Twitch, Mac, 1.8, 10.9.5: Very jerky

Streaming to twitch is jerky. Jerky like a bad de-interlacing.

*NB: This is not a duplicate of 40594. That was closed as "invalid", claiming that it was purely a bandwidth issue. That's not happening here.

Video: http://www.twitch.tv/keybounce/c/5292672

There are several issues:
1. Frames are out of order. If I am typing, I will see my characters disappear, and then re-appear.
2. Stream is not constant bit rate. Twitch complains that I am not doing CBR recording. Actual bit rate will max out at around twice the rate that I said to use.

Note that each individual frame is fine.
The average bitrate is well below my specified bitrate, and that is below my connection upload speed.

The issues of varying bit-rate, and out-of-order frames, is entirely under the control of the streaming software – in this case, vanilla minecraft.

This affects 1.7.10 as well as 1.8.0. (If the twitch streaming can be updated independently of the main program, then I'm hoping it can be back-ported as well.)