[FFmpeg-user] No audio or poor audio when converting HDTV broadcasts

[Suneet Shah]

Hello,

I'm trying to splice and convert HDTV broadcasts that I've recorded from
over the air with a Hauppage video card, using ffmpeg.

I'm running into problems where I can either get very poor audio, or no
audio.

Note: I am using ffmpeg on Win7, using static build from here:
http://ffmpeg.zeranoe.com/builds/

The source file is recorded via Windows Media Center in DVR-MS format, a
container format for MPEG2 video.

I am trying to encode using the following:

ffmpeg -ss 475 -t 120 -i INPUT -ac 2 -async 44100 test.mpeg
--> This produces very poor audio.. the original source file has 5.1 AC3
audio (dolby digital)

so then I try:

ffmpeg -ss 475 -t 120 -i INPUT -acodec copy -async 44100 test.mpeg
--> This fails

Question: how can I down mix the AC3 audio properly to 2 channels in an mpeg
file to preserve the high fidelity of the audio?

Thanks in advance