[FFmpeg-trac] #2484(FFmpeg:new): atempo - low accuracy

FFmpeg trac at avcodec.org
Fri Apr 19 10:54:07 CEST 2013


#2484: atempo - low accuracy
--------------------------------+---------------------------------------
             Reporter:  bars    |                     Type:  defect
               Status:  new     |                 Priority:  normal
            Component:  FFmpeg  |                  Version:  unspecified
             Keywords:          |               Blocked By:
             Blocking:          |  Reproduced by developer:  0
Analyzed by developer:  0       |
--------------------------------+---------------------------------------
 Summary of the bug: I can't reach an exact length (microseconds). The
 precision for atempo can only be specified up to 3 digits (x.xxx).
 How to reproduce:
 Example test.wav (Duration 00:40:44.864)

 To convert from 25 fps to 23.976fps (PAL->NTSC)
 (24000/1001)/25=0.959040959041 => atempo=0.959040959041
 00:40:44.864 => 00:42:29.407 (407ms) (atempo=0.959040959041)
 00:40:44.864 => 00:42:29.407 (407ms) (atempo=0.959)
 00:40:44.864 => 00:42:29.407 (407ms) (atempo=0.959999999999)
 00:40:44.864 => 00:42:29.407 (407ms) (atempo=0.959111111111)
 00:40:44.864 => 00:42:29.407 (407ms) (atempo=24000/25025)

 When 0.959040959041 correct length must be at 00:42:29.280 (280ms!)

 {{{
 ffmpeg -i "test.wav" -y -acodec pcm_s16le -af "atempo=0.959040959041"
 "test_atempo.wav"
 ffmpeg version N-52233-gee94362 Copyright (c) 2000-2013 the FFmpeg
 developers
   built on Apr 18 2013 02:55:39 with gcc 4.8.0 (GCC)
   configuration: --enable-gpl --enable-version3 --disable-w32threads
 --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r
 --enable-gnutls --enable-iconv --enable-libass --enable-libbluray
 --enable-libcaca --enable-libfreetype --enable-libgsm --enable-libilbc
 --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb
 --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-
 libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora
 --enable-libtwolame --enable-libvo-aacenc --enable-libvo-amrwbenc
 --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs
 --enable-libxvid --enable-zlib
   libavutil      52. 26.100 / 52. 26.100
   libavcodec     55.  2.100 / 55.  2.100
   libavformat    55.  2.100 / 55.  2.100
   libavdevice    55.  0.100 / 55.  0.100
   libavfilter     3. 56.103 /  3. 56.103
   libswscale      2.  2.100 /  2.  2.100
   libswresample   0. 17.102 /  0. 17.102
   libpostproc    52.  3.100 / 52.  3.100
 [wav @ 0000000000329fe0] max_analyze_duration 5000000 reached at 5013333
 microseconds
 Guessed Channel Layout for  Input Stream #0.0 : stereo
 Input #0, wav, from 'test.wav':
   Metadata:
     encoder         : Lavf55.2.100
   Duration: 00:40:44.86, bitrate: 1536 kb/s
     Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz,
 stereo, s16, 1536 kb/s
 Output #0, wav, to 'test_atempo.wav':
   Metadata:
     ISFT            : Lavf55.2.100
     Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz,
 stereo, s16, 1536 kb/s
 Stream mapping:
   Stream #0:0 -> #0:0 (pcm_s16le -> pcm_s16le)
 Press [q] to stop, [?] for help
 size=   16642kB time=00:01:28.75 bitrate=1536.0kbits/s
 size=   36550kB time=00:03:14.93 bitrate=1536.0kbits/s
 size=   46708kB time=00:04:09.11 bitrate=1536.0kbits/s
 size=   64952kB time=00:05:46.41 bitrate=1536.0kbits/s
 size=   78344kB time=00:06:57.83 bitrate=1536.0kbits/s
 size=   96750kB time=00:08:35.99 bitrate=1536.0kbits/s
 size=  109712kB time=00:09:45.13 bitrate=1536.0kbits/s
 size=  129966kB time=00:11:33.15 bitrate=1536.0kbits/s
 size=  144280kB time=00:12:49.49 bitrate=1536.0kbits/s
 size=  159015kB time=00:14:08.08 bitrate=1536.0kbits/s
 size=  172411kB time=00:15:19.52 bitrate=1536.0kbits/s
 size=  188794kB time=00:16:46.90 bitrate=1536.0kbits/s
 size=  203688kB time=00:18:06.33 bitrate=1536.0kbits/s
 size=  221898kB time=00:19:43.45 bitrate=1536.0kbits/s
 size=  234376kB time=00:20:50.00 bitrate=1536.0kbits/s
 size=  254330kB time=00:22:36.42 bitrate=1536.0kbits/s
 size=  264514kB time=00:23:30.73 bitrate=1536.0kbits/s
 size=  284585kB time=00:25:17.78 bitrate=1536.0kbits/s
 size=  305369kB time=00:27:08.63 bitrate=1536.0kbits/s
 size=  326328kB time=00:29:00.41 bitrate=1536.0kbits/s
 size=  342023kB time=00:30:24.12 bitrate=1536.0kbits/s
 size=  362457kB time=00:32:13.10 bitrate=1536.0kbits/s
 size=  374388kB time=00:33:16.73 bitrate=1536.0kbits/s
 size=  391906kB time=00:34:50.16 bitrate=1536.0kbits/s
 size=  401618kB time=00:35:41.96 bitrate=1536.0kbits/s
 size=  415769kB time=00:36:57.43 bitrate=1536.0kbits/s
 size=  431130kB time=00:38:19.35 bitrate=1536.0kbits/s
 size=  449682kB time=00:39:58.30 bitrate=1536.0kbits/s
 size=  467467kB time=00:41:33.15 bitrate=1536.0kbits/s
 size=  478014kB time=00:42:29.40 bitrate=1536.0kbits/s

 video:0kB audio:478014kB subtitle:0 global headers:0kB muxing overhead
 0.000016%
 }}}
 Patches should be submitted to the ffmpeg-devel mailing list and not this
 bug tracker.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2484>
FFmpeg <http://ffmpeg.org>
FFmpeg issue tracker


More information about the FFmpeg-trac mailing list