High ISO needs more HW resource

[miyake]

Is this a well known things?
I just understand it.

CBR 3.0 + ISO3200 = recording stop immediately
CBR 2.6 + ISO3200 = recording stop immediately
CBR 2.4 + ISO3200 = sometime recording stop
CBR 1.0 + ISO 3200 = no problem

CBR 3.0 + ISO200 = no problem
Then push ISO button and ISO change dynamically, will recording stop when we changed to over ISO 1600

[a1ex]

The noise is considered detail and requires higher bitrate.

[nanomad]

Right
A simple test is to compare the bitrate of ml vs Canon iso 500. On dark scenes I found Canon to be more noisy and with a higher bitrate

[miyake]

Thank you for your explaining.
Anyway, CBR is not Constant bitrate. We can't set maximum bitrate for CBR. right?

[a1ex]

CBR is maximum bitrate (not per frame, but with some kind of averaging). I think the process goes like this:

- record frame 1 with some fixed QScale
- see what frame size it got
- compute QScale for frame 2, according to CBR factor and other settings
- record frame 2 with this QScale
- repeat

[miyake]

I see. Thanx!