[libav-bugs] [Bug 900] New: Strange avconv audio ripping.

bugzilla-daemon at libav.org bugzilla-daemon at libav.org
Sat Oct 17 15:04:38 CEST 2015


https://bugzilla.libav.org/show_bug.cgi?id=900

            Bug ID: 900
           Summary: Strange avconv audio ripping.
           Product: Libav
           Version: 9
          Hardware: X86
                OS: Linux
            Status: NEW
          Severity: minor
          Priority: ---
         Component: utilities
          Assignee: bugzilla at libav.org
          Reporter: mariomey at gmail.com

I wrote on libav-tools at libav.org about this bug and we think it is a bug. Here
is the mail and the report. After the mail (*), I'm posting the subsequents
mails with Luca.

-----------------
Hi, there. I noted that converting a mp4 (from YouTube) to mp3, just to rip the
audio from it, avconv makes a strange job.

I'll call it "case A". As you can see here...

$ avconv -i test.mp4 -b:a 192k test.mp3
...
  Stream #0:0 -> #0:0 (h264 -> png)
  Stream #0:1 -> #0:1 (aac -> libmp3lame)
...

Avconv converts the video stream to PNG (virtually, I think) and the audio to
MP3. This appear to make a big CPU process, because it converts at 22-24fps. It
takes 1:27 minutes to do the process... and I don't have an old PC. It's like
it really does the "h264->png" conversion, but there are no PNG files.

But, if I rip the audio as WAV from the same file ("case B"), it says:

$ avconv -i test.mp4 test.wav
...
  Stream #0:1 -> #0:0 (aac -> pcm_s16le)
...

avconv does it in less than a second. Because it doesn't convert any video
stream.

I think this could be a bug. I'm writing to this list because it's something
about avconv. If it is a bug, then, I/we have to report it. Please tell me what
do you think. Full outputs below.

Case "A":

mario at circo3d:~$ avconv -i test.mp4 -b:a 192k test.mp3 
avconv version 9.18-6:9.18-0ubuntu0.14.04.1, Copyright (c) 2000-2014 the Libav
developers
  built on Mar 16 2015 13:19:10 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    title           : 870389093051784
    encoder         : Lavf56.4.101
  Duration: 00:01:09.26, start: 0.161134, bitrate: 1237 kb/s
    Stream #0.0(und): Video: h264 (High), yuv420p, 854x480 [PAR 1:1 DAR
427:240], 1186 kb/s, 29.97 fps, 29.97 tbr, 11988 tbn, 59.94 tbc
    Stream #0.1(eng): Audio: aac, 44100 Hz, stereo, fltp, 48 kb/s
Output #0, mp3, to 'test.mp3':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    TIT2            : 870389093051784
    TSSE            : Lavf54.20.4
    Stream #0.0(und): Video: png, rgb24, 854x480 [PAR 1:1 DAR 427:240], q=2-31,
200 kb/s, 90k tbn, 11988 tbc
    Stream #0.1(eng): Audio: libmp3lame, 44100 Hz, stereo, fltp, 192 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (h264 -> png)
  Stream #0:1 -> #0:1 (aac -> libmp3lame)
Press ctrl-c to stop encoding
[mp3 @ 0xf2a360] Got more than one picture in stream 0, ignoring.
frame= 2069 fps= 24 q=0.0 Lsize=    2207kB time=69.16 bitrate= 261.3kbits/s    
video:790635kB audio:1623kB global headers:0kB muxing overhead -99.721490%

Case "B"

mario at circo3d:~$ avconv -i test.mp4 test.wav
avconv version 9.18-6:9.18-0ubuntu0.14.04.1, Copyright (c) 2000-2014 the Libav
developers
  built on Mar 16 2015 13:19:10 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    title           : 870389093051784
    encoder         : Lavf56.4.101
  Duration: 00:01:09.26, start: 0.161134, bitrate: 1237 kb/s
    Stream #0.0(und): Video: h264 (High), yuv420p, 854x480 [PAR 1:1 DAR
427:240], 1186 kb/s, 29.97 fps, 29.97 tbr, 11988 tbn, 59.94 tbc
    Stream #0.1(eng): Audio: aac, 44100 Hz, stereo, fltp, 48 kb/s
Output #0, wav, to 'test.wav':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    INAM            : 870389093051784
    ISFT            : Lavf54.20.4
    Stream #0.0(eng): Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s
Stream mapping:
  Stream #0:1 -> #0:0 (aac -> pcm_s16le)
Press ctrl-c to stop encoding
size=   11936kB time=69.29 bitrate=1411.2kbits/s    
video:0kB audio:11936kB global headers:0kB muxing overhead 0.000835%




(*)
----------

Luca Barbato told me:

> The format supports a cover art so looks like it is picking the first
> frame from the video stream for it but then keeps processing the other
> frames, I suggest you to be explicit in what you want meanwhile:

> avconv -i test.mp4 -vn -b:a 192k test.mp3

-----------

I wrote:

> Yes, it makes the cover art with the first frame. So, this is a bug?
> Because it could convert only the first frame... not the rest.

-----------

Then, him:

> Being slow due that is surely a bug, the fact cover art is being
> generated is intended.

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