Re: [PATCH] ALSA: compress: allow pause and resume during draining

[Vinod Koul <vkoul@kernel.org>]

On 01-10-20, 10:28, Pierre-Louis Bossart wrote:
> 
> 
> 
> > > > > Hrm, this resulted in rather more complex changes than the original
> > > > > patch.  It shows that introducing yet another state is no good idea
> > > > > for this particular case.
> > > > > 
> > > > > Since the possible application's behavior after this pause is as same
> > > > > as the normal pause (i.e. either resuming pause or dropping), I find
> > > > > it OK to take the original approach.
> > > > Thank you for the review.
> > > > I think that I should resend the original patch.
> > > 
> > > Let's wait a bit for other opinions.  We may add rather a new flag
> > > instead of introducing a new state, too, for example.
> > 
> > I was out for a week, back now ;-)
> > 
> > So bigger question is if kernel should handle this change or we ask
> > userspace to handle this. Userland knows that bit rate is less so small
> > buffer can be for longer duration so instead of sending dumb X bytes,
> > should it not scale the buffer based on bit rate?
> 
> what about variable bit-rate? or cases where you have a 'bit reservoir' in
> previous frames?
> 
> You really cannot in general translate bytes to time with compressed data,
> which is the reason we introduced the API in the first place...
> 
> Userspace *may* know the duration for specific formats or based on metadata,
> but in some cases the only way to know is actually to decode the data.
> 
> I suggest we keep the compressed API based on bytes and non-periodic events
> when the bytes were consumed/generated.

Changing the API away from bytes was not proposed so not sure...

The SM in kernel might be bit more convoluted so was wondering if we can
handle this in userland. The changelog for this patch says that for
test case was sending whole file, surely that is not an optimal approach.
Should we allow folks to send whole file to kernel and then issue
partial drain?

-- 
~Vinod