Blackmagic Forum

Ok so should we stock up on 64G Extreme Pro 95mb/s Sandisk cards or just the 45mb/s extreme sd cards for raw or compressed ray on the BMPC.

That is actually 90 megabytes a second for the Sandisk extreme SDXC write, not 95.

the data rates for raw are:
10 bit 4:4:4 1920 x 1080 @ 24fps = 190 MB per second.
10 bit 4:2:2 1920 x 1080 @ 24fps = 127 MB per second.

So I'm curious how they will capture all the raw data.

I think you are definitely going to want to go with the 95mb option.

1920x1080 RAW 12 bit DNG will be 3.1MB.

X 24 fps = 74.6MB per sec.
X 30 fps = 93.3MB per sec.

If it isn't 12 bit raw that might change things. 10 bit RAW x 24 fps is 62.2MB. 8 bit RAW x 24fps is 49.8MB.

If they are somehow able to compress 2 to 1 lossless, which I believe is absolutely impossible then you still wouldn't have the bandwidth you need for 12 bit RAW at 30 fps.

i am the one wrote:That is actually 90 megabytes a second for the Sandisk extreme SDXC write, not 95.

the data rates for raw are:
10 bit 4:4:4 1920 x 1080 @ 24fps = 190 MB per second.
10 bit 4:2:2 1920 x 1080 @ 24fps = 127 MB per second.

So I'm curious how they will capture all the raw data.

The current 2.5k resolution is a RAW12 DNG at 5 megabytes or 120MB per second (24 fps). The Pocket camera I assume will create a RAW12 HD DNG at 3.1 megabytes or 74.6MB per second (24 fps).

Bandwidth is going to be TIGHT...

Hopefully there is a jump in technology over the next six months in SD cards. Who am I kidding? There undoubtedly will be.

AH well I'll just invest in 2 64G extreme pro cards then.

just linking for the pic but on my cards and the ones listed here is shows 95..

http://www.amazon.ca/SanDisk-Extreme-Cl ... e+pro+sdhc

aesnakes wrote:just linking for the pic but on my cards and the ones listed here is shows 95..

They are listing the read speed, not the write speed.

sfernald wrote:The current 2.5k resolution is a RAW12 DNG at 5 megabytes or 120MB per second (24 fps). The Pocket camera I assume will create a RAW12 HD DNG at 3.1 megabytes or 74.6MB per second (24 fps).

Bandwidth is going to be TIGHT...

Hopefully there is a jump in technology over the next six months in SD cards. Who am I kidding? There undoubtedly will be.

Can you tell me where these figures come from? I'm curious because their much smaller than the figures I have for 4:4:4 and 4:2:2. Thanks!

i am the one wrote:

sfernald wrote:The current 2.5k resolution is a RAW12 DNG at 5 megabytes or 120MB per second (24 fps). The Pocket camera I assume will create a RAW12 HD DNG at 3.1 megabytes or 74.6MB per second (24 fps).

Bandwidth is going to be TIGHT...

Hopefully there is a jump in technology over the next six months in SD cards. Who am I kidding? There undoubtedly will be.

Can you tell me where these figures come from? I'm curious because their much smaller than the figures I have for 4:4:4 and 4:2:2. Thanks!

Sure, I use this awesome site here:

http://web.forret.com/tools/megapixel.a ... eight=1366

sfernald wrote:Sure, I use this awesome site here:

http://web.forret.com/tools/megapixel.a ... eight=1366

Thanks, but that calculator has no variables for Chroma subsampling. 4:4:4 and 4:2:2 are going to be different sizes than what that calculator comes up with.

Raw on the pocket is going to be compressed by 1.5:1. Approx 30 minutes on a 128 GB card (73MB/s). Confirmed by blackmagic on newsshooter.com. No matter the actual size, I think you'll definitely need the fastest cards available. Even if a card is specced at 90MB/s that doesn't necessarily mean it won't drop a bit once in a while.

For a GH2 hack with high bitrate you really need a 95MB/s card for example. Even though the actual data is well within 45MB/s.

Julian wrote:Raw on the pocket is going to be compressed by 1.5:1. Approx 30 minutes on a 128 GB card (73MB/s). Confirmed by blackmagic on newsshooter.com. No matter the actual size, I think you'll definitely need the fastest cards available. Even if a card is specced at 90MB/s that doesn't necessarily mean it won't drop a bit once in a while.

For a GH2 hack with high bitrate you really need a 95MB/s card for example. Even though the actual data is well within 45MB/s.

I don't understand how they are going to do this. If they had the ability to do lossless compression, they would have implemented it on the original BMCC in order to reduce the bandwidth to the SSD.
It is also not clear if this "1.5:1" compression on the BMPC is lossless. If it is not lossless, then whether or not it originated as raw is completely superfluous.

It's lossless. Lossy compression would yield a much, much larger compression ratio.

Maybe the DNG specs or the firmware didn't allow it for the original BMCC? Just wait and see.. But this is what's Blackmagic is saying.

Julian wrote:It's lossless. Lossy compression would yield a much, much larger compression ratio.

Maybe the DNG specs or the firmware didn't allow it for the original BMCC? Just wait and see.. But this is what's Blackmagic is saying.

Got it. Thank you.

I don't see how even the best sd card on the market can write 73MB per second sustained without dropping a few frames eventually. I bet there will be many issues with this - worse than the ssd situation.

sfernald wrote:I don't see how even the best sd card on the market can write 73MB per second sustained without dropping a few frames eventually. I bet there will be many issues with this - worse than the ssd situation.

My Sandisk worked at a higher data rate almost without fail on my hacked GH2. It would barf once in a blue moon, but it was pretty close to perfect. If the BMPC causes it less stress than the GH2, I think I will be ok.