How does it all work?

Started by fauxtographer, April 09, 2013, 07:31:54 PM

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fauxtographer

I got some nice insights by 1% in regards to how video is captured in a Canon DSLR. But I still have some questions.

I understand there is a .422 file that is constantly updating and utilized somehow by hardware and creates a video. My question is how is the liveview image generated? The sensor of course is taking information the information in, I assume it then creates an HD liveview version of the sensor data, which is in turn recorded by the camera. Is the liveview stream in fact HD? Some files I have recorded indicated the video size is 1920x1088 (this could also be me doing something wrong.)

My question is, and I don't mean this in a condescending manner or disrespectful, but why does it seem to be so difficult to change the liveview streams resolution, when elements like bit rate control and HDR video seem to be relatively easy to implement. I assume this camera is more than capable to push the stream to something like 2048x1080 or 2048x1152, and the H.264 does support these resolutions.

6D | 24-105 f/4 | 70-200 f/4 | 28 - 35 - 50 - 50 - 135 |

g3gg0

there is no .422 file.
we know where in memory canon places its 422 data before it gets processed by MPEG hardware
and where the lower resolution version before it is displayed by the LCD controller.

knowing where to tweak which register values to get other resolutions is as simple as translating a pile of egyptian glyphs for you.
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1%

The buffers are generated via a fixed process. The encoder won't take anything over 1080P, just forget that, HW limitation.

The only option will be enlarging what is fed to it... ie "croping" image or making a bigger 422 or correctly YUV buffer and compressing that with jpeg.

Real image size is listed in debug menu for both buffers. There is 1 more scaling operation done by H264e from 1808x1256 or whatever.

Second that egyptian hieroglyphs part. Even naming *most" of the functions you get a ton of Mov R1, blahblah and call sub_whothefknows that you have to interpret.


coutts

i've tried translating, and lost tens (countless) of hours to it. I refuse to try again :D

fauxtographer

6D | 24-105 f/4 | 70-200 f/4 | 28 - 35 - 50 - 50 - 135 |

1%

I'm going to try again. Pharaoh's secrets are just too juicy. All in all took >6 months to understand how a bunch of things work and maybe I've even scratched 2% of the surface.

fauxtographer

I had no idea it was so cryptic... Are the Canon engineers using a program to make it less cryptic?

Is it seriously like changing a number in the code and seeing what happens?
6D | 24-105 f/4 | 70-200 f/4 | 28 - 35 - 50 - 50 - 135 |

a1ex

Canon engineers have the source code and docs; we don't.

fauxtographer

We just need to find a Greyhat Canon engineer.... or just buy BlackMagic cameras. haha
6D | 24-105 f/4 | 70-200 f/4 | 28 - 35 - 50 - 50 - 135 |