Question

I’m trying to create video from images using OpenGL ES and ffmpeg, but on iPad(4.3) I have a crash on glReadPixels

-(NSData *) glToUIImage {

    int numberOfComponents = NUMBER_OF_COMPONENTS; //4
    int width = PICTURE_WIDTH; 
    int height = PICTURE_HEIGHT;

    NSInteger myDataLength = width * height * numberOfComponents;   

    NSMutableData * buffer= [NSMutableData dataWithLength :myDataLength];    

    [self checkForGLError]; 

    GLenum type = NUMBER_OF_COMPONENTS == 3 ? GL_RGB : GL_RGBA; //RGBA
    glReadPixels(0, 0, width, height, type, GL_UNSIGNED_BYTE, [buffer mutableBytes]);   //EXC_BAD_ACCESS here

    return buffer; 
}

It is working on iPhone 4 (4.3) and iPod Touch, but have problems on iPhone 3G(3.0) and iPad(4.3). Can you help me with this issue?

Also on iPhone 3G(3.0) and iPad(4.3) I have problems with Video – first 5-20 video frames have trash. Maybe issue with optimization? Or architecture?

EDITED
Stack:

#0  0x33be3964 in void BlockNxN<64ul, 16ul, 1, BLOCK_CONVERTER_NULL_32>(unsigned long, int, int, unsigned long, int, int, unsigned int, unsigned int, unsigned int, unsigned int) ()
#1  0x33be1c76 in glrBIFDetile ()
#2  0x33b586b2 in sgxGetImage(SGXImageReadParams const*) ()
#3  0x33b50d38 in gldReadPixels ()
#4  0x31813e16 in glReadPixels_Exec ()
#5  0x31e3c518 in glReadPixels ()

Answer 1

I’ve figured out!!!

I’ve fixing this issue about two weeks.

You must call glReadPixels() before [(EAGLView *)eagleView presentFramebuffer];

And so you must bind colorRenderbuffer before you will read pixels.
Final method listing:

int numberOfComponents = NUMBER_OF_COMPONENTS;
int width = PICTURE_WIDTH;
int height = PICTURE_HEIGHT;

NSInteger myDataLength = width * height * numberOfComponents; 


NSMutableData * buffer= [NSMutableData dataWithLength :myDataLength];
glBindRenderbuffer(GL_RENDERBUFFER_OES, [((EAGLView *)eagleView) colorRenderbuffer]);
[self checkForGLError];
glPixelStorei(GL_PACK_ALIGNMENT, 4); // force 4 byte alignment

glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, [buffer mutableBytes]);
return buffer;