glReadPixels generates OUT_OF_MEMORY error

What device are you running on?

To help us give you a quick answer, can you also share a complete test case (source or Android APK is fine), so we're not trying to reproduce what you have done from the tiny snippet above?

A couple of starting points:

• Just to check the obvious, can you double check that the OpenGL ES error state is not set immediately before the call to glReadPixels() - the error state is sticky and may have been set by an earlier function.
• I think that version of the driver supports the KHR_debug extension, so you may get some more information about the error out via that channel, although with OUT_OF_MEMORY I'm not convinced that will necessarily be the case.

Cheers,
Pete

Hi, Mr. Harris.

My system is:  Odroid-XU3, running Ubuntu 14.04 LTS.

It is equipped with ARM armv7l and Mali-T628.

With its original OpenGL ES SDK, the "libmali.so" file works well for most applications.

But, it generates 0x505 OUT_OF_MEMORY error for any glReadPixels function call.

Sigh.

I made the very simple drawing function as follows:

void mydraw(void) {

static GLubyte buf[1024*1024] = { 0, 0, 0, 0 };

GL_CHECK( glClearColor(0.5f, 0.5f, 0.5f, 1.0f) );

GL_CHECK( glClear(GL_COLOR_BUFFER_BIT) );

GL_CHECK( glFinish() );

GL_CHECK( glReadPixels(0, 0, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, (void*)(&buf[0])) );

GL_CHECK( glFinish() );

}

It also generates OUT_OF_MEMORY.

I cannot understand why ReadPixels function call requires memory...

Sigh.

Thanks in advance.

--

Nakhoon Baek

Hi Oceancru,

Thank you for the code snippet you provided. Before I investigate the issue I was wondering if you could tell me more about the Ubuntu distribution you are currently running. As the Odroid XU3 only started shipping 2 days ago, I am guessing that you have access to pre release hardware? If this is the case where did you get the binary from? If it is directly from hard kernel, can you tell me which version you are using?

Cheers,

Stephen

oceancru,

All your drawing commands may be collected up and rendered at glFinish or glReadPixels and that may be when memory is allocated and a failure occurs.  I don't know why you wouldn't get the error at glFinish, but there are both draw and read contexts, so there may be a problem with the read context.

I haven't heard any other reports of glReadPixels issues on the version of the driver you reported at the start (r4p0), so I don't think this is a general problem with glReadPixels.  I don't think we can say until we see more of the context of how your application is calling the code.

Thank you for the draw function code snippet.  Can you send us a larger sample program source or even an APK which shows the problem including how you created your rendering surface and context and set them current?  How you created the surface and made it current may impact the behavior of glReadPixels.

Thank you.  -Brad