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

[FFmpeg]

#2484: atempo - low accuracy
------------------------------------+-------------------------------------
             Reporter:  bars        |                    Owner:  pkoshevoy
                 Type:  defect      |                   Status:  open
             Priority:  normal      |                Component:  avfilter
              Version:  git-master  |               Resolution:
             Keywords:  atempo      |               Blocked By:
             Blocking:              |  Reproduced by developer:  1
Analyzed by developer:  0           |
------------------------------------+-------------------------------------
Changes (by pkoshevoy):

 * owner:   => pkoshevoy


Comment:

 The error is much worse at lower sample rates (8000Hz) -- off by more than
 52 seconds.

 $ /Developer/x86_64/bin/ffmpeg -f lavfi -i
 'aevalsrc=s=8000:c=mono:exprs=sin(0.5*2*PI*t)*sin(440*2*PI*t):d=24000' -af
 atempo=23976/25000 -y /nfs/scratch/DataSets/Video/au/06h-40m-
 23976to25000-v2.au
 ffmpeg version N-52339-g0dd25e4 Copyright (c) 2000-2013 the FFmpeg
 developers
   built on Apr 20 2013 13:29:29 with llvm-gcc 4.2.1 (LLVM build
 2336.11.00)
   configuration: --prefix=/Developer/x86_64 --enable-swscale --enable-
 avfilter --enable-libmp3lame --enable-libvorbis --enable-libopus --enable-
 libtheora --enable-libschroedinger --enable-libopenjpeg --enable-
 libmodplug --enable-libvpx --enable-libspeex --enable-shared --enable-
 pthreads --enable-gpl --enable-version3 --enable-libopencore-amrnb
 --enable-libopencore-amrwb --enable-postproc --enable-libx264 --enable-
 libxvid --enable-yasm --enable-runtime-cpudetect --extra-
 cflags=-I/opt/local/include --extra-ldflags='-headerpad_max_install_names
 -L/opt/local/lib'
   libavutil      52. 27.100 / 52. 27.100
   libavcodec     55.  5.100 / 55.  5.100
   libavformat    55.  3.100 / 55.  3.100
   libavdevice    55.  0.100 / 55.  0.100
   libavfilter     3. 58.100 /  3. 58.100
   libswscale      2.  2.100 /  2.  2.100
   libswresample   0. 17.102 /  0. 17.102
   libpostproc    52.  3.100 / 52.  3.100
 Input #0, lavfi, from
 'aevalsrc=s=8000:c=mono:exprs=sin(0.5*2*PI*t)*sin(440*2*PI*t):d=24000':
   Duration: N/A, start: 0.000000, bitrate: 512 kb/s
     Stream #0:0: Audio: pcm_f64le, 8000 Hz, mono, dbl, 512 kb/s
 Output #0, au, to '/nfs/scratch/DataSets/Video/au/06h-40m-
 23976to25000-v2.au':
   Metadata:
     encoder         : Lavf55.3.100
     Stream #0:0: Audio: pcm_s16be ([3][0][0][0] / 0x0003), 8000 Hz, mono,
 s16, 128 kb/s
 Stream mapping:
   Stream #0:0 -> #0:0 (pcm_f64le -> pcm_s16be)
 Press [q] to stop, [?] for help
 size=  391837kB time=06:57:57.54 bitrate= 128.0kbits/s
 video:0kB audio:391837kB subtitle:0 global headers:0kB muxing overhead
 0.000008%

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2484#comment:5>
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