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

[Lukasz M]

On 2 January 2014 23:26, 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
>
> 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.
This is more backward compatible than changing default to other or
redefining meaning of the param.

In any case don't forget to update documentation.