Pixelation issue on mp4 output

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Level 1

8 points

Pixelation issue on mp4 output

Hi There. I'm hoping somebody can help me with an issue I've been having for quite a while now. We do a lot of projects that require mp4 (with h.264 encoding) output as final delivery format - at various bit rates (500kbit/s, 1500kbit/s and 3000kbit/s being the most common). Now and then I've experience an annoying pixelation problem. It happens right after a cut, for a few frames, and it can happen with or without a transition. When I first saw it, I tried all sorts of things to narrow it down but I have never been able to figure out why it happens. At first I just switched out the offending clip but I can't always do that. I finally tried exporting full rez from FCP, opening in Quicktime 7 and then exporting directly from there with the proper mp4 setting. That seems to fix the problem. Until now. I've also tried dragging the file into Compressor and outputting mp4 from there but that doesn't fix it either (also, is there a way to set an mp4 wrapper but h.264 encoding in Compressor? I couldn't find a place to change this). I thought that Final Cut basically used Quicktime, so why would dragging the .mov outputted from FCP into QT7 make a difference (rather than using Quicktime Conversion directly from withing FCP). It just doesn't make any sense to me.

This is really driving me crazy. Any ideas would be greatly appreciated. Enlightenment on what really affects the quality of output in general would be great as well. For instance, will output differ from an iMac to a Powerbook even when using the same version of software (with same settings)?

I am using:

FCP 6.0.6

Compressor 3.0.5

QuickTime™ Version 7.6.6 (1787)

iMac Intel Quad Core i7 (late 2009) with 12GB RAM, ATI Radeon HD 4850 Graphics Card

Thanks so much!

Karen

iMac, Mac OS X (10.6.7)

Posted on Oct 26, 2011 10:24 AM

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Answer 1

Oct 27, 2011 9:45 AM in response to buzzflix

export from fcp with current settings (quicktime movie export, not quicktime conversion). Bring this file into compressor and start playing with the presets. You don't say if you're scaling down from the original pixel dimensions. If so, you can play with the frame settings in compressor. I'm pretty sure mp4 is a subset of h264.

Remember that in compressor you can duplicate presets and customize and save the settings. You can also set an in and out in the preview window to test small sections.

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Answer 2

buzzflix Author

Level 1

8 points

Oct 27, 2011 10:06 AM in response to Michael Grenadier

Hi Michael,

Thanks for your response!

The reason I generally use the QT conversion option from FCP, is that there doesn't seem to be a way to change the encoding to h.264 in Compressor. It also doesn't allow me the bit rate flexibility of the QT interface (at least none that I've found).

I work with DV footage on an NTSC timeline. Again, the reason this is making me so crazy is that outputting using QT movie then dragging THAT into QT 7 and outputting with the settings I need (mp4 wrapper with h.264 encoding) seems to get rid of the pixellation problem. Weird.

I did finally get clean output this time but not sure why. Just tried it again and it worked.

In the past, I have tried all sorts of things to narrow this down (including trashing prefs, restarting etc). Just don't understand why it happens. Seems to be completely random.

Thanks,

Karen

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Answer 3

Oct 27, 2011 10:24 AM in response to buzzflix

there are many more controls in compressor and of course compressor can do h.264. You can either create a preset from scratch or choose one of the many h264 presets in the apple folder and customize and save them.

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Answer 4

buzzflix Author

Level 1

8 points

Oct 27, 2011 10:40 AM in response to Michael Grenadier

Hi Michael,

Thanks again for your response.

I know of course that compressor "does" h.264. What I mean is that when you choose the mp4 preset, it does not allow you to change the encoding to h.264. There are other areas that are greyed out on certain presets as well. The mp4 setting also will not allow you to go over 2048 bit rate. I much prefer Compressor, but it has some frustrating limitations in its presets. There are workarounds of course. A tip I got just yesterday recommended I use the H.264 preset but change the file format to mp4 - essentially doing the same thing backwards. I can change the bit rate this way as well.

I use Compressor in all other workflow situations except this mp4/h.26 situation - and I love being able to save custom presets. I have lots! Just wish it let me tweak what I want in every situation.

I do have an older version 3.0.5 so maybe they have changed this in the latest iterations.

Best,

Karen

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Answer 5

Oct 27, 2011 10:52 AM in response to buzzflix

You might try sorenson squeeze. It looks like it doesn't have these limitations for mp4's.

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Answer 6

Russ H

Level 7

22,432 points

Oct 27, 2011 12:28 PM in response to Michael Grenadier

And in addition to Squeeze, MPEG Streamclip might be worth a look. It can do an MP4 with H.264 encoding, and also doesn't appear to limit the bit rate.

Russ

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Answer 7

Oct 27, 2011 12:32 PM in response to Russ H

certainly worth a test, but mpegstreamclip doesn't have the scope of parameters squeze or compressor have. Also, I don't think you can customize and save a setting. Of course, the price is right.

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Answer 8

buzzflix Author

Level 1

8 points

Oct 27, 2011 1:09 PM in response to Russ H

Thanks Russ and Michael,

I'm not concerned so much with a program that will allow me to do this - I am able to output with these setting directly from FCP and Quicktime 7, as well as Compressor, now that I know to use the h.264 setting and just change the file type. I have MPEG Streamclip as well, but I find the quality and convenience of the former programs to be better.

I am really just looking for someone else that might have had the random pixellation problem and what they have done to fix it. Again, it is a random incident. Maybe one output in 10, if that - and there is no common denomitator that I can see. Using FCP export using QT Conversion works just fine most of the time. And then all of a sudden I will get those few frames - usually at a few spots.

I appreciate your help. Please let me know if you come across anyone with similar problems.

Best,

Karen

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Answer 9

Oct 27, 2011 1:15 PM in response to buzzflix

So you're saying that you don't have the problem if you export selfcontained qt from fcp with current settingts, and use compressor to make an h264 and just change the file extension?

Wondering if the problem could be caused by video that's out of spec. Have you tried applying the broadcast safe filter to your final output? This is the kind of thing that might cause problems erratically.

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