snd_pcm_channel_params_t

PCM channel parameters

Synopsis:

typedef struct snd_pcm_channel_params
{
    int32_t             channel;
    int32_t             mode;
    snd_pcm_sync_t      sync;               /* hardware synchronization ID */
    snd_pcm_format_t    format;
    snd_pcm_digital_t   digital;
    int32_t             start_mode;
    int32_t             stop_mode;
    int32_t             time:1, ust_time:1;
    uint32_t            why_failed;         /* SND_PCM_PARAMS_BAD_??? */
    union
    {
        struct
        {
            int32_t     queue_size;
            int32_t     fill;
            int32_t     max_fill;
            uint8_t     reserved[124];      /* must be filled with zero */
        }       stream;
        struct
        {
            int32_t     frag_size;
            int32_t     frags_min;
            int32_t     frags_max;
            uint8_t     reserved[124];      /* must be filled with zero */
        }       block;
        uint8_t     reserved[128];      /* must be filled with zero */
    }       buf;
    uint8_t     reserved[128];      /* must be filled with zero */
}       snd_pcm_channel_params_t;

Description:

The snd_pcm_channel_params_t structure describes the parameters of a PCM capture or playback channel. The members include:

channel

The channel direction; one of SND_PCM_CHANNEL_PLAYBACK or SND_PCM_CHANNEL_CAPTURE.

mode

The channel mode: SND_PCM_MODE_BLOCK. (SND_PCM_MODE_STREAM is deprecated.)

format

The data format; see snd_pcm_format_t.

digital

Not currently implemented.

start_mode

The start mode; one of:

• SND_PCM_START_DATA — start when some data is written (playback) or requested (capture).
• SND_PCM_START_FULL — start when the whole queue is filled (playback only).
• SND_PCM_START_GO — start on the Go command.

stop_mode

The stop mode; one of:

• SND_PCM_STOP_STOP — stop when an underrun or overrun occurs.
• SND_PCM_STOP_ERASE — stop and erase the whole buffer when an overrun occurs (capture only).
• SND_PCM_STOP_ROLLOVER — ROLLOVER (i.e. automatically reprepare and continue) when an underrun or overrun occurs.

time

If set, the driver offers, in the status structure, the time when the transfer began. The time is in the format used by gettimeofday() (see the QNX Neutrino Library Reference).

ust_time

If set, the driver offers, in the status structure, the time when the transfer began. The time is in UST format.

sync

The synchronization group. Not supported; don't use this member.

queue_size

The queue size, in bytes, for the stream mode. Not supported; don't use this member.

fill

The fill mode (SND_PCM_FILL_* constants). Not supported; don't use this member.

max_fill

The number of bytes to be filled ahead with silence. Not supported; don't use this member.

frag_size

The size of fragment in bytes.

frags_min

Depends on the mode:

• Capture — the minimum filled fragments to allow wakeup (usually one).
• Playback — the minimum free fragments to allow wakeup (usually one).

frags_max

For playback, the maximum filled fragments to allow wakeup. This value specifies the total number of fragments that could be written to by an application. This excludes the fragment that's currently playing, so the actual total number of fragments is frags_max + 1.

Classification:

QNX Neutrino

See also:

snd_pcm_channel_params(), snd_pcm_format_t