iPod h.264 questions

[rumplestiltskin]

The Max GOP size defaults to 250. Would there an advantage, quality-wise, to setting this to something lower? I don't mind adding some add'l time to the process if quality will improve substantially.

Let me set up a situation: Source is an AVI of about 100 minutes that's about 700MB. Destination is an iPod but we want to keep enough "quality" so that connecting the iPod to a TV results in a "pleasant user experience". I'm not talking about viewing on a 50" screen but, rather, a 25" 4:3 TV (and the source may be 16:9 viewed as letterbox). So I select the "iPod h.264" with a size of 320x176 (assuming 16:9) but I bump up the bitrate to 475 for quality purposes (on the TV).

Why don't I just use "plain" mpeg4 with a larger frame (640x or 480x)? Well, the quality of mpeg4 is lower than H264 so I have to bump up the bitrate even more and, all of a sudden, I've got a 650MB file. Wait a minute! I started with 700MB and all I've got to show is a lousy 50MB savings? See where I'm heading?

So what I'm asking is how to tweak the H264 settings to keep an iPod-compatible destination file at a reasonable size (around 3.5-3.75MB/minute) but produce a really high quality image.

Suggestions are welcome.

Thanks!

[major]

iPod supports h.264 only at 320 width, and such image size will never look good on TV, no matter what you do with the options. To user a larger image size, you must use the "iPod for TV" preset and use say, a width of 480.

[rumplestiltskin]

Actually, major, you've done a better job with your "iPod h.264" settings than you may have hoped. I've been testing many of the apps out there (MPEG Streamclip, MoviesForMyPod, Podner, iSquint, Handbrake, even exporting streams from VLC!) and your ffmpegX's iPod H264 is actually superior because it produces compatible files where others sometimes do not (claims to the contrary notwithstanding), and may be tweaked far more than the others to compensate for deficiencies in (or just differences between) source files.

There is really only one thing I can think of at this moment that would make ffmegX an even better app: Let me set "in" and "out" points (minuteseconds?) so I may run tests quickly (even with multi-pass encodings) and then decide which configuration I prefer for the current job.

Now, as for 320 width never looking good on TV, I'll have to disagree. Once the bitrate is set to 475 or a bit higher, it's okay (albeit not stellar). Two-pass is desirable (but with the MP4 H264 setting) but the biggest improvement seems to have been changing the adaptive quantizer settings to Q2-30. The files are undoubtedly larger (360MB vs 235 with the stock Q settings) but the quality really is something to behold. I've got to congratulate you (and probably will have to register to show that I mean it, eh? ).

The bottom line (in this overly long missive) is that you might want to consider another iPod H264 setting or maybe just a checkbox that tells your app to "make it a lot better". The app is already much faster than Apple's "H264 iPod export" from QT (and quality there is also quite good although the file is substantially larger). Perhaps something in between what Apple does and what your "iPod h.264" setting does now.

(That makes two items for the wish list.)

[major]

In/out points are also in to-do list. 320 width may look as good as a VCD, which may be said good, though a TV will support for more (when the height is about 300 then it starts to look really good). Indeed if better presets are found I can add them.