Recording in segments and encoding to a fixed file size

[Error]

I was wondering how people are able to determine the proper bitrate for a video when the encode is done in segments. Say I record something with my PVR and stop at the commericials giving me a separate .mpeg file every time I stop. I then want to encode the previous segment while the show is till on. Is there some kind of special technique to determining a bitrate when you don't have the actual length and audio file size if you use ABR.

Also what would be the proper way to mux these encoded files together? I am going to guess if I was using an ASP codec wrapped in avi I could use avisynth and vdubmod direct stream processing. If I used AVC in .mp4 I am going to assume avs and mp4box?

[manono]

If you know the length of the show, the final filesize after joining the segments, and the audio bitrate you'll be using, figuring video bitrate is easy. A weekly show is the same length every week, within a few seconds.

[Error]

How many MB a minute can you figure for ABR 128kbps mp3 or aac mp4. Megui told me around 20 MB for 23 min. During my test run the mp3 only came out to be 14MB. Also what is the best method to combine these files?

[manono]

Megui told me around 20 MB for 23 min. During my test run the mp3 only came out to be 14MB.
Bitrate is bitrate. It doesn't matter whether MP3 or AAC audio, XviD or MPEG-2 video. I get about 21 MB for 23 minutes at 128 kBits/s (21562 KB, to be exact). If yours wound up less than that, it's not 128 kBits/s. But that sometimes happens when making ABR audio.

For joining I usually use VDubMod. There might be problems with the audio, though, if their bitrates differ, so you might try AVIMux GUI which is more "forgiving". But honestly, I've never fooled around with segmented encoding of the type you're asking about. That's "scene" type stuff and gives inferior results. While it's fairly easy to wind up with the size you want, the various segments won't all have the same quality when encoded for the same bitrate. And since Doom9 is about quality, you'll want to wait until you have the entire episode, cut the commercials, and then do the encoding in order to ensure the best results.

For example, early in the episode you might have mostly static scenes, and that same bitrate will result in higher quality than scenes towards the end when all the fights and explosions might be taking place.