[libav-bugs] [Bug 731] New: avconv ignores video bitrate parameter when converting with 2 passes some files to VP8 or VP9

bugzilla at libav.org bugzilla at libav.org
Fri Aug 29 20:55:45 CEST 2014


https://bugzilla.libav.org/show_bug.cgi?id=731

           Summary: avconv ignores video bitrate parameter when converting
                    with 2 passes some files to VP8 or VP9
           Product: Libav
           Version: git HEAD
          Platform: X86
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: general
        AssignedTo: bugzilla at libav.org
        ReportedBy: mossroy at free.fr


On some files, avconv uses a very low bitrate if I transcode to VP8/VP9 in a
WebM container, with 2 passes. Even if I passed a "-b:v" parameter with a
higher birate.
The issue does not occur if transcoding with only one pass.
It only occurs on this kind of files (generated by my camera), not on any other
file I tried.

It happens with libav 11 beta 1 (compiled from source), and also with
9.16-6:9.16-0ubuntu0.14.04.1 (standard version from Ubuntu 14.04 repo).

Steps to reproduce :
- download the source file from
https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1323822/+attachment/4120893/+files/P5270914.MOV
- convert this file to webm (vp8/vorbis) with 2 passes, with command lines
"avconv -i P5270914.MOV -b:v 1000k -pass 1 -passlogfile logfile
P5270914-2-passes.webm" followed by "avconv -i P5270914.MOV -b:v 1000k -pass 2
-y -passlogfile logfile P5270914-2-passes.webm"
- the result is a file with a video bitrate around 250 kbps, which is not
correct
- convert the source file again with one pass, with command line "avconv -i
P5270914.MOV -b:v 1000k P5270914-1-pass.webm"
- the result is a file with a video bitrate around 1 Mbps, which is correct



$ avconv -v 9 -loglevel 99 -i P5270914.MOV
avconv version 11_beta1, Copyright (c) 2000-2014 the Libav developers
  built on Aug 29 2014 15:09:15 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
  configuration: --enable-libvpx --enable-libmp3lame --enable-libvorbis
--enable-libopus
  libavutil     54.  3. 0 / 54.  3. 0
  libavcodec    56.  0. 0 / 56.  0. 0
  libavformat   56.  1. 0 / 56.  1. 0
  libavdevice   55.  0. 0 / 55.  0. 0
  libavfilter    5.  0. 0 /  5.  0. 0
  libavresample  2.  1. 0 /  2.  1. 0
  libswscale     3.  0. 0 /  3.  0. 0
Splitting the commandline.
Reading option '-v' ... matched as option 'v' (set libav* logging level) with
argument '9'.
Reading option '-loglevel' ... matched as option 'loglevel' (set libav* logging
level) with argument '99'.
Reading option '-i' ... matched as input file with argument
'/home/mossroy/temp/P5270914.MOV'.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option v (set libav* logging level) with argument 9.
Successfully parsed a group of options.
Parsing a group of options: input file /home/mossroy/temp/P5270914.MOV.
Successfully parsed a group of options.
Opening an input file: /home/mossroy/temp/P5270914.MOV.
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x22fe080] Probed with size=2048 and score=100
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x22fe080] ISO: File Type Major Brand: qt  
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x22fe080] Referenced QT chapter track not found
[h264 @ 0x230a420] AVC: Consumed only 148390 bytes instead of 148396
[h264 @ 0x230a420] AVC: Consumed only 198909 bytes instead of 198916
[h264 @ 0x230a420] AVC: Consumed only 28312 bytes instead of 28316
[h264 @ 0x230a420] AVC: Consumed only 57213 bytes instead of 57220
[h264 @ 0x230a420] AVC: Consumed only 52142 bytes instead of 52148
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x22fe080] All info found
Guessed Channel Layout for  Input Stream #0.1 : stereo
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/home/mossroy/temp/P5270914.MOV':
  Metadata:
    major_brand     : qt  
    minor_version   : 538976288
    compatible_brands: qt  ####
    creation_time   : 2014-05-27 18:41:51
  Duration: 00:00:04.77, start: 0.000000, bitrate: 20160 kb/s
    Stream #0.0(eng), 30, 1/30000: Video: h264 (Constrained Baseline),
yuvj420p, 1920x1080 [PAR 1:1 DAR 16:9], 1001/60000, 18597 kb/s, 29.97 fps, 30k
tbn, 59.94 tbc (default)
    Metadata:
      creation_time   : 2014-05-27 18:41:51
    Stream #0.1(eng), 1, 1/48000: Audio: pcm_s16le, 48000 Hz, 2 channels, s16,
1536 kb/s (default)
    Metadata:
      creation_time   : 2014-05-27 18:41:51
Successfully opened the file.
At least one output file must be specified

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