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author | Andreas Rheinhardt <andreas.rheinhardt@outlook.com> | 2022-06-30 15:01:22 +0200 |
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committer | Andreas Rheinhardt <andreas.rheinhardt@outlook.com> | 2022-07-25 23:31:37 +0200 |
commit | 72d5ce9fa6cd67497fbfffc97031cb6b7ab23c6d (patch) | |
tree | a3c4c3b1c2a9c7b1e462cf229a6022e7e8e6664e /libavcodec/libopenjpegdec.c | |
parent | 8c4f95e1e1488bbbaca19bc6c6214393136e1b51 (diff) | |
download | ffmpeg-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/libopenjpegdec.c')
0 files changed, 0 insertions, 0 deletions