[Outdated] "-mt" affecting the output size, is it intended?

[MasterInQuestion]

    Fixed: https://github.com/webmproject/libwebp/commit/8852f89ab536dd0b5917f0b51d535baa09055d30

    ----

    The multi-threading might cause different output, e.g.
    cwebp -mt -z 9 "dazzle.webp" -o "dazzle.mt.webp"
# ^ 173,160 B
    cwebp -z 9 "dazzle.webp" -o "dazzle._.webp"
# ^ 173,096 B
    .
    Effective content remained identical though. (no image difference)

    Seems to be WebP 1.5.0 specific?
    (not reproducing with 1.4.0?)

    "-mt" related hint:
    https://github.com/MasterInQuestion/attach/commit/f315edd327b4ab4d80ae372ebddcbb5e25757a1d#commitcomment-140161442

[[
= Lossless multi-threading gave different output =

[ vrabaud@google.com @ CE 2025-06-20 13:17:14 UTC:
https://issues.webmproject.org/issues/426506716#comment1
    Lossless uses multi-threading to test for different configurations only.
    The one giving the smallest output is then chosen.
    There should be no difference.

    `git bisect` gave:
    @ 2024-09-24T08:44:22Z
    Search for best predictor transform bits: This is useful in cruncher mode.
    https://github.com/webmproject/libwebp/commit/220ee52967c121adf3c690fbd0605a7de6371943

    Pending changes:
    Have Lossless return the same results with/without "-mt"
    https://chromium-review.googlesource.com/c/webm/libwebp/+/6656946 ]
]]

[vrabaud]

Thx for reporting. Please use the official bug report site for next time: https://g-issues.webmproject.org/issues/new?component=1615215

I created a bug here: https://g-issues.webmproject.org/issues/426506716

[MasterInQuestion]

    Thanks for rapid response.
    Unfortunately I had difficulty registering a Google account. (also somewhat accessing "issues.webmproject.org")
    [ ^ Details: https://github.com/MasterInQuestion/talk/discussions/39#20241029_044927 ]
    .
    And maintaining the content be presented exactly as intended, is actually a quite challenging task...