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

[Timothy Gu]

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?

Sorry about being too late.

Timothy