[gst-devel] I420 + alpha
gwright at real.com
Thu Mar 17 14:29:06 CET 2005
If you are interested we have been using a YCrCbA format for a several
years now. It is exactly what you describe, I420 plus an alpha plane.
#define CID_I420 0 /* planar YCrCb 4:2:0 format (CCIR) */
#define CID_YV12 1 /* planar YVU 4:2:0 (ATI) */
#define CID_YVU9 2 /* planar YVU 16:2:0 (Intel,ATI) */
#define CID_YUY2 3 /* packed YVU 4:2:2 (ATI,S3,etc.) */
#define CID_UYVY 4 /* yet another packed 4:2:2 (3Dfx) */
#define CID_ARGB32 11 /* RGB32 with Alpha Channel. */
#define CID_YUVA 12 /* planar YCrCbA 4:2:0 */
#define BI_YUVA MAKEFOURCC('Y','U','V','A') /* planar YVU 420 plus alpha plane */
I guess I didn't pick the best name for it.
We also have hand optimized x86 assembly for doing alpha blending
with it and a variety of formats.
%define _I420andYUVAtoI420_MMX I420andYUVAtoI420_MMX
%define _I420andYUVAtoYV12_MMX I420andYUVAtoYV12_MMX
%define _I420andYUVAtoYUY2_MMX I420andYUVAtoYUY2_MMX
%define _I420andYUVAtoUYVY_MMX I420andYUVAtoUYVY_MMX
We also have C versions off all these as well.
The code can be found on the Helix Community web site:
Not sure how the licensing will work for you though.
Jan Schmidt wrote:
> On Thu, 2005-03-17 at 13:19 +0100, Benjamin Otte wrote:
>>On Wed, 16 Mar 2005, Gergely Nagy wrote:
>>>In our application, we have an I420 format source, which I need to
>>>modifiy (blend stuff on it), and pass it to theoraenc, which wants I420.
>>>Right now, I need to convert the whole thing to AYUV, and then back.
>>>This results in significantly more resource usage and it takes a lot of
>>>To solve this, I'd like to have a new format, which is essentially I420
>>>with a full-size alpha plane appended (appended, because then it is easy
>>>to strip, or simply ignore).
>>>This way, I could make our application able to work without any kind of
>>>expensive colorspace conversions, and could use the same buffer the
>>>first element in the pipeline gave me. In my experience, this makes the
>>>whole thing significantly faster.
>>>Question is, how should I call this new format? I thought of A420, but
>>>people here might have better ideas.
>>Does a format that does this already exist somewhere?
>>It sounds like a reasonable format to have to me and if it were already
>>existing somewhere we could just use that name.
>>Although converting from I420 to AYUV and back shouldn't really be that
>>performance-reducing, or is it?
> (720*576*1.5 + 720*576*4) * 30.0 = 65.25MB/s memory bandwidth. Even on
> my Athlon 2000, that's about 10% of the memory bandwidth for each
> Caching isn't going to help much, because even 1 frame is too big, so
> even on a fast machine, you don't want to do too many of them in any
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