Faster burst mode & RAW saving

mkmenuts

61
SD700 (1.01b)

Faster burst mode & RAW saving

« on: 19 / March / 2008, 15:21:18 »

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I guess one of the differences between cameras all using DiGic is the speed (MHz) at which the processor is running.

Is it possible to change the speed (make it higher) temporarily via CHDK whenever a RAW/JPG is being saved?

Would that positively affect burst mode?

The shorter battery life might be a good tradeoff for many.We could actually REDUCE the CPU speed at other times to balance this...

mkmenuts

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wontolla

413
S3 & G9 & A720

Re: Faster burst mode & RAW saving

« Reply #1 on: 19 / March / 2008, 16:01:10 »

I see it very difficult (but only because I don't like the word impossible).

I don't imagine a way to modify the processor's clock speed via software.
Either you open the camera and change the crystal responsible of generating pulses or add a multiplier to it.

But I really doubt the processor would work with a faster clock, it would get delay errors. It takes time for all the signals to travel through the silicon and if you augment the speed, some of them will not get in time resulting in a loss of data.

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ewavr

1057
A710IS

Re: Faster burst mode & RAW saving

« Reply #2 on: 19 / March / 2008, 16:24:36 »

Speed of RAW/JPEG writing limited by SD card speed - increasing CPU speed does not help. We need superfast SD cards or big RAM buffer to keep more images in memory.
Somebody produces SD cards with 128 Mbytes of cache memory? I would have bought

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mkmenuts

61
SD700 (1.01b)

Re: Faster burst mode & RAW saving

« Reply #3 on: 20 / March / 2008, 04:07:51 »

Quote

Speed of RAW/JPEG writing limited by SD card speed - increasing CPU speed does not help.

While what you say is of course true, we do see a huge speed difference between cameras using the SAME cards. How do you explain this? Perhaps the CPU /SD subsystem is doing more work than we think within the DIGIC?

For example, the DIGIC might not be using DMA controlled buffer but instead is feeding the card by itself.

Quote

big RAM buffer to keep more images in memory

If we're on the subject... I would guess some cameras have a few MBs lying around (especially if we do not use SuperFine JPEGs). Do you think it is possible to create a small (1-3 JPEG) buffer in memory to be used by CHDK?

This will make the recycle to next shot (as well as short burst) much faster (as long as RAW is disabled).

mkmenuts

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mkmenuts

61
SD700 (1.01b)

Re: Faster burst mode & RAW saving

« Reply #4 on: 25 / April / 2008, 11:19:44 »

I noticed the G7 has much higher write speeds (in the benchmarks section) than other DIGIC III cameras.

Is it due to additional hardware or could some special initialization/optimization be copied to other cameras?

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nextbond

Re: Faster burst mode & RAW saving

« Reply #5 on: 30 / April / 2008, 13:49:26 »

On my canon if i force turn off the flash, the burst mode is faster. Add a Class6 ExtremeIII SDHC card and it gets 20% better speed.

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