Bitrate setting doesn't work correctly on both CBR VBR on 4K test

Community Beginner ,
Mar 29, 2022 Mar 29, 2022

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I'm converting simple 4K X4K raw AVI to mp4 with 10Mbps bitrate for streaming test.
When I set CBR 10Mbps with maximum render setting, I get 300 Kbps..
When I set VBR 10Mbps with maximum render setting, I get 1-1.3Mbps..
Maybe it thinks that's enough, but the gradient doesn't look good as the original source.
Also I need accurate size of bit rate data for my test.

Note: When I switch to software encoding, it keeps the set bitrate, but the game engine can't read the file, so I need this hardware encoded.

Kye_TLM_0-1648589231706.png

 

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Adobe Community Professional ,
Mar 31, 2022 Mar 31, 2022

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Yes, when H264 Performance is set to Hardware, the encoding is not only faster but also better.  

 

If you need predictable results, use Software set to Constant Bit Rate (CBR).  The results with Hardware will be different as often as the picture is different.

 

For 4K, bring your bit rate up to between 30 mbps and 40 mbps.  10 mbps is appropriate for HD.

 

 

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Community Beginner ,
Apr 01, 2022 Apr 01, 2022

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Thanks for the answer, but it's not exactly what I was looking for.

Like I mentioned in the question, this test is not to achieve best result with smaller file size.

I need to make a video with specific resolution with specific bitrate (constant/hardware encoded) for texture streaming test.

  • The video content can be simple or complicated- but need to maintain constant bit rate
  • The size of the mp4 doesn't matter at the moment
  • Can not use software encoding option

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Adobe Community Professional ,
Apr 01, 2022 Apr 01, 2022

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Yes, I follow what you are trying to achieve.

 

Hardware encoding, by its very nature, is going to give you different results based on the video content.  Even with Software encoding, there's going to be some variaiton from video A to video B to video C.

 

This being the case, most video delivery specifications have a target bitate and a maximum bitrate.  DVD-Video is a good example of this.

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Community Beginner ,
Apr 01, 2022 Apr 01, 2022

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Giving it constant bitrate keeps the number in certain range - just not the number I set as target.

Funny thing is the playing file bitrate does get bigger when I use bigger number (and picture looks better) - just not matching my intended target bitrate..

I guess I'll do a test by increasing CBR number by eyeballing until it reaches REAL target bitrate.

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Adobe Community Professional ,
Apr 01, 2022 Apr 01, 2022

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For what you're looking for, you need to switch to a different kind of CODEC: one that doesn't compress both within the frame and between the frames.

 

CODECs with a fixed compression ratio do what your'e looking for, but those are not for delivery/streaming - they're for editing, like DV-NTSC and ProRes.

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