| Robert Martens |
March 16th, 2009 12:14 AM |
Chris' suggestion is what I'd go with, but I'd add a couple of things, first being what Jack mentioned; Youtube supports 30p, so use that if that's your project's framerate.
Where I must respectfully disagree with Jack, however, is with two pass encoding. It's my experience that multi pass encoding is a waste of time when it comes to Youtube, Vimeo, or other similar services. The only two reasons to run multiple passes are lowering the size of the file you create and increasing the quality at a given bitrate. With regard to the size, the file you'll be uploading is not the file Youtube will deliver; absolutely everything gets recompressed, according to their own settings, so there's no worry about uploading too large a file. The file won't get appreciably smaller with more than one pass, and you won't save much time on the upload; you'll just spend an unnecessarily long time compressing the video. As for quality, again, at these bitrates the increase is mathematical, and for all the testing I've done it never makes a lick of difference. Single pass and multi pass H.264 files at six to ten megabits per second are near indistinguishable side by side, and the end result of Youtube's compression makes the difference even less evident. If you were encoding video to give directly to your viewers, and/or using bitrates on the order of less than, say, two megabits per second, you'd do well to run the two pass, but for this particular application, I wouldn't bother.
I'd also suggest forcing a keyframe every Nth frame, N being your framerate. The phenomenon mentioned in the article Dave linked is also known as "keyframe flashing", and has never been a problem for me, despite the short intervals I use. Long GOP files are enough of a pain when you view them directly--random access gets more and more difficult the longer the group--but they also cause problems with Youtube. When using long groups I run into a kind of stuttering effect that I suspect is the same issue the author mentions. Forcing a keyframe once every second has successfully eliminated that in all of my upload tests.
Finally, don't forget to keep your audio in stereo, as Youtube has recently made that their standard. They even went back and converted all of my old videos, which was a nice surprise.
|
