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authorAndreas Rheinhardt <andreas.rheinhardt@outlook.com>2022-06-30 15:01:22 +0200
committerAndreas Rheinhardt <andreas.rheinhardt@outlook.com>2022-07-25 23:31:37 +0200
commit72d5ce9fa6cd67497fbfffc97031cb6b7ab23c6d (patch)
treea3c4c3b1c2a9c7b1e462cf229a6022e7e8e6664e /libavcodec/rangecoder.c
parent8c4f95e1e1488bbbaca19bc6c6214393136e1b51 (diff)
downloadffmpeg-72d5ce9fa6cd67497fbfffc97031cb6b7ab23c6d.tar.gz
avcodec/hevcdec: Add stat_coeffs to HEVCABACState
The HEVC decoder has both HEVCContext and HEVCLocalContext structures. The latter is supposed to be the structure containing the per-slicethread state. Yet that is not how it is handled in practice: Each HEVCLocalContext has a unique HEVCContext allocated for it and each of these coincides with the main HEVCContext except in exactly one field: The corresponding HEVCLocalContext. This makes it possible to pass the HEVCContext everywhere where logically a HEVCLocalContext should be used. This led to confusion in the first version of what eventually became commit c8bc0f66a875bc3708d8dc11b757f2198606ffd7: Before said commit, the initialization of the Rice parameter derivation state was incorrect; the fix for single-threaded as well as frame-threaded decoding was to add backup stats to HEVCContext that are used when the cabac state is updated*, see https://ffmpeg.org/pipermail/ffmpeg-devel/2020-August/268861.html Yet due to what has been said above, this does not work for slice-threading, because the each HEVCLocalContext has its own HEVCContext, so the Rice parameter state would not be transferred between threads. This is fixed in c8bc0f66a875bc3708d8dc11b757f2198606ffd7 by a hack: It rederives what the previous thread was and accesses the corresponding HEVCContext. Fix this by treating the Rice parameter state the same way the ordinary CABAC parameters are shared between threads: Make them part of the same struct that is shared between slice threads. This does not cause races, because the parts of the code that access these Rice parameters are a subset of the parts of code that access the CABAC parameters. *: And if the persistent_rice_adaptation_enabled_flag is set. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Diffstat (limited to 'libavcodec/rangecoder.c')
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