[Bug 778750] For vaapih264enc without h264parse, using the adaptive 8x8 DCT encoding tool breaks 720p 30 fps clips

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=778750

Víctor Manuel Jáquez Leal <vjaquez at igalia.com> changed:

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--- Comment #4 from Víctor Manuel Jáquez Leal <vjaquez at igalia.com> ---
Comment on attachment 347810
  --> https://bugzilla.gnome.org/attachment.cgi?id=347810
libs: encoder: h264: apply emulation prevention bytes

A couple comments about this patch:

1. I would document in the commit log what is the
emulation_prevention_three_bytes with the information in the H264 spec (7.3.1
NAL unit syntax and 7.4.1 NAL unit semantics)

2. This patch looks like a copy of what ffmpeg does here [1]. The license is
LGPL so we can reuse that code, but we have to honour the original author: Mark
Thompson <sw at jkqxz.net>  [2]

3. AFAIK H265 also uses this emulation prevention technique, so we should
refactor this code as a shared function.

4. My guts tell me that it could be a better way to add this emulation
prevention code, aligned with the gstvaapi code style.

1.
http://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavcodec/vaapi_encode_h26x.c;h=d806f9b52b354fdf55070f3d0acc44c79948df94;hb=HEAD#l23
2.
http://git.videolan.org/?p=ffmpeg.git;a=commit;h=2c62fcdf5d617791a653d7957d449f75569eede0

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