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| -rw-r--r-- | doc/libav-merge.txt | 115 |
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diff --git a/doc/libav-merge.txt b/doc/libav-merge.txt deleted file mode 100644 index bcd0aacba5..0000000000 --- a/doc/libav-merge.txt +++ /dev/null @@ -1,115 +0,0 @@ -CONTEXT -======= - -The FFmpeg project merges all the changes from the Libav project -(https://libav.org) since the origin of the fork (around 2011). - -With the exceptions of some commits due to technical/political disagreements or -issues, the changes are merged on a more or less regular schedule (daily for -years thanks to Michael, but more sparse nowadays). - -WHY -=== - -The majority of the active developers believe the project needs to keep this -policy for various reasons. - -The most important one is that we don't want our users to have to choose -between two distributors of libraries of the exact same name in order to have a -different set of features and bugfixes. By taking the responsibility of -unifying the two codebases, we allow users to benefit from the changes from the -two teams. - -Today, FFmpeg has a much larger user database (we are distributed by every -major distribution), so we consider this mission a priority. - -A different approach to the merge could have been to pick the changes we are -interested in and drop most of the cosmetics and other less important changes. -Unfortunately, this makes the following picks much harder, especially since the -Libav project is involved in various deep API changes. As a result, we decide -to virtually take everything done there. - -Any Libav developer is of course welcome anytime to contribute directly to the -FFmpeg tree. Of course, we fully understand and are forced to accept that very -few Libav developers are interested in doing so, but we still want to recognize -their work. This leads us to create merge commits for every single one from -Libav. The original commit appears totally unchanged with full authorship in -our history (and the conflict are solved in the merge one). That way, not a -single thing from Libav will be lost in the future in case some reunification -happens, or that project disappears one way or another. - -DOWNSIDES -========= - -Of course, there are many downsides to this approach. - -- It causes a non negligible merge commits pollution. We make sure there are - not several level of merges entangled (we do a 1:1 merge/commit), but it's - still a non-linear history. - -- Many duplicated work. For instance, we added libavresample in our tree to - keep compatibility with Libav when our libswresample was already covering the - exact same purpose. The same thing happened for various elements such as the - ProRes support (but differences in features, bugs, licenses, ...). There are - many work to do to unify them, and any help is very much welcome. - -- So much manpower from both FFmpeg and Libav is lost because of this mess. We - know it, and we don't know how to fix it. It takes incredible time to do - these merges, so we have even less time to work on things we personally care - about. The bad vibes also do not help with keeping our developers motivated. - -- There is a growing technical risk factor with the merges due to the codebase - differing more and more. - -MERGE GUIDELINES -================ - -The following gives developer guidelines on how to proceed when merging Libav commits. - -Before starting, you can reduce the risk of errors on merge conflicts by using -a different merge conflict style: - - $ git config --global merge.conflictstyle diff3 - -tools/libav-merge-next-commit is a script to help merging the next commit in -the queue. It assumes a remote named libav. It has two modes: merge, and noop. -The noop mode creates a merge with no change to the HEAD. You can pass a hash -as extra argument to reference a justification (it is common that we already -have the change done in FFmpeg). - -Also see tools/murge, you can copy and paste a 3 way conflict into its stdin -and it will display colored diffs. Any arguments to murge (like ones to suppress -whitespace differences) are passed into colordiff. - -TODO/FIXME/UNMERGED -=================== - -Stuff that didn't reach the codebase: -------------------------------------- - -- HEVC DSP and x86 MC SIMD improvements from Libav (see https://ffmpeg.org/pipermail/ffmpeg-devel/2015-December/184777.html) - - 1f821750f hevcdsp: split the qpel functions by width instead of by the subpixel fraction - - 818bfe7f0 hevcdsp: split the epel functions by width - - 688417399 hevcdsp: split the pred functions by width - - a853388d2 hevc: change the stride of the MC buffer to be in bytes instead of elements - - 0cef06df0 checkasm: add HEVC MC tests - - e7078e842 hevcdsp: add x86 SIMD for MC - - 7993ec19a hevc: Add hevc_get_pixel_4/8/12/16/24/32/48/64 -- use av_cpu_max_align() instead of hardcoding alignment requirements (see https://ffmpeg.org/pipermail/ffmpeg-devel/2017-September/215834.html) - - f44ec22e0 lavc: use av_cpu_max_align() instead of hardcoding alignment requirements - - 4de220d2e frame: allow align=0 (meaning automatic) for av_frame_get_buffer() -- Support recovery from an already present HLS playlist (see 16cb06bb30) -- Remove all output devices (see 8e7e042d41, 8d3db95f20, 6ce13070bd, d46cd24986 and https://ffmpeg.org/pipermail/ffmpeg-devel/2017-September/216904.html) -- avcodec/libaomenc: export the Sequence Header OBU as extradata (See a024c3ce9a) - -Collateral damage that needs work locally: ------------------------------------------- - -- Merge proresenc_anatoliy.c and proresenc_kostya.c -- Fix MIPS AC3 downmix - -Extra changes needed to be aligned with Libav: ----------------------------------------------- - -- Switching our examples to the new encode/decode API (see 67d28f4a0f) -- HEVC IDCT bit depth 12-bit support (Libav added 8 and 10 but doesn't have 12) |