encoder output mode using out-of-order jxlp#4745
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veluca93
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Can we add roundtrip tests for this, with and without TOC permutation?
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Initially TOC permutation was being ignored in output mode 2 (just like in output mode 1). Changed it to actually do the requested TOC permutation in mode 2, since even if modes 1 and 2 are inherently non-progressive, mode 2 can be easily converted to mode 0 by sorting and merging the jxlp boxes, so it may be useful to be able to do a center-first permutation even if it will only be usable after doing a conversion from ftyp 1 to ftyp 0. Added a test that checks that all output modes and TOC permutations produce different files but identical decoded images. |
veluca93
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Jun 9, 2026
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(builds on #4741)
This adds a new encoder option
JXL_ENC_FRAME_SETTING_OUTPUT_MODEto set the output mode:ftypversion 1 which allowsjxlpboxes to be in arbitrary order. Writes sections in the same order as in mode 1, but wraps each of them in its ownjxlpbox. The finaljxlpbox contains the TOC. No seeking is required during encode, and the 'logical' codestream does not use a permuted TOC, but it is shuffled at the file format level since it is split injxlpboxes that are out of order.It is not recommended to start using output mode 2 since current decoders do not support this yet. This is mostly just to create test bitstreams; it could be useful in some very specific use cases but generally sticking to mode 0 is recommended (to produce progressive-decodable output).