Ios4: How to Use Video File as an Opengl Texture

iOS4: how do I use video file as an OpenGL texture?

Apologies; typing on an iPhone so I'll be a little brief.

Create an AVURLAsset with the URL of your video - which can be a local file URL if you like. Anything QuickTime can do is fine, so MOV or M4V in H.264 is probably the best source.

Query the asset for tracks of type AVMediaTypeVideo. You should get just one unless your source video has multiple camera angles of something like that, so just taking objectAtIndex:0 should give you the AVAssetTrack you want.

Use that to create an AVAssetReaderTrackOutput. Probably you want to specify kCVPixelFormatType_32BGRA.

Create an AVAssetReader using the asset; attach the asset reader track output as an output. And call startReading.

Henceforth you can call copyNextSampleBuffer on the track output to get new CMSampleBuffers, putting you in the same position as if you were taking input from the camera. So you can lock that to get at pixel contents and push those to OpenGL via Apple's BGRA extension.

Is it possible using video as texture for GL in iOS?

As of iOS 4.0, you can use AVCaptureDeviceInput to get the camera as a device input and connect it to a AVCaptureVideoDataOutput with any object you like set as the delegate. By setting a 32bpp BGRA format for the camera, the delegate object will receive each frame from the camera in a format just perfect for handing immediately to glTexImage2D (or glTexSubImage2D if the device doesn't support non-power-of-two textures; I think the MBX devices fall into this category).

There are a bunch of frame size and frame rate options; at a guess you'll have to tweak those depending on how much else you want to use the GPU for. I found that a completely trivial scene with just a textured quad showing the latest frame, redrawn only exactly when a new frame arrives on an iPhone 4, was able to display that device's maximum 720p 24fps feed without any noticeable lag. I haven't performed any more thorough benchmarking than that, so hopefully someone else can advise.

In principle, per the API, frames can come back with some in-memory padding between scanlines, which would mean some shuffling of contents before posting off to GL so you do need to implement a code path for that. In practice, speaking purely empirically, it appears that the current version of iOS never returns images in that form so it isn't really a performance issue.

EDIT: it's now very close to three years later. In the interim Apple has released iOS 5, 6 and 7. With 5 they introduced CVOpenGLESTexture and CVOpenGLESTextureCache, which are now the smart way to pipe video from a capture device into OpenGL. Apple supplies sample code here, from which the particularly interesting parts are in RippleViewController.m, specifically its setupAVCapture and captureOutput:didOutputSampleBuffer:fromConnection: — see lines 196–329. Sadly the terms and conditions prevent a duplication of the code here without attaching the whole project but the step-by-step setup is:

1. create a CVOpenGLESTextureCacheCreate and an AVCaptureSession;
2. grab a suitable AVCaptureDevice for video;
3. create an AVCaptureDeviceInput with that capture device;
4. attach an AVCaptureVideoDataOutput and tell it to call you as a sample buffer delegate.

Upon receiving each sample buffer:

1. get the CVImageBufferRef from it;
2. use CVOpenGLESTextureCacheCreateTextureFromImage to get Y and UV CVOpenGLESTextureRefs from the CV image buffer;
3. get texture targets and names from the CV OpenGLES texture refs in order to bind them;
4. combine luminance and chrominance in your shader.

Video as texture in OpenGLES2.0

The issue is most likely somewhere else then the code you posted. To check the texture itself create a snapshot (a feature in Xcode) and see if you can see the correct texture there. Maybe your coordinates are incorrect or some parameters missing when displaying the textured object, could be you forgot to enable some attributes or the shaders are not present...

Since you got so far I suggest you first try to draw a colored square, then try to apply a texture (not from the video) to it until you get the correct result. Then implement the texture from video.

And just a suggestion since you are getting raw pixel data from the video you should consider creating only one texture and then use texture sub image function to update the texture directly with the data instead of doing some strange iterations and transformations to the image. The glTexSubImage2D will take your buffer pointer directly and do the update.

Render YpCbCr iPhone 4 Camera Frame to an OpenGL ES 2.0 Texture in iOS 4.3

OK. We have a working success here. The key was passing the Y and the UV as two separate textures to the fragment shader. Here is the final shader:

#ifdef GL_ES
precision mediump float;
#endif

varying vec2 textureCoordinate;

uniform sampler2D videoFrame; 
uniform sampler2D videoFrameUV;

const mat3 yuv2rgb = mat3(
                            1, 0, 1.2802,
                            1, -0.214821, -0.380589,
                            1, 2.127982, 0
                            );

void main() {    
    vec3 yuv = vec3(
                    1.1643 * (texture2D(videoFrame, textureCoordinate).r - 0.0625),
                    texture2D(videoFrameUV, textureCoordinate).r - 0.5,
                    texture2D(videoFrameUV, textureCoordinate).a - 0.5
                    );
    vec3 rgb = yuv * yuv2rgb;

    gl_FragColor = vec4(rgb, 1.0);
} 

You'll need to create your textures along like this:

int bufferHeight = CVPixelBufferGetHeight(cameraFrame);
int bufferWidth = CVPixelBufferGetWidth(cameraFrame);
glBindTexture(GL_TEXTURE_2D, videoFrameTexture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, bufferWidth, bufferHeight, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, CVPixelBufferGetBaseAddressOfPlane(cameraFrame, 0));

glBindTexture(GL_TEXTURE_2D, videoFrameTextureUV);
glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE_ALPHA, bufferWidth/2, bufferHeight/2, 0, GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, CVPixelBufferGetBaseAddressOfPlane(cameraFrame, 1));

and then pass them like this:

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, videoFrameTexture);

glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, videoFrameTextureUV);

glActiveTexture(GL_TEXTURE0);
glUniform1i(videoFrameUniform, 0);
glUniform1i(videoFrameUniformUV, 1);

Boy am I relieved!

P.S. The values for the yuv2rgb matrix are from here http://en.wikipedia.org/wiki/YUV and I copied code from here http://www.ogre3d.org/forums/viewtopic.php?f=5&t=25877 to figure out how to get the correct YUV values to begin with.

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