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GoPro through Resolve into Avid - Bad quality

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Michael Maxwell
GoPro through Resolve into Avid - Bad quality
on Feb 22, 2014 at 1:01:46 am

So we've been using Resolve to transcode GoPro through resolve to DNxHD36 Avid Media as it does this a lot faster than Avid. The quality looked perfect during this process, but once played back on a good HD Online Monitor the quality drop is really noticeable. It looks like a proxy file in comparison to the transocode an Avid churns out of GoPro (If taking twice as long to do it).

I've used Resolve with ARRI Alexa media with never so much as an issue, seems odd that it is really degrading the GoPro quality. When I say bad quality it begins to get almost choppy as if it's a proxy file.

The data rate of GoPro files we are using are around 30 so DNxHD36 should be more than enough and Avid MC turns them out fine at this quality.


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Juan Salvo
Re: GoPro through Resolve into Avid - Bad quality
on Feb 22, 2014 at 5:13:46 am
Last Edited By Juan Salvo on Feb 22, 2014 at 6:01:00 am

Isn't DNxHD36 in fact a proxy file? When you're transcoding direct in Avid are you doing to 36 or 185?

Just to add, data rate is not an absolute measure of quality, 36Mbps of DNxHD and 36Mbps of H264 are not the same thing. Just like 256KBps of MP3 and 256KBps of PCM are not the same thing.

http://JuanSalvo.com
http://theColourSpace.com


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Michael Maxwell
Re: GoPro through Resolve into Avid - Bad quality
on Feb 22, 2014 at 9:25:14 am

Hi, when transcoded within avid to dnx36 the quality is perfect, this is the res gopro has always been transcoded to anywhere I've ever worked, Anything more is kind of over kill for the format.


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stig olsen
Re: GoPro through Resolve into Avid - Bad quality
on Feb 22, 2014 at 1:15:50 pm

Hi Michael,

What you imply is not correct. DNx36 can not utilize the full potential of the GoPro material. You should transcode to DNx120.

Stig


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Glenn Sakatch
Re: GoPro through Resolve into Avid - Bad quality
on Feb 22, 2014 at 2:51:16 pm

Not sure how it works now, but years ago, before they were dnx36, 175, etc, and we were working with AVR 2 and 26, low res was only about a quarter of the screen size, and Avid blew it up to fill the screen...hence the picture looked like crap but took up less space. Again, not sure if that is still the basis behind lower resolution files. Either way, i wouldn't expect my 36 HD files to be of Pristine quality. I know when you do transcodes to Red in Avid it takes for ever, but it also defaults to full quality debayer. Perhaps there is something similar in Avid for other codecs. Check your settings and see if there is a full quality switch on somewhere. But again, i would be very surprised to see an avid dnx 36 looking just as clean as an Avid dnx 175 file, no matter what the source is.

I know you've answered this, but just to be clear, the resolution tab in your bin does say dnx 36 after the transcode is done?

I would be curious to see a couple of screen grabs.

Glenn


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Juan Salvo
Re: GoPro through Resolve into Avid - Bad quality
on Feb 22, 2014 at 10:16:49 pm

DNxHD36 is not over kill for anything, it's a very lossy offline format. Try DNxHD 110+ or similar from resolve, and double check exactly what codec you're looking at in avid when comparing. I'm certain it's not DNxHd36, might be 110,185,185X or perhaps native.

Best of luck,

http://JuanSalvo.com
http://theColourSpace.com


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