Firmware genius Tramm Hudson, who gave us the original Magic Lantern firmware, has released a new version that allows 5D Mark II owners to increase the video bitrate of their DSLR to 76MBps (the default is 38). This should make a world of difference in the battle against those pesky compression artifacts. Word on the street is that 76MBps is unstable, but the slightly lower 66MBps is working in 24p. This is very much in beta and I haven't had a chance to try it out myself yet. Here are the details from Tramm:
If the CF card is not able to keep up, the camera will display a buffer-level bar on the right side of the LCD and stop recording when it hits full. The parameter does not have any effect unless fixed bit rate encoding is selected via mvrFixQScale(int16_t *) (2.0.8 0xff9905d4). The default q-scale is -8 in VBR mode and has a nominal 42 Mbps with the 2.0.8 firmware. The 24p tests were done with the camera on a tripod writing to a Lexar 400x UDMA 16 GB card with all Magic Lantern tasks disabled (no zebras, cropmarks, etc). qscales less than -12 occasionally stopped recording.
- 24p seems to have less issues than 30p
- Locked-off shots seem less likely to trigger buffer overflows; amount of motion?
- Auto-exposure changes seems to lead to immediate overflows: shoot manual exposure mode
- -14 seems to be the best that can be sustained with the card with all other ML tasks running.
The firmware can be downloaded from the dev-log. Whoever gets this up and running, please leave your comments here!
UPDATE: Here are two videos comparing the new and old bitrates. It's going to be hard to tell on a compressed web video, so click on through to Vimeo, where Plus members (or is it everyone) can download the higher bitrate files.