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

[Lukasz M]

W dniu piątek, 3 stycznia 2014 użytkownik Michael Niedermayer napisał:

> On Fri, Jan 03, 2014 at 12:18:37AM +0100, Lukasz M wrote:
> > On 2 January 2014 23:26, Michael Niedermayer <michaelni at gmx.at<javascript:;>>
> 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
> > >
> > > and the frame_size either should be "redefined" to mean samples
> > > across all channels so that 8bit samples with 3 channels and a
> > > frame size of 1024 means 3072 bytes
> > >
> > > cutting frames between channels is quiet bad so a frame size
> > > in bytes is problematic but if its kept in bytes then a default of
> > > 3360 should avoid the fractional durations with the changed timebase
> > >
> >
> > Another solution is not to hardcode value as option default, but
> calculate
> > it in pulse_read_header to value around 1024 (near current value) that
> has
> > no issue with dividing if it is not provided explicitly.
>
> that does sort of, not work
>
> consider 7 channels and 44101 samplerate
> to get that to fit in a 1/1000000 timebase you need a frame size thats
> quite a bit larger than 1024
> why 44101, well that might be the true sample rate the hardware uses
>

I didn't mention that, but I conderered fixing timebase too. You may refer
my later email