# YUVOverlay performance problems

**URL:** <https://discourse.libsdl.org/t/yuvoverlay-performance-problems/4458>\
**Category:** SDL Development\
**Created:** [May 24, 2001, 11:10pm UTC](https://discourse.libsdl.org/t/yuvoverlay-performance-problems/4458 "2001-05-24T23:10:50Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Mikko\_Rantalainen](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/m/6bbea6/32.png) [@Mikko\_Rantalainen](https://discourse.libsdl.org/u/Mikko_Rantalainen)\
**Post date:** [May 24, 2001, 11:10pm UTC](https://discourse.libsdl.org/t/yuvoverlay-performance-problems/4458/1 "2001-05-24T23:10:50Z")

</div>

I’m trying to make program that can deinterlace full screen PAL (768x576  
25fps = 40ms/frame) video into progressive frames with scaling in real  
time and I’ve achieved this target. My deinterlace routine now tooks about  
20ms with my hardware. I’m still hoping to add real time noise filtering.  
Unfortunately, the problem is that showing the resulting YUV-image tooks  
too much time and I’m already using all my CPU power because of it. I’m  
currently using YV12 format because it seems to be fastest and I do  
deinterlacing directly to overlay.

Have I done something wrong or should displaying YUV-overlay really be  
this slow with hardware acceleration? Is there some another way of showing  
overlay but SDL\_DisplayYUVOverlay()? With the source below I have got  
following timings:

YV12: 17 ms Hardware: yes  
IYUV: 32 ms Hardware: no  
YUY2: 33 ms Hardware: yes  
UYVY: 33 ms Hardware: yes  
YVYU: 49 ms Hardware: no

Where “Hardware” is according to information gathered from  
SDLOverlay.hw\_overlay. I don’t know about you, but if YV12 is supported by  
hardware and I get direct(?) access to overlay memory, displaying the  
image shouldn’t take 17ms IMHO. If the call would just block for this time  
it wouldn’t matter but it eats all CPU…

I’ve tested with the following environment:

```
Linux 2.4.4
SDL 1.2.0
XFree 4.0.99.3 (from dri.sourceforge.net, Xvideo is supported)

MSI K7T Pro
AMD Duron 650
Matrox G400 Single 16MB
256MB

```

Also, is there a way to disable screen saver through SDL and a way to wait  
for Vertical Sync?

– Mikko

Code used for testing follows:  
( Compiling: gcc -o test test.c `sdl-config --cflags --libs` )  
------------- test.c ----------------  
int main(void)  
{  
SDL\_Surface\* screen;  
SDL\_Overlay\* overlay; /\* yuv overlay \*/  
SDL\_Rect drect;  
Uint32 stime,time;  
int i;

```
SDL_Init(SDL_INIT_VIDEO|SDL_INIT_TIMER); /* SDL_INIT_AUDIO */

screen = SDL_SetVideoMode(800, 600, 16, SDL_HWSURFACE);
overlay = SDL_CreateYUVOverlay(768, 576,SDL_YV12_OVERLAY, screen);

stime = SDL_GetTicks();
for (i = 0; i < 100; i++)
{
    time = SDL_GetTicks();
    SDL_LockYUVOverlay(overlay);

    /* real image rendering onto overlay pixels would be here */

    SDL_UnlockYUVOverlay(overlay);
    printf("SDL_Lock+UnlockYUVOverlay() took %d ms. ",
           SDL_GetTicks() - time);

    time = SDL_GetTicks();

    if (1)
    {
        drect.x=0;
        drect.y=0;
        drect.w=800;
        drect.h=600;
        SDL_DisplayYUVOverlay(overlay, &drect);
    }

    printf("SDL_DisplayYUVOverlay() took %d ms.\n",
           SDL_GetTicks() - time);
}

stime = SDL_GetTicks() - stime;
printf("Average %f ms per frame.\n",(float)stime/100);
printf("Hardware: %s\n", overlay->hw_overlay ? "yes" : "no");

SDL_FreeYUVOverlay(overlay);
SDL_Quit();

return 0;

```

}  
------------- /test.c ---------------

---

<div class="post-metadata">

**Author:** ![Ewald\_Snel](https://discourse.libsdl.org/letter_avatar_proxy/v4/letter/e/f14d63/32.png) [@Ewald\_Snel](https://discourse.libsdl.org/u/Ewald_Snel)\
**Post date:** [May 29, 2001, 9:34am UTC](https://discourse.libsdl.org/t/yuvoverlay-performance-problems/4458/2 "2001-05-29T09:34:43Z")

</div>

Hi Mikko,

> Where “Hardware” is according to information gathered from  
> SDLOverlay.hw\_overlay. I don’t know about you, but if YV12 is supported by  
> hardware and I get direct(?) access to overlay memory, displaying the  
> image shouldn’t take 17ms IMHO. If the call would just block for this time  
> it wouldn’t matter but it eats all CPU…

The YV12 overlay uses a YUY2 hardware overlay on Matrox G400 cards.  
I don’t know why the XFree86 developers have chosen not to include  
direct support for YV12, as it’s much faster. Now the YV12 overlay has  
to be copied byte-by-byte, multiplexing luminance and chrominance  
samples to form valid YUY2 overlay data for every frame.

I am working on a patch for Matrox G400 (I have noticed the same, poor  
performance). Although it’s still a bit buggy (distortions when down-  
scaling 720x576 overlays), the performance has increased A LOT.

“Average 4.050000 ms per frame.”

(test.c)  
RedHat 7.1  
Linux 2.4.5  
XFree86-4.0.99.901

Pentium II 350MHz  
Matrox G400 (SH) 16MB  
256MB

So your problem is probably caused by the current XFree86 mga driver,  
not SDL. If you want to try the patch, just let me know, and I’ll email  
it to you.

bye,

ewald