Real write bottleneck may not be the CF card

Started by mkrjf, June 30, 2013, 09:28:52 PM

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mkrjf

I have been struggling with getting CF cards to record continuously in raw mode on my 5DMK3
I posted a request for details on how the sensor is read and processed before writing to file NO RESPONSE :(
I suggested that maybe the camera circuitry has different capabilities by camera serial # / build date NO RESPONSE :(
But in trying all options I finally got around to trying the '5x crop mode' - actually 3x I think where a 1:1 1920x1080 portion of sensor is extracted, processed and written to CF card.

Guess what? this mode writes to the card as much as 20% faster. So how the F can the card be the bottleneck?

More likely the ML processing is the bottleneck and speed of processing depends on circuitry in the camera.
Not unusual for there to be variation as long as they all pass minimum engineering tolerance. So probably my camera exceeded minimum engineering spec less than some others. Would be nice to know if there is a pattern - as then we could look for cameras that have the higher speed circuitry.

But main point is - it would not be a lot of effort for senior developers to create a minimum flow chart showing how the two modes use internal code / hardware. And it is not god science to post charts showing absolute write capabilities of cards when it is actually showing build and camera dependent write capabilities. IMHO

So for now I will work with crop mode (and its quirks ;).
Maybe the code for 'full sensor read' raw can be optimized (or at least measured) to make it work across more of the 5DMK3 cameras.

And I REALLY appreciate the effort of this community - just looking for a little more communication and science.
Mike

eatstoomuchjam

I think you're posting too much and not reading enough.  Read all of the threads on camera/card performance and understand buffering, etc.  Then consider posting again for any follow-up questions.  Questions like this one demonstrate a profound lack of understanding which can only come from lack of having read the rest of the threads/topics.

1%

>>So how the F can the card be the bottleneck?

Edmac memcpy is like 600MB/s, more than fast enough.


>>Guess what? this mode writes to the card as much as 20% faster.

Smaller YUV buffer. Best writes in photo mode with LV off... not much processing happening on CPU or edmac.


>>Maybe the code for 'full sensor read' raw can be optimized (or at least measured) to make it work across more of the 5DMK3 cameras.

cactus?