Slow glTexSubImage2D performance on Nexus 10/Android 4.2.2 (Samsung Exynos 5 w/ Mali-T604)

Question

I have an Android app that decodes video into yuv420p format then renders video frames using OpenGLES. I use glTexSubImage2D() to upload y/u/v buffer to GPU then do a YUV2RGB conversion using shader. All EGL/OpenGL setup/rendering code is native code.

Now I am not saying there is no problem with my code, but considering the same code is running perfecting fine on iOS (iPad/iPhone), Nexus 7, Kindle HD 8.9, Samsung Note 1 and a few other cheap chinese tablets (A31/RockChip 3188) running Android 4.0/4.1/4.2. I would say it's less likely my code is wrong. On those devices, glTexSubImage2D() uses less than 16ms to upload a SD or 720P HD texture.

However, on Nexus 10, glTexSubImage2D() it takes about 50~90ms for a SD or 720P HD texture which is way too slow for a 30fps or 60fps video.

I would like to know

1) if I should pick a different texture format (RGBA or BGRA). Is there a ways to detect which is the best texture format used by a GPU?

2) if there is a feature that is 'OFF' on all other SOCs but set to 'ON' on Exynos 5. For example, the automatic MIPMAP generation option. (I have it off, btw)

3) if this is a known issue of Samsung Exynos SOC - I can't find a support forum for Exynos CPU

4) Is there any option I need to set when configure the EGL surface? like, transparency, surface format, etc? (I have no idea what I am talking about)

5) It could mean GPU is doing an implicit format conversion but I checked GL_LUMINANCE is always used. Again it works on all other platform.

6) anything else?

My EGL config:

const EGLint attribs[] = {
    EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
    EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
    EGL_BLUE_SIZE, 8,
    EGL_GREEN_SIZE, 8,
    EGL_RED_SIZE, 8,
    EGL_NONE
};

Initial setup:

glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, ctx->frameW, ctx->frameH, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, NULL); /* also for U/V  */

subsequent partial replacement:

glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, ctx->frameW, ctx->frameH, GL_LUMINANCE, GL_UNSIGNED_BYTE, yBuffer); /*also for U/V */

I am trying to render video at ~30FPS or ~60FPS at SD or 720P HD resolution.

Answer 1

This is a known driver issue that we have reported to ARM. A future update should fix it.

Answer 2

EDIT Status update

We've now managed to reproduce slow upload conditions for one path on the public firmware, which you are possibly hitting, and this will be fixed in the next driver release.

If you double-buffer texture IDs (e.g. frame N = ID X, N+1 = ID Y, N+2 = ID X, N+3 = ID Y, etc) for the textures you are uploading to it should help avoid this on the current firmware.

Thanks, Iso

Answer 3

I can confirm this has been fixed in Android 4.3 - I'm seeing a performance increase by a factor of 2-3 with RGBA format and by a factor of 10-50 with other texture formats over Android 4.2.2. These results apply for both glTexImage2D and glTexSubImage2D. (Can't add comments yet so I had to put this here)

EDIT: If you're stuck with 4.2.2, you could try using RGBA texture instead, it should have better performance (3-10x or so with larger power-of-two texture sizes).