Thanks!

I also found out about this workaround by looking at the patch to 7.7, which diff showed a change from 12,000,000 (in 7.5) to 8,000,000. I don't recommend lowering that value to 5,000,000 because more kb/s = smoother video. Though I noticed something strange:
1. After upgrading to 7.7 (8,000,000 bitrate), I tried catching a HD video with MiuiCamera, that produced a very choppy video (still...) with unsynced audio.
2. I catched another 720p video with Android Camera, and the result was better, though I don't like the m4v container for the output files.
3. I used MiuiCamera to record another HD video, but this time it was perfect!

4. The following videos shot by MiuiCamera were still as good, even after a reboot,
for now.
So, I don't think we require the Camera.apk to make MiuiCamera.apk work as it should. There is probably something about the governor or kernel ticks (HZ) which is clashing with the 720p recording. For the "record" (lol), I'm using the smartass governor on Zach's NEO 08, while scheduler and OC/UV don't seem to have a high relevance.
Also, why does MiuiCamera produce a
3gp video for 720p recordings, while it's clairly specified to use the mp4 container? I also used Avidemux and ffmpeg to check the video, and it has a 1280x720 resolution with H.264 and AAC codecs. So, why the 3gp extension?
EDIT: I forgot, have you understood why the m4v max bitrate was lowered to 2,000,000 while stock JVP has 12,000,000 ?