vpxenc --skip sets incorrect duration in webm.

[GoogleCodeExporter]

Using skip / limit to break up a movie into 100 frames sections, ffmpeg reports 
the first section correctly.  100 frames / 24 fps = 4.17 seconds.
But after that the 'start' is not considered, but --limit is.

Input #0, matroska,webm, from 'garden_0.vp9.webm':
  Duration: 00:00:04.17, start: 0.000000, bitrate: 5603 kb/s

Input #0, matroska,webm, from 'garden_100.vp9.webm':
  Duration: 00:00:08.34, start: 0.000000, bitrate: 2614 kb/s

Input #0, matroska,webm, from 'garden_200.vp9.webm':
  Duration: 00:00:12.51, start: 0.000000, bitrate: 1891 kb/s

When concatenated, the result has incorrect timing.
4 seconds play for first section
4 more seconds play for second section.  but its '8.34' seconds.
4 seconds paused.
4 more seconds play for third section.  but its 12.51 seconds.
8 seconds paused.
4 more seconds play...
each time with longer paused.

There are 27 sections - it should be 113.7 seconds.
But ffmpeg reports
Duration: 00:28:10.24, start: 0.000000, bitrate: 355 kb/s

ffmpeg should report that each section is 4.17 seconds duration, but different 
start times.

For IVF, vpxenc outputs the correct start time for each section.

Its unclear if start time or time stamps are correct for webm output by vpxenc?
If correct, the bug is in ffmpeg webm vp9 importer?

A work around would be avoiding --skip

If the bug can't be easily fixed, could vpxenc adjust time stamps/duration to 
start at zero?

e.g. --skip 1000 --limit 1100 would produce time stamps as if doing frames 0 to 
99.

Original issue reported on code.google.com by fbarch...@chromium.org on 13 Mar 2013 at 9:47

[GoogleCodeExporter]

Also note that --skip is slow.

As a work around, YUV can be extracted to different files.
Attached yuvcut tool can extract frames from yuv.

Original comment by fbarch...@chromium.org on 14 Mar 2013 at 12:50

• Added labels: ****
• Removed labels: ****

Attachments:

• yuvcut.cc

[GoogleCodeExporter]

VP9 bitstream is not yet finalized 

Original comment by albe...@google.com on 14 Mar 2013 at 10:27

• Changed state: Available
• Added labels: Mstone-12
• Removed labels: ****