Audio

Updates to the libasound library client APIs require audio applications to make some minor modifications.

For information on migration for audio drivers (deva-*), see Board Support Packages.

Audio mixer controls and channel mapping

The audio mixer controls and channel mapping have been updated to improve support for multichannel audio systems. The library now supports up to 64 channel positions (see snd_pcm_chmap_position in asound.h for the full list of supported channel positions). The majority of the changes affect drivers only, but the following changes to the snd_mixer_group_t structure may affect audio applications:

uint32_t channel is now uint64_tchannel_mask.
uint32_t mute is now uint64_tmute.
uint32_t capture is now uint64_tcapture.
SND_MIXER_CHN_* definitions that correspond to the SND_CHMAP_* definitions with a value over 31 have been created.

This change corresponds to a change in SND_MIXER_VERSION from 3.0.0 to 3.0.1. You can use this preprocessor switch to compile for the appropriate version as required. For example:

#if (SND_MIXER_VERSION >= SND_PROTOCOL_VERSION('M',3,0,1))
           if (((1ULL<<snd_mixer_chn) & gi.channel_mask)) {
#else
           if (((1UL<<snd_mixer_chn) & gi.channels)) {
#endif

For more information about snd_mixer_group_t, see the Audio Library chapter of the Audio Developer's Guide.

_flush() and _drain()

Previously, flush and drain behavior for playback was opposite to what the function name described, and the flush behavior for capture and playback were not consistent. To resolve these issues, QNX SDP 7.1 replaces the *_flush() and *_drain() functions with the following APIs:

snd_pcm_channel_drop(): Stop playback or capture immediately and discard buffered data.
snd_pcm_channel_drain(): For playback, block until buffered data is fully consumed by the hardware and then stop the stream. For capture, stop the stream immediately but preserve the buffered data so that clients can continue to read it until it is fully consumed.
snd_pcm_plugin_drop(): Plugin-aware version of snd_pcm_channel_drop().
snd_pcm_plugin_drain(): Plugin-aware version of snd_pcm_channel_drain().

This change corresponds to a change in SND_PCM_VERSION from 3.0.1 to 3.0.2. You can use this preprocessor switch to compile for the appropriate version as required. For example:

#if SND_PCM_VERSION >= SND_PROTOCOL_VERSION('P',3,0,2)
    if (channel == SND_PCM_CHANNEL_PLAYBACK)
        rtn = snd_pcm_plugin_drain (pcm_handle, SND_PCM_CHANNEL_PLAYBACK);
    else if (channel == SND_PCM_CHANNEL_CAPTURE)
        rtn = snd_pcm_plugin_drop(pcm_handle, SND_PCM_CHANNEL_CAPTURE);
#else
    rtn = snd_pcm_plugin_flush (pcm_handle, channel);
#endif

For more information on the drop and drain functions, see the Audio Library chapter of the Audio Developer's Guide.

snd_ctl_ducking_read()

The snd_ctl_ducking_read() function has been deprecated and will be removed in a future version of the product. Its replacement is snd_ctl_ducking_status_read(). For more information, see snd_ctl_ducking_status_read() in the Audio Developer's Guide.

snd_pcm_channel_params_t

Because the buffered playback mode has been deprecated, the frags_buffered_max member has been removed from snd_pcm_channel_params_t.

Page updated: March 12, 2026