Seeking Workflow/Tools for AAC Transcode

[defunkt]

Hello video enthusiasts. Wondering if somebody can help fast-track me into a workflow/toolset to extract LC-AAC 5.1 Audio from an MKV, downmix this to Dolby ProLogic II stereo, then re-encode as HE-AAC to be re-muxed with the original video.

It's been a while. Back in the (DVD Backup) day I'd use DGIndex to demux a vob, indicating any delay in the filenames, then use HeadAC3he to do the delay cut and DPL downmix. Finally I'd encode with Apple's AAC encoder.

I'd still like to use Apple's encoder (via qaac) but I'm scratching my head a little on up-to-date methods to;

- Extract the 5.1 AAC (from MKV) while correctly handling any start offset defined in the container.
- Downmix the extracted multi-channel audio to a DPL II stereo wav ready for encoding.

If you can help, or just indicate some tools I should be looking at, I'd be most grateful.

Thanks!