[FFmpeg-user] Piping audio from ffmpeg to faad

[Philip Hoffman]

I'm trying to develop a list of commands to transcode a h.264 encoded video
with 5.1 aac audio to flv with stereo mp3. I believe I can do this by using
the following process:
- Extract audio with ffmpeg
- Downmix audio with faad
- Encode with lame
- Encode video with new audio stream with ffmpeg

However, I cannot seem to get ffmpeg to pipe it's output to faad. This is an
example of the kind of command that will not work.

ffmpeg -v 0 -i Avatar\ \(HD\).mp4 -acodec copy - | faad --downmix -o
avatar.wav -

I get the following output:
FFmpeg version 0.6.3, Copyright (c) 2000-2010 the FFmpeg developers
  built on Jun 12 2011 15:33:39 with gcc 4.6.0 20110509 (Red Hat 4.6.0-7)
  configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64
--mandir=/usr/share/man --enable-shared --enable-runtime-cpudetect
--enable-gpl --enable-version3 --enable-nonfree --enable-postproc
--enable-avfilter --enable-pthreads --enable-x11grab --enable-vdpau
--disable-avisynth --enable-libdc1394 --enable-libdirac --enable-libfaac
--enable-libgsm --enable-libmp3lame --enable-libopencore-amrnb
--enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp
--enable-libschroedinger --enable-libspeex --enable-libtheora
--enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid
--extra-cflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
-fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -fPIC'
--disable-stripping
  libavutil     50.15. 1 / 50.15. 1
  libavcodec    52.72. 2 / 52.72. 2
  libavformat   52.64. 2 / 52.64. 2
  libavdevice   52. 2. 0 / 52. 2. 0
  libavfilter    1.19. 0 /  1.19. 0
  libswscale     0.11. 0 /  0.11. 0
  libpostproc   51. 2. 0 / 51. 2. 0
Error opening file: -
<VIDEO_CHAPTERS>
    Stream #0.0(und): Video: h264, yuv420p, 1920x1080 [PAR 1:1 DAR 16:9],
7040 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc
    Stream #0.1(eng): Audio: aac, 48000 Hz, 5.1, s16, 259 kb/s
Unable to find a suitable output format for 'pipe:'

Thanks,
Philip