Assaf Hoffman wrote:
> Thank you for your reply.
> Please let me clarify. What you say is that my device can deliver a raw
> ICE958 data from the capture channel to the DMA buffer and the ALSA
> stack will know how to deal with it? No need for the device to strip
> down the payload and only then transfer it to the DMA buffer?
> In case the sound card can strip down the IEC958 frames into raw sound
> data + ch status + user data, how would the ALSA stack expect the data?
> Is there an API for that?
> Thanks again.
>
If you don't strip the IEC958 frames, tell ALSA the format is:
SNDRV_PCM_FMTBIT_IEC958_SUBFRAME_LE
SNDRV_PCM_FMTBIT_IEC958_SUBFRAME_BE
If you do strip the IEC958 frames, tell ALSA the format is:
SNDRV_PCM_FMTBIT_S24_LE or
SNDRV_PCM_FMTBIT_S16_LE
Or whatever format your hardware decides to send.
The API for this is contained in the following structure in the sound
driver:
This example is from the snd-emu10k1 driver.
static struct snd_pcm_hardware snd_emu10k1_capture =
{
.info = (SNDRV_PCM_INFO_MMAP |
SNDRV_PCM_INFO_INTERLEAVED |
SNDRV_PCM_INFO_BLOCK_TRANSFER |
SNDRV_PCM_INFO_RESUME |
SNDRV_PCM_INFO_MMAP_VALID),
.formats = SNDRV_PCM_FMTBIT_S16_LE,
.rates = SNDRV_PCM_RATE_8000_48000,
.rate_min = 8000,
.rate_max = 48000,
.channels_min = 1,
.channels_max = 2,
.buffer_bytes_max = (64*1024),
.period_bytes_min = 384,
.period_bytes_max = (64*1024),
.periods_min = 2,
.periods_max = 2,
.fifo_size = 0,
};
As you can see, it tells use that this device can do only
SNDRV_PCM_FMTBIT_S16_LE format.
James
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