Codec bitrate to MB/s

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jaybee

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Codec bitrate to MB/s

PostTue Nov 26, 2019 11:17 am

Can anyone explain how I can convert the Codec Bitrate values (given in Resolve) to MB/s?

Are these values in bytes, so 8.4MB ?

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Andrew Kolakowski

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Re: Codec bitrate to MB/s

PostTue Nov 26, 2019 12:40 pm

Most likely.
It's crap GUI as it should sow units as well (not just some number which you need to guess).
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CaptainHook

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Re: Codec bitrate to MB/s

PostWed Nov 27, 2019 8:25 pm

The label explains it. Codec BITrate. It's in Bits.
Resolve also has a limitation in that in only displays the value for the first frame, not the average for the entire clip.
http://www.captainhook.co.nz/blackmagic-cinema-camera-lut/

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jaybee

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Re: Codec bitrate to MB/s

PostFri Nov 29, 2019 9:12 am

CaptainHook wrote:The label explains it. Codec BITrate. It's in Bits.
Resolve also has a limitation in that in only displays the value for the first frame, not the average for the entire clip.


Thanks. So:

8425472 bits = 1053184 bytes or 1.053184 MB. This seems low for a UHD BRAW clip in 12:1? I'd expect closer to 40 MB/s?

I'm just interested in how various compression rates convert to MB/s.
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CaptainHook

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Re: Codec bitrate to MB/s

PostFri Nov 29, 2019 10:32 am

Its the bit rate for the first frame (the SDK can provide bitrate for each frame but currently Resolve only displays the first frame).

Multiply it by your frame rate for the p/s value, so for 24fps its around 25MB/s. But you also can't assume every frame is the same size as the rate control is trying to adapt to whats in frame to achieve the desired size/compression ratio - it will get close but not perfect. That aside I wouldn't expect ~45MB/s unless it was say 4.6K @30fps 12:1

( ( 4640 x 2624 x 12bit* ) / 8 / 1000 / 1000 / 12:1 ) x 30fps = 45.66MBs


*12bit non-linear encoding
http://www.captainhook.co.nz/blackmagic-cinema-camera-lut/

**Any post by me prior to Aug 2014 was before i started working for Blackmagic**
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CaptainHook

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Re: Codec bitrate to MB/s

PostFri Nov 29, 2019 10:39 am

These are on our website FYI:

Image

Image

Image
http://www.captainhook.co.nz/blackmagic-cinema-camera-lut/

**Any post by me prior to Aug 2014 was before i started working for Blackmagic**
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jaybee

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Re: Codec bitrate to MB/s

PostFri Nov 29, 2019 10:56 am

CaptainHook wrote:Its the bit rate for the first frame (the SDK can provide bitrate for each frame but currently Resolve only displays the first frame).

Multiply it by your frame rate for the p/s value, so for 24fps its around 25MB/s. But you also can't assume every frame is the same size as the rate control is trying to adapt to whats in frame to achieve the desired size/compression ratio - it will get close but not perfect. That aside I wouldn't expect ~45MB/s unless it was say 4.6K @30fps 12:1

( ( 4640 x 2624 x 12bit* ) / 8 / 1000 / 1000 / 12:1 ) x 30fps = 45.66MBs


*12bit non-linear encoding
Perfect, thanks for the info.

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