[FFmpeg-cvslog] Merge commit '85770f2a2651497861ed938efcd0df3696ff5e45'

[Michael Niedermayer]

On Sun, May 01, 2011 at 12:01:35PM +0200, Stefano Sabatini wrote:
> On date Sunday 2011-05-01 10:31:12 +1000, Peter Ross wrote:
> > On Sun, May 01, 2011 at 02:04:58AM +0200, Stefano Sabatini wrote:
> [...]
> > > String default value setting doesn't work, that's because
> > > av_set_string3() doesn't accept NULL values for val, so for example:
> > > 
> > > av_set_string3(obj, name, NULL, 1, NULL);
> > > 
> > > will always return AVERROR(EINVAL).
> > > 
> > > Here there is a problem since you can't represent a NULL value string
> > > with a string safely, you could set "" but that's not the very same
> > > thing.
> > 
> > But you could define a valid string that FFmpeg treats always as NULL.
> > 
> > e.g.
> > 
> > avcodec/string.h
> > extern const char * av_null_string;
> > 
> > avutil/string.c
> > const char *av_null_string = "(null)";
> > 
> > av_set_string(..)
> > 
> >     if (str == av_null_string)
> > 
> >         behave this way
> 

> That's possible, an alternative could be to make av_set_string()
> accept the NULL vale for string options.

already done locally


> 
> But this is only part of the problem, when you set options for the
> first time you have random values in the context, so you need a
> function for initing the context, that is av_opt_set_defaults2() is
> not anymore sufficient, you need at least to pass a flag to it for
> telling that it has to init the context (and ignore the already
> present string fubar values).

contexts should be allocated with av_mallocz() or if they are on
the stack they should be memset(0).

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The misfortune of the wise is better than the prosperity of the fool.
-- Epicurus
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