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Caution: This version of this document is no longer maintained. For the latest documentation, see http://www.qnx.com/developers/docs.

snd_pcm_channel_status_t

PCM channel status structure

Synopsis:

typedef struct snd_pcm_channel_status
{
    int32_t         channel;
    int32_t         mode;
    int32_t         status;
    uint32_t        scount;
    struct timeval  stime;
    uint64_t        ust_stime;
    int32_t         frag;
    int32_t         count;
    int32_t         free;
    int32_t         underrun;
    int32_t         overrun;
    int32_t         overrange;
    uint32_t        subbuffered;
    uint8_t         reserved[128];  /* must be filled with zero */
}       snd_pcm_channel_status_t;

Description:

The snd_pcm_channel_status_t structure describes the status of a PCM channel. The members include:

channel
The channel direction; one of SND_PCM_CHANNEL_PLAYBACK or SND_PCM_CHANNEL_CAPTURE.
mode
The transfer mode: SND_PCM_MODE_BLOCK. (SND_PCM_MODE_STREAM is deprecated.)
status
The channel status. Valid values are:
  • SND_PCM_STATUS_NOTREADY -- the driver isn't prepared for any operation. After a successful call to snd_pcm_channel_params(), the state is changed to SND_PCM_STATUS_READY.
  • SND_PCM_STATUS_READY -- the driver is ready for operation. You can mmap() the audio buffer only in this state, but the samples still can't be transferred. After a successful call to snd_pcm_channel_prepare(), snd_pcm_capture_prepare(), snd_pcm_playback_prepare(), or snd_pcm_plugin_prepare(), the state is changed to SND_PCM_STATUS_PREPARED.
  • SND_PCM_STATUS_PREPARED -- the driver is prepared for operation. The samples may be transferred in this state.
  • SND_PCM_STATUS_RUNNING -- the driver is actively transferring data through the hardware. The samples may be transferred in this state.
  • SND_PCM_STATUS_UNDERRUN -- the playback channel is in an underrun state. The driver completely drained the buffers before new data was ready to be played. You must reprepare the channel before continuing, by calling snd_pcm_channel_prepare(), snd_pcm_playback_prepare(), or snd_pcm_plugin_prepare(). See the wave.c example in the appendix.
  • SND_PCM_STATUS_OVERRUN -- the capture channel is in an overrun state. The driver has processed the incoming data faster than it's coming in; the channel is stalled. You must reprepare the channel before continuing, by calling snd_pcm_channel_prepare(), snd_pcm_capture_prepare(), or snd_pcm_plugin_prepare(). See the waverec.c example in the appendix.
  • SND_PCM_STATUS_PAUSED -- the playback is paused (not supported by QSA).
scount
The number of bytes processed since the playback/capture last started. This value is clipped when it reaches the SND_PCM_BOUNDARY value, and is reset when you prepare the channel.
stime
The playback/capture start time, in the format used by gettimeofday() (see the QNX Neutrino Library Reference).

This member is valid only when the time flags is active in the snd_pcm_channel_params_t, structure.

ust_stime
The playback/capture start time, in UST format. This member is valid only when the ust_time flags is active in the snd_pcm_channel_params_t, structure.
frag
The current fragment number (available only in the block mode).
count
The number of bytes in the queue/buffer; see the note below.
free
The number of bytes in the queue that are still free; see the note below.
underrun
The number of playback underruns since the last status.
overrun
The number of capture overruns since the last status.
overrange
The number of ADC capture overrange detections since the last status.
subbuffered
The number of bytes subbuffered in the plugin interface.

Note: The count and free members aren't used if the mmap plugin is used. To disable the mmap plugin, call snd_pcm_plugin_set_disable().

Classification:

QNX Neutrino


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