What's wrong with this shared video?

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Level 1

28 points

What's wrong with this shared video?

Subsequent to my previous question in this section I thought it best to provide an example. Here's a 1080p file, actually this one was converted from Prores to 1080p in Quicktime but sharing from either FCPX or Compressor gives exactly the same result: a strange pulsing, at intervals of about one second, that make all my shared files unusable. When the Prores file is played, it is perfectly smooth but the odd pulsing appears in all 1080 and 4K exports, whatever the setting I use.

The files was shot on A7s direct to Atoms Shogun over HDMI, then graded from Slog2 in FCPX and shared.

Can't for the life of me figure what is going on but the same thing happens if I shoot 1080p to the camera's memory card and then grade in FCPX and share.

HELP!

(please!)

https://dl.dropboxusercontent.com/u/76366907/meadowsweet%204k%20for%20QT_1080p.m ov

Mac Pro, OS X Mavericks (10.9.2)

Posted on May 29, 2015 3:55 PM

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Answer 1

Best reply

David Bogie Chq-1

Level 7

26,590 points

May 29, 2015 4:05 PM in response to Tim Ashley

I cannot access dropbox from behind my corporate firewall.

Rhythmic compression artifacts can be keyframe settings (every 30 frames, say) in Compressor or a subtle original media frame rate mismatch that regularly cycles into a periodic harmonic with the timebase of the delivery codec.

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Answer 2

Tim Ashley Author

Level 1

28 points

May 29, 2015 4:14 PM in response to David Bogie Chq-1

Thanks - it certainly looks either like a 'beat' or the sort of compression artefact that results from the compression looking for those parts of the frame that move less, and updating them less often.

In terms of frame rates, it was shot at native 25fps and stayed that way throughout AFAIK but then I am a relative new...

Thanks for the comments though. Would love to hear what you think when you see the file, if you have a moment...

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Answer 3

Russ H

Level 7

22,432 points

May 29, 2015 4:25 PM in response to Tim Ashley

I'm not seeing the pulsing you describe.

Russ

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Answer 4

Tim Ashley Author

Level 1

28 points

May 29, 2015 4:32 PM in response to Russ H

Try looking at the dappled tree right of frame - look at the pattern on the bark. It happens on any machine on which I view it. Once you've noticed it, you become aware that it's affecting the whole frame. The fluttering leaves and flower heads have enough motion of their own to disguise it.

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Answer 5

Tom Wolsky

Level 10

151,004 points

May 29, 2015 4:43 PM in response to Tim Ashley

Probably one of the most difficult images in video to compress; all it needs is to add a babbling brook. As David said, this looks like keyframes in the codec. It looks like they're at the default setting, which will make for a quite large file. Using a codec like H.264 there is really no way to avoid this with this type of video. The only way to avoid it is to use an I-frame codec, which of course are quite large especially in HD and larger formats.

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Answer 6

Tim Ashley Author

Level 1

28 points

May 29, 2015 4:51 PM in response to Tom Wolsky

So what would I do Tom, in order to get a good end result? The aim is that it should look as close as possible to a still photo, and I will re-shoot it on a less windy day to that effect. I just want the faintest flutter of movement in leaves and grass but really smooth video. Are FCPX and my gear in combination not up to that task for good 4K output?

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Answer 7

Russ H

Level 7

22,432 points

May 29, 2015 5:00 PM in response to Tim Ashley

Tim Ashley wrote:

Are FCPX and my gear in combination not up to that task for good 4K output?

I don't know about your gear,

As to FCP X, you can get a pretty good idea of what role it may play in your issue by copying the card to the Finder and opening the clip in a video player like QuickTime Player or VLC.

Russ

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Answer 8

Tom Wolsky

Level 10

151,004 points

May 29, 2015 5:01 PM in response to Tim Ashley

TTry outputting a ProRes 422 file and see how it looks.

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Answer 9

Tim Ashley Author

Level 1

28 points

May 29, 2015 5:08 PM in response to Tom Wolsky

Tom, Russ, the Shogun records prores and it plays smoothly. It's only when I share the file as h.264 that this happens, whether at 1080p or 4k, whatever the bit rate... Even though I am matching the 25fps of the original during the export.

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Answer 10

Russ H

Level 7

22,432 points

May 29, 2015 5:22 PM in response to Tim Ashley

What resolution was it shot as? Was it scaled down to 1080?

Russ

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Answer 11

Tom Wolsky

Level 10

151,004 points

May 29, 2015 5:37 PM in response to Tim Ashley

TThat's what I said. If you want really high quality video you can't use H.264. You have to use an I-frame codec, which H.264 isn't. Especially for this type of video, with this complexity, if you want high quality you cannot use a format that has a GOP structure with keyframes.

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Answer 12

May 29, 2015 6:35 PM in response to Tim Ashley

I downloaded the video file and played it in Quicktime X. The video is heavily compressed for the content and video size (1920x1080)...

The video might you say pluses badly in this area...

Double the Data Rate to around 20 Mbit/s and that should fix it (or be on the way to fixing it).

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Answer 13

Tim Ashley Author

Level 1

28 points

May 30, 2015 1:19 AM in response to David M Brewer

Thanks for the suggestions guys.

It was shot as 4k in prores And when played as prores prior to sharing, there is no pulsing. This particular clip was transcoded from quicktime, however I have tried sharing from FCPX both with and without compressor into just about every format that allows 4k and 1080p at data rates up to 30mps and the pulsing is clearly there all the time. AFAIK iframe is a recording format only and maxes at 720p but I am not overly familiar with it.

I have to go to a wedding today (thankfully without a camera!) so I will start this experiment from the top tomorrow, with fresh footage, and document every step.

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Answer 14

Tom Wolsky

Level 10

151,004 points

May 30, 2015 3:04 AM in response to Tim Ashley

IM not talking about shooting the codec that Apple stupidly called iFrame. I'm talking about using a video that's based on individual frame compression like ProRes. This has nothing at all to do with the shooting as you've said already. It's has only to do with the delivery compression.

David's information is absolutely correct. The data rate is way too low for media of this size and complexity.

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Answer 15

Russ H

Level 7

22,432 points

May 30, 2015 6:17 AM in response to Tim Ashley

Reason I asked about scaling is that can sometimes introduce artifacts. Compressor has a Resize filter that sometimes can improve the compression results. Mark a short section in the preview window and set the filter setting to Best. See if it helps.

Russ

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