Author Topic: Lossy DNG compression for archiving  (Read 5045 times)

savale

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Lossy DNG compression for archiving
« on: May 30, 2013, 01:28:37 PM »
Hi, I was just thinking if there was a way to save the RAW movies we shoot in such a way that there is a possibility to keep the raw format. When the set of DNG's are converted to any other format the real RAW information is gone and will limit any processing in the future.

So I think there are two possibilities:

1) compress the DNG's using zip (lossless compression) -> Not sure what the benefit will be in file size?
2) lossy DNG -> will bring back the size with a factor 3

I will dig in the technical possibilities later. But I am interested in any opinions about this.




IliasG

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Re: Lossy DNG compression for archiving
« Reply #1 on: May 30, 2013, 07:49:10 PM »
There are many options depending on the needed robustness of the compressed file.

Ready to use ..
- GoPro Cineform ...

- Just lossless compression 14bit linear, by running through Adobe DNG converter. No loss like zip but better compression. File goes from 100% to 70%-50% depending on the file (noisy and hi-key compress less) when including medium size jpeg preview. A little up or down if you choose full size or small preview.

- Adobe DNG converter lossy is "visually lossless" with decreased robustness. RGB 8bit log file with around 1.0MB (from 3.5). Needs testing about robustness (green screen). Not supported by third parties at first only adobe products supported it but things go better .. latest Dcraw has support when linked with libjpeg and others follow.

Not yet implemented but under consideration http://www.magiclantern.fm/forum/index.php?topic=5601.msg40980#msg40980
It could be implemented even in camera or by a utility like raw2dng.
- Proprietary format but I bet DNG converter and all DNG decoders will support it as is now (instead if blocked by Adobe). Compressed from 14bit linear to 12 bit log (highlights compression) and then run through DNG lossless compression (in Camera or in raw2dng if code is available) or AdobeDNG converter like above. Visually lossless (it's the way Nikon - Sony use to compress their RAWs. 99%+) equivalent to 14bit linear. Size goes to around 60-50%.
- Αs above but 14bit linear to 10bit log. Equivalent to industry standard 10 bit log 4:2:2 (or 4:4:4). Size at around 50-40%.