Latest post Thu, Sep 21 2023 8:33 PM by Learn1. 4 replies.
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  • Tue, Sep 19 2023 10:45 PM

    • Learn1
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    DNxHDQx to ProResHQ becomes signifcantly smaller

    If import a ProResHQ source file to MC as DNxHQX that is about 132Gb. I then Export file as ProResHQ, my resultant file is about 87Gb. It looks right and MediaInfo says it is ProResHQ but the file was rejected because it is too small.

    This was recently produced on MC Ver. 2023.3 but also reproduced problem on many other systems here running 2021.9

    If I import the same source as ProResHQ media into MC then if I export as ProResHQ the size is about the same.

    If I export the Avid ingested DNxHDQx to a MXF the result is very close tot the original size, a little lager actually. If I then use that new DNxHD HQX file and send to other encoders (Vantage) to produce ProResHQ, they all do the same, they produce a smaller file size.

    I do mot think this is correct. Looking for some understanding in this. Have checked that we are all 10bit in and out. What I am seeing makes no sense.

    The bitrate displayed in MediaInfo shows a dramatic drop in rate as well a the Bits/(Pixel*Frame)

    This was noticed on longform files. It is present in shorter files as well but not a dramatic.

    Started support ticket but no response yet.

    Thank you

  • Tue, Sep 19 2023 11:20 PM In reply to

    • jef
    • Top 25 Contributor
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    Re: DNxHDQx to ProResHQ becomes signifcantly smaller

    ProRes is a variable bit rate codec. Its file size can be much smaller than DNX, depending on the complexity of the imagery.

    DNX is a constant bit rate codec. 

    Jef 

    Avid DS 11.0.2 R.I.P | MC "Well, it depends ..." 2023.3.1 iMac w Big Sur and 2018.12.7 on Windows 10 Boot Camp [view my complete system specs]

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  • Tue, Sep 19 2023 11:35 PM In reply to

    • Learn1
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    Re: DNxHDQx to ProResHQ becomes signifcantly smaller

    Thanks for the reply. That makes sense. But I a, lossing about a third of the program size, the stream size gets smaller as well as the Bits/(Pixel*Frame). When a studio sends a ProresHQ and we do our process and return a ProResHQ it is now significantly smaller. The only change to the original was we brought it into Avid as DNxHQx. That file is a little larger than the original ProResHQ which totaly makes sense. Are we losing that much data in the turn around? 

    If I bring the oringinal ProResHQ into Avid as a ProResHQ Avid creates its normal mxf file with the ProRes essensice. We do our process of editing then export back to ProRes and it is very close to the original size.

    I am not convinced that it is normal to loose that much. I still need to be convinced as these files are getting rejected, not for qualty issues but just because of the significantly smaller file size.

     

    Thanks

     

  • Tue, Sep 19 2023 11:45 PM In reply to

    • JCBond
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    Re: DNxHDQx to ProResHQ becomes signifcantly smaller

    Even though Pro Res is a variable bitrate codec, some cameras encode it as a fixed bit rate codec (like DNx is), explaining the large file size of your originals.

    Pro Res is a "Native" codec for Media Composer. When you bring it in and say to keep it as Pro Res the file is not reencoded but just rewrapped. If you then export that Media Composer also just "cuts the files" but does not reencode it. It just exports is "as is".

    On the other hand when exporting if the codecs do not match Media Composer reencodes the file. Unfortunately Media Composer does NOT give you the option to export Pro Res as a Constant Bitrate codec so any export that involves rencoding to Pro Res will generate a variable rate file.

    Windows 10 - Custom Built Intel i9 Gigabyte based system. 18 Cores. 128GB of RAM. nVidia Quadro RTX 4000. [view my complete system specs]
  • Thu, Sep 21 2023 8:33 PM In reply to

    • Learn1
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    Re: DNxHDQx to ProResHQ becomes signifcantly smaller

    I appreciate your answer, but these are not camera files. These are files originally encoded on a Vanatage system. The originl size is very typical for a 132 minute ProResHQ. I just cannt beleive that if I make it into a DNxHQx and then export it back as a ProResHQ that I will loose 25% of the file size. The encoders are not that efficient. There is something going on here. Just the facyt that my overall bit drops so much leads me to conclude that the out file is getting changed in a very significant way.

    i tend to believe that the problem is with the Avid DNx api hand off to other encoders. I can and have tried to make a CBR ProRes in Vantage but the size increse still falls very short of the original size.

    Thanks for your help

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