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si235312002eua
Participating Frequently
March 11, 2022
질문

Confused about export bitrates (software vs hardware encoding)

  • March 11, 2022
  • 2 답변들
  • 4406 조회

I'm trying to make sense of different results I got from exporting the same HD sequence to identical target bitrates (25 mbps) but with different settings. There is a world of differences between these results and I cannot understand why. Only settings that changed were VBR (1 / 2 pass) or CBR and software or hardware encoding. 

 

Here are the average bitrates it generated:

 

- VBR 1 pass (hardware): 8.2 mbps

- VBR 1 pass (software): 22 mbps

- CBR (hardware): 8.5 mbps

- VBR 2 passes (software): 22 mbps

 

Considering I used a target bitrate of 25 mbps (max bitrate of 30 for VBR 2 passes), the software encoded bitrates make sense to me. This was expected. The hardware encoded bitrates however (CBR and VBR 1 pass) don't.

 

Visually all these exported videos look identical when compared at 200% in Premiere, meaning 25 mbps was completely overkill for these jobs, but I'd still like to understand what is happening. What can explain such a huge gap between the target bitrate and end result during hardware encoding? Is it ignoring user set target bitrate and computing its own receipe?

 

My graphics card is a Quadro K4200 if that matters.

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2 답변

Warren Heaton
Community Expert
Warren HeatonCommunity Expert
Community Expert
March 11, 2022

 

The resulting files should always be close to the Target Bitrate without exceeding the Maximum Bitrate.

 

With Performance set to Hardware instead of Software, the encode times should be faster while the results are similar if not identical.

 

The difference between Variable Bitrate and Constant Bitrate is temporal, so Spatial differences may not be obvious to the naked eye.

 

For delivery of a 1st generation HD H264 file to social media like YouTube and Vimeo, 1-pass VBR 16 should be fine.  For UHD, it comes up to 2-pass VBR 40.

For source footage in an edit, 35 Mbps is the floor professionally.   

 

 

 

 

    S
    si235312002eua작성자
    Participating Frequently
    March 11, 2022

    Warren that's what is puzzling. How do you explain the differences I got in file size between software and hardware encoding? So far, I can't. I don't understand what is happening. These exportations have a lot of static graphical elements so there's that, but why am I getting an exported bitrate so far off the target bitrate when I hardware encode with a Quadro K4200? I'm going to try to test this again on a different system later on.

    S
    si235312002eua작성자
    Participating Frequently
    March 11, 2022

    @si235312002eua If you'd like to make the source available, I'm happy to test it on a few different machines over the weekend.


    Thanks for the offer @Warren Heaton10841144 but this will not be possible, company policy about data confidentiality doesn't permit this. However if you feel so inclined you could just use this simple setup to try and reproduce as this is mostly what I tested on this afternoon and I was able to consistenly get 3 times lower bitrate on hardware encoding.

    - 10 second HD 29.97 sequence

    - A still png of some kind of simple graphic for the whole duration, covering 100% of the frame (here's one: )

    - any talking head footage scaled down to occupy around 20% of the frame, picture in picture style (see joined graphic). Mine was HD h.264.

     

    Then export to VBR 1-pass 25mbps (max 30mbps) at maximum render quality in software and then in hardware, without changing any other setting. There was audio too but I don't think it matters.

     

    I just tried it again and get 3 x lower bitrate when hardware encoding.

     

     

     

    Joost van der Hoeven
    Community Expert
    Joost van der HoevenCommunity Expert
    Community Expert
    March 11, 2022

    Can you please share your system info? Like OS and version, CPU, RAM, GPU vRAM, Pr version? Thanks. Also a screen grab of your issue will be helpful.

    FAQ: What information should I provide when asking a question on this forum?
    https://community.adobe.com/t5/premiere-pro-discussions/faq-what-information-should-i-provide-when-asking-a-question-on-this-forum/td-p/3929027

    S
    si235312002eua작성자
    Participating Frequently
    March 11, 2022

    Here are the specs of that computer:

     

    Windows 10 Enterprise (1803)

    Media Encoder 22.1.1 (Build 25)

    Premiere 22.1.2 (Build 1)

    16 GB RAM

    Intel i7-6700 3.4Ghz CPU

    Quadro K4200 GPU

     

    As for a screen grab not sure it adds much to the discussion. The issue is actual exported file size vs set target bitrate in export settings.

    These exportations were all done using Media Encoder with a set target bitrate of 25 mbps. 2 were hardware encoded, the other 2 software.

     

     

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