Over the past 5 or 6 years, I've had my TiVo HR10-250 setup to extract videos off of it. Please see my other posts on how I set that up with Zipper and mfs_ftp. There are some newer programs to help with the video extraction, but I have a cobbled together system that works OK enough for now, so I'll not go into those here. Today I'll explore how to convert the files mfs_ftp can produce into something that looks good, at least on the TV I have :). I'm in the US, so all these instructions are NTSC-centric. Sorry for all my pals out there that have PAL.
What I will talk about is converting the tmf files (or the .ty files) into something useful. For me, useful varies with time. The tmf files are like ty files, except they are big tar balls of a series of .ty files (all smaller than some limit that I can't recall) and a xml file that describes the show. The tytompeg program is what I use to convert them to a mpg file. You can find info on how to snag this here DVRpedia entry on TyToMpg.
The tytompg program produces video that is 480x480 with a 4:3 pixel aspect ratio. This turns out to be the SVCD resolution, so many tricks for turning SVCDs into DVDs work when processing these files. However, they aren't fully compliant SVCD files. There's some audio delay issues that cause problems and many tools have difficulties with these files. I've only overcome the synchronization problems by trial and error at this point (certain ffmpeg operations causes something to remove the stutter, sometimes on some versions). One problem with tytompg is that I lose the subtitles. I'll explore that problem more later...
A number of cartoons are broadcast these days on the SD stations in letterbox. My son watches them. It would sure by nice if I could process these files to produce a nice, 16x9 videos that play nicely. Since these files are 480x480, the actual video is in the pixels from 8,60 to 472,360 (the extra 8 pixels is a band that many stations seem to put around the picture for reasons unknown). Sometimes there's only a few pixels on each side, so it isn't worth the hassle to get rid of them (in which case the picture is bounded by 0,60 to 480x360). 720x480 is the only DVD resolution that supports a 16:9 aspect ratio. Speaking of aspect ratios, please see the writeup at http://howto-pages.org/ffmpeg/ which covers this in extreme detail. Here's the ffmpeg 1.0.1 command line I use to convert them (the 0.x command needs to crop based on the 720x480 image size).
ffmpeg -i 002-ty.mpg -vf yadif,crop=464:360:8:60,scale=720:480 -aspect 16:9 -vcodec mpeg2video -s 720x480 -b 4500k 002-nice.mpg
mpeg2video is easy to create and fairly ubiquitous, but has a couple of draw backs. First, it is large. The above command typically doubles the size of the file. It looks really nice on the big screen HD TV (so ffmpeg's upscaler is a little better than the upscaling in the TV), but eats up the storage space. Second, many of the media renders I have in the house do mpeg2 rendering in software, so the playback can be a bit jerky on those devices.
Converting to h.264 is an option that I'll explore in later columns. The current level of tool integration isn't so nice, so would be a much longer write up.