cannot prevent webm encoding from dropping frames (and default)

[Christof Petig]

Binary package hint: ffmpeg

libvpx will drop frames by default (without the user to notice) when the bitrate is set too low.

You can recreate this bug by simply invoking
  ffmpeg -i someDVD.vob test.webm
and analyzing the resulting webm file by
 mkvinfo -v test.webm | fgrep "Track Nummer 1" | less
usually the frame dropping starts around 14s. This can cumulate in a file which contains every (second) frame as a key frame.

The following web page contains information about the problem and hints to the fixing commit:
https://groups.google.com/a/webmproject.org/group/webm-discuss/browse_thread/thread/7152b4a42825530

The following upstream patch fixes this (and came after the 0.6 release)
http://git.ffmpeg.org/?p=ffmpeg;a=commitdiff;h=b82e38a409e329718c256f25ac25da0222790b24;hp=a8d597ab7b8dcdc1bb22e6ba4115e99eee7e50ad

I consider this bug critical to the reputation of webm if ffmpeg is used naively.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: ffmpeg 4:0.6-2ubuntu2
ProcVersionSignature: Ubuntu 2.6.32-24.39-generic 2.6.32.15+drm33.5
Uname: Linux 2.6.32-24-generic i686
NonfreeKernelModules: fglrx wl
Architecture: i386
Date: Mon Aug 23 19:42:40 2010
ProcEnviron:
 PATH=(custom, user)
 LANG=de_DE.utf8
 SHELL=/bin/bash
SourcePackage: ffmpeg

[Christof Petig (christof-petig)]

Sorry, the correct invokation of the mkvinfo/fgrep in English locale is:
 mkvinfo -v herrderdiebe.webm | fgrep "track number 1" | less

[Christof Petig (christof-petig)]

Added an upstream bug report / release request as https://roundup.ffmpeg.org/issue2182

[Christof Petig (christof-petig)]

changing the title to "cannot prevent webm encoding from dropping frames (and does by default)" would make the meaning clearer, but I can not change it

[Reinhard Tartler (siretart)]

seems a good candidate to me to backport to 0.6.1

[Oibaf (oibaf)]

Note that since libvpx 0.9.2 frame dropping is disabled by default:
http://review.webmproject.org/gitweb?p=libvpx.git;a=commitdiff;h=23216211bc27bd90bd4b32a4730e839a4de29559

[Oibaf (oibaf)]

This should be properly fixed upgrading libvpx to 0.9.2. Please test after upgrading to it.

[Oibaf (oibaf)]

No feedback and this should be fixed in 10.10 with the updated libvpx. Reopen if needed.