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@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@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%
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