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Ragged, pixelated images when there is lots of movement

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Kris De Meyer
Ragged, pixelated images when there is lots of movement
on Apr 11, 2014 at 6:23:06 pm

We are working on a documentary for which we shot on a Canon XF305 in HD format (1920x1080 at 50mbps).

We imported the footage into FCP7 as ProRes Proxy for offline editing. Two days ago I had the opportunity to test our cut on a big screen in a cinema, and something I had faintly noticed when watching on the small screen became annoyingly obvious on the big screen: images look pixelated and frayed at the surface edges when there is lots of movement.

The clip I tested was exported from FCP as Quicktime video with the sequence settings unchanged. I then compressed it using Compressor 3.5 with the recommended settings for Vimeo HD (720p - 5000kbps - multi-pass). However, I think that the pixelation problem is not caused by the compression but lies earlier in how we shot or imported he rushes into FCP.

Two possible culprits I can think of:

(1) Perhaps we made a mistake somewhere along the line in interlacing/de-interlacing images? I think we shot in 50i (but would have to double-check on our rushes drive). Was that wrong? If the footage is 50i, should we de-interlace the footage when we import the rushes into FCP or should we de-interlace when we export/compress using Compressor?
(2) Is it a problem of the ProRes Proxy codec and would it disappear if we used the full ProRes 422?

Would really appreciate if somebody could confirm what the most likely cause is.

Thanks in advance,

Kris


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Mark Suszko
Re: Ragged, pixelated images when there is lots of movement
on Apr 11, 2014 at 6:49:29 pm

Wait, didn't you import the full-rez video to replace the proxy media when you finished editing? Are you looking at up-rezzed versions of proxy media?


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Kris De Meyer
Re: Ragged, pixelated images when there is lots of movement
on Apr 11, 2014 at 8:08:19 pm

Hi Mark,

Thanks for your comment. We've not picture-locked yet so have not replaced the ProRes proxy footage with ProRes 422. The ProRes Proxy footage is 1920x1080 though, so no uprezzing is taking place.

I was testing our cut for a test screening we will have soon. If (as Shane suggests) it is the compression of the Proxy format, we'll have to import all our rushes as ProRes 422 before the test screening.

Thanks,

Kris


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Shane Ross
Re: Ragged, pixelated images when there is lots of movement
on Apr 11, 2014 at 7:42:20 pm

If you screened Proxy on the big screen...yeah, you'll see artifacting. Proxy is an offline, low res codec, as you know. it's highly compressed to save space. So blowing that up will show off the artifacting for sure.

If you didn't shoot interlaced, or edit in an interlaced sequence...what you are seeing might just be the compression.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Kris De Meyer
Re: Ragged, pixelated images when there is lots of movement
on Apr 11, 2014 at 8:11:53 pm

Thanks Shane. As I said in my reply to Mark, we're test-screening soon, and it looks like we'll have to import our rushes as ProRes 422 before this if artifacting is the problem. We can try tomorrow on a small clip to see if that is the problem.

Thanks,

Kris


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