mirror of https://git.ffmpeg.org/ffmpeg.git
avcodec/mpegvideo_dec: Sync linesize and uvlinesize between threads
linesize and uvlinesize are supposed to be the common linesize of all the Y/UV-planes of all the currently cached pictures. ff_mpeg_update_thread_context() syncs the pictures, yet it did not sync linesize and uvlinesize. This mostly works, because ff_alloc_picture() only accepts new pictures if they coincide with the linesize of the already provided pictures (if any). Yet there is a catch: Linesize changes are accepted when the dimensions change (in which case the cached frames are discarded). So imagine a scenario where all frame threads use the same dimension A until a frame with a different dimension B is encountered in the bitstream, only to be instantly reverted to A in the next picture. If the user changes the linesize of the frames upon the change to dimension B and keeps the linesize thereafter (possible if B > A), ff_alloc_picture() will report an error when frame-threading is in use: The thread decoding B will perform a frame size change and so will the next thread in ff_mpeg_update_thread_context() as well as when decoding its picture. But the next thread will (presuming it is not the same thread that decoded B, i.e. presuming >= 3 threads) not perform a frame size change, because the new frame size coincides with its old frame size, yet the linesize it expects from ff_alloc_picture() is outdated, so that it errors out. It is also possible for the user to use the original linesizes for the frame after the frame that reverted back to A; this will be accepted, yet the assumption that of all pictures are the same will be broken, leading to segfaults. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
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@ -127,6 +127,9 @@ do {\
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UPDATE_PICTURE(last_picture);
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UPDATE_PICTURE(next_picture);
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s->linesize = s1->linesize;
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s->uvlinesize = s1->uvlinesize;
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#define REBASE_PICTURE(pic, new_ctx, old_ctx) \
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((pic && pic >= old_ctx->picture && \
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pic < old_ctx->picture + MAX_PICTURE_COUNT) ? \
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