Magic Lantern is working on a true RAW and 14 bit video recording along with 4:2:2 to the card, something we'll never see from Canon.And they've already said it will never be something that will work for video people...best they've gotten so far is 720 at 24fps for 2s...the reality is you'll never get long recording times because the camera has a buffer to deal with. 1080p wont happen.
Really, it's an upgrade for time lapsers and may have some cool other uses.
If this is the case, the soft output of the 5DmkIII compared to other cameras, as documented on many of his tests, may in fact be impossible to fix with a firmware update, at least one from canon.
That said, what they did find interesting was that the resolution of the DNGs they got from their RAW mode were way higher resolution than just the traditional h.264 video stream from Canon. Not sure if that means that Canon intentionally is crippling it, or if the h.264 encoding loses a lot of resolution, but, that could be useful for some purposes.
Of course, if you want Raw video at 2k, you'd just spend the same amount on a BMCC instead and get a much nicer workflow.
I wonder if they can feed that 'raw' DNG stuff into the h.264 compressor and get better quality out? Or if they can push it out frame by frame over the HDMI and delete each frame from the buffer afterwards so nothing would ever overflow and you could at least get an 8bit or maybe 10bit crisper image out over HDMI? It seems like it should be possible but it's hard to know the internal Canon subsystem, it might not be, or even if it is, it quite likely might require all sorts of knowledge far beyond what they have been able to hack out so far and might only be reasonably doable by Canon people with full docs and access?
I checked out the DNG file posted on eoshd.com. Each file is about 5MB. Therefore, to get 30fps, you need a sustained write bandwidth of 150MByte/s (that is 1.2Gbits/s). That will be quite challenging even for the fastest notebook SSD. A 64GB CF card, even if it were fast enough, would only store about 7 minutes of video.
Therefore your suggestion to use the HDMI out is potentially the solution. HDMI 1.0/1.2 supports a bandwidth of 4.95Gbit/s and HDMI 1.3 supports about 10Gbit/s. BTW, does anyone know which version of HDMI is supported by 5D3?
Ofcourse, I am no camera engineer. These are just rough calculations that I came up with.
Lastly, pardon my ignorance in video, doesn't the 'uncompressed HDMI' output as provided by firmware v1.2.1 mean raw? Is the ML DNG just a higher resolution raw compared to the one provided by firmware v1.2.1?
So Magic Lantern seem to have found the source of the sensor scan for video, the "file" is a 2K resolution 14bit RAW image but the actual "usable image" is about 1920x1080 pixels, the rest of the 2K file are black bars. Even the "720p mode" is still the same sized 2K file only with a "usable image" of 1920x720 pixels.
Alex (from Magic Lantern) then threw in CHDK's Canon DNG converter to save these RAW images to card. (which I think uses the same CR2 RAW converter already in the camera but instead spits it out as a DNG rather then a CR2) each frame (or DNG "file") is about 5.09MBs for all "usable image" resolutions. (1920x1080 or 1920x720 "useable images" are in the same 2K RAW file, just with more black bars on the 720 one so they are actually the same file size)
The "frame buffer" where these images were found only allows 7.5MB/s through it so it can't write the images to the card fast enough and when the buffer is all fill up with as much as it can take it stops the video recording, at most it's getting about 50 frames, which at 24fps is about 2 seconds of video. (setting the camera's photo mode to JPEG only seems to increase the buffer's write speed, having RAW+JPEG or RAW set limits to 4.9MB/s and about 30 frames before recording stops)
HDMI won't work, Canon's HDMI out basically can't display that much detail; it's limited to 8bit, requires "debayering", 4:2:2 "sub-sampling", and needs to resize that 2K image down to 1920x1080. Once you do all that "compressing" guess what we're left with? Yep the 8bit 4:2:2 uncompressed (not RAW) image that Canon just gave us with this update.
The only way to get these images to card is to "compress" them before sending them through this 7.5MB/s buffer. I don't believe the Magic Lantern team has the ability...http://diffractedmedia.blogspot.com/