Welcome to the WebM VP8/VP9 Codec SDK!
COMPILING THE APPLICATIONS/LIBRARIES:
The build system used is similar to autotools. Building generally consists of
"configuring" with your desired build options, then using GNU make to build
the application.
1. Prerequisites
* All x86 targets require the Yasm[1] assembler be installed[2].
* All Windows builds require that Cygwin[3] or MSYS2[4] be installed.
* Building the documentation requires Doxygen[5]. If you do not
have this package, the install-docs option will be disabled.
* Downloading the data for the unit tests requires curl[6] and sha1sum.
sha1sum is provided via the GNU coreutils, installed by default on
many *nix platforms, as well as MinGW and Cygwin. If coreutils is not
available, a compatible version of sha1sum can be built from
source[7]. These requirements are optional if not running the unit
tests.
[1]: http://www.tortall.net/projects/yasm
[2]: For Visual Studio the base yasm binary (not vsyasm) should be in the
PATH for Visual Studio. For VS2017 it is sufficient to rename
yasm-<version>-<arch>.exe to yasm.exe and place it in:
Program Files (x86)/Microsoft Visual Studio/2017/<level>/Common7/Tools/
[3]: http://www.cygwin.com
[4]: http://www.msys2.org/
[5]: http://www.doxygen.org
[6]: http://curl.haxx.se
[7]: http://www.microbrew.org/tools/md5sha1sum/
2. Out-of-tree builds
Out of tree builds are a supported method of building the application. For
an out of tree build, the source tree is kept separate from the object
files produced during compilation. For instance:
$ mkdir build
$ cd build
$ ../libvpx/configure <options>
$ make
3. Configuration options
The 'configure' script supports a number of options. The --help option can be
used to get a list of supported options:
$ ../libvpx/configure --help
4. Compiler analyzers
Compilers have added sanitizers which instrument binaries with information
about address calculation, memory usage, threading, undefined behavior, and
other common errors. To simplify building libvpx with some of these features
use tools/set_analyzer_env.sh before running configure. It will set the
compiler and necessary flags for building as well as environment variables
read by the analyzer when testing the binaries.
$ source ../libvpx/tools/set_analyzer_env.sh address
5. Cross development
For cross development, the most notable option is the --target option. The
most up-to-date list of supported targets can be found at the bottom of the
--help output of the configure script. As of this writing, the list of
available targets is:
arm64-android-gcc
arm64-darwin-gcc
arm64-darwin20-gcc
arm64-darwin21-gcc
arm64-darwin22-gcc
arm64-darwin23-gcc
arm64-linux-gcc
arm64-win64-gcc
arm64-win64-vs15
arm64-win64-vs16
arm64-win64-vs16-clangcl
arm64-win64-vs17
arm64-win64-vs17-clangcl
armv7-android-gcc
armv7-darwin-gcc
armv7-linux-rvct
armv7-linux-gcc
armv7-none-rvct
armv7-win32-gcc
armv7-win32-vs14
armv7-win32-vs15
armv7-win32-vs16
armv7-win32-vs17
armv7s-darwin-gcc
armv8-linux-gcc
loongarch32-linux-gcc
loongarch64-linux-gcc
mips32-linux-gcc
mips64-linux-gcc
ppc64le-linux-gcc
sparc-solaris-gcc
x86-android-gcc
x86-darwin8-gcc
x86-darwin8-icc
x86-darwin9-gcc
x86-darwin9-icc
x86-darwin10-gcc
x86-darwin11-gcc
x86-darwin12-gcc
x86-darwin13-gcc
x86-darwin14-gcc
x86-darwin15-gcc
x86-darwin16-gcc
x86-darwin17-gcc
x86-iphonesimulator-gcc
x86-linux-gcc
x86-linux-icc
x86-os2-gcc
x86-solaris-gcc
x86-win32-gcc
x86-win32-vs14
x86-win32-vs15
x86-win32-vs16
x86-win32-vs17
x86_64-android-gcc
x86_64-darwin9-gcc
x86_64-darwin10-gcc
x86_64-darwin11-gcc
x86_64-darwin12-gcc
x86_64-darwin13-gcc
x86_64-darwin14-gcc
x86_64-darwin15-gcc
x86_64-darwin16-gcc
x86_64-darwin17-gcc
x86_64-darwin18-gcc
x86_64-darwin19-gcc
x86_64-darwin20-gcc
x86_64-darwin21-gcc
x86_64-darwin22-gcc
x86_64-darwin23-gcc
x86_64-iphonesimulator-gcc
x86_64-linux-gcc
x86_64-linux-icc
x86_64-solaris-gcc
x86_64-win64-gcc
x86_64-win64-vs14
x86_64-win64-vs15
x86_64-win64-vs16
x86_64-win64-vs17
generic-gnu
The generic-gnu target, in conjunction with the CROSS environment variable,
can be used to cross compile architectures that aren't explicitly listed, if
the toolchain is a cross GNU (gcc/binutils) toolchain. Other POSIX toolchains
will likely work as well. For instance, to build using the mipsel-linux-uclibc
toolchain, the following command could be used (note, POSIX SH syntax, adapt
to your shell as necessary):
$ CROSS=mipsel-linux-uclibc- ../libvpx/configure
In addition, the executables to be invoked can be overridden by specifying the
environment variables: AR, AS, CC, CXX, LD, STRIP. Additional flags can be
passed to these executables with ASFLAGS, CFLAGS, CXXFLAGS, and LDFLAGS.
6. Configuration errors
If the configuration step fails, the first step is to look in the error log.
This defaults to config.log. This should give a good indication of what went
wrong. If not, contact us for support.
VP8/VP9 TEST VECTORS:
The test vectors can be downloaded and verified using the build system after
running configure. To specify an alternate directory the
LIBVPX_TEST_DATA_PATH environment variable can be used.
$ ./configure --enable-unit-tests
$ LIBVPX_TEST_DATA_PATH=../libvpx-test-data make testdata
CODE STYLE:
The coding style used by this project is enforced with clang-format using the
configuration contained in the .clang-format file in the root of the
repository.
Before pushing changes for review you can format your code with:
# Apply clang-format to modified .c, .h and .cc files
$ clang-format -i --style=file \
$(git diff --name-only --diff-filter=ACMR '*.[hc]' '*.cc')
Check the .clang-format file for the version used to generate it if there is
any difference between your local formatting and the review system.
See also: http://clang.llvm.org/docs/ClangFormat.html
PROFILE GUIDED OPTIMIZATION (PGO)
Profile Guided Optimization can be enabled for Clang builds using the
commands:
$ export CC=clang
$ export CXX=clang++
$ ../libvpx/configure --enable-profile
$ make
Generate one or multiple PGO profile files by running vpxdec or vpxenc. For
example:
$ ./vpxdec ../vpx/out_ful/vp90-2-sintel_1280x546_tile_1x4_1257kbps.webm \
-o - > /dev/null
To convert and merge the raw profile files, use the llvm-profdata tool:
$ llvm-profdata merge -o perf.profdata default_8382761441159425451_0.profraw
Then, rebuild the project with the new profile file:
$ make clean
$ ../libvpx/configure --use-profile=perf.profdata
$ make
Note: Always use the llvm-profdata from the toolchain that is used for
compiling the PGO-enabled binary.
To observe the improvements from a PGO-enabled build, enable and compare the
list of failed optimizations by using the -Rpass-missed compiler flag. For
example, to list the failed loop vectorizations:
$ ../libvpx/configure --use-profile=perf.profdata \
--extra-cflags=-Rpass-missed=loop-vectorize
For guidance on utilizing PGO files to identify potential optimization
opportunities, see: tools/README.pgo.md
SUPPORT
This library is an open source project supported by its community. Please
email webm-discuss@webmproject.org for help.
BUG REPORTS
Bug reports can be filed in the libvpx issue tracker:
https://issues.webmproject.org/.