Bug#815673: ffmpeg: VP9 seek broken in ffplay

[George B.]

Package: ffmpeg
Version: 7:2.8.6-1+b1
Severity: normal

Hello,

I have encoded a video as VP9 using ffmpeg with the following settings
and I am unable to seek forward in the video (tested with mpv and
ffplay).

```
ffmpeg -i raw/00040.MTS -c:v libvpx-vp9 -b:v 3500K -threads 8 -speed 1 -tile-columns 6 -frame-parallel 1 -auto-alt-ref 1 -lag-in-frames 25 -c:a libopus -b:a 64k -f webm 00040_1pass.webm
```

The output I get from ffplay:

```
ffplay version 2.8.6-1+b1 Copyright (c) 2003-2016 the FFmpeg developers
  built with gcc 5.3.1 (Debian 5.3.1-8) 20160205
  configuration: --prefix=/usr --extra-version=1+b1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-libx264 --enable-libopencv
  libavutil      54. 31.100 / 54. 31.100
  libavcodec     56. 60.100 / 56. 60.100
  libavformat    56. 40.101 / 56. 40.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 40.101 /  5. 40.101
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.101 /  1.  2.101
  libpostproc    53.  3.100 / 53.  3.100
Input #0, matroska,webm, from '00040_1pass.webm': sq=    0B f=0/0   
  Metadata:
    encoder         : Lavf56.40.101
  Duration: 00:01:44.68, start: 0.007000, bitrate: 2594 kb/s
    Stream #0:0: Video: vp9 (Profile 0), yuv420p(tv), 1920x1080, SAR 1:1 DAR 16:9, 25 fps, 25 tbr, 1k tbn, 1k tbc (default)
    Stream #0:1: Audio: opus, 48000 Hz, 5.1, fltp (default)
[matroska,webm @ 0x7fe7d4009240] seek_frame_generic failed as this stream seems to contain no keyframes after the target timestamp, 1002 non keyframes found
[matroska,webm @ 0x7fe7d4009240] seek_frame_generic failed as this stream seems to contain no keyframes after the target timestamp, 1002 non keyframes found
00040_1pass.webm: error while seeking
```

You can find the file here: https://gir.me.uk/files/tmp/20160223-ffmpeg_bug/00040_1pass.webm


Thanks,

George

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.3.0-1-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages ffmpeg depends on:
ii  libavcodec-ffmpeg56    7:2.8.6-1+b1
ii  libavdevice-ffmpeg56   7:2.8.6-1+b1
ii  libavfilter-ffmpeg5    7:2.8.6-1+b1
ii  libavformat-ffmpeg56   7:2.8.6-1+b1
ii  libavresample-ffmpeg2  7:2.8.6-1+b1
ii  libavutil-ffmpeg54     7:2.8.6-1+b1
ii  libc6                  2.21-9
ii  libpostproc-ffmpeg53   7:2.8.6-1+b1
ii  libsdl1.2debian        1.2.15+dfsg1-2
ii  libswresample-ffmpeg1  7:2.8.6-1+b1
ii  libswscale-ffmpeg3     7:2.8.6-1+b1
ii  libvdpau1              1.1.1-3
ii  libx11-6               2:1.6.3-1

ffmpeg recommends no packages.

Versions of packages ffmpeg suggests:
pn  ffmpeg-doc  <none>

-- no debconf information