decoding). Look at @file{libavcodec/apiexample.c} to see how to use it.
@item libavformat is the library containing the file format handling (mux and
-demux code for several formats). Look at @file{ffplay.c} to use it in a
+demux code for several formats). Look at @file{avplay.c} to use it in a
player. See @file{libavformat/output-example.c} to use it to generate
audio or video streams.
@end itemize
-@section Integrating libavcodec or libavformat in your program
-
-You can integrate all the source code of the libraries to link them
-statically to avoid any version problem. All you need is to provide a
-'config.mak' and a 'config.h' in the parent directory. See the defines
-generated by ./configure to understand what is needed.
-
-You can use libavcodec or libavformat in your commercial program, but
-@emph{any patch you make must be published}. The best way to proceed is
-to send your patches to the FFmpeg mailing list.
+@section Integrating libav in your program
+
+Shared libraries should be used whenever is possible in order to reduce
+the effort distributors have to pour to support programs and to ensure
+only the public api is used.
+
+You can use Libav in your commercial program, but you must abide to the
+license, LGPL or GPL depending on the specific features used, please refer
+to @uref{http://libav.org/legal.html, our legal page} for a quick checklist and to
+the following links for the exact text of each license:
+@uref{http://git.libav.org/?p=libav.git;a=blob;f=COPYING.GPLv2, GPL version 2},
+@uref{http://git.libav.org/?p=libav.git;a=blob;f=COPYING.GPLv3, GPL version 3},
+@uref{http://git.libav.org/?p=libav.git;a=blob;f=COPYING.LGPLv2.1, LGPL version 2.1},
+@uref{http://git.libav.org/?p=libav.git;a=blob;f=COPYING.LGPLv3, LGPL version 3}.
+Any modification to the source code can be suggested for inclusion.
+The best way to proceed is to send your patches to the
+@uref{https://lists.libav.org/mailman/listinfo/libav-devel, libav-devel}
+mailing list.
@anchor{Coding Rules}
@section Coding Rules
-FFmpeg is programmed in the ISO C90 language with a few additional
-features from ISO C99, namely:
+@subsection Code formatting conventions
+The code is written in K&R C style. That means the following:
@itemize @bullet
@item
-the @samp{inline} keyword;
+The control statements are formatted by putting space between the statement
+and parenthesis in the following way:
+@example
+for (i = 0; i < filter->input_count; i++) @{
+@end example
@item
-@samp{//} comments;
+The case statement is always located at the same level as the switch itself:
+@example
+switch (link->init_state) @{
+case AVLINK_INIT:
+ continue;
+case AVLINK_STARTINIT:
+ av_log(filter, AV_LOG_INFO, "circular filter chain detected");
+ return 0;
+@end example
@item
-designated struct initializers (@samp{struct s x = @{ .i = 17 @};})
+Braces in function declarations are written on the new line:
+@example
+const char *avfilter_configuration(void)
+@{
+ return LIBAV_CONFIGURATION;
+@}
+@end example
@item
-compound literals (@samp{x = (struct s) @{ 17, 23 @};})
+Do not check for NULL values by comparison, @samp{if (p)} and
+@samp{if (!p)} are correct; @samp{if (p == NULL)} and @samp{if (p != NULL)}
+are not.
+@item
+In case of a single-statement if, no curly braces are required:
+@example
+if (!pic || !picref)
+ goto fail;
+@end example
+@item
+Do not put spaces immediately inside parentheses. @samp{if (ret)} is
+a valid style; @samp{if ( ret )} is not.
@end itemize
-These features are supported by all compilers we care about, so we will not
-accept patches to remove their use unless they absolutely do not impair
-clarity and performance.
-
-All code must compile with GCC 2.95 and GCC 3.3. Currently, FFmpeg also
-compiles with several other compilers, such as the Compaq ccc compiler
-or Sun Studio 9, and we would like to keep it that way unless it would
-be exceedingly involved. To ensure compatibility, please do not use any
-additional C99 features or GCC extensions. Especially watch out for:
+There are the following guidelines regarding the indentation in files:
@itemize @bullet
@item
-mixing statements and declarations;
-@item
-@samp{long long} (use @samp{int64_t} instead);
+Indent size is 4.
@item
-@samp{__attribute__} not protected by @samp{#ifdef __GNUC__} or similar;
+The TAB character is forbidden outside of Makefiles as is any
+form of trailing whitespace. Commits containing either will be
+rejected by the git repository.
@item
-GCC statement expressions (@samp{(x = (@{ int y = 4; y; @})}).
+You should try to limit your code lines to 80 characters; however, do so if
+and only if this improves readability.
@end itemize
-
-Indent size is 4.
The presentation is one inspired by 'indent -i4 -kr -nut'.
-The TAB character is forbidden outside of Makefiles as is any
-form of trailing whitespace. Commits containing either will be
-rejected by the Subversion repository.
-The main priority in FFmpeg is simplicity and small code size in order to
+The main priority in Libav is simplicity and small code size in order to
minimize the bug count.
-Comments: Use the JavaDoc/Doxygen
-format (see examples below) so that code documentation
+@subsection Comments
+Use the JavaDoc/Doxygen format (see examples below) so that code documentation
can be generated automatically. All nontrivial functions should have a comment
above them explaining what the function does, even if it is just one sentence.
All structures and their member variables should be documented, too.
+
+Avoid Qt-style and similar Doxygen syntax with @code{!} in it, i.e. replace
+@code{//!} with @code{///} and similar. Also @@ syntax should be employed
+for markup commands, i.e. use @code{@@param} and not @code{\param}.
+
@example
/**
- * @@file mpeg.c
+ * @@file
* MPEG codec.
* @@author ...
*/
...
@end example
+@subsection C language features
+
+Libav is programmed in the ISO C90 language with a few additional
+features from ISO C99, namely:
+@itemize @bullet
+@item
+the @samp{inline} keyword;
+@item
+@samp{//} comments;
+@item
+designated struct initializers (@samp{struct s x = @{ .i = 17 @};})
+@item
+compound literals (@samp{x = (struct s) @{ 17, 23 @};})
+@end itemize
+
+These features are supported by all compilers we care about, so we will not
+accept patches to remove their use unless they absolutely do not impair
+clarity and performance.
+
+All code must compile with recent versions of GCC and a number of other
+currently supported compilers. To ensure compatibility, please do not use
+additional C99 features or GCC extensions. Especially watch out for:
+@itemize @bullet
+@item
+mixing statements and declarations;
+@item
+@samp{long long} (use @samp{int64_t} instead);
+@item
+@samp{__attribute__} not protected by @samp{#ifdef __GNUC__} or similar;
+@item
+GCC statement expressions (@samp{(x = (@{ int y = 4; y; @})}).
+@end itemize
+
+@subsection Naming conventions
+All names are using underscores (_), not CamelCase. For example,
+@samp{avfilter_get_video_buffer} is a valid function name and
+@samp{AVFilterGetVideo} is not. The only exception from this are structure
+names; they should always be in the CamelCase
+
+There are following conventions for naming variables and functions:
+@itemize @bullet
+@item
+For local variables no prefix is required.
+@item
+For variables and functions declared as @code{static} no prefixes are required.
+@item
+For variables and functions used internally by the library, @code{ff_} prefix
+should be used.
+For example, @samp{ff_w64_demuxer}.
+@item
+For variables and functions used internally across multiple libraries, use
+@code{avpriv_}. For example, @samp{avpriv_aac_parse_header}.
+@item
+For exported names, each library has its own prefixes. Just check the existing
+code and name accordingly.
+@end itemize
+
+@subsection Miscellanous conventions
+@itemize @bullet
+@item
fprintf and printf are forbidden in libavformat and libavcodec,
please use av_log() instead.
-
+@item
Casts should be used only when necessary. Unneeded parentheses
should also be avoided if they don't make the code easier to understand.
+@end itemize
+
+@subsection Editor configuration
+In order to configure Vim to follow Libav formatting conventions, paste
+the following snippet into your @file{.vimrc}:
+@example
+" indentation rules for libav: 4 spaces, no tabs
+set expandtab
+set shiftwidth=4
+set softtabstop=4
+set cindent
+set cinoptions=(0
+" allow tabs in Makefiles
+autocmd FileType make set noexpandtab shiftwidth=8 softtabstop=8
+" Trailing whitespace and tabs are forbidden, so highlight them.
+highlight ForbiddenWhitespace ctermbg=red guibg=red
+match ForbiddenWhitespace /\s\+$\|\t/
+" Do not highlight spaces at the end of line while typing on that line.
+autocmd InsertEnter * match ForbiddenWhitespace /\t\|\s\+\%#\@@<!$/
+@end example
+
+For Emacs, add these roughly equivalent lines to your @file{.emacs.d/init.el}:
+@example
+(c-add-style "libav"
+ '("k&r"
+ (c-basic-offset . 4)
+ (indent-tabs-mode nil)
+ (show-trailing-whitespace t)
+ (c-offsets-alist
+ (statement-cont . (c-lineup-assignments +)))
+ )
+ )
+(setq c-default-style "libav")
+@end example
@section Development Policy
an "or any later version" clause is also acceptable, but LGPL is
preferred.
@item
- You must not commit code which breaks FFmpeg! (Meaning unfinished but
- enabled code which breaks compilation or compiles but does not work or
- breaks the regression tests)
- You can commit unfinished stuff (for testing etc), but it must be disabled
- (#ifdef etc) by default so it does not interfere with other developers'
- work.
+ All the patches MUST be reviewed in the mailing list before they are
+ committed.
+@item
+ The Libav coding style should remain consistent. Changes to
+ conform will be suggested during the review or implemented on commit.
+@item
+ Patches should be generated using @code{git format-patch} or directly sent
+ using @code{git send-email}.
+ Please make sure you give the proper credit by setting the correct author
+ in the commit.
+@item
+ The commit message should have a short first line in the form of
+ @samp{topic: short description} as header, separated by a newline
+ from the body consting in few lines explaining the reason of the patch.
+ Referring to the issue on the bug tracker does not exempt to report an
+ excerpt of the bug.
+@item
+ Work in progress patches should be sent to the mailing list with the [WIP]
+ or the [RFC] tag.
@item
- You do not have to over-test things. If it works for you, and you think it
- should work for others, then commit. If your code has problems
- (portability, triggers compiler bugs, unusual environment etc) they will be
- reported and eventually fixed.
+ Branches in public personal repos are advised as way to
+ work on issues collaboratively.
+@item
+ You do not have to over-test things. If it works for you and you think it
+ should work for others, send it to the mailing list for review.
+ If you have doubt about portability please state it in the submission so
+ people with specific hardware could test it.
@item
Do not commit unrelated changes together, split them into self-contained
pieces. Also do not forget that if part B depends on part A, but A does not
Keeping changes well split into self-contained parts makes reviewing and
understanding them on the commit log mailing list easier. This also helps
in case of debugging later on.
- Also if you have doubts about splitting or not splitting, do not hesitate to
- ask/discuss it on the developer mailing list.
-@item
- Do not change behavior of the programs (renaming options etc) or public
- API or ABI without first discussing it on the ffmpeg-devel mailing list.
- Do not remove functionality from the code. Just improve!
-
- Note: Redundant code can be removed.
-@item
- Do not commit changes to the build system (Makefiles, configure script)
- which change behavior, defaults etc, without asking first. The same
- applies to compiler warning fixes, trivial looking fixes and to code
- maintained by other developers. We usually have a reason for doing things
- the way we do. Send your changes as patches to the ffmpeg-devel mailing
- list, and if the code maintainers say OK, you may commit. This does not
- apply to files you wrote and/or maintain.
-@item
- We refuse source indentation and other cosmetic changes if they are mixed
- with functional changes, such commits will be rejected and removed. Every
- developer has his own indentation style, you should not change it. Of course
- if you (re)write something, you can use your own style, even though we would
- prefer if the indentation throughout FFmpeg was consistent (Many projects
- force a given indentation style - we do not.). If you really need to make
- indentation changes (try to avoid this), separate them strictly from real
- changes.
-
- NOTE: If you had to put if()@{ .. @} over a large (> 5 lines) chunk of code,
- then either do NOT change the indentation of the inner part within (do not
- move it to the right)! or do so in a separate commit
-@item
- Always fill out the commit log message. Describe in a few lines what you
- changed and why. You can refer to mailing list postings if you fix a
- particular bug. Comments such as "fixed!" or "Changed it." are unacceptable.
-@item
- If you apply a patch by someone else, include the name and email address in
- the log message. Since the ffmpeg-cvslog mailing list is publicly
- archived you should add some SPAM protection to the email address. Send an
- answer to ffmpeg-devel (or wherever you got the patch from) saying that
- you applied the patch.
+@item
+ Patches that change behavior of the programs (renaming options etc) or
+ public API or ABI should be discussed in depth and possible few days should
+ pass between discussion and commit.
+ Changes to the build system (Makefiles, configure script) which alter
+ the expected behavior should be considered in the same regard.
@item
When applying patches that have been discussed (at length) on the mailing
list, reference the thread in the log message.
@item
- Do NOT commit to code actively maintained by others without permission.
- Send a patch to ffmpeg-devel instead. If no one answers within a reasonable
- timeframe (12h for build failures and security fixes, 3 days small changes,
- 1 week for big patches) then commit your patch if you think it is OK.
- Also note, the maintainer can simply ask for more time to review!
-@item
- Subscribe to the ffmpeg-cvslog mailing list. The diffs of all commits
- are sent there and reviewed by all the other developers. Bugs and possible
- improvements or general questions regarding commits are discussed there. We
- expect you to react if problems with your code are uncovered.
+ Subscribe to the
+ @uref{https://lists.libav.org/mailman/listinfo/libav-devel, libav-devel} and
+ @uref{https://lists.libav.org/mailman/listinfo/libav-commits, libav-commits}
+ mailing lists.
+ Bugs and possible improvements or general questions regarding commits
+ are discussed on libav-devel. We expect you to react if problems with
+ your code are uncovered.
@item
Update the documentation if you change behavior or add features. If you are
- unsure how best to do this, send a patch to ffmpeg-devel, the documentation
- maintainer(s) will review and commit your stuff.
+ unsure how best to do this, send an [RFC] patch to libav-devel.
@item
- Try to keep important discussions and requests (also) on the public
- developer mailing list, so that all developers can benefit from them.
+ All discussions and decisions should be reported on the public developer
+ mailing list, so that there is a reference to them.
+ Other media (e.g. IRC) should be used for coordination and immediate
+ collaboration.
@item
Never write to unallocated memory, never write over the end of arrays,
always check values read from some untrusted source before using them
- as array index or other risky things.
+ as array index or other risky things. Always use valgrind to doublecheck.
@item
Remember to check if you need to bump versions for the specific libav
parts (libavutil, libavcodec, libavformat) you are changing. You need
Incrementing the third component means a noteworthy binary compatible
change (e.g. encoder bug fix that matters for the decoder).
@item
- Compiler warnings indicate potential bugs or code with bad style. If a type of
- warning always points to correct and clean code, that warning should
- be disabled, not the code changed.
- Thus the remaining warnings can either be bugs or correct code.
+ Compiler warnings indicate potential bugs or code with bad style.
If it is a bug, the bug has to be fixed. If it is not, the code should
be changed to not generate a warning unless that causes a slowdown
or obfuscates the code.
+ If a type of warning leads to too many false positives, that warning
+ should be disabled, not the code changed.
@item
If you add a new file, give it a proper license header. Do not copy and
paste it from a random place, use an existing file as template.
We think our rules are not too hard. If you have comments, contact us.
-Note, these rules are mostly borrowed from the MPlayer project.
+Note, some rules were borrowed from the MPlayer project.
@section Submitting patches
-First, (@pxref{Coding Rules}) above if you did not yet.
+First, read the @ref{Coding Rules} above if you did not yet, in particular
+the rules regarding patch submission.
-When you submit your patch, try to send a unified diff (diff '-up'
-option). We cannot read other diffs :-)
-
-Also please do not submit a patch which contains several unrelated changes.
+As stated already, please do not submit a patch which contains several
+unrelated changes.
Split it into separate, self-contained pieces. This does not mean splitting
file by file. Instead, make the patch as small as possible while still
keeping it as a logical unit that contains an individual change, even
if it spans multiple files. This makes reviewing your patches much easier
for us and greatly increases your chances of getting your patch applied.
-Use the patcheck tool of FFmpeg to check your patch.
+Use the patcheck tool of Libav to check your patch.
The tool is located in the tools directory.
-Run the regression tests before submitting a patch so that you can
-verify that there are no big problems.
+Run the @ref{Regression Tests} before submitting a patch in order to verify
+it does not cause unexpected problems.
Patches should be posted as base64 encoded attachments (or any other
encoding which ensures that the patch will not be trashed during
-transmission) to the ffmpeg-devel mailing list, see
-@url{http://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel}
+transmission) to the
+@uref{https://lists.libav.org/mailman/listinfo/libav-devel, libav-devel}
+mailing list.
It also helps quite a bit if you tell us what the patch does (for example
'replaces lrint by lrintf'), and why (for example '*BSD isn't C99 compliant
-and has no lrint()')
+and has no lrint()'). This kind of explanation should be the body of the
+commit message.
Also please if you send several patches, send each patch as a separate mail,
do not attach several unrelated patches to the same mail.
+Use @code{git send-email} when possible since it will properly send patches
+without requiring extra care.
+
Your patch will be reviewed on the mailing list. You will likely be asked
to make some changes and are expected to send in an improved version that
incorporates the requests from the review. This process may go through
-several iterations. Once your patch is deemed good enough, some developer
-will pick it up and commit it to the official FFmpeg tree.
+several iterations. Once your patch is deemed good enough, it will be
+committed to the official Libav tree.
Give us a few days to react. But if some time passes without reaction,
send a reminder by email. Your patch should eventually be dealt with.
AVInputFormat/AVOutputFormat struct?
@item
Did you bump the minor version number (and reset the micro version
- number) in @file{avcodec.h} or @file{avformat.h}?
+ number) in @file{libavcodec/version.h} or @file{libavformat/version.h}?
@item
Did you register it in @file{allcodecs.c} or @file{allformats.c}?
@item
even if it is only a decoder?
@item
Did you add a rule to compile the appropriate files in the Makefile?
- Remember to do this even if you're just adding a format to a file that is
- already being compiled by some other rule, like a raw demuxer.
+ Remember to do this even if you are just adding a format to a file that
+ is already being compiled by some other rule, like a raw demuxer.
@item
Did you add an entry to the table of supported formats or codecs in
@file{doc/general.texi}?
If it depends on a parser or a library, did you add that dependency in
configure?
@item
- Did you "svn add" the appropriate files before commiting?
+ Did you @code{git add} the appropriate files before committing?
+@item
+ Did you make sure it compiles standalone, i.e. with
+ @code{configure --disable-everything --enable-decoder=foo}
+ (or @code{--enable-demuxer} or whatever your component is)?
@end enumerate
+
@section patch submission checklist
@enumerate
@item
- Do the regression tests pass with the patch applied?
-@item
- Does @code{make checkheaders} pass with the patch applied?
-@item
- Is the patch a unified diff?
+ Does @code{make check} pass with the patch applied?
@item
- Is the patch against latest FFmpeg SVN?
+ Is the patch against latest Libav git master branch?
@item
- Are you subscribed to ffmpeg-dev?
- (the list is subscribers only due to spam)
+ Are you subscribed to the
+ @uref{https://lists.libav.org/mailman/listinfo/libav-devel, libav-devel}
+ mailing list? (Only list subscribers are allowed to post.)
@item
Have you checked that the changes are minimal, so that the same cannot be
achieved with a smaller patch and/or simpler final code?
Did you test your decoder or demuxer against damaged data? If no, see
tools/trasher and the noise bitstream filter. Your decoder or demuxer
should not crash or end in a (near) infinite loop when fed damaged data.
-@item
- Is the patch created from the root of the source tree, so it can be
- applied with @code{patch -p0}?
@item
Does the patch not mix functional and cosmetic changes?
@item
If the patch fixes a bug, did you provide enough information, including
a sample, so the bug can be reproduced and the fix can be verified?
Note please do not attach samples >100k to mails but rather provide a
- URL, you can upload to ftp://upload.ffmpeg.org
+ URL, you can upload to ftp://upload.libav.org
@item
Did you provide a verbose summary about what the patch does change?
@item
patch easily?
@item
If you added a new file, did you insert a license header? It should be
- taken from FFmpeg, not randomly copied and pasted from somewhere else.
+ taken from Libav, not randomly copied and pasted from somewhere else.
@item
You should maintain alphabetical order in alphabetically ordered lists as
long as doing so does not break API/ABI compatibility.
Lines with similar content should be aligned vertically when doing so
improves readability.
@item
- Did you provide a suggestion for a clear commit log message?
+ Make sure you check the return values of function and return appropriate
+ error codes. Especially memory allocation functions like @code{malloc()}
+ are notoriously left unchecked, which is a serious problem.
@end enumerate
@section Patch review process
-All patches posted to ffmpeg-devel will be reviewed, unless they contain a
-clear note that the patch is not for SVN.
+All patches posted to the
+@uref{https://lists.libav.org/mailman/listinfo/libav-devel, libav-devel}
+mailing list will be reviewed, unless they contain a
+clear note that the patch is not for the git master branch.
Reviews and comments will be posted as replies to the patch on the
mailing list. The patch submitter then has to take care of every comment,
that can be by resubmitting a changed patch or by discussion. Resubmitted
We will review all submitted patches, but sometimes we are quite busy so
especially for large patches this can take several weeks.
-When resubmitting patches, please do not make any significant changes
-not related to the comments received during review. Such patches will
-be rejected. Instead, submit significant changes or new features as
-separate patches.
-
-@section Regression tests
-
-Before submitting a patch (or committing to the repository), you should at least
-test that you did not break anything.
+When resubmitting patches, if their size grew or during the review different
+issues arisen please split the patch so each issue has a specific patch.
-The regression tests build a synthetic video stream and a synthetic
-audio stream. These are then encoded and decoded with all codecs or
-formats. The CRC (or MD5) of each generated file is recorded in a
-result file. A 'diff' is launched to compare the reference results and
-the result file. The output is checked immediately after each test
-has run.
+@anchor{Regression Tests}
+@section Regression Tests
-The regression tests then go on to test the FFserver code with a
-limited set of streams. It is important that this step runs correctly
-as well.
+Before submitting a patch (or committing to the repository), you should at
+least make sure that it does not break anything.
-Run 'make test' to test all the codecs and formats. Commands like
-'make regtest-mpeg2' can be used to run a single test. By default,
-make will abort if any test fails. To run all tests regardless,
-use make -k. To get a more verbose output, use 'make V=1 test' or
-'make V=2 test'.
+If the code changed has already a test present in FATE you should run it,
+otherwise it is advised to add it.
-Run 'make fulltest' to test all the codecs, formats and FFserver.
+Improvements to codec or demuxer might change the FATE results. Make sure
+to commit the update reference with the change and to explain in the comment
+why the expected result changed.
-[Of course, some patches may change the results of the regression tests. In
-this case, the reference results of the regression tests shall be modified
-accordingly].
+Please refer to @url{fate.html}.
@bye
projects / ffmpeg / blobdiff