Date: 16/10/2007
| Today I was developing a mp4 encode path for my private stock VidEnc application which takes mpeg2 from Digital TV and re-encodes it. It has for a long time supported mpeg2 to xvid/avi via besweet and mencoder. But mencoder has a problem on longer videos where it drops the first 'n' frames, somewhere between 1 and 6 seconds of video. I could never figure this out so I just print out the "offset" to remux the A/V in VirtualDub. A right pain I can tell you.
So after using Handbrake a lot I decided that the pain of developing a new video pipeline would be offset by the better quality of H.264 and the smaller filesizes. So today I had some time and got into it. Things went fairly smoothly until I got my output mp4 file, and it wouldn't play in Quicktime.
This, as I'm finding out, is not unusual because Quicktime7 doesn't fully support H.264, just a subset of it. Anyway that wasn't what was causing this: "Error -50: An unknown error has occured" when I tried to open the file. My pipeline as it stands is:
- Mpeg2 -> Pvastrumento -> separate a/v
- Audio -> besweet to wav -> faac to aac
- Video -> x264 to mp4
- Mp4box to mux the A/V back together
I now know that I can do the Audio -> aac in one step using Besweet, but I havn't gotten around to fixing it yet. However there are a few gotchas in creating suitable mp4 files for QT7.
- The AAC audio must be of the type MPEG4, rather than MPEG2. The faac option is "-w" to do that.
- x264 should output to .mp4, not .264
- Don't go higher then "--bframes 2" for x264.
- Don't use "--b-pyramid" for x264 either.
This should give you a playable mp4.
Should...
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