[Ffmpeg-devel] [PATCH] ported SGI decoder to the new API

[Michael Niedermayer]

Hi

On Wed, Apr 04, 2007 at 09:05:31AM +0800, Xiaohui Sun wrote:
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> Michael Niedermayer wrote:
> > Hi
> > 
> 
> > 
> >>> [...]
> >>>> +            start_offset = bytestream_get_be32(&start_table);
> >>>> +            if(start_offset > end_buf - in_buf) {
> >>>> +                return AVERROR_INVALIDDATA;
> >>>> +            }
> >>> excelent, finally the check looks good
> >>>
> >>>
> >>>> +            if (expand_rle_row(in_buf + start_offset, end_buf, 
> >>> dest_row,
> >>>> +                dest_row + s->linesize, z, s->depth) != s->width)
> >>>> +                return AVERROR_INVALIDDATA;
> >>> linesize can be negative
> >>>
> >> I modified, but not sure.
> > 
> > it should have been dest_row + width*pixelsize or dest_row + FFABS(s->linesize)
> 
> I found width*pixelsize is not equal to(actually less than)
> FFABS(s->linesize). because I found in avcodec_default_get_buffer it
> will add some extra EDGE_WIDTH to it, is that right?

yes


> 
> 
> [...]
> 
> > [...]
> >> +    out_ptr = p->data[0];
> >> +
> >> +    end_ptr = out_ptr + p->linesize[0] * s->height;
> >> +
> >> +    if(p->linesize[0] < 0) {
> >> +        s->linesize = - p->linesize[0];
> >> +        FFSWAP(uint8_t*, end_ptr, out_ptr);
> >> +    } else {
> >> +        s->linesize = p->linesize[0];
> >> +    }
> > 
> > this is wrong
> > first, it simply wont work as the pointers are off by one line
> > second, if the pointers where not off by one line it would store a
> > vertically fliped image
> 
> so we simply make an abstract of linesize without the need of adjusting
> corresponding pointers?

the nth pixel of the mth line is data + n + m*linesize always

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

When you are offended at any man's fault, turn to yourself and study your
own failings. Then you will forget your anger. -- Epictetus
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