[FFmpeg-devel] [PATCH] Implement pixdesc.h:write_line()

Michael Niedermayer michaelni
Fri Apr 3 00:23:35 CEST 2009


On Thu, Apr 02, 2009 at 11:31:45PM +0200, Stefano Sabatini wrote:
> On date Thursday 2009-04-02 23:03:04 +0200, Michael Niedermayer encoded:
> > On Thu, Apr 02, 2009 at 10:53:25PM +0200, Stefano Sabatini wrote:
> > > On date Thursday 2009-04-02 22:40:50 +0200, Michael Niedermayer encoded:
> [...]
> > > > [...]
> > > > > +        while (w--) {
> > > > > +            int val = *src++;
> > > > > +            put_bits(&pb, depth, val);
> > > > > +            if (step - depth)
> > > > 
> > > > > +                skip_put_bits(&pb, step - depth);
> > > > 
> > > > i suspect this will randomize the bits
> > > 
> > > That's why I added the if (step - depth) check (yes without that it
> > > was broken).
> > > Am I missing something?
> > /**
> >  * Skips the given number of bits.
> >  * Must only be used if the actual values in the bitstream do not matter.
> >     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> Well I read it as "the actual values in the bitstream do not matter,
> that is the skipped bits are simply discarded".
> 
> Now I can't say if the various put_bits() optimized implementation
> randomize the skipped bits or not.
> 
> So I cannot say if we have to simply update the documentation or we
> have somehow to extend the API to support such a functionality (which
> looks to me - preserving the skipped bits - such a basic requirement
> that I'm puzzled discovering that it isn't supported).

Iam not even sure if put/get bits is the right tool for the job

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Awnsering whenever a program halts or runs forever is
On a turing machine, in general impossible (turings halting problem).
On any real computer, always possible as a real computer has a finite number
of states N, and will either halt in less than N cycles or never halt.
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