Re: [PATCH v15 00/16] Add audio support in v4l2 framework

[Jaroslav Kysela]

On 09. 05. 24 12:44, Shengjiu Wang wrote:
> > > mem2mem is just like the decoder in the compress pipeline. which is
> > > one of the components in the pipeline.
> >
> > I was thinking of loopback with endpoints using compress streams,
> > without physical endpoint, something like:
> >
> > compress playback (to feed data from userspace) -> DSP (processing) ->
> > compress capture (send data back to userspace)
> >
> > Unless I'm missing something, you should be able to process data as fast
> > as you can feed it and consume it in such case.
>
> Actually in the beginning I tried this,  but it did not work well.
> ALSA needs time control for playback and capture, playback and capture
> needs to synchronize.  Usually the playback and capture pipeline is
> independent in ALSA design,  but in this case, the playback and capture
> should synchronize, they are not independent.

The core compress API core no strict timing constraints. You can eventually0 
have two half-duplex compress devices, if you like to have really independent 
mechanism. If something is missing in API, you can extend this API (like to 
inform the user space that it's a producer/consumer processing without any 
relation to the real time). I like this idea.

					Jaroslav

--
Jaroslav Kysela <perex@xxxxxxxx>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.