wrong duration with voc files

[ami_stuff]

seems like voc demuxer lacks duration calcalation, so it's calculated incorrectly and as a result seeking doesn't work as expected (issue 1082)

VLC/WinAMP reports correct duration (0:17)

​http://samples.mplayerhq.hu/voc/pcm_s16_2/nem.voc

C:\>ffmpeg -i nem.voc
ffmpeg version N-31329-g58257ea, Copyright (c) 2000-2011 the FFmpeg developers
  built on Jul  8 2011 22:27:48 with gcc 4.6.1
  configuration: --enable-gpl --enable-version3 --enable-memalign-hack --enable-
runtime-cpudetect --enable-avisynth --enable-bzlib --enable-frei0r --enable-libo
pencore-amrnb --enable-libopencore-amrwb --enable-libfreetype --enable-libgsm --
enable-libmp3lame --enable-libopenjpeg --enable-librtmp --enable-libschroedinger
 --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libvpx --enabl
e-libx264 --enable-libxavs --enable-libxvid --enable-zlib
  libavutil    51. 11. 0 / 51. 11. 0
  libavcodec   53.  7. 0 / 53.  7. 0
  libavformat  53.  5. 0 / 53.  5. 0
  libavdevice  53.  2. 0 / 53.  2. 0
  libavfilter   2. 24. 3 /  2. 24. 3
  libswscale    2.  0. 0 /  2.  0. 0
  libpostproc  51.  2. 0 / 51.  2. 0
[voc @ 01E6A600] max_analyze_duration 5000000 reached at 5011200
[voc @ 01E6A600] Estimating duration from bitrate, this may be inaccurate
Input #0, voc, from 'nem.voc':
  Duration: 00:00:34.56, bitrate: 705 kb/s
    Stream #0.0: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s
At least one output file must be specified

[reimar]

Ah, I missed that patch (didn't get an email notification for it).
Anyway, I also sent one to ffmpeg-dev now.
Either way, it would only happen for stereo voc files.