Quote from: Levas on July 16, 2020, 11:52:49 PM
I'm using adobe dng converter to compress 'old' uncompressed 14bit ML dng files.
Adobe dng converter has this option to only use lossless compression. I was always assuming adobe dng converter uses lj92 compression. But after last few posts in this topic, I'm in doubt? Isn't adobe dng converter lossless compression option the same as lj92 compression used in mlv's ?
Anything "lossless dng" uses the same spec when compressing the pixel data. But the spec allows for a lot of wiggle room and choices to make, which accounts for significant differences in compressed pixel data size. SlimRAW will produce files significantly smaller than DNG Converter and way smaller than anything that uses Blackmagic's setup for Canon linear raw (usually ~15% smaller, sometimes more). That's because slimraw tries a lot of stuff on the fly to get the smallest results (and even more stuff to try can be enabled through an option), while the others fix parameters in advance. Regardless, results will be truly lossless with any compressor, and compressed files will decompress to the same original file. (Well, DNG Converter will convert all input to nominal 16-bit regardless of true input bit depth, so the decompressed file will be nominally 16-bit, but that's mostly technical details.)
The thing is, DNG Converter is made for photos, and it has the peculiarity that it inserts thumbnails (previews) in each frame which certainly is pointless for video, and it adds a bunch of useless conjured metadata. All this bloats the output size. This is what gets stripped by DNGStrip. But the main issue that initially pushed me towards making slimraw back in the day was the excruciatingly slow processing of DNG Converter. Well, that and the fact that there was no log raw output in DNG Converter.