How is the Pocket 4K supposed to record 4K DCI at 60fps?

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Mark Grgurev

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How is the Pocket 4K supposed to record 4K DCI at 60fps?

PostSun Aug 05, 2018 11:54 am

According to the Blackmagic website, lossless 4K DCI at 30 fps is roughly 272 MB/s which means it would be 544 MB/s at 60fps. This exceeds the maximum usable bandwidth of the USB 3.1 Gen 1 specification that the USB-C port supports and while it's just in range of what Cfast 2.0 can do, the fastest CFast card I can find only has a max write speed of 510 MB/s.

Is there some means of recording that the Pocket 4K supports that we don't know about? I know it can't record to SD and Cfast at the same time but can it record to either one of those and USB-C at the same time? That's really the only way I can imagine that working. Or is BMD expecting sufficiently fast CFast cards to eventually come out?

Also, if this dilemma is at all putting the camera at risk of being delayed then just drop the feature and limit us to compressed formats in that mode lol
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AndreeMarkefors

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Re: How is the Pocket 4K supposed to record 4K DCI at 60fps?

PostSun Aug 05, 2018 8:46 pm

Why do you think the PCC4K is supposed to be able to record uncompressed raw at 4K 60 fps?
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rick.lang

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Re: How is the Pocket 4K supposed to record 4K DCI at 60fps?

PostSun Aug 05, 2018 10:28 pm

Frame Rates
“Maximum sensor frame rate dependent on resolution and codec selected. Project frame rates of 23.98, 24, 25, 29.97, 30, 50, 59.94 and 60 fps supported.
Off-speed frame rates up to 60 fps in 4K DCI, 120 fps in HD windowed.”

The first sentence is the key to understanding the unstated limits. When the camera is released, the updated manual will likely describe the limits by codec.


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Mark Grgurev

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Re: How is the Pocket 4K supposed to record 4K DCI at 60fps?

PostSun Aug 05, 2018 11:54 pm

rick.lang wrote:Frame Rates
“Maximum sensor frame rate dependent on resolution and codec selected. Project frame rates of 23.98, 24, 25, 29.97, 30, 50, 59.94 and 60 fps supported.
Off-speed frame rates up to 60 fps in 4K DCI, 120 fps in HD windowed.”

The first sentence is the key to understanding the unstated limits. When the camera is released, the updated manual will likely describe the limits by codec.


My apologies! Good catch! :-)
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Rakesh Malik

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Re: How is the Pocket 4K supposed to record 4K DCI at 60fps?

PostMon Aug 06, 2018 5:44 pm

Mark Grgurev wrote:Is there some means of recording that the Pocket 4K supports that we don't know about?


There's one that we already DO know about: compressed RAW. Odds are that's the ticket.

Want an example? Look at Red's recording frame rate specs for any of its cameras; they trade off resolution, frame rate, and compression ratio. One of them has to give. Black Magic already has a compressed raw option.

BMD's 3:1 raw compression would probably do the trick quite handily.
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Savannah Miller

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Re: How is the Pocket 4K supposed to record 4K DCI at 60fps?

PostTue Aug 07, 2018 8:25 am

It's kind of interesting that a $1295 camera can record higher internal datarate than any RED camera. Not that you need such large files, but the option is always there.
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Rakesh Malik

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Re: How is the Pocket 4K supposed to record 4K DCI at 60fps?

PostThu Aug 09, 2018 4:15 pm

Savannah Miller wrote:It's kind of interesting that a $1295 camera can record higher internal datarate than any RED camera. Not that you need such large files, but the option is always there.


I thought it was pretty ironic also... until I met with Sony's Peter Crithary at NAB. He pointed out that one major benefit in using a high end camera like an F55 rather than a Black Magic is the efficiency of their recording codecs.

On a recent production we recorded in 8K raw with 4K ProRes 422 simultaneous proxies.

The proxies, as it turned out, were as big as the raw files...

The DIT was not amused.
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rick.lang

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Re: How is the Pocket 4K supposed to record 4K DCI at 60fps?

PostThu Aug 09, 2018 4:21 pm

Rakesh, did you pass on that ‘efficiency’ to the Sony rep?


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Rakesh Malik

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Re: How is the Pocket 4K supposed to record 4K DCI at 60fps?

PostThu Aug 09, 2018 5:55 pm

rick.lang wrote:Rakesh, did you pass on that ‘efficiency’ to the Sony rep?


Do you mean the size of the ProRes proxies?

No, I just stopped using simultaneous proxies. Problem solved! :)
Rakesh Malik
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http://WinterLight.studio
System:
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