5D Mk III: 40 fps, nope. 39 fps, yep. WTF?

[Thomas Worth]

I see that with the latest build of ML on a 5D Mark III, I can FPS override in 24 fps mode to a max of 40 fps. This is great, but when I set the FPS to 40, it records with mega-ultra-corrupted frames. However, if I back off to 39 fps, it records just fine. Am I doing something wrong? Did I fail to read something about this? Is there anything I can set in the camera to make this work at 40.000?

[jimmyD30]

Try setting to 30fps in Canon menu.

[Thomas Worth]

Tried that, but no luck. Same thing. I'm assuming this has been tested to work at 40.000.

By the way, I'm running Canon firmware 1.2.3. I compiled from the 5D3.123 branch. Has 40 fps been tested under 1.2.3?

[a1ex]

I've tested it only on 1.2.3, and I had better luck with a SD card. Of course, it will only record as much as it fits into RAM.

So, while the sensor and LiveView tasks can go to 40 fps, the bottleneck seems to be elsewhere (even the extra load on memory bus caused by fast CF writes can be too much).

On 5D3, the FPS you are starting from is not relevant, as long as you are in 1080p. On cameras with older FPS implementation, it is.

[filo99]

On 5D3, the FPS you are starting from is not relevant, as long as you are in 1080p. On cameras with older FPS implementation, it is.

Is the 6D an older implemented camera?

[Levas]

If you want to have high FPS on the 6d, you should try the nightly build from 15-march-2014 for 6d.
With this build I can get 35FPS with fps override in 1080p25fps PAL mode.

The newer builds for 6d only go to 26FPS in 1080p25fps PAL mode

[Thomas Worth]

So, while the sensor and LiveView tasks can go to 40 fps, the bottleneck seems to be elsewhere (even the extra load on memory bus caused by fast CF writes can be too much).

I tried with a fast SD card (I originally tried with CF), but got the exact same result. It's only at 40.000 fps the corruption shows up. And it shows up in the first frame or two. It's constant corruption throughout the entire video, not just at the end because recording stopped due to slow media. Every other frame rate (less than 40) is fine. Can you confirm that you were actually able to capture at 40 fps without corruption, whether to SD or CF?

[a1ex]

Back then when I tried it, I've got clean files (but I did the first tests on SD, because the CF was full). Later, I tried it on CF and got corrupted files.

May be worth trying with some slower cards, or with the silent picture burst mode.

[Thomas Worth]

Tried it again, and I had slightly better results with the SD card. There was still corruption at 40 fps, just not as much.

Is this due to 40 fps approaching the limit of the camera's internal bandwidth or something like that? That would make sense since 40 fps sort of works (but not really), but 39 does seem to work pretty consistently. Perhaps 39 is just under this corruption threshold.

Was 40 fps the limit you picked based on your testing? If so, does that imply you could have increased the frame rate beyond 40, but limited it to 40 due to this bandwidth issue?

[a1ex]

Yes, and 40 was a round number. IIRC I could push it to 40.5 or so.

Also worth trying with global draw off and hacked preview; don't remember if I actually used these in my tests.

[hjfilmspeed]

I tried on 1.1.3 on the first build that allowed 40.00 fps. I tried 40.00 exact fps at 1920x818 and it got mad at me and froze ha ha. I havent tried 39.00 but If that works that should still have a decent slow effect. Does 2:35:1 crop work with fps? Sorry if this was covered.