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Mali T604 and eglImageKHR and FBO

Sebastien Baudouin
Note: This was originally posted on 12th June 2013 at http://forums.arm.com

Hi,

i'm implementing an Android application using the GPU and especially ImageKHR and FrameBuffer Objects.
In a thread and its GLES context i'm creating a texture and its eglImageKHR then i share the eglImageKHR handle with another thread. In this second thread i'm creating a FrameBuffer Object with the given eglImageKHR as color buffer and a renderbuffer (for the depth) . Then from this second thread i'm drawing using openGLES 1.x commands into the just created FBO. The result is displayed on screen by the First thread.

All that is working well with a MALI-400 but running that application on a nexus 10 which use MALI-T604 i have some issue.
1- NO GL ERROR appear.
2- the FBO status is OK

but the screen is sometime OK sometime completely black.

I try to replace the drawing operation by a simple clear color where the color is changing at each call and sometime i can see part of the screen with a color and part that is black.

Is someone aware of differences between MALI-400 and MALI-T604 that could cause such kind of issue. unfortunately i do not have any documentation on T604 to really understand what is happening. I tried to enable auto MIMAP generation in case of T604 as for (NVidia GPU it was a mandatory condition the make the texture "complete") but nothing has changed.

I suspect that it is coming from ImageKHR because i have a JAVA application where i'm uising FBO without ImageKHR and it seems to work fine.

Here is the sequence to create the FBO with EGLImageKHR:
glGenFramebuffersOES(1, (GLuint*) 0x777ada1c);
glBindFramebufferOES(GL_FRAMEBUFFER_OES, 1);

glGenRenderbuffersOES(1, (GLuint*) 0x777ada1c);
glBindRenderbufferOES(GL_RENDERBUFFER_OES, 1);

glRenderbufferStorageOES(GL_RENDERBUFFER_OES, GL_DEPTH_COMPONENT16_OES, 1184, 694);
glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_DEPTH_ATTACHMENT_OES, GL_RENDERBUFFER_OES, 1);

glGenTextures(1, (GLuint *) 0x777ada0c);
glBindTexture(GL_TEXTURE_2D, 3);
glEGLImageTargetTexture2DOES(GL_TEXTURE_2D, (GLeglImageOES) 0x752d700c);

glFramebufferTexture2DOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_TEXTURE_2D, 3, 0);

glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES);



I hope someone will be able to help me to understand what i'm missing .

Br

Seb
Parents
  • Note: This was originally posted on 24th July 2013 at http://forums.arm.com

    Is the glFlush();glFinish() an acceptable fix or is it preferable to use other mechanism ?


    You shouldn't need the glFlush call; glFinish implies a flush of the stream.

    In terms of acceptability it is certainly functionally going to do what you want, but it will block the resource loading thraed until the GPU rendering has finished processing the glCopyTexImage2D call, so will stop that application thread processing other work. This may be acceptable for your use case, but if you want to keep that thread alive for processing Mali-T600 also supports the EGL fences. The thread loading the resource creates a fence after calling glCopyTexImage, and then calls glFlush. The other thread consuming the resource can either block waiting on the fence object, or poll it. 

    Is that behaviour specific to Mali-T604 as that was not needed on Mali-400 or even other GPU ?


    Without synchronization you are "out of spec", so while it might work on other implementations there are no guarantees it will work reliably.

    HTH,
    Iso
Reply
  • Note: This was originally posted on 24th July 2013 at http://forums.arm.com

    Is the glFlush();glFinish() an acceptable fix or is it preferable to use other mechanism ?


    You shouldn't need the glFlush call; glFinish implies a flush of the stream.

    In terms of acceptability it is certainly functionally going to do what you want, but it will block the resource loading thraed until the GPU rendering has finished processing the glCopyTexImage2D call, so will stop that application thread processing other work. This may be acceptable for your use case, but if you want to keep that thread alive for processing Mali-T600 also supports the EGL fences. The thread loading the resource creates a fence after calling glCopyTexImage, and then calls glFlush. The other thread consuming the resource can either block waiting on the fence object, or poll it. 

    Is that behaviour specific to Mali-T604 as that was not needed on Mali-400 or even other GPU ?


    Without synchronization you are "out of spec", so while it might work on other implementations there are no guarantees it will work reliably.

    HTH,
    Iso
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