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Loss of resolution converting ProRes to H.264

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Katt Qian
Loss of resolution converting ProRes to H.264
on Jul 26, 2012 at 2:46:09 am

Hey everyone,

I'm having so much trouble with inconsistent resolutions in FCP7. All my footage is at 1920x1080 in ProRes 422 (HQ), and I'm trying to export the whole sequence out as H.264 for web, but two of the videos keep losing resolution quality after I render them. These two were videos exported out from After Effects as ProRes files and they have a lot going on in them, so I wonder if that has something to do with it? Another thing is that the data rate of these two videos is around 20MB/second while the other videos are around 25MB/second - I don't know anything about data rates, but would that be something that would affect the output resolution?

After doing some research, I've tried deleting the time codes of those two videos, changing my render settings, and clearing up space on my drive, but the issue is still there. Can anyone shed any insight on this?

Any help is appreciated!
Thanks -


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Andrew Rendell
Re: Loss of resolution converting ProRes to H.264
on Jul 28, 2012 at 9:22:20 am

Well, as a rule H264 is generally much lower quality than ProRes 422 (although you can increase the data rate very significantly from the normal kind of figures and get close, but that would defeat the point of it).

H264 is also somewhat variable in subjective quality depending on the source material, lots of detail and movement in a shot will strain the system a lot more than more stationary shots and those shots will look poorer than the less demanding ones, so having material with lots going on may well be part of your problem.

There are a couple of things you can try when you do the conversion to H264 (by stepping into the config settings in whatever software you're using for the conversion):

Increase the data rate. Unfortunately that'll make your files bigger and can get you into problems streaming, so it's fine for playing a file on a computer but not ideal for playing over the internet.

Decrease the picture size. Using the same data rate to encode fewer pixels can increase the subjective quality of the pictures even though you're technically reducing the resolution.

Are you doing a single pass encoding? If so, I'd suggest trying a two-pass conversion. That takes twice as long to do, but the system fine tunes the encoding process much better than a single pass encoding and the subjective increase in quality can be quite striking, depending on the material.

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