[FFmpeg-devel] [RFC] [PATCH] hevc_ps: reorder SPS reading to allow some errors

[Michael Niedermayer]

On Thu, Aug 21, 2014 at 10:07:23PM -0700, Timothy Gu wrote:
> On Aug 21, 2014 10:14 AM, "Christophe Gisquet" <christophe.gisquet at gmail.com>
> wrote:
> >
> > Hi,
> >
> > 2014-08-21 3:06 GMT+02:00 Michael Niedermayer <michaelni at gmx.at>:
> > > heres a narrower solution for this file
> > > not sure its better
> > > i can apply whichever you prefer, probably we wont find out which
> > > is the best solution before pushing something and waiting for more
> > > bug reports
> >
> > Thanks for narrowing it done, and now I have dug it further.
> >
> > When you look at what get parsed before that,
> > vui->def_disp_win.left_offset gets an insane value unrelated to the
> > video dimensions. I tried  instead to do as if
> > vui->default_display_window_flag and related syntax does not exist.
> >
> > Then, the timing info is decoded, and the values are actually normal:
> > vui_num_units_in_tick = 1000
> > vui_time_scale = 23976
> > (rest less relevant and meaningfull)
> >
> > So I think the actual "bug" in that stream is that it does not contain
> > any default_display_window information. Why is that? Probably because
> > the encoder writes an older VUI syntax, and several bits get
> > misinterpreted. By luck they don't bother us. It would be nice to know
> > what syntax is used, but there could be so many variations...
> >
> > The attached therefore barely improves on your patch.
> 
> > -    int sar_present;
> > +    GetBitContext backup;
> > +    int sar_present, alt = 1;
> 
> Shouldn't alt be initialized to 0?

fixed

thanks

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Avoid a single point of failure, be that a person or equipment.
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