[FFmpeg-devel] BFI video decoder

[Sisir Koppaka]

Updated decoder attached

On Fri, Apr 18, 2008 at 2:05 AM, Michael Niedermayer <michaelni at gmx.at>
wrote:

> On Fri, Apr 18, 2008 at 01:33:58AM +0530, Sisir Koppaka wrote:
> > Updated decoder attached. (Works!!! :) thanks)
> [...]
> > >
> > > >             *pal = 0;
> > > >             for (j = 0; j < 3; j++, shift -= 8)
> > > >                 *pal +=
> > >
> > > >                     ((avctx->extradata[i * 3 + j] << 2) | (avctx->
> > > >
>  extradata[i *
> > > >
>  3 +
> > > >
>  j]
> > > >>
> > > >                                                            4)) <<
> shift;
> > >
> > > following looks nicer:
> > >                       ((avctx->extradata[i * 3 + j] << 2) |
> > >                       (avctx->extradata[i * 3 + j] >> 4)  ) << shift;
> > >
> > > Also how large is the pal array? How large is extradata_size? is there
> a
> > > possibility later might be larger?
> > >
> > pal is only a uint32_t * pointer, extradata_size is currently 768 for
> all
> > our purposes, but if we add AVI transmuxing support like you said
> earlier,
> > we might need/want to use more so, in that case the palette can be made
> > larger, though I don't think doing so offers any significant value
> without
> > first altering the codec itself.
> > I'm not sure what you meant by the possibility that the latter might be
> > larger...can you please explain?
>
> pal points to bfi->frame.data[1] which is not infinitly large, if
> extradata_size is larger (from bfi in avi for example) then this still
> could do nasty things.
>
> I could find only the pointer definition of data[] in avcodec.h, if I
could know the size of data[], then I suppose a check of extradata_size>size
of data[1] => exit will work?

>
> [...]
> > static int bfi_decode_init(AVCodecContext * avctx)
> > {
> >     BFIContext *bfi = avctx->priv_data;
>
> >     bfi->frame.reference = 1;
>
> this should be before get_buffer()
>
> Moved

>
> [...]
> >     bytestream_get_le32(&buf); //Unpacked size, not required.
>
> buf+= 4;
> should do
>
> Changed...

>
> >
> >     while (dst != frame_end) {
> >         static const uint8_t lentab[4]={0,2,0,1};
>
> >         byte = *buf++;
> >         code = byte >> 6;
> >         length = byte & ~0xC0;
>
> declaration and initialization can be merged for these as well
>
Done

>
>
> [...]
> >         /* Do boundary check */
> >         for(i=0;i<4;i++)
> >             if (dst + (length<<lentab[i]) > frame_end)
> >                 break;
>
> this does not make sense
>
removed the redundant for, don't know why it got there - it's 3 here again,
maybe that has something to do with it :) sorry for this one

-----------------
Sisir Koppaka
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