[MPlayer-dev-eng] draw_alpha

[David Holm]

Kim Minh Kaplan wrote:

>David Holm writes:
>
>>Could someone please explain the arguments sent to draw_alpha for me?
>>Iive on #MPlayerDEV tried two times but I still didn't get it. For one
>>thing, if src is an 8bpp grayscale then why would you need a srcstride?
>>Etc, need to know so I can start using spuenc...
>>
>
>Here is what I understood from it.
>
>    void draw_alpha(int x0,int y0, int w,int h,
>                    unsigned char* src, unsigned char *srca,
>                    int stride)
>
>The first four arguments are quite clear: they define the video output
>area that will be drawn into.  The fifth (src) is the color plane
>(always 1 byte per pixel?) to use for drawing.  The sixth (srca) is
>the corresponding alpha value plane¹.  The seventh (stride) argument
>is the amount of bytes you have to skip in the color and alpha planes
>to get to the next line (that is first line of data is at src, second
>line is at src+stride, Nth line is at (src+stride*(N-1)) etc...)
>
>I am not sure why it needs a stride argument, but I think it is meant
>for OSD fonts where fonts are just small rectangular are in a bigger
>image, in which you need the extra information (the width if the
>bigger picture) to know how to get to the next line.
>
>BTW I wrote most of spudec (is that what you meant when you wrote
>spuenc?) so if you need more info about it just go ahead.
>
>While on the subject of spudec, I just came across a DVD (Fargo) that
>uses 0x7 control code...  Does anybody know how to interpret them?  I
>can't view subtitles on it :-(
>
>Kim-Minh.
>
>¹ A few weird rules about alpha values:
>    - The sum of color+alpha has to be less than 256.
>    - If alpha is 0 then nothing is drawn.  Otherwise the smaller the
>      value the more opaque the point.
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>
Thanks, this outta help me out =D...
No, I'm talking about spuenc, it was derived from spudec by someone 
who's domain is long gone. I need a spu encoder to use the spu channel 
of the dxr3 for osd.
regarding 0x7, check this page: http://members.aol.com/mpucoder/DVD/spu.html

//David Holm