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Canon EOS Crop Sensor for HD
APS-C sensor cameras including the 80D, 70D, 7D Mk. II, 7D, EOS M and Rebel models for HD video recording.

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Old February 28th, 2010, 02:53 PM   #1
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Location: Gloucestershire, UK
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Blockiness and codec choice

I recently took a pick up shot across a river coming into sun set, sun in front and to left of frame with the 7D. As the shot is to be a composited in background, and I haven't seen the foreground yet, I took a few versions at different exposures, from slightly blown out - balanced - highcontrast dark shot.

This last shot when played through quicktimeX has noticeable (and distracting) blockiness in the top right hand corner, where the picture is gray. Tonal range across this frame goes from white to black and obviously some bit in between.

If the same file is played in Quicktime 7 pro, no blockiness is seen.

It's difficult to compare in FCP, as it struggles to play h.264 clips at full speed.

So, as normal, I convert the H.264 into Prores 422 (LT). Blockiness is still apparent in Quicktime X. I then tried Prores 422 (HQ) and the blockiness is not there in QuicktimeX.

Is this an issue with QuicktimeX or the 7D compressed clips and / or I am I better off transcoding to prores 422 (HQ) ? If I Transcode to 422 (HQ) then transcode that clip to prores 422 (LT) the blockiness returns (in quicktimeX).

I have attached two photos, Sunset-Block.jpg (H.264), and Sunset-422.jpg (Prores 422(HQ)). Both are screen grabs from QuicktimeX.

Thanks in advance
Attached Thumbnails
Blockiness and codec choice-sunset-block.jpg   Blockiness and codec choice-sunset-422.jpg  

Declan Smith is offline   Reply With Quote
Old February 28th, 2010, 03:17 PM   #2
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There used to be a setting in Quicktime 7 (and below) to play the clip at full quality (not on be default?). Window > Show Movie Properties... then select the video track and check the box "High Quality" in the bottom right.

ProRes LT might be compressing it too much? I don't have Studio 3 at the moment to conform. I only have ProRes and HQ and regular ProRes works fine for me.
David Chapman
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Old April 5th, 2010, 06:35 PM   #3
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I managed to reduce the blockiness by using magic bullet looks, however I now get banding where the colour changes ( which I can use the reduce banding filter to remove).

Is there something I can do whilst shooting to avoid this either using picture style or maybe iso settings. Not all clips suffer from this. This particular clip is high contrast so not sure whether this is a factor or not? Clearly the h264 compression is probably responsible, so any tips on how to expose the shot for maximum quality from a h264 point of view would be useful.
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Old April 6th, 2010, 07:34 PM   #4
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I convert everything to ProRes 422 for editing, no problems. Some shots may play jerky in FCP, but when the project is completed and I make a master, there's no problem.
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