Re: [PATCH 04/23] ASoC: soc-compress: Implement trigger FE-BE sequencing as with normal PCMs

["Péter Ujfalusi" <peter.ujfalusi@linux.intel.com>]

On 07/09/2026 22:55, Pierre-Louis Bossart wrote:
> On 9/7/26 18:53, Vinod Koul wrote:
>> On 07-09-26, 17:03, Péter Ujfalusi wrote:
>>>
>>>
>>> On 07/09/2026 14:26, Pierre-Louis Bossart wrote:
>>>>>> ...otherwise it'll end up with -EINVAL instead of getting passed
>>>>>> through.  Also a switch statement would be a bit more idiomatic.
>>>>>
>>>>> OK, I will add the NEXT_TRACK and convert the if to switch.
>>>>
>>>> ICYMI for testing, NEXT_TRACK and PARTIAL_DRAIN are only enabled in the
>>>> 'fcplay' application with the '-p 1' argument for gapless playback, not
>>>> in the initial cplay application.
>>>
>>> With SOF/Intel/IPC4 we can only support DRAIN, NEXT_TRACK and
>>> PARTIAL_DRAIN are not supported, but there were mismatch between fcplay
>>
>> Those should be optional always. Gapless support should not be mandatory
> well in practice it's a non-negotiable requirement from users... We had
> to add this as the request of the Android team, and it's a standard
> feature on most players, not a nice-to-have.

The only 'documentation' for the gapless (next_track + partial_drain)
that I could find was the fcplay (and that could not have been worked
(metadata and next_track was in wrong order).

But, reading the code it implies that gapless must support anything
thrown at it in any order as for consecutive files:
metadata
next_track
set_codec_params
partial_drain

With IPC4 the NOP strategy works (just streaming the files without
stopping, but they mus be of same format and property), but then you
loose the position, so not so great.

> Note that the NEXT_TRACK only works if the two consecutive tracks have
> the same format, if the platform wants 'perceived' gapless playback with
> a x-fade then two devices are required.

If I can ever test this I might add support for it, it is not clear how
the pointer should behave after partial_drain, we won't stop the DMAs in
this case.
With the cadence module (compress support in fw) the metadata is not
supported, so true gapless is really something which needs more work.

This has not been planned for the initial IPC4 compress support, it is
unclear how it can be done to me atm.

-- 
Péter