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

[Vinod Koul <vkoul@kernel.org>]

On 08-09-26, 17:13, Péter Ujfalusi wrote:
> 
> >>>> 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.
> > 
> > I wanted to ask earlier, whats IPC4?
> 
> SOF supports 2 major IPC mode, IPC3 which was used up to TGL family (and
> by NXP, AMD and MediaTek) and IPC4 which is from MTL onward (with
> unofficial support for TGL).
> 
> They have different operating principles and we just got the compress
> support for IPC4 (so TGL and up) only on Intel platforms.
> 
> NXP is using the compressed with IPC3.

aha, joy of changing IPC with SoC! I dont envy you Peter :-)

> 
> > The kernel should view this as a continuous bit stream and wont know
> > EOF. Only firmware will know about it and with metadata, able to skip
> > those.
> 
> I see, the issue is that I cannot find any way to give the metadata to
> the decoder module, it is a black box to us.
> 
> Also I'm not sure how the fw could get any idea where one
> flac/vorbis/aac/mp3 ends and where it starts, the black box does not
> seam to be able to detect this or if it does, it will not emit this
> information to outside.

It is supposed to be filled by media frameworks that parse the file and
send it down to kernel. That is why in fcplay chose to use libav for
getting information for few formats I had... I might have some fork in
my old pc, I will check if I had something more that could help you.

Feel free to extend it, if this is not working and use something else to
get the metadata.

> >> Also: I have assorted ogg/mp3/flac in my music library and I tend
> >> to play them in random, which defeats the gapless.
> > 
> > You are a non typical users :-) To test this, we would same track in
> > album. A typical user would be running spotify with same format :-)
> 
> Yes, Spotify will shuffle, but use the same format mostly for the
> random 'files', true.
> 
> >> The gapless support is not covered in this initial version, but can
> >> be added later.
> I will likely need to do this at some point, but again, w/o the
> ability to test it, it is hard to declare victory ;)

I was testing on few formats on Qualcomm platforms and this seemed
to work for them... It is not elegant but got the work done for me back
then.

-- 
~Vinod