atempo filter cuts off data

[rmk]

The following command line with a file containein two click sounds (one in the beginning, the other right before the end) demonstrates the problem:

ffmpeg -i two-clicks.wav -af "atempo=0.5" -acodec pcm_s16le two-clicks-half-speed.wav
ffmpeg version N-65311-g6f3e15a Copyright (c) 2000-2014 the FFmpeg developers
  built on Aug  5 2014 17:28:11 with Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)
  configuration: --enable-gpl --enable-libx264 --enable-libfaac --enable-nonfree --extra-ldflags=-L/usr/local/lib --extra-cflags=-I/usr/local/include
  libavutil      52. 97.100 / 52. 97.100
  libavcodec     55. 72.101 / 55. 72.101
  libavformat    55. 51.101 / 55. 51.101
  libavdevice    55. 13.102 / 55. 13.102
  libavfilter     4. 11.102 /  4. 11.102
  libswscale      2.  6.100 /  2.  6.100
  libswresample   0. 19.100 /  0. 19.100
  libpostproc    52.  3.100 / 52.  3.100
Guessed Channel Layout for  Input Stream #0.0 : mono
Input #0, wav, from 'two-clicks.wav':
  Duration: 00:00:01.00, bitrate: 705 kb/s
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 1 channels, s16, 705 kb/s
Output #0, wav, to 'two-clicks-half-speed.wav':
  Metadata:
    ISFT            : Lavf55.51.101
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, mono, s16, 705 kb/s
    Metadata:
      encoder         : Lavc55.72.101 pcm_s16le
Stream mapping:
  Stream #0:0 -> #0:0 (pcm_s16le (native) -> pcm_s16le (native))
Press [q] to stop, [?] for help
size=     168kB time=00:00:01.95 bitrate= 705.9kbits/s    
video:0kB audio:168kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.045340%

Then checking the output shows the file is 0.05 seconds too short:

ffmpeg -i two-clicks-half-speed.wav 
ffmpeg version N-65311-g6f3e15a Copyright (c) 2000-2014 the FFmpeg developers
  built on Aug  5 2014 17:28:11 with Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)
  configuration: --enable-gpl --enable-libx264 --enable-libfaac --enable-nonfree --extra-ldflags=-L/usr/local/lib --extra-cflags=-I/usr/local/include
  libavutil      52. 97.100 / 52. 97.100
  libavcodec     55. 72.101 / 55. 72.101
  libavformat    55. 51.101 / 55. 51.101
  libavdevice    55. 13.102 / 55. 13.102
  libavfilter     4. 11.102 /  4. 11.102
  libswscale      2.  6.100 /  2.  6.100
  libswresample   0. 19.100 /  0. 19.100
  libpostproc    52.  3.100 / 52.  3.100
Guessed Channel Layout for  Input Stream #0.0 : mono
Input #0, wav, from 'two-clicks-half-speed.wav':
  Metadata:
    encoder         : Lavf55.51.101
  Duration: 00:00:01.95, bitrate: 705 kb/s
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 1 channels, s16, 705 kb/s
At least one output file must be specified

And looking at the file in a wave editor (and listening to it), you see/hear that the second click was cut off.

[Pavel Koshevoy]

I am taking a look at this

[Pavel Koshevoy]

Patch submitted - https://ffmpeg.org/pipermail/ffmpeg-devel/2014-August/161444.html

[Elon Musk]

Fixed in 6380f2e3670a8cfc29b9b02da0f2be0c537315f8