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Diffstat (limited to 'ffmpeg1/doc/multithreading.txt')
| -rw-r--r-- | ffmpeg1/doc/multithreading.txt | 70 |
1 files changed, 0 insertions, 70 deletions
diff --git a/ffmpeg1/doc/multithreading.txt b/ffmpeg1/doc/multithreading.txt deleted file mode 100644 index 2b992fc..0000000 --- a/ffmpeg1/doc/multithreading.txt +++ /dev/null @@ -1,70 +0,0 @@ -FFmpeg multithreading methods -============================================== - -FFmpeg provides two methods for multithreading codecs. - -Slice threading decodes multiple parts of a frame at the same time, using -AVCodecContext execute() and execute2(). - -Frame threading decodes multiple frames at the same time. -It accepts N future frames and delays decoded pictures by N-1 frames. -The later frames are decoded in separate threads while the user is -displaying the current one. - -Restrictions on clients -============================================== - -Slice threading - -* The client's draw_horiz_band() must be thread-safe according to the comment - in avcodec.h. - -Frame threading - -* Restrictions with slice threading also apply. -* For best performance, the client should set thread_safe_callbacks if it - provides a thread-safe get_buffer() callback. -* There is one frame of delay added for every thread beyond the first one. - Clients must be able to handle this; the pkt_dts and pkt_pts fields in - AVFrame will work as usual. - -Restrictions on codec implementations -============================================== - -Slice threading - - None except that there must be something worth executing in parallel. - -Frame threading - -* Codecs can only accept entire pictures per packet. -* Codecs similar to ffv1, whose streams don't reset across frames, - will not work because their bitstreams cannot be decoded in parallel. - -* The contents of buffers must not be read before ff_thread_await_progress() - has been called on them. reget_buffer() and buffer age optimizations no longer work. -* The contents of buffers must not be written to after ff_thread_report_progress() - has been called on them. This includes draw_edges(). - -Porting codecs to frame threading -============================================== - -Find all context variables that are needed by the next frame. Move all -code changing them, as well as code calling get_buffer(), up to before -the decode process starts. Call ff_thread_finish_setup() afterwards. If -some code can't be moved, have update_thread_context() run it in the next -thread. - -If the codec allocates writable tables in its init(), add an init_thread_copy() -which re-allocates them for other threads. - -Add CODEC_CAP_FRAME_THREADS to the codec capabilities. There will be very little -speed gain at this point but it should work. - -If there are inter-frame dependencies, so the codec calls -ff_thread_report/await_progress(), set AVCodecInternal.allocate_progress. The -frames must then be freed with ff_thread_release_buffer(). -Otherwise leave it at zero and decode directly into the user-supplied frames. - -Call ff_thread_report_progress() after some part of the current picture has decoded. -A good place to put this is where draw_horiz_band() is called - add this if it isn't -called anywhere, as it's useful too and the implementation is trivial when you're -doing this. Note that draw_edges() needs to be called before reporting progress. - -Before accessing a reference frame or its MVs, call ff_thread_await_progress(). |