Hi guys,
Last two weeks I've been investigating lossles JPEG (92) specs, LJ92Lib from Andrew Baldwin and MLV files produced by both a1ex's lovely crop_rec_4k/mlv_lite and by mlv_dump from lj92 branch, also DNGs produced by MLRAWviewer.
It seems that Andrew Baldwin's implementation is somewhat weird. It encodes raw data as two images each with its own headers, one scan and one component in it. That means that encoded data has two SOI (0xFFD8, Start of image) and EOI (0xFFD9, End of image) markers and each image has its own SOF3 (0xFFC3, Start of frame header), DHT (0xFFC4, Huffman table) and SOS (0xFFDA, Start of scan header) with its own one image component with full width and half height. Also baldand chose the prediction method 6 in his encoder because of reasons explained
here. If someone interested the original
document is here.
Meanwile the raw data encoded (as configured by a1ex) by Canon HW compressor fully follows the specs and has one SOI/EOI, which accordingly have DHT, SOF3 and SOS in it. SOS consists of two components with full width and half height. Predictor used is number 1.
This is the reason why LJ92lib can not decode ML files out of the box despite it supports all 7 predictors while decoding (not only number 6). The component number should be correctly taken into account.
While studying all these I came across
Syoyo Fujita's github account with his modified header file based on baldand's LJ92lib. ( which also was pointed out by @martinherring
)
In short Syoyo correctly modded the main loop in parseScan function to support components and changed decoder struct and added 'components' field to it. Also he added multiple Huffmann table support to the lib which is really unnecessary at least for ML compressed data. So I edited lj92.c accordingly. Unfortunatelly encoder still needs some work. However for MLVFS encoder is unnecessary
Using all this info I pathched MLVFS and it works nicely with all its bells and whistles (on the fly raw processing). I want to thank Danne as usual
for testing/support and MAC binary.
David Milligan merged changes to
MLVFS repo.
Download latest MAC binary
here and Windows x64 binary
here.
The latest 'DokanSetup_redist.exe' installer is
here.
I also modified
mlv_dump-on-steroids but unfortunatelly it's not ready for prime time yet. Needs more time. Always time 
. Now supports all latest stuff plus some features that none of the mlv_dump versions have. Binaries uploaded.
Note: mlv_dump-on-steroids merged in ML repository to crop_rec_4K branch.
regards
bb
