add hacking notes

Original commit message from CVS:
add hacking notes
parent 87324f82
2004-03-11 Thomas Vander Stichele <thomas at apestaart dot org>
* configure.ac: use new setup with mirrored cvs tree
* configure.ac: use new setup with mirrored cvs tree
2004-03-10 David Schleef <ds@schleef.org>
......
THE GOAL
--------
What we are trying to achieve:
satisfy:
......@@ -8,32 +10,63 @@ satisfy:
make distcheck
non-srcdir build (ie, mkdir build; cd build; ../configure; make)
How it works:
THE SETUP
---------
There is a "mirror" root CVS module that contains "ffmpeg".
This directory contains a vendor-branch checkout of upstream FFmpeg CVS
of a given day.
* configure checks whether or not it should update ffmpeg from CVS by looking
at the nano version number
- if it's 1, we're in cvs mode, and it should check it out
- if it's not 1, we're in prerel or rel mode, and the code should already
be on disk
FIXME: we could change this to really check out the source code if some
required files aren't there just in case someone checks out from CVS
but CVS is not at nano 1
On head, the following things have been commited on top of this:
* patches/, which is a directory with a set of patches, and a series file
listing the order, as generated by quilt
* .pc/, which is a tree of files that quilt uses to keep control of its state.
It contains a list of applied patches, and one directory per patch,
containing a tree of hardlinked files that were added to the patchset, and
a .pc file listing all files part of the patchset.
* the result of having all these patches commited (ie, quilt push -a) to the
ffmpeg tree.
* patching of the checked-out copy happens at
Both the actually patched CVS ffmpeg code as well as the .pc dir need to be
commited to CVS so the state of quilt wrt. the source is in sync.
Axioms under which we work:
- the dist tarball needs to include either
- the pristine ffmpeg checkout + our patches + a patch mechanism on make
or
- the ffmpeg checkout with patches already applied
THE WAY
-------
- configure/make is not allowed to touch files that already live in the source
tree; if they need to then they need to be copied first and cleaned
afterward
- it would be very nice if, on update of either the Tag file or the patch set,
make would know exactly what to do with it.
- If you want to hack on our copy of the FFmpeg code, there are some basic
rules you need to respect:
- you need to use quilt. If you don't use quilt, you can't hack on it.
- we separate patches based on the functionality they patch, and whether
or not we want to send stuff upstream. Make sure you work in the right
patch. use "quilt applied" to check which patches are applied.
- before starting to hack, run cvs diff. There should be NO diffs, and
NO files listed with question mark. If there are, somebody before you
probably made a mistake. To manage the state correctly, it is vital that
none of the files are unknown to CVS.
- if you want to add a file to a patchset, you need to:
- be in the right patchset
- quilt add (file)
- cvs add .pc/(patchsetname)/(file)
- cvs commit .pc/(patchsetname) (to update the state of quilt in cvs)
- edit the file
- quilt refresh
- quilt push -a (This one is IMPORTANT, otherwise you'll have a huge diff)
- cvs commit
- if you want to add a patchset, you need to:
- go over the procedure with thomas to check it's correct
- decide where in the stack to put it. ask for help if you don't know.
- go there in the patch stack (use quilt pop/push)
- quilt new (patchsetname).patch (don't forget .patch !)
- quilt add (files)
- cvs add .pc/(patchsetname) the whole tree
- cvs commit .pc/(patchsetname)
- quilt refresh
- quilt push -a
- cvs commit
- cvs diff (to check if any of the files are unknown to CVS; if they are,
you need to add them to CVS)
THE PLUGIN
----------
Some notes on how ffmpeg wrapping inside GStreamer currently works:
* gstffmpeg{dec,enc,demux,mux}.c are wrappers for specific element types from
their ffmpeg counterpart. If you want to wrap a new type of element in
......
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