gt;</span>
    <span>/// &lt;para&gt;</span>
    <span>///   Which are the most common PCM formats.</span>
    <span>/// &lt;/para&gt;</span>
    <span>/// &lt;example&gt;</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>/// &lt;code&gt;</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>/// &lt;/code&gt;</span>
    <span>/// &lt;/example&gt;</span>
    <span>/// &lt;/remarks&gt;</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>/// &lt;summary&gt;</span>
        <span>///   Converts a array of signed 8-bit int samples</span>
        <span>///   into a array of 32-bit float-point samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; j++)
                <span>for</span> (<span>int</span> i = 0; i &lt; from[0].Length; i++)
                to[i][j] = (Int16)((from[i][j] - 128) &lt;&lt; 8);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a array of signed 8-bit int samples</span>
        <span>///   into a array of 32-bit float-point samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; i++)
                to[i] = (Int16)((from[i] - 128) &lt;&lt; 8);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a signed 8-bit int sample</span>
        <span>///   into a 32-bit float-point sample.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</span>
        <span>public</span> <span>static</span> <span>void</span> Convert(<span>byte</span> from, <span>out</span> Int16 to)
        {
            to = (Int16)((from - 128) &lt;&lt; 8);
        }
        <span>#endregion</span>
        
        <span>#region</span> From UInt8 (<span>byte</span>) to Int32 (<span>int</span>)
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a matrix of unsigned 8-bit int samples</span>
        <span>///   into a matrix of 32-bit float-point samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; i++)
                <span>for</span> (<span>int</span> j = 0; j &lt; from[0].Length; j++)
                to[i][j] = ((from[i][j] - 128) &lt;&lt; 24);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a array of unsigned 8-bit int samples</span>
        <span>///   into a array of 32-bit float-point samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; i++)
                to[i] = ((from[i] - 128) &lt;&lt; 24);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a unsigned 8-bit int sample</span>
        <span>///   into a 32-bit float-point sample.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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) &lt;&lt; 24);
        }
        <span>#endregion</span>
        
        <span>#region</span> From UInt8 (<span>byte</span>) to Single (<span>float</span>)
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a matrix of unsigned 8-bit int samples</span>
        <span>///   into a matrix of 32-bit float-point samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; i++)
                <span>for</span> (<span>int</span> j = 0; j &lt; from[0].Length; j++)
                to[i][j] = (from[i][j] - 128) * const_1_div_128_;
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a array of unsigned 8-bit int samples</span>
        <span>///   into a array of 32-bit float-point samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; i++)
                to[i] = (from[i] - 128) * const_1_div_128_;
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a unsigned 8-bit int sample</span>
        <span>///   into a 32-bit float-point sample.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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>/// &lt;summary&gt;</span>
        <span>///   Converts a matrix of signed 16-bit int samples</span>
        <span>///   into a matrix of 8-bit unsigned byte samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; j++)
                <span>for</span> (<span>int</span> i = 0; i &lt; from[i].Length; i++)
                to[i][j] = (<span>byte</span>)(((from[i][j]) &gt;&gt; 8) + 128);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a array of signed 16-bit int samples</span>
        <span>///   into a array of 8-bit unsigned byte samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; i++)
                to[i] = (<span>byte</span>)(((from[i]) &gt;&gt; 8) + 128);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a signed 16-bit int sample</span>
        <span>///   into a 8-bit unsigned byte sample.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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) &gt;&gt; 8) + 128);
        }
        <span>#endregion</span>
        
        <span>#region</span> From Int16 (<span>short</span>) to Int32 (<span>int</span>)
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a matrix of signed 16-bit int samples</span>
        <span>///   into a matrix of 32-bit signed integer samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</span>
        <span>public</span> <span>static</span> <span>void</span> Convert(Int16[][] from, Int32[][] to)
        {
            <span>for</span> (<span>int</span> j = 0; j &lt; from.Length; j++)
                <span>for</span> (<span>int</span> i = 0; i &lt; from[i].Length; i++)
                to[i][j] = (<span>byte</span>)(((from[i][j]) &gt;&gt; 8) + 128);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a array of signed 16-bit int samples</span>
        <span>///   into a array of 32-bit signed integer samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</span>
        <span>public</span> <span>static</span> <span>void</span> Convert(Int16[] from, Int32[] to)
        {
            <span>for</span> (<span>int</span> i = 0; i &lt; from.Length; i++)
                to[i] = (<span>byte</span>)(((from[i]) &gt;&gt; 8) + 128);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a signed 16-bit int sample</span>
        <span>///   into a 32-bit signed integer sample.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</span>
        <span>public</span> <span>static</span> <span>void</span> Convert(Int16 from, <span>out</span> Int32 to)
        {
            to = (<span>byte</span>)(((from) &gt;&gt; 8) + 128);
        }
        <span>#endregion</span>
        
        <span>#region</span> From Int16 (<span>short</span>) to Single (<span>float</span>)
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a matrix of signed 16-bit int samples</span>
        <span>///   into a matrix of 32-bit float-point samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; j++)
                <span>for</span> (<span>int</span> i = 0; i &lt; from[i].Length; i++)
                to[i][j] = (<span>float</span>)(from[i][j]*const_1_div_32768_);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a array of signed 16-bit int samples</span>
        <span>///   into a array of 32-bit float-point samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; i++)
                to[i] = (<span>float</span>)(from[i]*const_1_div_32768_);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a signed 16-bit int sample</span>
        <span>///   into a 32-bit float-point sample.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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>/// &lt;summary&gt;</span>
        <span>///   Converts a matrix of signed 32-bit int samples</span>
        <span>///   into a matrix of 8-bit unsigned byte samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; j++)
                <span>for</span> (<span>int</span> i = 0; i &lt; from[i].Length; i++)
                to[i][j] = (<span>byte</span>)(((from[i][j]) &gt;&gt; 24) + 128);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a array of signed 32-bit int samples</span>
        <span>///   into a array of 8-bit unsigned byte samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; i++)
                to[i] = (<span>byte</span>)(((from[i]) &gt;&gt; 24) + 128);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a signed 32-bit int sample</span>
        <span>///   into a 8-bit unsigned byte sample.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &gt;&gt; 24) + 128);
        }
        <span>#endregion</span>
        
        <span>#region</span> From Int32 (<span>int</span>) to Int16 (<span>short</span>)
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a matrix of signed 32-bit int samples</span>
        <span>///   into a matrix of 16-bit signed integer samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</span>
        <span>public</span> <span>static</span> <span>void</span> Convert(Int32[][] from, Int16[][] to)
        {
            <span>for</span> (<span>int</span> j = 0; j &lt; from.Length; j++)
                <span>for</span> (<span>int</span> i = 0; i &lt; from[i].Length; i++)
                to[i][j] = (Int16)(from[i][j] &gt;&gt; 16);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a array of signed 32-bit int samples</span>
        <span>///   into a array of 16-bit signed integer samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</span>
        <span>public</span> <span>static</span> <span>void</span> Convert(Int32[] from, Int16[] to)
        {
            <span>for</span> (<span>int</span> i = 0; i &lt; from.Length; i++)
                to[i] = (Int16)(from[i] &gt;&gt; 16);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a signed 32-bit int sample</span>
        <span>///   into a 16-bit signed integer sample.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</span>
        <span>public</span> <span>static</span> <span>void</span> Convert(Int32 from, <span>out</span> Int16 to)
        {
            to = (Int16)(from &gt;&gt; 16);
        }
        <span>#endregion</span>
        
        <span>#region</span> From Int32 (<span>int</span>) to Single (<span>float</span>)
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a matrix of signed 32-bit int samples</span>
        <span>///   into a matrix of 32-bit float-point samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; j++)
                <span>for</span> (<span>int</span> i = 0; i &lt; from[i].Length; i++)
                to[i][j] = (<span>float</span>)(from[i][j]*const_1_div_2147483648_);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a array of signed 32-bit int samples</span>
        <span>///   into a array of 32-bit float-point samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; i++)
                to[i] = (<span>float</span>)((<span>double</span>)from[i]*const_1_div_2147483648_);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a signed 32-bit int sample</span>
        <span>///   into a 32-bit float-point sample.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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>/// &lt;summary&gt;</span>
        <span>///   Converts a matrix of signed 32-bit float samples</span>
        <span>///   into a matrix of 8-bit unsigned byte samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; j++)
                <span>for</span> (<span>int</span> i = 0; i &lt; from[i].Length; i++)
                to[i][j] = (<span>byte</span>)(128 + ((<span>byte</span>)(to[i][j]*(127.0f))));
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a array of signed 32-bit float samples</span>
        <span>///   into a array of 8-bit unsigned byte samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; i++)
                to[i] = (<span>byte</span>)(128 + ((<span>byte</span>)(to[i]*(127.0f))));
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a signed 32-bit float sample</span>
        <span>///   into a 8-bit unsigned byte sample.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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>/// &lt;summary&gt;</span>
        <span>///   Converts a matrix of signed 32-bit float samples</span>
        <span>///   into a matrix of signed 16-bit integer samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; j++)
                <span>for</span> (<span>int</span> i = 0; i &lt; from[i].Length; i++)
                to[i][j] = (<span>short</span>) (from[i][j] * (32767.0f));
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a array of signed 32-bit float samples</span>
        <span>///   into a array of signed 16-bit integer samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; i++)
                to[i] = (<span>short</span>) (from[i] * (32767.0f));
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a signed 32-bit float sample</span>
        <span>///   into a signed 16-bit integer sample.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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>/// &lt;summary&gt;</span>
        <span>///   Converts a matrix of signed 32-bit float samples</span>
        <span>///   into a matrix of signed 32-bit integer samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; j++)
                <span>for</span> (<span>int</span> i = 0; i &lt; from[i].Length; i++)
                to[i][j] = (<span>int</span>)((<span>double</span>)from[i][j] * 0x7FFFFFFF);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a array of signed 32-bit float samples</span>
        <span>///   into a array of signed 32-bit integer samples.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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 &lt; from.Length; i++)
                to[i] = (<span>int</span>)((<span>double</span>)from[i] * 0x7FFFFFFF);
        }
        
        <span>/// &lt;summary&gt;</span>
        <span>///   Converts a signed 32-bit floating-point sample</span>
        <span>///   into a signed 32-bit integer sample.</span>
        <span>/// &lt;/summary&gt;</span>
        <span>/// &lt;param name="from"&gt;The original sample.&lt;/param&gt;</span>
        <span>/// &lt;param name="to"&gt;The resulting sample.&lt;/param&gt;</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>
        
    }
}

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namespace cSouza.Audio

{

using System;

/// <summary>

/// Static methods to convert between different sample formats.

/// </summary>

/// <remarks>

/// <para>

/// Code is mainly based on information available on the original

/// C source code pa_converters.c from Portable Audio I/O Library.

/// </para>

/// <para>

/// This class try to be as fast as possible without using unsafe code.

/// </para>

/// <para>

/// Dither isn't currently supported. Currently supported conversions

/// are 'to' and 'from' conversions between the following value types:

/// </para>

/// <para>

/// Integer 8-bit (byte),

/// Integer 16-bit (Int16),

/// Integer 32-bit (Int32),

/// Single precision 32-bit floating point (float).

/// </para>

/// <para>

/// Which are the most common PCM formats.

/// </para>

/// <example>

/// To use it, just call Convert. The compiler will automatically detect

/// which method to call based on your data types. Couldn't be simplier.

/// <code>

/// int[] srcPcm16samples = new int[] { 1, 2, 3};

/// float[] destIeeeFloat32samples = new float[3];

///

/// SampleConverter.Convert(srcPcm16samples, destIeeeFloat32samples);

///

/// // destIeeeFloat32samples now contains the converted samples.

/// </code>

/// </example>

/// </remarks>

public static class SampleConverter

{

#region Consts: Standard values used in almost all conversions.

private const float const_1_div_128_ = 1.0f / 128.0f; // 8 bit multiplier

private const float const_1_div_32768_ = 1.0f / 32768.0f; // 16 bit multiplier

private const double const_1_div_2147483648_ = 1.0 / 2147483648.0; // 32 bit

#endregion

#region From UInt8 (byte)

#region From UInt8 (byte) to Int16 (short)

/// <summary>

/// Converts a array of signed 8-bit int samples

/// into a array of 32-bit float-point samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(byte[][] from, Int16[][] to)

{

for (int j = 0; j < from.Length; j++)

for (int i = 0; i < from[0].Length; i++)

to[i][j] = (Int16)((from[i][j] - 128) << 8);

}

/// <summary>

/// Converts a array of signed 8-bit int samples

/// into a array of 32-bit float-point samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(byte[] from, Int16[] to)

{

for (int i = 0; i < from.Length; i++)

to[i] = (Int16)((from[i] - 128) << 8);

}

/// <summary>

/// Converts a signed 8-bit int sample

/// into a 32-bit float-point sample.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(byte from, out Int16 to)

{

to = (Int16)((from - 128) << 8);

}

#endregion

#region From UInt8 (byte) to Int32 (int)

/// <summary>

/// Converts a matrix of unsigned 8-bit int samples

/// into a matrix of 32-bit float-point samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(byte[][] from, int[][] to)

{

for (int i = 0; i < from.Length; i++)

for (int j = 0; j < from[0].Length; j++)

to[i][j] = ((from[i][j] - 128) << 24);

}

/// <summary>

/// Converts a array of unsigned 8-bit int samples

/// into a array of 32-bit float-point samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(byte[] from, int[] to)

{

for (int i = 0; i < from.Length; i++)

to[i] = ((from[i] - 128) << 24);

}

/// <summary>

/// Converts a unsigned 8-bit int sample

/// into a 32-bit float-point sample.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(byte from, out int to)

{

to = ((from - 128) << 24);

}

#endregion

#region From UInt8 (byte) to Single (float)

/// <summary>

/// Converts a matrix of unsigned 8-bit int samples

/// into a matrix of 32-bit float-point samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(byte[][] from, float[][] to)

{

for (int i = 0; i < from.Length; i++)

for (int j = 0; j < from[0].Length; j++)

to[i][j] = (from[i][j] - 128) * const_1_div_128_;

}

/// <summary>

/// Converts a array of unsigned 8-bit int samples

/// into a array of 32-bit float-point samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(byte[] from, float[] to)

{

for (int i = 0; i < from.Length; i++)

to[i] = (from[i] - 128) * const_1_div_128_;

}

/// <summary>

/// Converts a unsigned 8-bit int sample

/// into a 32-bit float-point sample.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(byte from, out float to)

{

to = (from - 128) * const_1_div_128_;

}

#endregion

#region From Int16 (short)

#region From Int16 (short) to UInt8 (byte)

/// <summary>

/// Converts a matrix of signed 16-bit int samples

/// into a matrix of 8-bit unsigned byte samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int16[][] from, byte[][] to)

{

for (int j = 0; j < from.Length; j++)

for (int i = 0; i < from[i].Length; i++)

to[i][j] = (byte)(((from[i][j]) >> 8) + 128);

}

/// <summary>

/// Converts a array of signed 16-bit int samples

/// into a array of 8-bit unsigned byte samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int16[] from, byte[] to)

{

for (int i = 0; i < from.Length; i++)

to[i] = (byte)(((from[i]) >> 8) + 128);

}

/// <summary>

/// Converts a signed 16-bit int sample

/// into a 8-bit unsigned byte sample.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int16 from, out byte to)

{

to = (byte)(((from) >> 8) + 128);

}

#endregion

#region From Int16 (short) to Int32 (int)

/// <summary>

/// Converts a matrix of signed 16-bit int samples

/// into a matrix of 32-bit signed integer samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int16[][] from, Int32[][] to)

{

for (int j = 0; j < from.Length; j++)

for (int i = 0; i < from[i].Length; i++)

to[i][j] = (byte)(((from[i][j]) >> 8) + 128);

}

/// <summary>

/// Converts a array of signed 16-bit int samples

/// into a array of 32-bit signed integer samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int16[] from, Int32[] to)

{

for (int i = 0; i < from.Length; i++)

to[i] = (byte)(((from[i]) >> 8) + 128);

}

/// <summary>

/// Converts a signed 16-bit int sample

/// into a 32-bit signed integer sample.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int16 from, out Int32 to)

{

to = (byte)(((from) >> 8) + 128);

}

#endregion

#region From Int16 (short) to Single (float)

/// <summary>

/// Converts a matrix of signed 16-bit int samples

/// into a matrix of 32-bit float-point samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int16[][] from, float[][] to)

{

for (int j = 0; j < from.Length; j++)

for (int i = 0; i < from[i].Length; i++)

to[i][j] = (float)(from[i][j]*const_1_div_32768_);

}

/// <summary>

/// Converts a array of signed 16-bit int samples

/// into a array of 32-bit float-point samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int16[] from, float[] to)

{

for (int i = 0; i < from.Length; i++)

to[i] = (float)(from[i]*const_1_div_32768_);

}

/// <summary>

/// Converts a signed 16-bit int sample

/// into a 32-bit float-point sample.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int16 from, out float to)

{

to = (float)(from*const_1_div_32768_);

}

#endregion

#region From Int32 (int)

#region From Int32 (int) To UInt8 (byte)

/// <summary>

/// Converts a matrix of signed 32-bit int samples

/// into a matrix of 8-bit unsigned byte samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int32[][] from, byte[][] to)

{

for (int j = 0; j < from.Length; j++)

for (int i = 0; i < from[i].Length; i++)

to[i][j] = (byte)(((from[i][j]) >> 24) + 128);

}

/// <summary>

/// Converts a array of signed 32-bit int samples

/// into a array of 8-bit unsigned byte samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int32[] from, byte[] to)

{

for (int i = 0; i < from.Length; i++)

to[i] = (byte)(((from[i]) >> 24) + 128);

}

/// <summary>

/// Converts a signed 32-bit int sample

/// into a 8-bit unsigned byte sample.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int32 from, out byte to)

{

to = (byte)((from >> 24) + 128);

}

#endregion

#region From Int32 (int) to Int16 (short)

/// <summary>

/// Converts a matrix of signed 32-bit int samples

/// into a matrix of 16-bit signed integer samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int32[][] from, Int16[][] to)

{

for (int j = 0; j < from.Length; j++)

for (int i = 0; i < from[i].Length; i++)

to[i][j] = (Int16)(from[i][j] >> 16);

}

/// <summary>

/// Converts a array of signed 32-bit int samples

/// into a array of 16-bit signed integer samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int32[] from, Int16[] to)

{

for (int i = 0; i < from.Length; i++)

to[i] = (Int16)(from[i] >> 16);

}

/// <summary>

/// Converts a signed 32-bit int sample

/// into a 16-bit signed integer sample.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int32 from, out Int16 to)

{

to = (Int16)(from >> 16);

}

#endregion

#region From Int32 (int) to Single (float)

/// <summary>

/// Converts a matrix of signed 32-bit int samples

/// into a matrix of 32-bit float-point samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int32[][] from, float[][] to)

{

for (int j = 0; j < from.Length; j++)

for (int i = 0; i < from[i].Length; i++)

to[i][j] = (float)(from[i][j]*const_1_div_2147483648_);

}

/// <summary>

/// Converts a array of signed 32-bit int samples

/// into a array of 32-bit float-point samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int32[] from, float[] to)

{

for (int i = 0; i < from.Length; i++)

to[i] = (float)((double)from[i]*const_1_div_2147483648_);

}

/// <summary>

/// Converts a signed 32-bit int sample

/// into a 32-bit float-point sample.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(Int32 from, out float to)

{

to = (float)((double)from*const_1_div_2147483648_);

}

#endregion

#region From Single (float)

#region From Single (float) to UInt8 (byte)

/// <summary>

/// Converts a matrix of signed 32-bit float samples

/// into a matrix of 8-bit unsigned byte samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(float[][] from, byte[][] to)

{

for (int j = 0; j < from.Length; j++)

for (int i = 0; i < from[i].Length; i++)

to[i][j] = (byte)(128 + ((byte)(to[i][j]*(127.0f))));

}

/// <summary>

/// Converts a array of signed 32-bit float samples

/// into a array of 8-bit unsigned byte samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(float[] from, byte[] to)

{

for (int i = 0; i < from.Length; i++)

to[i] = (byte)(128 + ((byte)(to[i]*(127.0f))));

}

/// <summary>

/// Converts a signed 32-bit float sample

/// into a 8-bit unsigned byte sample.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(float from, out byte to)

{

to = (byte)(128 + ((byte)(from*(127.0f))));

}

#endregion

#region From Single (float) to Int16 (short)

/// <summary>

/// Converts a matrix of signed 32-bit float samples

/// into a matrix of signed 16-bit integer samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(float[][] from, short[][] to)

{

for (int j = 0; j < from.Length; j++)

for (int i = 0; i < from[i].Length; i++)

to[i][j] = (short) (from[i][j] * (32767.0f));

}

/// <summary>

/// Converts a array of signed 32-bit float samples

/// into a array of signed 16-bit integer samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(float[] from, short[] to)

{

for (int i = 0; i < from.Length; i++)

to[i] = (short) (from[i] * (32767.0f));

}

/// <summary>

/// Converts a signed 32-bit float sample

/// into a signed 16-bit integer sample.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(float from, out short to)

{

to = (short) (from * (32767.0f));

}

#endregion

#region From Single (float) to Int32 (int)

/// <summary>

/// Converts a matrix of signed 32-bit float samples

/// into a matrix of signed 32-bit integer samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(float[][] from, Int32[][] to)

{

for (int j = 0; j < from.Length; j++)

for (int i = 0; i < from[i].Length; i++)

to[i][j] = (int)((double)from[i][j] * 0x7FFFFFFF);

}

/// <summary>

/// Converts a array of signed 32-bit float samples

/// into a array of signed 32-bit integer samples.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(float[] from, Int32[] to)

{

for (int i = 0; i < from.Length; i++)

to[i] = (int)((double)from[i] * 0x7FFFFFFF);

}

/// <summary>

/// Converts a signed 32-bit floating-point sample

/// into a signed 32-bit integer sample.

/// </summary>

/// <param name="from">The original sample.</param>

/// <param name="to">The resulting sample.</param>

public static void Convert(float from, out Int32 to)

{

to = (int)((double)from * 0x7FFFFFFF);

}

#endregion

}

Other thoughts

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.

5 Comments

nlight says:

December 22, 2009 at 10:42 am

You are a God amongst men. Been searching for that for two days now (; Thanks

Anonymous says:

June 21, 2010 at 1:13 pm

Hello, great example, Can you give a tip how to seperate left & right channel from captured stream ?
Thx
Schift

César Souza says:

June 21, 2010 at 1:27 pm

Hi Schift,

The audio channels are usually interleaved. There is a nice discussion about deinterleaving audio channels in C# here.

Regards,
César

Mr Blue says:

October 29, 2012 at 11:43 pm

Thank you sir !

Allie says:

December 4, 2012 at 3:19 pm

How do I convert from a 16-bit signed to a 16-bit unsigned PCM file?

Converting between different sample bit depths in C#

Other thoughts

5 Comments

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