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;
uint32_t ducking_state;
snd_pcm_status_data_t status_data
struct timeval stop_time;
uint8_t reserved[112]; /* must be filled with zeros */
} 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.
- ducking_state
- The audio concurrency management ducking state. These are the valid states:
- SND_PCM_DUCKING_STATE_INACTIVE—Ducking isn't active.
- SND_PCM_DUCKING_STATE_ACTIVE—Ducking is active due because
the stream is active.
- SND_PCM_DUCKING_STATE_HARD_SUSPENDED —The subchannel is
hard-suspended and can't transition from the SUSPENDED state if you call
snd_pcm_*_resume().
- SND_PCM_DUCKING_STATE_SOFT_SUSPENDED—The subchannel is
soft-suspended and an can transition from the SUSPENDED state if you call
snd_pcm_*_resume().
- SND_PCM_DUCKING_STATE_PAUSED—The subchannel will transition
to the PAUSED state from the SUSPENDED state.
- SND_PCM_DUCKING_STATE_FORCED_ACTIVE—Ducking is active because
the snd_pcm_channel_audio_ducking() was called.
- SND_PCM_DUCKING_STATE_MUTE_BY_HIGHER—Ducking occurred because
a higher priority subchannel has started running.
- SND_PCM_DUCKING_STATE_MUTE_BY_SAME—Ducking occurred because a
same priority subchannel has started running.
- 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.
- SND_PCM_STATUS_RUNNING — the driver is actively
transferring data through the hardware.
- SND_PCM_STATUS_PAUSED — the channel has stopped playing.
- SND_PCM_STATUS_SUSPENDED — the driver has stopped playing.
- 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 wraps around to 0 when it passes the value of SND_PCM_BOUNDARY,
and is reset when you prepare the channel.
- stime
- The playback/capture start time, in the format used by
gettimeofday()
(see the QNX Neutrino C 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.
- status_data
- Additional data relevant to a particular value for status.
- stop_time
- The time at which the last sample was played or recorded in the most recent
case where the channel stopped for any reason.
Note:
The stop_time and stime members hold valid data only
if there's data present in the channel; they aren't necessarily valid as soon as the
channel goes to a SND_PCM_STATUS_RUNNING state, but they're guaranteed to be
valid as soon as scount indicates that some data has been processed.
Classification:
QNX Neutrino