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Video Transition Pixelation – How to Prevent?
Hello,
Does anyone know why video transition effects would cause pixelation distortion? I am using PPRO CS4 on a 3.06 GHz Intel iMac with 4 GB of RAM.
The footage is of a ‘talking head’, shot in HD 24 fps on a Canon HV20 (HDV 1080i – NTSC). The sequence setting in Premiere is 1280×720 with 24 fps timecode. Whatever falls outside of this parameter within the original footage is not used. In other words, I am not trying to squeeze 1080 in 720.
The footage that comes before, and should thus fade into the talking head footage, is an After Effects CS4 file (1280X720, 24 fps) which consists of a solid black layer and some lens flare effects. It’s about 20 seconds long. This file has been imported into PPRO (as opposed to using dynamic link).
The final Quicktime MP4 file is about an hour long, and exported as H.264, 640X480, 24 fps. The file size is about 475 MB.
I am not sure how to describe it, but these transitions seem to cause some kind of pixelation ‘blast’ every second or two. And this occurs in the area of the face and head – which is really all that moves in the footage. These ‘blasts’ gradually decrease as the footage moves on (i.e. away from the transition).
Initially I thought that the AE file might be too complex in terms of Premiere rendering it and fading it into the talking head footage. But I just tested the transitions with a black matte (instead of the AE file) and the same problems arise. The only time the pixelation doesn’t occur is when I don’t use any transition at all… but that isn’t an option.
These distortions happen when I use the crossfade video transition, and the dip to black or dip to white transitions (whether ending or centering on cut, 1 or 2 seconds).
For some reason none of this occurs in the .FLV files that I have exported of the same footage. These, however, were 1280×720 in size.
Thanks in advance,
Roger
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3 Replies
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I think what you are seeing is plain old compression artifacts.
Basically, the bit rate in your Mp4 is too low or the compression keyframes are too far appart. Clean compression mostly depends on similarities (repeated pixels) between consecutive frames.
In the event of a crossfade, or fade in / fade out, each frame if different so the compressor will struggle to keep it clean. You can also try manually increasing the number of compression keyframes in your export settings, either way you will be increasing file size.
Go look at a satellite channel up close and watch the crossfades, that might make you feel better…
Vince Becquiot
Director | EditorKaptis Studios
San Francisco – Bay Area -
Thank you, good to know.
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I just had the same issue when I played the sequence.
I read the post, but wasn’t sure how to change the compression, but when I right clicked on the playback frame, selected “playback resolution” it showed “1/2” and the “pause resolution” was “FULL”. Well, I changed the playback resolution to “FULL” and now it plays back perfectly.
Hopefully the rendering works fine also!
Hope this helps…
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