[FFmpeg-devel] [PATCH] Make avcodec_thread_init set the thread_count in the encoder when there isn't support for threads compiled in

[Stefano Sabatini]

On date Saturday 2008-03-08 20:31:25 +0100, Michael Dorr encoded:
> On Saturday 08 March 2008 07:25:49 pm Stefano Sabatini wrote:
> > On date Saturday 2008-03-08 18:55:26 +0100, Michael Niedermayer encoded:
> > > On Sat, Mar 08, 2008 at 06:33:27PM +0100, Stefano Sabatini wrote:
> > > > Hi,
> > > > as in $subject.
> > > >
> > > > If threads support is not enabled and threads count is set to a
> > > > value greater than MAX_THREADS (currently is 8), then encoder is
> > > > initialized with a value of thread_count equal to 1, then
> > > > enc->threads_count is set to the value set by the user, finally
> > > > libavcodec crashes when it tryies to free the first thread beyond
> > > > MAX_THREADS (this happens when quitting ffplay).
> > >
> > > the command line parsing code should not accept >MAX_THREADS
> >
> > [...]
> >
> > I agree, but MAX_THREADS is defined in libavcodec/mpegvideo.h, which
> > is not public, furthermore the patch implements the correct behaviour
> > for opening an encoder so I'd like to see it applied.
> 
> Shouldn't manually setting enc->thread_count be omitted completely, since it 
> gets set correctly in avcodec_thread_init anyway (and if thread_init isn't 
> called, it defaults to 1, which is also correct)? Theoretically, 
> avcodec_thread_init could fail, then enc->thread_count and the 'real' number 
> of threads will differ, and ffmpeg will crash ...

Hi,

if thread support is enabled, enc->thread_count is setted by
avcodec_thread_init, and if this number is greater than THREADS_MAX
the avcodec_open (condition which isn't checked by
avcodec_init_threads) will fail when opening the encoder.

If thread support isn't enabled, the reasonable thing to do seems to
me to set enc->thread_count to thread_count rather than require the
user to do it manually as in ffplay.c, then the avcodec_open will fail
anyway.

This patch implements this solution.

By the way: shouldn't avcodec_thread_init if threads support is not
compiled *always* return 0 as opposed to the current behaviour of
returning -1?

A further fix could make avcodec_thread_init fail when thread_count is
greater than THREADS_MAX.

Furthermore we should check for the error code returned by
avcodec_thread_init as suggested by Michael Dorr.

Best regards.
-- 
Stefano Sabatini
Linux user number 337176 (see http://counter.li.org)
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