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Improve multi-channel playback compatibility in WASAPI exclusive mode #1234

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Improve multi-channel playback compatibility in WASAPI exclusive mode #1234

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b436c22
Try a different speaker placement for 4ch setting in GetFallbackFormat()
kashiken Sep 5, 2025
3ba3534
Add more speaker placement options.
kashiken Sep 13, 2025
58799ec
Fix type of channelMask to int.
kashiken Sep 13, 2025
7af0d9b
Rename variable for consistency with existing code.
kashiken Sep 13, 2025
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13 changes: 10 additions & 3 deletions NAudio.Core/Wave/WaveFormats/WaveFormatExtensible.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -25,15 +25,22 @@ public class WaveFormatExtensible : WaveFormat
/// <summary>
/// Creates a new WaveFormatExtensible for PCM or IEEE
/// </summary>
public WaveFormatExtensible(int rate, int bits, int channels)
public WaveFormatExtensible(int rate, int bits, int channels, int channelMask = 0)
: base(rate, bits, channels)
{
waveFormatTag = WaveFormatEncoding.Extensible;
extraSize = 22;
wValidBitsPerSample = (short) bits;
for (int n = 0; n < channels; n++)
if (channelMask != 0)
{
dwChannelMask |= (1 << n);
dwChannelMask = channelMask;
}
else
{
for (int n = 0; n < channels; n++)
{
dwChannelMask |= (1 << n);
}
}
if (bits == 32)
{
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31 changes: 28 additions & 3 deletions NAudio.Wasapi/WasapiOut.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -269,15 +269,40 @@ private WaveFormat GetFallbackFormat()
if (!bitDepthsToTry.Contains(24)) bitDepthsToTry.Add(24);
if (!bitDepthsToTry.Contains(16)) bitDepthsToTry.Add(16);

var channelMasksToTry = new List<int>() { 0 };
// The WaveFormatExtensible constructor covers the following channel masks by default.
// 0x0003 2.0: FL|FR (KSAUDIO_SPEAKER_STEREO)
// 0x0007 3.0: FL|FR|FC (KSAUDIO_SPEAKER_3POINT0)
// 0x000F 3.1: FL|FR|FC|LFE (KSAUDIO_SPEAKER_3POINT1)
// 0x003F 5.1: FL|FR|FC|LFE|BL|BR (KSAUDIO_SPEAKER_5POINT1_BACK; obsolete)
// 0x00FF 7.1: FL|FR|FC|LFE|BL|BR|FLC|FRC (KSAUDIO_SPEAKER_7POINT1_WIDE; obsolete)
// Add masks for other configurations.
// Candidates are taken from ksmedia.h in the Windows Driver Kit.
if (channelCountsToTry.Contains(1)) channelMasksToTry.Add(0x0004); // 1.0: FC (KSAUDIO_SPEAKER_MONO)
if (channelCountsToTry.Contains(2)) channelMasksToTry.Add(0x000C); // 1.1: FC|LFE (KSAUDIO_SPEAKER_1POINT1)
if (channelCountsToTry.Contains(3)) channelMasksToTry.Add(0x000B); // 2.1: FL|FR|LFE (KSAUDIO_SPEAKER_2POINT1)
if (channelCountsToTry.Contains(4))
{
channelMasksToTry.Add(0x0033); // 4.0: FL|FR|BL|BR (KSAUDIO_SPEAKER_QUAD)
channelMasksToTry.Add(0x0107); // 4.0: FL|FR|FC|BC (KSAUDIO_SPEAKER_SURROUND)
}
if (channelCountsToTry.Contains(5)) channelMasksToTry.Add(0x0607); // 5.0: FL|FR|FC|SL|SR (KSAUDIO_SPEAKER_5POINT0)
if (channelCountsToTry.Contains(6)) channelMasksToTry.Add(0x060F); // 5.1: FL|FR|FC|LFE|SL|SR (KSAUDIO_SPEAKER_5POINT1_SURROUND)
if (channelCountsToTry.Contains(7)) channelMasksToTry.Add(0x0637); // 7.0: FL|FR|FC|BL|BR|SL|SR (KSAUDIO_SPEAKER_7POINT0)
if (channelCountsToTry.Contains(8)) channelMasksToTry.Add(0x063F); // 7.1: FL|FR|FC|LFE|BL|BR|SL|SR (KSAUDIO_SPEAKER_7POINT1_SURROUND)

foreach (var sampleRate in sampleRatesToTry)
{
foreach (var channelCount in channelCountsToTry)
{
foreach (var bitDepth in bitDepthsToTry)
{
var format = new WaveFormatExtensible(sampleRate, bitDepth, channelCount);
if (audioClient.IsFormatSupported(shareMode, format))
return format;
foreach (var channelMask in channelMasksToTry)
{
var format = new WaveFormatExtensible(sampleRate, bitDepth, channelCount, channelMask);
if (audioClient.IsFormatSupported(shareMode, format))
return format;
}
}
}
}
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