[FFmpeg-devel] [PATCH] pulse: set default frame_size to 4608

[Michael Niedermayer]

On Fri, Jan 03, 2014 at 04:55:33PM +0100, Federico Simoncelli wrote:
> On Fri, Jan 3, 2014 at 3:44 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
> > On Fri, Jan 03, 2014 at 01:21:41AM +0100, Federico Simoncelli wrote:
> >> On Thu, Jan 2, 2014 at 11:26 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> >> > On Thu, Jan 02, 2014 at 04:36:45PM +0100, Federico Simoncelli wrote:
> >> >> Given the current defaults (channels = 2, sample_rate = 48000) the
> >> >> frame_size is changed to 4608 in order to obtain whole numbers for
> >> >> frame_duration (both 16 and 24 bits_per_sample).
> >> >>
> >> >>  frame_duration = (frame_size * 1000000 * 8) /
> >> >>                   (sample_rate * channels * bits_per_sample)
> >> >>
> >> >> A message has been added to warn the user when the frame duration
> >> >> is not an integer.
> >> >
> >> > the timebase should be changed to a multiple of the sample rate
> >> > see the avpriv_set_pts_info() call
> >> > that avoids the problem of the durations being not exactly
> >> > representable
> >>
> >> If I understand correctly what you're suggesting is:
> >>
> >> avpriv_set_pts_info(st, 64, 1, pd->sample_rate);
> >
> > yes
> >
> >> and it will generate non-representable timebases:
> >>
> >> 1/48 = .020833...
> >> 1/44.1 = .0226757
> >
> > rational numbers are quite representable, and really 1/1000000 is
> > a rational number in no way different than 1/48 or 1/48000 is
> > also if you dont like fractions you can just change the base of
> > your representation
> >
> > ...
> >
> > so really the non representability is just an artifact of humans
> > having 10 fingers
> 
> Yes, that's clear, what I meant is that there was 10-fingered code
> around somewhere since I was getting pts warnings after changing the
> timebase.
> Instead I pinpointed this to be something related to the mp3 encoder
> (I don't know what yet).

how can i reproduce that issue ?
can you share the work in progress patch ?


> 
> In fact for some reason it generates a (imo) weird initial frame:
> 
> frame_pts = 1105, frame_ts = 0.023021, base_ts = 0.000021
> frame_pts = 1152, frame_ts = 0.024000, base_ts = 0.000021
> frame_pts = 2304, frame_ts = 0.048000, base_ts = 0.000021
> frame_pts = 3456, frame_ts = 0.072000, base_ts = 0.000021
> ...
> 
> something that the aac encoder is not doing:
> 
> frame_pts = 1024, frame_ts = 0.021333, base_ts = 0.000021
> frame_pts = 2048, frame_ts = 0.042667, base_ts = 0.000021
> frame_pts = 3072, frame_ts = 0.064000, base_ts = 0.000021
> frame_pts = 4096, frame_ts = 0.085333, base_ts = 0.000021
> 
> -- 
> Federico
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> 

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

When the tyrant has disposed of foreign enemies by conquest or treaty, and
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