[FFmpeg-trac] #6540(avfilter:new): Atempo filter cuts off data at the end

[FFmpeg]

#6540: Atempo filter cuts off data at the end
----------------------------------+----------------------------------
             Reporter:  asdamos   |                     Type:  defect
               Status:  new       |                 Priority:  normal
            Component:  avfilter  |                  Version:  3.2.4
             Keywords:  atempo    |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
----------------------------------+----------------------------------
 When using atempo filter it cuts off sound data at the end of file.

 I was also using atempo filter from C API in similar way to
 [https://www.ffmpeg.org/doxygen/trunk/filter_audio_8c-example.html].

 I noticed that, when I pushed frame to filter graph, I had to push few
 more frames before I could get frame number one from filter graph. So at
 the end of filtering, I did not get all the frames I pushed to filter
 graph.

 Following command should produce 1 second file but produces 0.97 second
 file.
 {{{
 ./ffmpeg -i one-second-file.wav -filter:a "atempo=1.0" -vn
 output.wavffmpeg version N-86695-g0a24d7c Copyright (c) 2000-2017 the
 FFmpeg developers
   built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
   configuration: --prefix=/home/user/ffmpeg_build --pkg-config-
 flags=--static --extra-cflags=-I/home/user/ffmpeg_build/include --extra-
 ldflags=-L/home/user/ffmpeg_build/lib --bindir=/home/user/bin --enable-
 nonfree
   libavutil      55. 67.100 / 55. 67.100
   libavcodec     57.100.103 / 57.100.103
   libavformat    57. 75.100 / 57. 75.100
   libavdevice    57.  7.100 / 57.  7.100
   libavfilter     6. 94.100 /  6. 94.100
   libswscale      4.  7.101 /  4.  7.101
   libswresample   2.  8.100 /  2.  8.100
 Guessed Channel Layout for Input Stream #0.0 : mono
 Input #0, wav, from 'one-second-file.wav':
   Duration: 00:00:01.00, bitrate: 705 kb/s
     Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, mono,
 s16, 705 kb/s
 Stream mapping:
   Stream #0:0 -> #0:0 (pcm_s16le (native) -> pcm_s16le (native))
 Press [q] to stop, [?] for help
 Output #0, wav, to 'output.wav':
   Metadata:
     ISFT            : Lavf57.75.100
     Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, mono,
 s16, 705 kb/s
     Metadata:
       encoder         : Lavc57.100.103 pcm_s16le
 size=      84kB time=00:00:00.97 bitrate= 706.2kbits/s speed=6.55x
 video:0kB audio:84kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: 0.090681%
 }}}

 Following command should produce 2 seconds file but produces 1.92 seconds
 file.
 {{{
 ./ffmpeg -i one-second-file.wav -filter:a "atempo=0.5" -vn output.wav
 ffmpeg version N-86695-g0a24d7c Copyright (c) 2000-2017 the FFmpeg
 developers
   built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
   configuration: --prefix=/home/user/ffmpeg_build --pkg-config-
 flags=--static --extra-cflags=-I/home/user/ffmpeg_build/include --extra-
 ldflags=-L/home/user/ffmpeg_build/lib --bindir=/home/user/bin --enable-
 nonfree
   libavutil      55. 67.100 / 55. 67.100
   libavcodec     57.100.103 / 57.100.103
   libavformat    57. 75.100 / 57. 75.100
   libavdevice    57.  7.100 / 57.  7.100
   libavfilter     6. 94.100 /  6. 94.100
   libswscale      4.  7.101 /  4.  7.101
   libswresample   2.  8.100 /  2.  8.100
 Guessed Channel Layout for Input Stream #0.0 : mono
 Input #0, wav, from 'one-second-file.wav':
   Duration: 00:00:01.00, bitrate: 705 kb/s
     Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, mono,
 s16, 705 kb/s
 Stream mapping:
   Stream #0:0 -> #0:0 (pcm_s16le (native) -> pcm_s16le (native))
 Press [q] to stop, [?] for help
 Output #0, wav, to 'output.wav':
   Metadata:
     ISFT            : Lavf57.75.100
     Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, mono,
 s16, 705 kb/s
     Metadata:
       encoder         : Lavc57.100.103 pcm_s16le
 size=     166kB time=00:00:01.92 bitrate= 705.9kbits/s speed= 282x
 video:0kB audio:166kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: 0.045887%
 }}}

--
Ticket URL: <https://trac.ffmpeg.org/ticket/6540>
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