[FFmpeg-devel] [RFC] execute2/simplify dnxhdenc threading

[Reimar Döffinger]

On Mon, Oct 12, 2009 at 08:52:29AM +0200, Michael Niedermayer wrote:
> On Sat, Oct 10, 2009 at 05:08:35PM +0200, Reimar D?ffinger wrote:
> > Hello,
> > this is my second try to simplify dnxhdenc and also change the code so
> > that number of jobs/tasks > number of threads, avoiding performance
> > issues if not all threads finish with the same speed.
> > Obviously execute2 must be implemented for the other thread
> > implementations, too, and dnxhdenc can probably be further simplified
> > (in particular, I doubt that setting start_mb_y and end_mb_y is actually
> > necessary), but I wanted to hear if this is on the right track before
> > I take it further.
> > I haven't tested it too well since I just now realized that all the time
> > I had compiled FFmpeg without thread support, if someone volunteers to
> > benchmark the speeds of the different implementations they are more than
> > welcome.
> 
> >  avcodec.h  |   15 ++++++++++++-
> [...]
> >  options.c  |    1 
> >  pthread.c  |   13 ++++++++++-
> >  utils.c    |   10 ++++++++
> >  6 files changed, 72 insertions(+), 37 deletions(-)
> > 1306d5ea93f2e82357f7e328c84a913c2f022ab3  dnxhdthread.diff
> [...]
> >  #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
> > @@ -2526,6 +2526,18 @@
> >       * - decoding: Set by libavcodec
> >       */
> >      enum AVChromaLocation chroma_sample_location;
> > +
> > +    /**
> > +     * The codec may call this to execute several independent things.
> > +     * It will return only after finishing all tasks.
> > +     * The user may replace this with some multithreaded implementation,
> > +     * the default implementation will execute the parts serially.
> > +     * @param count the number of things to execute
> > +     * @param arg2 argument passed unchanged to func
> > +     * - encoding: Set by libavcodec, user can override.
> > +     * - decoding: Set by libavcodec, user can override.
> > +     */
> > +    int (*execute2)(struct AVCodecContext *c, int (*func)(struct AVCodecContext *c2, void *arg, int jobnr, int threadnr), void *arg2, int *ret, int count);
> 
> doxy is missing a few things, like the arguments of func()

I hope I added all docs necessary.
I also hope you are fine with my vague "future-proof" specification of
the return value.
While it is not _really_ necessary yet I think it is preferable to keep
it at least as an option, that array of return values is not really
comfortable to use and quite wasteful of space.