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

Christophe Gisquet christophe.gisquet at gmail.com
Thu Aug 21 19:14:03 CEST 2014


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.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0001-hevc_ps-check-overflow-and-test-alternate-syntax.patch
Type: text/x-patch
Size: 2702 bytes
Desc: not available
URL: <https://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20140821/524b3dad/attachment.bin>

More information about the ffmpeg-devel mailing list