Increasing the number of slices decreases the quality, which is why the default is 0 in x264...
Not the same thing. Jpcore slice qp is basically the quality of the input frame. All VBR/CBR does is alter this parameter... ie at Qscale +16 sliceqpd is high number (low quality, low BR). At -16 its 112 which is the highest official quality. Camera goes down to 86/87 in theory which is like qscale -25 or something.
In the file itself slice qp delta per frame stays at -10 after 112... but BR increases from 112-87 so in theory you're getting higher than q-16.
I have a theory too that encoder just alters sliceqpd and line skip (not sure how) for a given frame. That's why at high quality with lots of complexity it kills the buffer and dies... that input frame gets bigger and bigger and it gets harder to encode it. In crop mode BR gets much higher.
All CBR does is compute slice quality on the fly from those I/P/Gopt sizes. When you lock the slice, qscale and all of those parameters don't do anything. The other Jpcore registers aren't touched by many functions and there is only one path which shows JPcore OPMR3 as SPS/PPS. Another register is frame size and another is from deblocking filter. Not much left over.
Also I have an idea. 600D released in 2011? TMP19A43CDXBG released when, and is it the controller for SD Card? What is the highest bus speed it supports? Toshiba is one of the developers of high speed SD technology and made some of the first UHS-1 cards ... in 2009/10. Quite possible it could support higher speeds just canon didn't implement them, there were all of 4 cards on the market. What is the new chip used in the T4i? Does 5dMk3 support UHS-1, I think it has dual slot?
We have functions like:
NSTUB(0xFF3BACE8, SDCOM_ChangeBusClock)
but no list of available clocks.
Camera first does read speed test and sets parameters in 0xCD7C (aAJ_0x14320_SDIOTSK_QuickReadData. I think there are 2 options based on how the read speed goes but all of that can now be modified. The bandwith of the camera itself can go much higher than now and if SD controller supports another mode it will probably happily write as fast as the SD card can go, 1/2 the bottleneck is there.
Anyone with 5d3 look? Or know what the Toshiba chip supports or how SD driver section of fw works? Already canon had planned for 64bit file addressing, not used till T4i. If we can do something here maybe we can record at slice 87 all day.
Thoughts?