[SOLVED] No audio when previewing youtube .mp4 videos (mp4a audio codec) on Unity Linux

[Spiralofhope]

I'm creating and solving this issue so that it's searchable by others who may have the same issue.

This was reproduced on a fresh install of Unity Linux 32bit 2010.1, updated 2010-09-06.

ffmpeg was installed via commandline, with:
\smart-root install ffmpeg

The version which was installed was 0.6-0.22960.1@i586

Problem:
Downloading what seems to be any YouTube video in .mp4 (as opposed to .flv) format gives a file which is playable in regular audio players (e.g. mplayer, vlc, xine) but has no audio with Openshot or ffplay.

Solution:
Downgrade ffmpeg.

Enter the gui smart with:
\smart-root --gui

Select the earlier version of ffmpeg for install:
0.6-0.21383.1@i586

The earlier version (and related files) will be downgraded.

Exit Openshot, re-start it and now the previously mute videos will have audio.

---

Before:
       $ ffmpeg -i

FFmpeg version 0.6, Copyright (c) 2000-2010 the FFmpeg developers
  built on Jul 17 2010 22:46:28 with gcc 4.4.2
  configuration: --prefix=/usr --enable-shared --libdir=/usr/lib --shlibdir=/usr/lib --incdir=/usr/include --disable-stripping --enable-postproc --enable-gpl --enable-pthreads --enable-libtheora --enable-libvorbis --disable-encoder=vorbis --enable-libvpx --enable-x11grab --enable-runtime-cpudetect --enable-libdc1394 --enable-libschroedinger --enable-libxvid --disable-decoder=aac --disable-encoder=aac
  libavutil 50.15. 1 / 50.15. 1
  libavcodec 52.72. 2 / 52.72. 2
  libavformat 52.64. 2 / 52.64. 2
  libavdevice 52. 2. 0 / 52. 2. 0
  libswscale 0.11. 0 / 0.11. 0
  libpostproc 51. 2. 0 / 51. 2. 0
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x8273440]max_analyze_duration reached

Seems stream 1 codec frame rate differs from container frame rate: 29834.00 (29834/1) -> 14.92 (14917/1000)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'seanbedlam - My Pal Satan.mp4':
  Metadata:
    major_brand : mp42
    minor_version : 0
    compatible_brands: isomavc1mp42
  Duration: 00:02:01.90, start: 0.000000, bitrate: 240 kb/s
    Stream #0.0(und): Audio: mp4a / 0x6134706D, 0 channels, 105 kb/s
    Stream #0.1(und): Video: h264, yuv420p, 192x144 [PAR 1:1 DAR 4:3], 133 kb/s, 14.92 fps, 14.92 tbr, 14917 tbn, 29834 tbc

---

After:
       $ ffmpeg -i

FFmpeg version UNKNOWN, Copyright (c) 2000-2010 Fabrice Bellard, et al.
  built on Jan 27 2010 07:56:31 with gcc 4.4.2
  configuration: --prefix=/usr --enable-shared --libdir=/usr/lib --shlibdir=/usr/lib --incdir=/usr/include --enable-postproc --enable-gpl --enable-pthreads --enable-libtheora --enable-libvorbis --enable-x11grab --enable-runtime-cpudetect --enable-libdc1394 --enable-libschroedinger
  libavutil 50. 7. 0 / 50. 7. 0
  libavcodec 52.48. 0 / 52.48. 0
  libavformat 52.47. 0 / 52.47. 0
  libavdevice 52. 2. 0 / 52. 2. 0
  libswscale 0. 9. 0 / 0. 9. 0
  libpostproc 51. 2. 0 / 51. 2. 0

Seems stream 1 codec frame rate differs from container frame rate: 29834.00 (29834/1) -> 14.92 (179/12)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'seanbedlam - My Pal Satan.mp4':
  Metadata:
    major_brand : mp42
    minor_version : 0
    compatible_brands: isomavc1mp42
  Duration: 00:02:01.90, start: 0.000000, bitrate: 240 kb/s
    Stream #0.0(und): Audio: aac, 44100 Hz, stereo, s16, 105 kb/s
    Stream #0.1(und): Video: h264, yuv420p, 192x144 [PAR 1:1 DAR 4:3], 133 kb/s, 14.92 fps, 14.92 tbr, 14917 tbn, 29834 tbc

---

This issue will be reported to the ffmpeg package maintainer on Unity Linux.

[Spiralofhope (spiralofhope)]

A ticket for Unity Linux was opened here:
http://dev.unity-linux.org/issues/236

Hopefully others who have a similar issue (on any distribution) will also learn to play with their ffmpeg versions.