decode or recode mkv and mp4 (avc) to mpg

[Rat Killer]

I have a good deal of HD video stored in both mkv (x264/aac) and mp4 (AVC/AAC) formats. I need to be able to convert it back to a mpg file. Mpeg-2 with ac3 audio for use on a Tivo. Want to keep the HD resolutions. I have searched and there is lots of info for building both mkv and mp4 files which have been helpful in the past but not much for going the other way.

I have tried several paths and not been all that successful.

If someone could suggest a workpath that they know works I would sure appreciate it. A one shot piece of software would be nice but not holding my breath. I have no fear of learning a couple pieces of new software to make this happen, just need the combo that works well and has good final results.

Any help much appreciated. Thanks.

[bond]

whats the source and content of those mkv/mp4 files?

[Rat Killer]

whats the source and content of those mkv/mp4 files?

Guess I figured it would not matter where they originally came from but they started life as TIVO recordings transferred to pc via TivoDesktop and stored in mkv or mp4 containers. The mp4 conversion is easier as nero pretty much automates it. But if it makes getting back when need be, I could stick with .mkv files.

I no longer have the .tivo files as they are MUCH larger than the .mkv or mp4 files (being mpeg2 with ac3 sound in most)

I still am interested in how to get back if myself or others wish to watch the files on thier tivo. Tivo only accepts mpeg2 files in hd resolutions at the moment.

I have been trying to learn comand line ffmpeg.exe and think I may be close to a working command line for at least the .mkv files. At the moment I am getting good video in mpeg-2 format but no audio so I am doing something wrong. Thought perhaps there are folks her that know a bunch more about ffmpeg and other software than I do and perhaps give me some pointers.

here is the ffmpeg command line I am currently using while figureing this out:

ffmpeg -i input.mkv -f mpeg2video -b 10M -maxrate 16000k -bufsize 1024k -r 23.98 -acodec ac3 -ab 384k -ac 6 -ar 48000 output.mpg

for now ffmpeg and the video file I am working on are both in C:\program files\ffmpeg

Any idea what I am doing wrong? why no audio in the output file?

[bond]

what is the audio format in mkv and mp4? if it is aac you need a ffmpeg compile including the libfaad aac decoder, which is not included by default in ffmpeg