Set AVFMT_FLAG_GENPTS when demuxing AVI content.

Set AVFMT_FLAG_GENPTS when demuxing AVI content.

Storing MPEG-4 B-frames in AVI has always been a bit of a hack and by default av_read_frame() will return non-timestamped video packets for such content. AVFMT_FLAG_GENPTS takes advantage of AVI's constant framerate to generate presentation timestamps at the expense of parsing delay.

BUG=169570
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=182310

[scherkus (not reviewing), 2013-02-12 02:49:48]

I'm not going to commit it just yet -- I want to dig in to see what exactly the
flag does :)

[rbultje1, 2013-02-12 17:16:05]

lgtm - feel free to commit anytime once you're comfortable with what it does. If
it triggers scary code, let's ask the security guys to do a new fuzz round after
this patch is in?

[scherkus (not reviewing), 2013-02-12 17:50:41]

dalecurtis: care to take a look as well?

[DaleCurtis, 2013-02-12 19:23:30]

lgtm % running the playback test under asan.

https://codereview.chromium.org/12209111/diff/1/media/filters/ffmpeg_demuxer.cc
File media/filters/ffmpeg_demuxer.cc (right):

https://codereview.chromium.org/12209111/diff/1/media/filters/ffmpeg_demuxer....
media/filters/ffmpeg_demuxer.cc:483: if (strcmp(format_context->iformat->name,
"avi") == 0)
avi_crazy_codec_would_still_match_strcmp_reminder

[scherkus (not reviewing), 2013-02-13 17:53:14]

https://codereview.chromium.org/12209111/diff/1/media/filters/ffmpeg_demuxer.cc
File media/filters/ffmpeg_demuxer.cc (right):

https://codereview.chromium.org/12209111/diff/1/media/filters/ffmpeg_demuxer....
media/filters/ffmpeg_demuxer.cc:483: if (strcmp(format_context->iformat->name,
"avi") == 0)
On 2013/02/12 19:23:30, DaleCurtis wrote:
> avi_crazy_codec_would_still_match_strcmp_reminder

gcc disagrees:
strcmp("avi", "avi") -> 0
strcmp("avi", "avi_long") -> -1

Perhaps you were thinking of the strncmp() case with n=3?
strncmp("avi", "avi", 3) -> 0
strncmp("avi", "avi", sizeof("avi")) -> 0
strncmp("avi", "avi_long", 3) -> 0
strncmp("avi", "avi_long", sizeof("avi")) -> -1

[DaleCurtis, 2013-02-13 19:31:57]

Oy, it's been so long since I've touched strcmp, you're right, I was thinking of
strncmp.