ffmpeg, webm, and multiple audio streams

I'm trying to convert an MPEG-2 file from a DVD into WebM, but I can't get it to include more than the default audio track (I'd like to preserve the commentary as well). Is this a limitation of WebM, libvpx, weak ffmpeg-fu, or what?

(One of) the command(s) I've been trying:

Code:

---

$ ffmpeg -i input.mpg -ac 2 output.webm

---

My ffmpeg version, libraries, and such:

Code:

---

$ ffmpeg
FFmpeg version 0.6.2-4:0.6.2-1, Copyright (c) 2000-2010 the Libav developers
  built on Mar 29 2011 16:14:25 with gcc 4.5.2
  configuration: --extra-version=4:0.6.2-1 --prefix=/usr --enable-avfilter --enable-avfilter
-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-
libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-
libvpx --disable-stripping --enable-runtime-cpudetect --enable-vaapi --enable-
libopenjpeg --enable-gpl --enable-postproc --enable-x11grab --enable-libdirac --enable-
libfaad --enable-librtmp --enable-libdc1394 --enable-shared --disable-static
  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

---

It depends upon the version of ffmpeg that you are using. I am running 0.6.1 and it has a couple of options that may help:

1. -ar - set number of audio channels
2. -newaudio - add a new audio stream
3. -request_channels N - set desired number (N) of audio channels

See the VideoLAN - Official page for VLC media player, the Open Source video framework! website for more information.