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BTIC1C Screen Capture: Performance and older HW...

Posted by BGB, 29 March 2014 · 357 views

I had recently fiddled some with BTIC1C real-time recording, and have got some interesting results:

main desktop PC, mostly holds a solid 29/30 fps for recording.
* 1680x1050p30 on a 3.4 GHz Phenom II X4 with 16GB PC3-1066 RAM.

it holds 25-28 fps on my newer laptop:
* 1440x900p30 on a 2.1 GHz Pentium Dual-Core with 4GB RAM.

it does a solid 30 fps on my older laptop:
* 1024x768p30 on a 1.6 GHz Mobile Athlon (single-core) with 1GB RAM.
** thought it was 1.2 GHz, seems I was misremembering.
** kind of kills things though as comparatively, this laptop is too fast for the screen resolution.
*** to be fair, for this resolution, the CPU would have needed to be ~ 1.2-1.4 GHz.

was half-considering testing on an ASUS EEE, but I seem to have misplaced it.
running off other calculations, there is a statistically high chance that an EEE would be able to record full-screen video at ~ 20 fps or so (given its clock-speeds and resolution).


or, if I could build for Android, maybe testing on my tablet or phone (Sony Xperia X8, *).

*: like the EEE, it is basically what sorts of video encoding I can get out of an ~ 600MHz CPU.
linear extrapolation implies it should be able to pull around 20 fps from 800x480 and ~ 30fps from 640x480.

my tablet has HW stats on-par with my laptops though, so it may not mean a whole lot (ran 3DMark, got 5225... CPU speed is similar to old laptop, but graphics and framerates look a lot prettier than either of my laptops).

actually, theoretically, the Ouya also has HW stats on par with my laptops as well (raw clock speed in-between them, but has 4 cores and fast RAM).


ADD: ( testing desktop PC with 3DMark
Cloud Gate: 10890
Ice Storm: 81583
Fire Strike: 4083 (*)
*: Updated, didn't crash this time... )

here is from another test involving desktop recording and Minecraft:


most of the lag/jerkiness was actually from Minecraft itself, which is basically how it plays on my computer (but I was happy originally when I got some newer parts, mostly because Minecraft usually stays above 20).


otherwise:
messed recently with special 4:2:0 block-modes, which can improve image quality but hurt encoder speeds (they effectively store color information for each 2x2 pixel sub-block, rather than for the whole 4x4 block, and require more arithmetic in the pixel-to-block transform).

I did introduce a more limited form of differential color-coding, which seems to have actually increased encoder speed for some reason (colors will often be stored as a delta from the prior color rather than the color itself, *).

generally, color prediction has been largely restricted down to last-seen-color prediction, generally because this can be done without needing to retrieve colors from the output blocks (it will simply keep track of the last-seen colors, using these as the predictors, which is a little cheaper, and also less problematic).

*: as-is, for 23-bit colors, a 15-bit delta-color will be used, and will fall back to explicit colors for large deltas.




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