Thanks for the reply, that's what I thought after reading Mark's code,
it implicitly confirms that data[0] points to the yuv array:
y = yptr[px*width+py];
u = uptr[px/2*width/2+py/2];
v = vptr[px/2*width/2+py/2];
But unfortunately either way it still doesn't work, do you think
something is wrong with the yuv -> rgb formulas ?
On Sat, Jan 30, 2010 at 3:51 PM, Thomas Worth <[email protected]> wrote:
> From my limited testing, I am pretty sure data[0] points to the entire
> video stream. Also, you have to keep in mind that if you are working
> with planar YUV data (YUV420P), ALL of the luminance comes first, then
> U and V. It's not packed like you'd expect, YUYV,YUYV,YUYV,YUYV over
> and over. It's like this:
>
> YYYYYYYY
> YYYYYYYY
> UUUUUUUU
> VVVVVVVV
>
> I hope that helps. I just figured this out recently myself.
>
> Thomas
>
>
> On Sat, Jan 30, 2010 at 4:00 AM, ·´`·.¸.»ÐëÄdMäñ·´`·.¸.»
> <[email protected]> wrote:
>> Mark,
>>
>>> This would work for chroma subsampling type 411 but not 420. For 420 there
>>> is 1 chroma pixel for ever 4 pixels, 2 in the X direction and 2 in the Y
>>> direction.
>>>
>>> So you need something more like:
>>>
>>> for (py=0; py < height; py++)
>>> for (px =0; px < width; px++) {
>>>
>>> y = yptr[px*width+py];
>>> u = uptr[px/2*width/2+py/2];
>>> v = vptr[px/2*width/2+py/2];
>>>
>>
>> Thank you very much for your time and your excellent explanation, okay
>> so I tried that and still no luck :
>>
>> unsigned char *yptr = src->data[0];
>> unsigned char *uptr = src->data[1];
>> unsigned char *vptr = src->data[2];
>> int i =0;
>>
>> for (int py=0; py < height; py++)
>> {
>> for (int px =0; px < width; px++, i+= 3)
>> {
>> y = yptr[px*width+py];
>> u = uptr[px/2*width/2+py/2];
>> v = vptr[px/2*width/2+py/2];
>>
>> rgb[i] = y + 1.140 * v;
>> rgb[i+1] = y - 0.395 *u - 0.581 *v;
>> rgb[i+2] = y + 2.032 * u;
>> }
>> }
>>
>> Then I thought maybe data[0] points to the whole yuv array, so I tried this:
>>
>> unsigned char *yptr = src->data[0];
>> unsigned char *uptr = yptr + width * height;
>> unsigned char *vptr = uptr + width/4;
>>
>> but it still doesn't work any suggestions ?
>>
>> Thanks again.
>> _______________________________________________
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>>
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