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ALSA: Add a new config option to use the default channel layout.

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This can sometimes be more reliable than `snd_pcm_get_chmap()`.
This commit is contained in:
David Reid
2025-07-22 15:29:51 +10:00
parent 20b9b9c533
commit 2d4cc9c910
1 changed files with 50 additions and 44 deletions
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miniaudio.h
+50 -44
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@@ -6830,10 +6830,11 @@ MA_API ma_context_config_alsa ma_context_config_alsa_init(void);
typedef struct ma_device_config_alsa
{
ma_bool32 noMMap; /* Disables MMap mode. */
ma_bool32 noAutoFormat; /* Opens the ALSA device with SND_PCM_NO_AUTO_FORMAT. */
ma_bool32 noAutoChannels; /* Opens the ALSA device with SND_PCM_NO_AUTO_CHANNELS. */
ma_bool32 noAutoResample; /* Opens the ALSA device with SND_PCM_NO_AUTO_RESAMPLE. */
ma_bool32 noMMap; /* Disables MMap mode. */
ma_bool32 noAutoFormat; /* Opens the ALSA device with SND_PCM_NO_AUTO_FORMAT. */
ma_bool32 noAutoChannels; /* Opens the ALSA device with SND_PCM_NO_AUTO_CHANNELS. */
ma_bool32 noAutoResample; /* Opens the ALSA device with SND_PCM_NO_AUTO_RESAMPLE. */
ma_bool32 assumeDefaultChannelLayout; /* Forces the use of the "default" ALSA channel layout. */
} ma_device_config_alsa;
MA_API ma_device_config_alsa ma_device_config_alsa_init(void);
@@ -29801,58 +29802,63 @@ static ma_result ma_device_init_by_type__alsa(ma_context* pContext, ma_context_s
/* Grab the internal channel map. For now we're not going to bother trying to change the channel map and instead just do it ourselves. */
{
ma_snd_pcm_chmap_t* pChmap = NULL;
if (pContextStateALSA->snd_pcm_get_chmap != NULL) {
pChmap = pContextStateALSA->snd_pcm_get_chmap(pPCM);
}
if (pDeviceConfigALSA->assumeDefaultChannelLayout) {
ma_snd_pcm_chmap_t* pChmap = NULL;
if (pContextStateALSA->snd_pcm_get_chmap != NULL) {
pChmap = pContextStateALSA->snd_pcm_get_chmap(pPCM);
}
if (pChmap != NULL) {
ma_uint32 iChannel;
if (pChmap != NULL) {
ma_uint32 iChannel;
/* There are cases where the returned channel map can have a different channel count than was returned by snd_pcm_hw_params_set_channels_near(). */
if (pChmap->channels >= internalChannels) {
/* Drop excess channels. */
for (iChannel = 0; iChannel < internalChannels; ++iChannel) {
internalChannelMap[iChannel] = ma_convert_alsa_channel_position_to_ma_channel(pChmap->pos[iChannel]);
}
} else {
ma_uint32 i;
/* There are cases where the returned channel map can have a different channel count than was returned by snd_pcm_hw_params_set_channels_near(). */
if (pChmap->channels >= internalChannels) {
/* Drop excess channels. */
for (iChannel = 0; iChannel < internalChannels; ++iChannel) {
internalChannelMap[iChannel] = ma_convert_alsa_channel_position_to_ma_channel(pChmap->pos[iChannel]);
}
} else {
ma_uint32 i;
/*
Excess channels use defaults. Do an initial fill with defaults, overwrite the first pChmap->channels, validate to ensure there are no duplicate
channels. If validation fails, fall back to defaults.
*/
ma_bool32 isValid = MA_TRUE;
/*
Excess channels use defaults. Do an initial fill with defaults, overwrite the first pChmap->channels, validate to ensure there are no duplicate
channels. If validation fails, fall back to defaults.
*/
ma_bool32 isValid = MA_TRUE;
/* Fill with defaults. */
ma_channel_map_init_standard(ma_standard_channel_map_alsa, internalChannelMap, ma_countof(internalChannelMap), internalChannels);
/* Fill with defaults. */
ma_channel_map_init_standard(ma_standard_channel_map_alsa, internalChannelMap, ma_countof(internalChannelMap), internalChannels);
/* Overwrite first pChmap->channels channels. */
for (iChannel = 0; iChannel < pChmap->channels; ++iChannel) {
internalChannelMap[iChannel] = ma_convert_alsa_channel_position_to_ma_channel(pChmap->pos[iChannel]);
}
/* Overwrite first pChmap->channels channels. */
for (iChannel = 0; iChannel < pChmap->channels; ++iChannel) {
internalChannelMap[iChannel] = ma_convert_alsa_channel_position_to_ma_channel(pChmap->pos[iChannel]);
}
/* Validate. */
for (i = 0; i < internalChannels && isValid; ++i) {
ma_uint32 j;
for (j = i+1; j < internalChannels; ++j) {
if (internalChannelMap[i] == internalChannelMap[j]) {
isValid = MA_FALSE;
break;
/* Validate. */
for (i = 0; i < internalChannels && isValid; ++i) {
ma_uint32 j;
for (j = i+1; j < internalChannels; ++j) {
if (internalChannelMap[i] == internalChannelMap[j]) {
isValid = MA_FALSE;
break;
}
}
}
/* If our channel map is invalid, fall back to defaults. */
if (!isValid) {
ma_channel_map_init_standard(ma_standard_channel_map_alsa, internalChannelMap, ma_countof(internalChannelMap), internalChannels);
}
}
/* If our channel map is invalid, fall back to defaults. */
if (!isValid) {
ma_channel_map_init_standard(ma_standard_channel_map_alsa, internalChannelMap, ma_countof(internalChannelMap), internalChannels);
}
free(pChmap);
pChmap = NULL;
} else {
/* Could not retrieve the channel map. Fall back to a hard-coded assumption. */
ma_channel_map_init_standard(ma_standard_channel_map_alsa, internalChannelMap, ma_countof(internalChannelMap), internalChannels);
}
free(pChmap);
pChmap = NULL;
} else {
/* Could not retrieve the channel map. Fall back to a hard-coded assumption. */
/* The caller has requested that we always use the default ALSA channel layout. */
ma_channel_map_init_standard(ma_standard_channel_map_alsa, internalChannelMap, ma_countof(internalChannelMap), internalChannels);
}
}