PCC4k: RAW compression 3, Datarate too low

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Frank2021

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PCC4k: RAW compression 3, Datarate too low

PostThu Jun 10, 2021 3:01 pm

Hi,
I made datarate measurements at three compression rates.
Compression 8 and 5 are fine, but not compression 3:

RAW UHD 3840 x 2160, 50 fps

Compression 8
Datarate calculated: 78 MByte/s
Datarate measured: 79 MByte/s, OK

Compression 5
Datarate calculated: 124 MByte/s
Datarate measured: 123 MByte/s, OK

Compression 3
Datarate calculated: 207 MByte/s
Datarate measured: 120 MByte/s, NOT OK

Same results with SD Card Sony Tough SF-M256T and CFast Card Transcend CFX650 128GB

Measurement done with a 10 sec file, Filesize (GB) devided by 10 sec.

The files look fine, no loss of frames

Any idea, what could be wrong?
Thanks
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Robert Niessner

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Re: PCC4k: RAW compression 3, Datarate too low

PostThu Jun 10, 2021 3:27 pm

It depends on the content you've shot. Even when set to 3:1 it does not make sense to artificially inflate the data rate if unnecessary. If you shot something with a lot of bokeh then there is not enough texture and it will compress better than 3:1.

Do your test on a scenery with lots of detailed textures like trees, gras, a landscape.
Saying "Thx for help!" is not a crime.
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rick.lang

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PCC4k: RAW compression 3, Datarate too low

PostThu Jun 10, 2021 4:38 pm

That is interesting as I thought the fixed ratios had a constant bitrate. So 3:1 is about a third of what uncompressed video would be, 5:1 about a fifth, etc.

The Q0-Q5 rates are variable bitrate within a clip.

That’s not saying Robert is incorrect as it may be 3:1 is a constant bit rate for the clip, just not as many bits as we expect.
Rick Lang
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Mark Foster

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Re: PCC4k: RAW compression 3, Datarate too low

PostThu Jun 10, 2021 8:08 pm

cMP 5.1 2x3,46/96GB/2x2TB 860pro/4x4TB HGST/SSD7101A 4x2TB 970evoplus/HP1344/BMD4k/Radeon VII
macOS 11.2.3

BMPCC 6k pro (7.3.1)
BMPCC 4k (7.3)+ MB speedbooster ultra 0.71 (3.60)
resolve studio 17.2.1
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Frank2021

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Re: PCC4k: RAW compression 3, Datarate too low

PostFri Jun 11, 2021 10:25 am

Mark Foster wrote:https://www.blackmagicdesign.com/support/faq/59025


see above: CFast Card Transcend CFX650 128GB
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Frank2021

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Re: PCC4k: RAW compression 3, Datarate too low

PostFri Jun 11, 2021 10:59 am

Robert Niessner wrote:It depends on the content you've shot. Even when set to 3:1 it does not make sense to artificially inflate the data rate if unnecessary. If you shot something with a lot of bokeh then there is not enough texture and it will compress better than 3:1.

Do your test on a scenery with lots of detailed textures like trees, gras, a landscape.


Thanks, recording a complex test chart at compression 3 indeed leads to 207 MByte/s as calculated.
BMD should not name this mode "constant bitrate", this is misleading.
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Robert Niessner

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Re: PCC4k: RAW compression 3, Datarate too low

PostFri Jun 11, 2021 11:50 am

Frank2021 wrote:
Robert Niessner wrote:It depends on the content you've shot. Even when set to 3:1 it does not make sense to artificially inflate the data rate if unnecessary. If you shot something with a lot of bokeh then there is not enough texture and it will compress better than 3:1.

Do your test on a scenery with lots of detailed textures like trees, gras, a landscape.


Thanks, recording a complex test chart at compression 3 indeed leads to 207 MByte/s as calculated.
BMD should not name this mode "constant bitrate", this is misleading.


Well, it is "constant" where necessary but does not waste bitrate when unnecessary. It is more like a constant maximum bitrate.
Saying "Thx for help!" is not a crime.
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Robert Niessner
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Read the blog in English via Google Translate:
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rick.lang

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Re: PCC4k: RAW compression 3, Datarate too low

PostFri Jun 11, 2021 1:03 pm

Live and learn! Of course I nearly always used to shoot with the Q0 setting on fairly complex scenes so perhaps that’s different given the huge variable bitrate range within a given quantization. I expect when I start using Q1, I’ll save space but I think I should test that to see.
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Mark Foster

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Re: PCC4k: RAW compression 3, Datarate too low

PostFri Jun 11, 2021 2:21 pm

Frank2021 wrote:
Mark Foster wrote:https://www.blackmagicdesign.com/support/faq/59025


see above: CFast Card Transcend CFX650 128GB


yes, this card is NOT in the recommended list
cMP 5.1 2x3,46/96GB/2x2TB 860pro/4x4TB HGST/SSD7101A 4x2TB 970evoplus/HP1344/BMD4k/Radeon VII
macOS 11.2.3

BMPCC 6k pro (7.3.1)
BMPCC 4k (7.3)+ MB speedbooster ultra 0.71 (3.60)
resolve studio 17.2.1
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Frank2021

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Re: PCC4k: RAW compression 3, Datarate too low

PostFri Jun 11, 2021 5:11 pm

Mark Foster wrote:
Frank2021 wrote:
Mark Foster wrote:https://www.blackmagicdesign.com/support/faq/59025


see above: CFast Card Transcend CFX650 128GB


yes, this card is NOT in the recommended list


(I) In the camera manual from Jan. 2021 this card is recommended 10 times
(II) we found out, that it is not a card issue.
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Mark Foster

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Re: PCC4k: RAW compression 3, Datarate too low

PostFri Jun 11, 2021 7:43 pm

you read an other manual?

Screenshot 2021-06-11 at 21.41.07.jpg
Screenshot 2021-06-11 at 21.41.07.jpg (55.86 KiB) Viewed 94 times


and yes, it is a problem when BMD not support the card

the touch is also too slow

Sony Tough SF-M256T.png
Sony Tough SF-M256T.png (137.61 KiB) Viewed 87 times



and i had never any problems in my 4K and 6K pro with my angelbird CFast cards
in Q0 or 3:1 with 4K DCI or 6K



.






.
cMP 5.1 2x3,46/96GB/2x2TB 860pro/4x4TB HGST/SSD7101A 4x2TB 970evoplus/HP1344/BMD4k/Radeon VII
macOS 11.2.3

BMPCC 6k pro (7.3.1)
BMPCC 4k (7.3)+ MB speedbooster ultra 0.71 (3.60)
resolve studio 17.2.1
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Frank2021

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Re: PCC4k: RAW compression 3, Datarate too low

PostSat Jun 12, 2021 8:43 am

Mark Foster wrote:you read an other manual?

Screenshot 2021-06-11 at 21.41.07.jpg


and yes, it is a problem when BMD not support the card

the touch is also too slow

Sony Tough SF-M256T.png



and i had never any problems in my 4K and 6K pro with my angelbird CFast cards
in Q0 or 3:1 with 4K DCI or 6K
.


Yes, Mr. Foster, my eyes are open and I do read another manual: Jan. 2021.
You can easily read this in my message above.
And I know, that the Tough is to slow. But the CFast Card Transcend CFX650 is fast enough!

PROBLEM SOLVED!
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Mark Foster

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Re: PCC4k: RAW compression 3, Datarate too low

PostSat Jun 12, 2021 8:59 am

ok, i found the CFX650 card in the january manual.
but it seems that it is no longer supported since firmware 7.3.x

THIS WAS NOT MY PROBLEM ; -)


.
cMP 5.1 2x3,46/96GB/2x2TB 860pro/4x4TB HGST/SSD7101A 4x2TB 970evoplus/HP1344/BMD4k/Radeon VII
macOS 11.2.3

BMPCC 6k pro (7.3.1)
BMPCC 4k (7.3)+ MB speedbooster ultra 0.71 (3.60)
resolve studio 17.2.1

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