On Wed, 15 Apr 2015 09:36:09 +0000 (UTC) Carl Eugen Hoyos <ceho...@ag.or.at> wrote:
> wm4 <nfxjfg <at> googlemail.com> writes: > > > > > > this breaks seeking in CBR files with a xing toc > > > > > > > > > > see: https://trac.ffmpeg.org/ticket/2590 for testcase/example > > > From what I can tell, this can't be used to reproduce the problem. > > I tested the following: > $ ffmpeg -ss 50 -i Underworld_sample_cut.mp3 -t 10 out.wav > ffmpeg version 1.0 Copyright (c) 2000-2012 the FFmpeg developers > built on Feb 10 2013 11:28:07 with gcc 4.7 (SUSE Linux) > configuration: --enable-gpl > libavutil 51. 73.101 / 51. 73.101 > libavcodec 54. 59.100 / 54. 59.100 > libavformat 54. 29.104 / 54. 29.104 > libavdevice 54. 2.101 / 54. 2.101 > libavfilter 3. 17.100 / 3. 17.100 > libswscale 2. 1.101 / 2. 1.101 > libswresample 0. 15.100 / 0. 15.100 > libpostproc 52. 0.100 / 52. 0.100 > [mp3 @ 0x2b72280] max_analyze_duration 5000000 reached at 5015510 > Input #0, mp3, from 'Underworld_sample_cut.mp3': > Metadata: > artist : Lilith > album : Underworld > genre : Gothic Metal > date : 2007 > Duration: 00:42:36.63, start: 0.000000, bitrate: 4 kb/s > Stream #0:0: Audio: mp3, 44100 Hz, stereo, s16, 192 kb/s > Output #0, wav, to 'out.wav': > Metadata: > artist : Lilith > album : Underworld > genre : Gothic Metal > date : 2007 > encoder : Lavf54.29.104 > Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo, > s16, 1411 kb/s > Stream mapping: > Stream #0:0 -> #0:0 (mp3 -> pcm_s16le) > Press [q] to stop, [?] for help > size= 5936kB time=00:00:10.02 bitrate=4851.8kbits/s > video:0kB audio:5936kB subtitle:0 global headers:0kB muxing overhead 0.000757% > > The output file does not start at 0:50 and is too long. Alright, I can confirm that CBR seeking has better precision. The original file was 60MB, and the xing toc has only 100 entries, so it's not surprising seeking is a bit imprecise. However, if this file used VBR mode, seeking would be wrong anyway, so this is at best a special case to make CBR seeks work better. If you insist you can drop the 5th patch. But the problem remains: libavformat fundamentally can not seek correctly in mp3s. (And a lot of other audio formats.) _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
