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?