Hi,

I see that the ALSA Loop driver supports only the following formats:

.formats = (SNDRV_PCM_FMTBIT_S16_LE | SNDRV_PCM_FMTBIT_S16_BE | SNDRV_PCM_FMTBIT_S24_LE | SNDRV_PCM_FMTBIT_S24_BE | SNDRV_PCM_FMTBIT_S24_3LE | SNDRV_PCM_FMTBIT_S24_3BE | SNDRV_PCM_FMTBIT_S32_LE | SNDRV_PCM_FMTBIT_S32_BE | SNDRV_PCM_FMTBIT_FLOAT_LE | SNDRV_PCM_FMTBIT_FLOAT_BE),

I'd like to have Loopback service with A_LAW format, I though it would just require to add SNDRV_PCM_FMTBIT_A_LAW to the format above as the Loopback driver just loops the samples.

But it doesn't work, I still get only the following formats:

ALSA ERROR hw_params: set (FORMAT) value = A_LAW : Invalid argument ACCESS: RW_INTERLEAVED FORMAT: S16_LE S16_BE S24_LE S32_LE S32_BE S24_3LE SUBFORMAT: STD SAMPLE_BITS: [16 32] FRAME_BITS: [16 1024] CHANNELS: [1 32] RATE: [8000 192000] PERIOD_TIME: (5 65536000] PERIOD_SIZE: [1 524288] PERIOD_BYTES: [2 67108864] PERIODS: [1 1024] BUFFER_TIME: (5 131072000] BUFFER_SIZE: [1 1048576] BUFFER_BYTES: [2 134217728] TICK_TIME: ALL ALSA lib pcm.c:8644:(snd_pcm_set_params) Sample format not available for CAPTURE: Invalid argument

What am I missing, what needs to be added to the Loop driver to support A_LAW format ?

Thanks for your help Christophe