| \input texinfo @c -*- texinfo -*- |
| @documentencoding UTF-8 |
| |
| @settitle Developer Documentation |
| @titlepage |
| @center @titlefont{Developer Documentation} |
| @end titlepage |
| |
| @top |
| |
| @contents |
| |
| @chapter Notes for external developers |
| |
| This document is mostly useful for internal FFmpeg developers. |
| External developers who need to use the API in their application should |
| refer to the API doxygen documentation in the public headers, and |
| check the examples in @file{doc/examples} and in the source code to |
| see how the public API is employed. |
| |
| You can use the FFmpeg libraries in your commercial program, but you |
| are encouraged to @emph{publish any patch you make}. In this case the |
| best way to proceed is to send your patches to the ffmpeg-devel |
| mailing list following the guidelines illustrated in the remainder of |
| this document. |
| |
| For more detailed legal information about the use of FFmpeg in |
| external programs read the @file{LICENSE} file in the source tree and |
| consult @url{https://ffmpeg.org/legal.html}. |
| |
| @chapter Contributing |
| |
| There are 2 ways by which code gets into FFmpeg: |
| @itemize @bullet |
| @item Submitting patches to the ffmpeg-devel mailing list. |
| See @ref{Submitting patches} for details. |
| @item Directly committing changes to the main tree. |
| @end itemize |
| |
| Whichever way, changes should be reviewed by the maintainer of the code |
| before they are committed. And they should follow the @ref{Coding Rules}. |
| The developer making the commit and the author are responsible for their changes |
| and should try to fix issues their commit causes. |
| |
| @anchor{Coding Rules} |
| @chapter Coding Rules |
| |
| @section Code formatting conventions |
| |
| There are the following guidelines regarding the indentation in files: |
| |
| @itemize @bullet |
| @item |
| Indent size is 4. |
| |
| @item |
| 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 |
| You should try to limit your code lines to 80 characters; however, do so if |
| and only if this improves readability. |
| |
| @item |
| K&R coding style is used. |
| @end itemize |
| The presentation is one inspired by 'indent -i4 -kr -nut'. |
| |
| The main priority in FFmpeg is simplicity and small code size in order to |
| minimize the bug count. |
| |
| @section 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 codec. |
| * @@author ... |
| */ |
| |
| /** |
| * Summary sentence. |
| * more text ... |
| * ... |
| */ |
| typedef struct Foobar @{ |
| int var1; /**< var1 description */ |
| int var2; ///< var2 description |
| /** var3 description */ |
| int var3; |
| @} Foobar; |
| |
| /** |
| * Summary sentence. |
| * more text ... |
| * ... |
| * @@param my_parameter description of my_parameter |
| * @@return return value description |
| */ |
| int myfunc(int my_parameter) |
| ... |
| @end example |
| |
| @section C language features |
| |
| FFmpeg 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 @};}). |
| |
| @item |
| for loops with variable definition (@samp{for (int i = 0; i < 8; i++)}); |
| |
| @item |
| Variadic macros (@samp{#define ARRAY(nb, ...) (int[nb + 1])@{ nb, __VA_ARGS__ @}}); |
| |
| @item |
| Implementation defined behavior for signed integers is assumed to match the |
| expected behavior for two's complement. Non representable values in integer |
| casts are binary truncated. Shift right of signed values uses sign extension. |
| @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 |
| |
| @section Naming conventions |
| All names should be composed with underscores (_), not CamelCase. For example, |
| @samp{avfilter_get_video_buffer} is an acceptable function name and |
| @samp{AVFilterGetVideo} is not. The exception from this are type names, like |
| for example structs and enums; they should always be in CamelCase. |
| |
| There are the following conventions for naming variables and functions: |
| |
| @itemize @bullet |
| @item |
| For local variables no prefix is required. |
| |
| @item |
| For file-scope variables and functions declared as @code{static}, no prefix |
| is required. |
| |
| @item |
| For variables and functions visible outside of file scope, but only used |
| internally by a library, an @code{ff_} prefix should be used, |
| e.g. @samp{ff_w64_demuxer}. |
| |
| @item |
| For variables and functions visible outside of file scope, used internally |
| across multiple libraries, use @code{avpriv_} as prefix, for example, |
| @samp{avpriv_report_missing_feature}. |
| |
| @item |
| Each library has its own prefix for public symbols, in addition to the |
| commonly used @code{av_} (@code{avformat_} for libavformat, |
| @code{avcodec_} for libavcodec, @code{swr_} for libswresample, etc). |
| Check the existing code and choose names accordingly. |
| Note that some symbols without these prefixes are also exported for |
| retro-compatibility reasons. These exceptions are declared in the |
| @code{lib<name>/lib<name>.v} files. |
| @end itemize |
| |
| Furthermore, name space reserved for the system should not be invaded. |
| Identifiers ending in @code{_t} are reserved by |
| @url{http://pubs.opengroup.org/onlinepubs/007904975/functions/xsh_chap02_02.html#tag_02_02_02, POSIX}. |
| Also avoid names starting with @code{__} or @code{_} followed by an uppercase |
| letter as they are reserved by the C standard. Names starting with @code{_} |
| are reserved at the file level and may not be used for externally visible |
| symbols. If in doubt, just avoid names starting with @code{_} altogether. |
| |
| @section Miscellaneous 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 |
| |
| @section Editor configuration |
| In order to configure Vim to follow FFmpeg formatting conventions, paste |
| the following snippet into your @file{.vimrc}: |
| @example |
| " indentation rules for FFmpeg: 4 spaces, no tabs |
| set expandtab |
| set shiftwidth=4 |
| set softtabstop=4 |
| set cindent |
| set cinoptions=(0 |
| " Allow tabs in Makefiles. |
| autocmd FileType make,automake 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}: |
| @lisp |
| (c-add-style "ffmpeg" |
| '("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 "ffmpeg") |
| @end lisp |
| |
| @chapter Development Policy |
| |
| @section Patches/Committing |
| @subheading Licenses for patches must be compatible with FFmpeg. |
| Contributions should be licensed under the |
| @uref{http://www.gnu.org/licenses/lgpl-2.1.html, LGPL 2.1}, |
| including an "or any later version" clause, or, if you prefer |
| a gift-style license, the |
| @uref{http://opensource.org/licenses/isc-license.txt, ISC} or |
| @uref{http://mit-license.org/, MIT} license. |
| @uref{http://www.gnu.org/licenses/gpl-2.0.html, GPL 2} including |
| an "or any later version" clause is also acceptable, but LGPL is |
| preferred. |
| 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. |
| |
| @subheading You must not commit code which breaks FFmpeg! |
| This means unfinished code which is enabled and breaks compilation, |
| or compiles but does not work/breaks the regression tests. Code which |
| is unfinished but disabled may be permitted under-circumstances, like |
| missing samples or an implementation with a small subset of features. |
| Always check the mailing list for any reviewers with issues and test |
| FATE before you push. |
| |
| @subheading Keep the main commit message short with an extended description below. |
| The commit message should have a short first line in the form of |
| a @samp{topic: short description} as a header, separated by a newline |
| from the body consisting of an explanation of why the change is necessary. |
| If the commit fixes a known bug on the bug tracker, the commit message |
| should include its bug ID. Referring to the issue on the bug tracker does |
| not exempt you from writing an excerpt of the bug in the commit message. |
| |
| @subheading Testing must be adequate but not excessive. |
| If it works for you, others, and passes FATE then it should be OK to commit |
| it, provided it fits the other committing criteria. You should not worry about |
| over-testing things. If your code has problems (portability, triggers |
| compiler bugs, unusual environment etc) they will be reported and eventually |
| fixed. |
| |
| @subheading Do not commit unrelated changes together. |
| They should be split them into self-contained pieces. Also do not forget |
| that if part B depends on part A, but A does not depend on B, then A can |
| and should be committed first and separate from B. 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. |
| |
| @subheading Ask before you change the build system (configure, etc). |
| 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. |
| |
| @subheading Cosmetic changes should be kept in separate patches. |
| 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 |
| |
| @subheading Commit messages should always be filled out properly. |
| 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. |
| Recommended format: |
| |
| @example |
| area changed: Short 1 line description |
| |
| details describing what and why and giving references. |
| @end example |
| |
| @subheading Credit the author of the patch. |
| Make sure the author of the commit is set correctly. (see git commit --author) |
| If you apply a patch, send an |
| answer to ffmpeg-devel (or wherever you got the patch from) saying that |
| you applied the patch. |
| |
| @subheading Complex patches should refer to discussion surrounding them. |
| When applying patches that have been discussed (at length) on the mailing |
| list, reference the thread in the log message. |
| |
| @subheading Always wait long enough before pushing changes |
| Do NOT commit to code actively maintained by others without permission. |
| Send a patch to ffmpeg-devel. If no one answers within a reasonable |
| time-frame (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! |
| |
| @section Code |
| @subheading API/ABI changes should be discussed before they are made. |
| 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 widely used functionality or features (redundant code can be removed). |
| |
| @subheading Remember to check if you need to bump versions for libav*. |
| Depending on the change, you may need to change the version integer. |
| Incrementing the first component means no backward compatibility to |
| previous versions (e.g. removal of a function from the public API). |
| Incrementing the second component means backward compatible change |
| (e.g. addition of a function to the public API or extension of an |
| existing data structure). |
| Incrementing the third component means a noteworthy binary compatible |
| change (e.g. encoder bug fix that matters for the decoder). The third |
| component always starts at 100 to distinguish FFmpeg from Libav. |
| |
| @subheading Warnings for correct code may be disabled if there is no other option. |
| 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. |
| 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. |
| |
| @subheading Check untrusted input properly. |
| 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. |
| |
| @section Documentation/Other |
| @subheading Subscribe to the ffmpeg-devel mailing list. |
| It is important to be subscribed to the |
| @uref{https://lists.ffmpeg.org/mailman/listinfo/ffmpeg-devel, ffmpeg-devel} |
| mailing list. Almost any non-trivial patch is to be sent there for review. |
| Other developers may have comments about your contribution. We expect you see |
| those comments, and to improve it if requested. (N.B. Experienced committers |
| have other channels, and may sometimes skip review for trivial fixes.) Also, |
| discussion here about bug fixes and FFmpeg improvements by other developers may |
| be helpful information for you. Finally, by being a list subscriber, your |
| contribution will be posted immediately to the list, without the moderation |
| hold which messages from non-subscribers experience. |
| |
| However, it is more important to the project that we receive your patch than |
| that you be subscribed to the ffmpeg-devel list. If you have a patch, and don't |
| want to subscribe and discuss the patch, then please do send it to the list |
| anyway. |
| |
| @subheading Subscribe to the ffmpeg-cvslog mailing list. |
| Diffs of all commits are sent to the |
| @uref{https://lists.ffmpeg.org/mailman/listinfo/ffmpeg-cvslog, ffmpeg-cvslog} |
| mailing list. Some developers read this list to review all code base changes |
| from all sources. Subscribing to this list is not mandatory. |
| |
| @subheading Keep the documentation up to date. |
| 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. |
| |
| @subheading Important discussions should be accessible to all. |
| Try to keep important discussions and requests (also) on the public |
| developer mailing list, so that all developers can benefit from them. |
| |
| @subheading Check your entries in MAINTAINERS. |
| Make sure that no parts of the codebase that you maintain are missing from the |
| @file{MAINTAINERS} file. If something that you want to maintain is missing add it with |
| your name after it. |
| If at some point you no longer want to maintain some code, then please help in |
| finding a new maintainer and also don't forget to update the @file{MAINTAINERS} file. |
| |
| We think our rules are not too hard. If you have comments, contact us. |
| |
| @chapter Code of conduct |
| |
| Be friendly and respectful towards others and third parties. |
| Treat others the way you yourself want to be treated. |
| |
| Be considerate. Not everyone shares the same viewpoint and priorities as you do. |
| Different opinions and interpretations help the project. |
| Looking at issues from a different perspective assists development. |
| |
| Do not assume malice for things that can be attributed to incompetence. Even if |
| it is malice, it's rarely good to start with that as initial assumption. |
| |
| Stay friendly even if someone acts contrarily. Everyone has a bad day |
| once in a while. |
| If you yourself have a bad day or are angry then try to take a break and reply |
| once you are calm and without anger if you have to. |
| |
| Try to help other team members and cooperate if you can. |
| |
| The goal of software development is to create technical excellence, not for any |
| individual to be better and "win" against the others. Large software projects |
| are only possible and successful through teamwork. |
| |
| If someone struggles do not put them down. Give them a helping hand |
| instead and point them in the right direction. |
| |
| Finally, keep in mind the immortal words of Bill and Ted, |
| "Be excellent to each other." |
| |
| @anchor{Submitting patches} |
| @chapter Submitting patches |
| |
| First, read the @ref{Coding Rules} above if you did not yet, in particular |
| the rules regarding patch submission. |
| |
| When you submit your patch, please use @code{git format-patch} or |
| @code{git send-email}. We cannot read other diffs :-). |
| |
| Also 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. |
| The tool is located in the tools directory. |
| |
| Run the @ref{Regression tests} before submitting a patch in order to verify |
| it does not cause unexpected problems. |
| |
| 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()') |
| |
| Also please if you send several patches, send each patch as a separate mail, |
| do not attach several unrelated patches to the same mail. |
| |
| Patches should be posted to the |
| @uref{https://lists.ffmpeg.org/mailman/listinfo/ffmpeg-devel, ffmpeg-devel} |
| mailing list. Use @code{git send-email} when possible since it will properly |
| send patches without requiring extra care. If you cannot, then send patches |
| as base64-encoded attachments, so your patch is not trashed during |
| transmission. Also ensure the correct mime type is used |
| (text/x-diff or text/x-patch or at least text/plain) and that only one |
| patch is inline or attached per mail. |
| You can check @url{https://patchwork.ffmpeg.org}, if your patch does not show up, its mime type |
| likely was wrong. |
| |
| 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. |
| |
| 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. |
| |
| |
| @chapter New codecs or formats checklist |
| |
| @enumerate |
| @item |
| Did you use av_cold for codec initialization and close functions? |
| |
| @item |
| Did you add a long_name under NULL_IF_CONFIG_SMALL to the AVCodec or |
| AVInputFormat/AVOutputFormat struct? |
| |
| @item |
| Did you bump the minor version number (and reset the micro version |
| 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 |
| Did you add the AVCodecID to @file{avcodec.h}? |
| When adding new codec IDs, also add an entry to the codec descriptor |
| list in @file{libavcodec/codec_desc.c}. |
| |
| @item |
| If it has a FourCC, did you add it to @file{libavformat/riff.c}, |
| 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. |
| |
| @item |
| Did you add an entry to the table of supported formats or codecs in |
| @file{doc/general.texi}? |
| |
| @item |
| Did you add an entry in the Changelog? |
| |
| @item |
| If it depends on a parser or a library, did you add that dependency in |
| configure? |
| |
| @item |
| 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 |
| |
| |
| @chapter Patch submission checklist |
| |
| @enumerate |
| @item |
| Does @code{make fate} pass with the patch applied? |
| |
| @item |
| Was the patch generated with git format-patch or send-email? |
| |
| @item |
| Did you sign-off your patch? (@code{git commit -s}) |
| See @uref{https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/Documentation/process/submitting-patches.rst, Sign your work} for the meaning |
| of @dfn{sign-off}. |
| |
| @item |
| Did you provide a clear git commit log message? |
| |
| @item |
| Is the patch against latest FFmpeg git master branch? |
| |
| @item |
| Are you subscribed to ffmpeg-devel? |
| (the list is subscribers only due to spam) |
| |
| @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? |
| |
| @item |
| If the change is to speed critical code, did you benchmark it? |
| |
| @item |
| If you did any benchmarks, did you provide them in the mail? |
| |
| @item |
| Have you checked that the patch does not introduce buffer overflows or |
| other security issues? |
| |
| @item |
| Did you test your decoder or demuxer against damaged data? If no, see |
| tools/trasher, the noise bitstream filter, and |
| @uref{http://caca.zoy.org/wiki/zzuf, zzuf}. Your decoder or demuxer |
| should not crash, end in a (near) infinite loop, or allocate ridiculous |
| amounts of memory when fed damaged data. |
| |
| @item |
| Did you test your decoder or demuxer against sample files? |
| Samples may be obtained at @url{https://samples.ffmpeg.org}. |
| |
| @item |
| Does the patch not mix functional and cosmetic changes? |
| |
| @item |
| Did you add tabs or trailing whitespace to the code? Both are forbidden. |
| |
| @item |
| Is the patch attached to the email you send? |
| |
| @item |
| Is the mime type of the patch correct? It should be text/x-diff or |
| text/x-patch or at least text/plain and not application/octet-stream. |
| |
| @item |
| If the patch fixes a bug, did you provide a verbose analysis of the bug? |
| |
| @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 @url{https://streams.videolan.org/upload/}. |
| |
| @item |
| Did you provide a verbose summary about what the patch does change? |
| |
| @item |
| Did you provide a verbose explanation why it changes things like it does? |
| |
| @item |
| Did you provide a verbose summary of the user visible advantages and |
| disadvantages if the patch is applied? |
| |
| @item |
| Did you provide an example so we can verify the new feature added by the |
| 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. |
| |
| @item |
| You should maintain alphabetical order in alphabetically ordered lists as |
| long as doing so does not break API/ABI compatibility. |
| |
| @item |
| Lines with similar content should be aligned vertically when doing so |
| improves readability. |
| |
| @item |
| Consider adding a regression test for your code. |
| |
| @item |
| If you added YASM code please check that things still work with --disable-yasm. |
| |
| @item |
| Make sure you check the return values of function and return appropriate |
| error codes. Especially memory allocation functions like @code{av_malloc()} |
| are notoriously left unchecked, which is a serious problem. |
| |
| @item |
| Test your code with valgrind and or Address Sanitizer to ensure it's free |
| of leaks, out of array accesses, etc. |
| @end enumerate |
| |
| @chapter Patch review process |
| |
| All patches posted to ffmpeg-devel 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 |
| patches will themselves be reviewed like any other patch. If at some point |
| a patch passes review with no comments then it is approved, that can for |
| simple and small patches happen immediately while large patches will generally |
| have to be changed and reviewed many times before they are approved. |
| After a patch is approved it will be committed to the repository. |
| |
| We will review all submitted patches, but sometimes we are quite busy so |
| especially for large patches this can take several weeks. |
| |
| If you feel that the review process is too slow and you are willing to try to |
| take over maintainership of the area of code you change then just clone |
| git master and maintain the area of code there. We will merge each area from |
| where its best maintained. |
| |
| 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. |
| |
| Everyone is welcome to review patches. Also if you are waiting for your patch |
| to be reviewed, please consider helping to review other patches, that is a great |
| way to get everyone's patches reviewed sooner. |
| |
| @anchor{Regression tests} |
| @chapter Regression tests |
| |
| Before submitting a patch (or committing to the repository), you should at least |
| test that you did not break anything. |
| |
| Running 'make fate' accomplishes this, please see @url{fate.html} for details. |
| |
| [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]. |
| |
| @section Adding files to the fate-suite dataset |
| |
| When there is no muxer or encoder available to generate test media for a |
| specific test then the media has to be included in the fate-suite. |
| First please make sure that the sample file is as small as possible to test the |
| respective decoder or demuxer sufficiently. Large files increase network |
| bandwidth and disk space requirements. |
| Once you have a working fate test and fate sample, provide in the commit |
| message or introductory message for the patch series that you post to |
| the ffmpeg-devel mailing list, a direct link to download the sample media. |
| |
| @section Visualizing Test Coverage |
| |
| The FFmpeg build system allows visualizing the test coverage in an easy |
| manner with the coverage tools @code{gcov}/@code{lcov}. This involves |
| the following steps: |
| |
| @enumerate |
| @item |
| Configure to compile with instrumentation enabled: |
| @code{configure --toolchain=gcov}. |
| |
| @item |
| Run your test case, either manually or via FATE. This can be either |
| the full FATE regression suite, or any arbitrary invocation of any |
| front-end tool provided by FFmpeg, in any combination. |
| |
| @item |
| Run @code{make lcov} to generate coverage data in HTML format. |
| |
| @item |
| View @code{lcov/index.html} in your preferred HTML viewer. |
| @end enumerate |
| |
| You can use the command @code{make lcov-reset} to reset the coverage |
| measurements. You will need to rerun @code{make lcov} after running a |
| new test. |
| |
| @section Using Valgrind |
| |
| The configure script provides a shortcut for using valgrind to spot bugs |
| related to memory handling. Just add the option |
| @code{--toolchain=valgrind-memcheck} or @code{--toolchain=valgrind-massif} |
| to your configure line, and reasonable defaults will be set for running |
| FATE under the supervision of either the @strong{memcheck} or the |
| @strong{massif} tool of the valgrind suite. |
| |
| In case you need finer control over how valgrind is invoked, use the |
| @code{--target-exec='valgrind <your_custom_valgrind_options>} option in |
| your configure line instead. |
| |
| @anchor{Release process} |
| @chapter Release process |
| |
| FFmpeg maintains a set of @strong{release branches}, which are the |
| recommended deliverable for system integrators and distributors (such as |
| Linux distributions, etc.). At regular times, a @strong{release |
| manager} prepares, tests and publishes tarballs on the |
| @url{https://ffmpeg.org} website. |
| |
| There are two kinds of releases: |
| |
| @enumerate |
| @item |
| @strong{Major releases} always include the latest and greatest |
| features and functionality. |
| |
| @item |
| @strong{Point releases} are cut from @strong{release} branches, |
| which are named @code{release/X}, with @code{X} being the release |
| version number. |
| @end enumerate |
| |
| Note that we promise to our users that shared libraries from any FFmpeg |
| release never break programs that have been @strong{compiled} against |
| previous versions of @strong{the same release series} in any case! |
| |
| However, from time to time, we do make API changes that require adaptations |
| in applications. Such changes are only allowed in (new) major releases and |
| require further steps such as bumping library version numbers and/or |
| adjustments to the symbol versioning file. Please discuss such changes |
| on the @strong{ffmpeg-devel} mailing list in time to allow forward planning. |
| |
| @anchor{Criteria for Point Releases} |
| @section Criteria for Point Releases |
| |
| Changes that match the following criteria are valid candidates for |
| inclusion into a point release: |
| |
| @enumerate |
| @item |
| Fixes a security issue, preferably identified by a @strong{CVE |
| number} issued by @url{http://cve.mitre.org/}. |
| |
| @item |
| Fixes a documented bug in @url{https://trac.ffmpeg.org}. |
| |
| @item |
| Improves the included documentation. |
| |
| @item |
| Retains both source code and binary compatibility with previous |
| point releases of the same release branch. |
| @end enumerate |
| |
| The order for checking the rules is (1 OR 2 OR 3) AND 4. |
| |
| |
| @section Release Checklist |
| |
| The release process involves the following steps: |
| |
| @enumerate |
| @item |
| Ensure that the @file{RELEASE} file contains the version number for |
| the upcoming release. |
| |
| @item |
| Add the release at @url{https://trac.ffmpeg.org/admin/ticket/versions}. |
| |
| @item |
| Announce the intent to do a release to the mailing list. |
| |
| @item |
| Make sure all relevant security fixes have been backported. See |
| @url{https://ffmpeg.org/security.html}. |
| |
| @item |
| Ensure that the FATE regression suite still passes in the release |
| branch on at least @strong{i386} and @strong{amd64} |
| (cf. @ref{Regression tests}). |
| |
| @item |
| Prepare the release tarballs in @code{bz2} and @code{gz} formats, and |
| supplementing files that contain @code{gpg} signatures |
| |
| @item |
| Publish the tarballs at @url{https://ffmpeg.org/releases}. Create and |
| push an annotated tag in the form @code{nX}, with @code{X} |
| containing the version number. |
| |
| @item |
| Propose and send a patch to the @strong{ffmpeg-devel} mailing list |
| with a news entry for the website. |
| |
| @item |
| Publish the news entry. |
| |
| @item |
| Send an announcement to the mailing list. |
| @end enumerate |
| |
| @bye |