[Ffmpeg-devel] [PATCH] TIFF encoder (Google SoC qualification task)
Tue Apr 3 01:25:25 CEST 2007
On Mon, Apr 02, 2007 at 08:18:40PM +0200, Michael Niedermayer wrote:
> > and in loop:
> > *out++ = ((count - 1) | b) * a
> > ?
> > Or maybe I don't see a more simple solution? (I see only two analogous
> > with +, and ^ instead of |)
> well your solution is close to what i had in mind but it can be simplified
> further (your needs 2 simply arithmetic operations and 1 multiply, it can
> be done with only 2 simple arithmetic operations too)
Huh, Bartlomiej has overtaken me with a good idea of xor and + ;-). I
think it'll be good to use it.
> > > > Index: libavcodec/tiffenc.c
> > > > ===================================================================
> > > > --- libavcodec/tiffenc.c (wersja 0)
> > > > +++ libavcodec/tiffenc.c (wersja 0)
> > > [...]
> > >
> > > > + uint16_t *color_map;
> > >
> > > this could as well be a local array
> > Shouldn't I rather allocate the memory for that in tiff_init and free
> > in tiff_end ? I forgot about moving it there...
> why? its not needed after encoding the current frame or?
Although the solution with local array is somewhat simpler, I think that
allocating the memory for palette once in tiff_init and freeing in
tiff_end is somewhat more elegant than reserving it each time (even if
it the palette is not used at all) on the stack.
> > > > + case 0: // XXX: when a user chose vlc it also assigns the default
> > > > + s->compression = TIFF_DEFAULT;
> > > > + break;
> > >
> > > hmm maybe its better to fail with an error if a unsupported compression is
> > > choosen
> > Yes, but the coder_type is 0 both in cases when user uses "-coder vlc" and
> > when he doesn't use -coder at all. My idea is to redefine:
> > #define FF_CODER_TYPE_VLC 0
> > #define FF_CODER_TYPE_AC 1
> > #define FF_CODER_TYPE_RAW 2 // no coder
> > #define FF_CODER_TYPE_RLE 3 // run-length
> > #define FF_CODER_TYPE_DEFLATE 4
> > in avcodec.h to something like that
> > #define FF_CODER_TYPE_DEFAULT 0
> > #define FF_CODER_TYPE_VLC 1
> > #define FF_CODER_TYPE_AC 2
> > #define FF_CODER_TYPE_RAW 3 // no coder
> > #define FF_CODER_TYPE_RLE 4 // run-length
> > #define FF_CODER_TYPE_DEFLATE 5
> > However, it needs changes in ffv1.c. I guess, that the separate patch is
> > needed ;-). Should I do it in such way?
> well either leave them as is and let the user specifiy the coder or
> add a
> FF_CODER_TYPE_DEFAULT -1
> your suggestion might break applications which dont use AVOption to set the
> parameters ...
I have applied the second solution.
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