ffmpeg delete source folder and use deps to pull in all content....

third_party/ffmpeg/README.chromium

Index: third_party/ffmpeg/README.chromium
===================================================================
--- third_party/ffmpeg/README.chromium	(revision 48686)
+++ third_party/ffmpeg/README.chromium	(working copy)
@@ -1,210 +0,0 @@
-Name: ffmpeg
-URL: http://ffmpeg.org/
-License File: source/patched-ffmpeg-mt/LICENSE
-
-This file describes how to produce the FFmpeg include directory, and how to
-create the ffmpeg.gyp file and related configurations.
-
--- FFmpeg headers in the 'include' directory.
-
-The include directory contains FFmpeg's public header files from the output of
-a "make install" command.  The header files are from Chromium's copy of FFmpeg.
-
-Steps to reproduce:
-  1) If on Windows, refer to our MinGW/MSYS environment setup:
-       http://src.chromium.org/viewvc/chrome/trunk/deps/third_party/mingw/
-  2) Grab Chromium's copy of FFmpeg:
-       http://src.chromium.org/viewvc/chrome/trunk/deps/third_party/ffmpeg/
-  3) Follow the instructions to build and install.
-  4) Go to your install location and copy the following into the Chromium tree:
-       /path/to/install/include/libavcodec
-       /path/to/install/include/libavformat
-       /path/to/install/include/libavutil
-
-The project contains some hand-written DEF files used to generate import
-libraries to permit dynamically loading FFmpeg.  On Windows, the libraries are
-linked in using /DELAYLOAD to avoid having the DLLs present at run-time.  On
-POSIX systems, dlopen() is used to achieve a similar effect.
-
-We don't use the import libraries generated from building FFmpeg because they
-export every method by ordinal, which makes binary compatibility with different
-builds of FFmpeg difficult if not impossible.  Furthermore, it is much easier
-to update a DEF file instead of rebuilding FFmpeg to generate new import
-libraries.
-
-
--- Recreating the ffmpeg.gyp file and populating the config directory.
-The ffmpeg.gyp file is meant to be used in place of FFmpeg's
-
-   ./configure && make
-
-steps.  The file was created by inspecting the build log from above.
-The FFmpeg build is relatively straightforward.  All files are built with
-the same CFLAGS.  The config.h and version.h files are the only files generated
-by ./configure that are included elsewhere.  They require a small bit of
-post-processing.
-
-Other than the configure step, FFmpeg just compiles its .c files, assembles a
-few more using yasm, and that's it.  Exact instructions for reproducing
-ffmpeg.gyp are in the "Detailed Directions" section.
-
-Here is a list of gotchas that have shown up.
-  1) FFmpeg requires special configure (--disable-optimizations) in order
-     to be built with -O0 successfully due to some of the hand-written
-     assembler using ebp.  -O0 implies -fno-omit-frame-pointer which breaks
-     this. This will produce compiler errors like:
-       libavcodec/cabac.h:527: error: can't find a register in class
-       'GENERAL_REGS' while reloading 'asm'
-       cabac.h:527: error: 'asm' operand has impossible constraints
-
-  2) On ia32, FFmpeg cannot be built with -fPIC, again due to assembly
-     issues. There may be a workaround, but the performance impact is
-     unknown.
-
-  3) Sometimes, with -O0, invalid code will be exposed because dead-branch
-     pruning is disabled in gcc.  This can manifest itself as strange link
-     issues or compile issues.  Be careful to read all warnings in this case.
-
-  4) Since config.h is generated via ./configure, the generated file will
-     be sensitive to the configuration of the machine it was produced on.
-     In particular, yasm does not seem to always be detected if
-     cross-compiling for 32-bit on a 64-bit machine. Since yasm is built in
-     tree, make sure to force things with --enable-yasm.
-
-  5) Similar to issue #4, ./configure may detect the presence of SDL and
-     adjust config.h accordingly. This is harmless because all the SDL
-     related code has been disabled in our configuration.
-
-  6) On ia32, we want to be able to compile with WITHOUT -fomit-frame-pointer
-     (so breakpad can function).  To do this, we need to disable the use of the
-     EBP register, otherwise some of FFmpeg's inline assembly will cause
-     compilation errors similar to gotcha #1.  For more details, see the file
-     comment in the munge_config_optimizations.sh. This script will fix up
-     the generated config.h to be building without -fomit-frame-pointer.
-
-
-Detailed Directions:
-  1) Get a clean version of the patched tree.  This should be here:
-
-      src/third_party/ffmpeg/source/patched-ffmpeg-mt
-
-  2) Run the configure in a directory out of the tree with the arguments you
-     want.  To see what was used before, find the config.h for the platform
-     of interest in:
-
-       src/third_party/ffmpeg/source/config/[branding]/[platform]/[variant]
-
-     The value of the FFMPEG_CONFIGURATION macro should have the configure
-     commandline that generated the file.
-
-     Note that if you are trying to build a 32-bit FFmpeg for linux on a
-     64-bit box, the extra flags you want to pass to ./configure are
-
-       --arch=i686 --extra-cflags=-m32 --extra-ldflags=-m32
-
-     Also, as noted in gotcha #4, explicitly setting --enable-yasm is
-     a good idea.
-
-  3) Copy the newly generated config.h and version.h into the correct platform
-     location:
-
-       src/third_party/ffmpeg/source/config/[branding]/[platform]/[variant]
-
-     Make sure to double-check that config.h and version.h are the only files
-     of interest.  By that, I mean check that the other generated files are
-     makefiles, documentation, .pc files, or something else that is not
-     relevant to our build.
-
-     TODO(ajwong): Check if we can modify version.h to tag our builds.
-
- 3b) If on ia32, handle gotcha #6 by munging the geneated config.h file to
-     disable use of EBP.  Call the munge_config_optimizations.sh script on
-     the config.h for each ia32 variant.
-
-     ** This script is not idempotent. Don't run it twice **
-
-     Remember, this is only necessary for ia32 config.h files.  Running this
-     on config.h files for other platforms (in particular, for x64) will
-     likely result in unecessarily slow code, or compile failures.
-
-  4) Next, capture all the output from a build of libavcodec.so and
-     libavformat.so.  We will use the build log as a reference for making
-     the ffmpeg.gyp file.
-
-       make libavcodec/libavcodec.so libavformat/libavformat.so \
-          > ffmpeg_build_log 2> ffmpeg_build_err
-
-     For Mac, replace the ".so" in the files above with ".dylib".
-
-  5) Check ffmpeg_build_err to see if there are any significant
-     anomalies.  FFmpeg source generates a lot of compiler warnings; it
-     is safe to ignore those.
-
-  6) Examine all non-gcc commands to see if we're missing anything
-     interesting:
-
-       grep -v '^gcc' ffmpeg_build_log
-
-     There should be yasm commands for assembling two yasm files, but nothing
-     else.  Include those yasm files in the sources list for gyp.  That means
-
-       grep -v '^gcc\|^yasm'
-
-     should generate nothing beyond "cd" and "ln" commands.
-
-  7) Verify that the all the gcc commands have the same compiler flags.
-     Do that with the following "one-liner":
-
-       grep - '^gcc' ffmpeg_build_log |
-       grep -v ' -MM ' |
-       grep -v ' -shared ' |
-       sed -e 's/ -o .*$//' |
-       sort | uniq -c
-
-     This should find all gcc commands, exclude the dependency generation
-     lines, the link lines, and strip the output/input file names leaving
-     just the compiler flags + invocation.  You should only see one "line"
-     of output.  If there is more than one, figure out if the differences
-     in compiler flags are significant, and then use your best judgment.
-
-     Look at gotcha #2 in for notes about the -fPIC flag in particular.
-
-  8) Examine the output from step 7 and update the compiler flags in
-     ffmpeg.gyp. For easier cut/paste, append the following to the previous
-     command line to isolate each flag on its own line and add
-     single-quotes:
-
-       tr -s ' ' | tr ' ' '\n' | sed -e "s/\(.*\)/'\1',/" | sort -u
-
-  9) Next, examine the link flags to see if anything interesting appears.
-
-        grep ' -shared ' ffmpeg_build_log  |
-        tr ' ' '\n' |
-        grep -Ev '^[^-].*' |
-        grep -v rpath |
-        grep -Ev '^-L' |
-        sort -u
-
-     This should find all link lines, move each flag to its own line,
-     remove any argument that isn't a flag, remove all the rpaths (not
-     useful for us anyways), and remove all the -L lines (also not useful
-     for us).
-
-     The most interesting will likely be the -Wl,.* lines. Update the
-     ldflags section in ffmpeg.gyp accordingly.
-
- 10) Lastly, Find all the build .c files and update the sources line (this is
-     very similar to step 7):
-
-       grep -E '^gcc' ffmpeg_build_log |
-       grep -v ' -MM ' |
-       grep -v ' -shared ' |
-       sed -e "s|.* -o .* \(.*\)$|'source/patched-ffmpeg-mt/\1',|" |
-       sort
-
- 11) Attempt to build. :)
-
-*12) Update the the sources! clause to exclude files that should only be built
-     for Chromium.  For this, you basically need to do the steps above once
-     with the configure options for Chrome, then once with the options for
-     Chromium and diff the list of .c and .asm source files.