[FFmpeg-user] Ticket#5936: Purple haze on ffmpeg mpeg4 decoding

[Andy Furniss]

Toerless Eckert wrote:
> Thanks a lot, Andy

Looking at trac it seems Carl Eugen beat me to it.

> Mind explaining how you did that trick with git bisect ?

In this case as you gave working revisions I started with those.

git tag shows lots and you can see that the more recent tags start with n.

so clean tree

make distclean
git clean -dfx

git bisect start
git bisect bad n2.3
git bisect good n2.2.16

build - ./confugure --enable-gpl --disable-doc && make -j5
test - ./ffplay ...

clean

git bisect good or bad repeat from build.

I haven't bisected ffmpeg for a while, this one was easy.
Sometimes, historically,  a commit from libav ends up building
avconv - you can clean and use git bisect skip to hopefully find
a commit that doesn't.

When getting closer to the bad commit you can usually skip the
clean/configure and just make to save a bit of build time. For ffmpeg it's
not that bad anyway, but for bigger projects like kernels or llvm
it's handy (when it works).

git bisect log will keep a record of progress so if you get stuck
you can save a copy and in combination with git log or git reset --hard
hopefully find different/closer starting points for a fresh bisect if
you need to,

When you've finished clean up and git bisect reset to get back on master.