Latest post Thu, Mar 29 2018 10:08 PM by jef. 11 replies.
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  • Fri, Mar 9 2018 8:42 AM

    • reckoner
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    Quality loss on export

    Hi all,

    I'm having an issue with video quality being noticably reduced on export.

    This is my workflow:

    Sony XAVC 4K files > AMA into Avid MC 2018.2 in a 1080p project > Finish edit and do a video mixdown DNxHD 185X > Export same as source.

    On comparing the resulting Qucktime file with the original clips from the camera, noticable detail has been lost and the image is a lot softer. I realise I'm going from 4K to 1080p, but the image should still be nice and sharp. Even when viewed on a 1080p monitor, it's soft.

    I'm not sure if this is a new issue, or something I've not noticed before - I've used MC for years. But it doesn't make much sense as the mixdown and same as source export should be vitually lossless.

    If anyone could shed any light on this issue, it'd be really appreciated!

    Thanks very much.

    Media Composer 2018.2 | i7 4390K | 32GB RAM | Quadro K620 | 256GB SSD | 8TB RAID 0 media drive [view my complete system specs]
  • Fri, Mar 9 2018 11:08 AM In reply to

    Re: Quality loss on export

    Well it should look 4x softer as there is only a quarter of the resolution.

    Are you able to see the timeline output on a HD monitor? how does that look before the export?

    And as a comparrison have you tried taking one of the 4K (well its UHD not 4K I suspect) into squeeze or similar and transcoding to DNx185x as a comparrison?

     

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  • Fri, Mar 9 2018 12:53 PM In reply to

    Re: Quality loss on export

    Pat Horridge:

    Well it should look 4x softer as there is only a quarter of the resolution.

    +1

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  • Sun, Mar 11 2018 3:06 AM In reply to

    • reckoner
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    Re: Quality loss on export

    Before the export, the clips look great.

    As a comparison, I've exported the same clips same as source from a UHD project, and then converted to a 1920x1080 file using Adobe Media Encoder. The resulting video is much higher quality than if I'd exported the same clip from a 1080p project. My only conclusion is that Avid doesn't do a great job of downscaling from 4K/UHD to 1080p. 

    This is unfortunate with the obvious benefits of working with UHD footage in a 1080p project.

     

    Media Composer 2018.2 | i7 4390K | 32GB RAM | Quadro K620 | 256GB SSD | 8TB RAID 0 media drive [view my complete system specs]
  • Sun, Mar 11 2018 10:04 AM In reply to

    Re: Quality loss on export

    reckoner:

    My only conclusion is that Avid doesn't do a great job of downscaling from 4K/UHD to 1080p

    Haven't seen that, however I always export SAS and do the transcode at an encoder.

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    Larry as long as I live I will remember you.

     

    3 Heads Digital Films

  • Sun, Mar 11 2018 11:52 AM In reply to

    • reckoner
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    Re: Quality loss on export

    Yes so do I. But I'm using AMA to bring 4K files into a 1080P project - then mixing down before exporting SAS. So the issue must lie in the mixdown process. 

    Media Composer 2018.2 | i7 4390K | 32GB RAM | Quadro K620 | 256GB SSD | 8TB RAID 0 media drive [view my complete system specs]
  • Sun, Mar 11 2018 2:12 PM In reply to

    • jef
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    Re: Quality loss on export

    reckoner:

    On comparing the resulting Qucktime file with the original clips from the camera, noticable detail has been lost and the image is a lot softer. I realise I'm going from 4K to 1080p, but the image should still be nice and sharp. Even when viewed on a 1080p monitor, it's soft.

    Can you tell us how you are doing this comparison?  Are you bringing the export back into Avid, stacking it above the final mixdown and comparing that way?

    Jef

    Avid DS 11.0.2 R.I.P | MC "Well, it depends ..." | OS 10.11.x - various MacPro Towers - home system MacPro Dual 2.8 8core GTX680 "Harpertown"... [view my complete system specs]

    _____________________________________________

    Jef Huey

    Senior Editor

    Old Stuff  http://vimeo.com/album/3037796

  • Sun, Mar 11 2018 3:00 PM In reply to

    • smrpix
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    Re: Quality loss on export

    reckoner:

    Yes so do I. But I'm using AMA to bring 4K files into a 1080P project - then mixing down before exporting SAS. So the issue must lie in the mixdown process. 

    Why not flip your project to 4K before doing the mixdown, export to QT Reference, then encode to 1080 with AME?

     

  • Sun, Mar 11 2018 10:34 PM In reply to

    • reckoner
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    Re: Quality loss on export

    I didn't think of that - will give it a try. Thanks!

    Media Composer 2018.2 | i7 4390K | 32GB RAM | Quadro K620 | 256GB SSD | 8TB RAID 0 media drive [view my complete system specs]
  • Thu, Mar 15 2018 10:34 AM In reply to

    • fkurz
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    Re: Quality loss on export

    Hi,

    in my experience the downconversion of 4k/UHD to HD in Avid MC is noticeable softer than in other apps like Resolve etc.. Avid should optimise that scaling algorithm!

    Regards

    Flo

    Avid MC 2018.2 symphony option HP Z820 Win 7 64Bit, SP 1 Mojo-DX Interface [view my complete system specs]
  • Thu, Mar 29 2018 9:20 AM In reply to

    • reckoner
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    Re: Quality loss on export

    Thanks for the feedback.

     

    I've now changed my workflow to a 4K/UHD project > output same as source > convert to 1080p with Adobe Media Encoder. The result is a MUCH sharper image.

     

    This is unfortunate as it just makes for larger file sizes, longer output times and loses the ability to crop into the 4K/UHD image in a full HD project.

    Media Composer 2018.2 | i7 4390K | 32GB RAM | Quadro K620 | 256GB SSD | 8TB RAID 0 media drive [view my complete system specs]
  • Thu, Mar 29 2018 10:08 PM In reply to

    • jef
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    Re: Quality loss on export

    reckoner:

    This is unfortunate as it just makes for larger file sizes, longer output times and loses the ability to crop into the 4K/UHD image in a full HD project.

    The quality of any scaling can be effected by the filter algorithm being used.  If you look in Blackmagic Fusion (a compositing tool, not an editing tool for sure) there are at least 11 filter types to choose from.  All with various best uses.

    In Avid .....

    The best I have seen is the HQ setting in the 3D Warp tool and in Render Settings.  And that, if you dig enough in the doc, is described as "PolyPhase".  I have not found a great explanation of exactly what filter type that is.

    Bottom line, some Avid features seem to be designed for the lowest common denominator user, not the nit picky, image quality obsessed former DS users.  .... Sorry - that just slipped out.  Smile

    Jef

    Avid DS 11.0.2 R.I.P | MC "Well, it depends ..." | OS 10.11.x - various MacPro Towers - home system MacPro Dual 2.8 8core GTX680 "Harpertown"... [view my complete system specs]

    _____________________________________________

    Jef Huey

    Senior Editor

    Old Stuff  http://vimeo.com/album/3037796

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