{"id":28650,"date":"2013-02-03T21:36:59","date_gmt":"2013-02-03T21:36:59","guid":{"rendered":"http:\/\/philipbloom.net\/?p=28650"},"modified":"2013-02-05T00:45:33","modified_gmt":"2013-02-05T00:45:33","slug":"canon-1dc-mjpeg-compression","status":"publish","type":"post","link":"https:\/\/philipbloom.net\/blog\/canon-1dc-mjpeg-compression\/","title":{"rendered":"Canon 1DC \/ MJPEG Compression Banding"},"content":{"rendered":"

Canon 1DC \/ MJPEG compression banding and blocking<\/strong><\/p>\n

The Canon 1DC uses Motion Jpeg \/\u00a0YUV 4:2:2 to compress the massive 4k 24p resolution video files. It’s a variable bit rate of around 500 Mbps that will change depending on the shot and ISO level.<\/p>\n

NOTE:\u00a0These are only my thoughts and guess work, none of this is confirmed by Canon or any body else. My recommendations should be disregarded unless you have tested the camera yourself.<\/p>\n

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Pre-Production<\/h4>\n

Some users have found shooting Canon Log at lower than the native ISO value of 400 can cause extreme banding. I’ve made some tests below to show that the compression used and it’s quality value is the main cause for banding and compression dithering blocking.<\/p>\n

I’m confident that the 1DC would produce stunning delicate graduated imagery if not constrained by the MJPEG format at lower that 100% quality. The tests below also show what happens when simulated gain of ISO400 is applied before post production on the images.<\/p>\n

Images below are shown at 670 x 400 centre crops of the 4096 x 2160 full 4k frame. To view the full frame please click on the image. Images are saved as compressed jpeg for web. This will alter the structure of the image but will still give an accurate comparison. The images are graded very harshly to aggravate and break the codec.<\/p>\n

You will see below the blocking dithering of the graduations in this simulated sky reflection. Also that at 100% quality the MJPEG produces a very good compression to artifact ratio. What is most improved is the introduction to slight grain or ISO in the image this helps break up the 8bit banding on the native image. And whilst it does not stop banding on the 1DC the native ISO of 400 should be used where possible.<\/p>\n

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The frames below show simulated ISO value of 400.<\/p>\n

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\"MJPEG

I would love to see the compression changeable by the user. A bit like how you can adjust the jpeg compression level in camera. At the moment 10 seconds uses about 500MB of data. If Canon did change the quality setting of the MJPEG at 100% quality you would get 615MB of data for 10 seconds but higher ISO’s could push that up to 900MB for 10 seconds. Still I would love the choice if the compression chips could take it.<\/p>\n

A 128GB 1000x UDMA 7 card will hold around 34mins of 4k Video and that is broken up into 32 4.12GB\u00a0chunks.<\/p>\n

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