There are two/three processes here:
A 1. Record video, i.e. the capture and storage of visual infomation
A 2. Record sound i.e. the capture and storage of auditory information.
B. Encode audio-video, i.e. transformation and combination of data from at least one source and configuration into another.


Aside from whether the device is up to doing all of this at once, you need to ensure both the recording and encoding processes are operating before you can try to join them up.

Re: encoding
On you N900, what software do you have installed capable of encoding videos? What formats is it capable of producing?
Tests:
- Try simply changing a pre-recorded video from one format to another.
- Try combining a pre-recorded sound track with a pre-recorded video file.
** can you synchroise the two files well enough for tv playback?

re Recording:
- Are you actually capturing visual information?
- If so, is this data being stored for more than 1 frame?
- once you know the data is being stored, try encoding it offline (once record is complete)
- if recording sound with video rolling is a problem, try something like "recaller" and tying the audio and video together with ffmpeg (or similar).

-post 200