I am trying to read a high resolution video using OpenCV VideoCapture and it seems to be extremely slow. I read somewhere changing the buffer sizes might help, but I tried setting all kinds of buffer sizes and its still slow.
Any help here on what settings can help improve reading high resolution videos for java opencv is really appreciated
I am using VideoCapture to read a video from disk. I am using Mac OSX. Here is a snippet of my code:
while(camera.read(frame))
{
BufferedImage bufferedImage = MatToBufferedImage(frame);
BufferedImage scaledImage = (BufferedImage)getScaledImage(bufferedImage, frameWidth, frameHeight);
ImageIcon icon = new ImageIcon(scaledImage);
publish(icon);
}
I am using swingworker and doing this in the background thread.
I am not explicitly setting any openCV properties. Should I be setting any explicit properties is something I am not sure of.
Here is what I observe: My video starts off well and then around 50th frame or so, i see some lag and then again at around 120th frame and it almost completely stops at frame number 190ish.
Have you tried resizing the individual frames?
while(camera.read(frame))
{
resize(frame,frame,Size(640,360));
imshow("frame",frame);
}
Related
I'm using webgl to do YUV to RGB conversions on a custom video codec.
The video has to play at 30 fps. In order to make this happen I'm doing all my math every other requestAnimationFrame.
This works great, but I noticed when profiling that uploading the textures to the gpu takes the longest amount of time.
So I uploaded the "Y" texture and the "UV" texture separately.
Now the first "requestAnimationFrame" will upload the "Y" texture like this:
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, yTextureRef);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.LUMINANCE, textureWidth, textureHeight, 0, gl.LUMINANCE, gl.UNSIGNED_BYTE, yData);
The second "requestAnimationFrame" will upload the "UV" texture in the same way, and make a draw call to the fragment shader doing the math between them.
But this doesn't change anything in the profiler. I still show nearly 0 gpu time on the frame that uploads the "Y" texture, and the same amount of time as before on the frame that uploads the "UV" texture.
However if I add a draw call to my "Y" texture upload function, then the profiler shows the expected results. Every frame has nearly half the gpu time.
From this I'm guessing the Y texture isn't really uploaded to the gpu using the texImage2d function.
However I don't really want to draw the Y texture on the screen as it doesn't have the correct UV texture to do anything with until a frame later. So is there any way to force the gpu to upload this texture without performing a draw call?
Update
I mis-understood the question
It really depends on the driver. The problem is OpenGL/OpenGL ES/WebGL's texture API really sucks. Sucks is a technical term for 'has unintended consequences'.
The issue is the driver can't really fully upload the data until you draw because it doesn't know what things you're going to change. You could change all the mip levels in any order and any size and then fix them all in between and so until you draw it has no idea which other functions you're going to call to manipulate the texture.
Consider you create a 4x4 level 0 mip
gl.texImage2D(
gl.TEXTURE_2D,
0, // mip level
gl.RGBA,
4, // width
4, // height
...);
What memory should it allocate? 4(width) * 4(height) * 4(rgba)? But what if you call gl.generateMipmap? Now it needs 4*4*4+2*2*4+1*1*4. Ok but now you allocate an 8x8 mip on level 3. You intend to then replace levels 0 to 2 with 64x64, 32x32, 16x16 respectively but you did level 3 first. What should it do when you replace level 3 before replacing the levels above those? You then add in levels 4 8x8, 5 as 4x4, 6 as 2x2, and 7 as 1x1.
As you can see the API lets you change mips in any order. In fact I could allocate level 7 as 723x234 and then fix it later. The API is designed to not care until draw time when all the mips must be the correct size at which point they can finally allocate memory on the GPU and copy the mips in.
You can see a demonstration and test of this issue here. The test uploads mips out of order to verify that WebGL implementations correctly fail with they are not all the correct size and correctly start working once they are the correct sizes.
You can see this was arguably a bad API design.
They added gl.texStorage2D to fix it but gl.texStorage2D is not available in WebGL1 only WebGL2. gl.texStorage2D has new issues though :(
TLDR; textures get uploaded to the driver when you call gl.texImage2D but the driver can't upload to the GPU until draw time.
Possible solution: use gl.texSubImage2D since it does not allocate memory it's possible the driver could upload sooner. I suspect most drivers don't because you can use gl.texSubImage2D before drawing. Still it's worth a try
Let me also add that gl.LUMIANCE might be a bottleneck as well. IIRC DirectX doesn't have a corresponding format and neither does OpenGL Core Profile. Both support a RED only format but WebGL1 does not. So LUMIANCE has to be emulated by expanding the data on upload.
Old Answer
Unfortunately there is no way to upload video to WebGL except via texImage2D and texSubImage2D
Some browsers try to make that happen faster. I notice you're using gl.LUMINANCE. You might try using gl.RGB or gl.RGBA and see if things speed up. It's possible browsers only optimize for the more common case. On the other hand it's possible they don't optimize at all.
Two extensions what would allow using video without a copy have been proposed but AFAIK no browser as ever implemented them.
WEBGL_video_texture
WEBGL_texture_source_iframe
It's actually a much harder problem than it sounds like.
Video data can be in various formats. You mentioned YUV but there are others. Should the browser tell the app the format or should the browser convert to a standard format?
The problem with telling is lots of devs will get it wrong then a user will provide a video that is in a format they don't support
The WEBGL_video_texture extensions converts to a standard format by re-writing your shaders. You tell it uniform samplerVideoWEBGL video and then it knows it can re-write your color = texture2D(video, uv) to color = convertFromVideoFormatToRGB(texture(video, uv)). It also means they'd have to re-write shaders on the fly if you play different format videos.
Synchronization
It sounds great to get the video data to WebGL but now you have the issue that by the time you get the data and render it to the screen you've added a few frames of latency so the audio is no longer in sync.
How to deal with that is out of the scope of WebGL as WebGL doesn't have anything to do with audio but it does point out that it's not as simple as just giving WebGL the data. Once you make the data available then people will ask for more APIs to get the audio and more info so they can delay one or both and keep them in sync.
TLDR; there is no way to upload video to WebGL except via texImage2D and texSubImage2D
We have a VoIP app for iOS platform. Where we are using TPCircularBuffer for audio buffering and it's performance is so good.
So i was wondering if it's possible to use TPCircularBuffer for Video buffering also. I have searched a lot but didn't find anything useful on "Using TPCircularBuffer for Video". Is that even possible ?? If yes, then can anyone shade some light on it ? And any code sample would be highly appreciated.
I guess you could copy your video frame's pixels into a TPCircularBuffer, and you'd technically have a video ring buffer, but you've already lost the efficiency race at that point because you don't have time to copy that much data around. You need to keep a reference to your frames.
Or, if you really wanted to mash a solution into TPCircularBuffer, you could write the CMSampleBuffer pointers into the buffer (carefully respecting retain and release). But that seems heavy handed, as you're really not gaining anything from TPCircularBuffer's magical memory mapping wrapping because pointers are so small.
I would simply make my own CMSampleBufferRef ring buffer. You can grab a prebuilt circular buffer or do the clock arithmetic yourself:
CMSampleBufferRef ringBuffer[10]; // or some other number
ringBuffer[(++i) % 10] = frame;
Of course your real problem is not the ring buffer itself, but dealing with the fact that decompressed video is very high bandwidth, e.g. each frame is 8MB for 1080p, or 200MB to store 1 second's worth at 24fps, so you're going to have to get pretty creative if you need anything other than a microscopic video buffer.
Some suggestions:
the above numbers are for RGBA, so try working in YUV, where the numbers become 3MB and 75MB/s
try lower resolutions
how to make two video run at same time and same fps ?
VideoCapture capture("../video/Success/NT 1.1.wmv");
VideoCapture capture2("../video/Success/NT 1.wmv");
capture.set(CV_CAP_PROP_FPS , 30);
capture2.set(CV_CAP_PROP_FPS , 60);
waitKey(30);
For example, i have this two video and i set the fps for these two videos already but this capture.set(CV_CAP_PROP_FPS , 30) doesn't work for my program..
OpenCV is not a playback library, nor it was ever intended to support such functions. Setting FPS does absolutely nothing there.
The only thing that OpenCV does it to offer you the possibility to extract frames from a video, one after another.
You'll have to devise your own, complete, timing sequences to control the speed at which images are displayed on screen.
Or, better, use VLC.
what is problem in writing very simple code for same fps:
// Open videos
VideoCapture capture("../video/Success/NT 1.1.wmv");
VideoCapture capture2("../video/Success/NT 1.wmv");
Mat frame, frame2;
while(..)
{
capture >> frame;
capture2 >> frame2;
//imSHOW or do anything with these frame..
waitKey(30);
}
//Close video
Am I missing something or you?
I apologize in advance if this question sounds dumb.
I have an array of images produced by another project, and I want to show them on the screen in sequence as fast as possible to assemble them to animation. How should I do this to achieve a frame rate at least higher than 30FPS?
I'm new to iOS development and I'm not sure where to start with. Should I look into Core Animation or OpenGL or Quartz2D or something else? Can someone please point me a direction?
Thanks a lot! Really appreciate the help.
imageView.animationImages = imagesArray;
imageView.animationRepeatCount = 0;
imageView.animationDuration = 35;//depends on how fast you want it
imagesArray is the array of images. Each image for each frame.
Hope this helps..
You should not be using the imageView.animationImages API. It will consume all your app memory. A complete description of the problem with Video and Memory usage on iOS devices is available. A quick fix would be to save your frames as a series of PNG images, but that will not give you 60FPS because it will take too long to decode each PNG image and blit it to the screen. The real solution that will give you 60FPS is to decode each image into "keyframes" of raw binary data in BGRA format and then memory map each frame as needed. My own code that implements this solution can be found at the link above.
I have used the following method iOS4: how do I use video file as an OpenGL texture? to get video frames rendering in openGL successfully.
This method however seems to fall down when you want to scrub (jump to a certain point in the playback) as it only supplies you with video frames sequentially.
Does anyone know a way this behaviour can successfully be achieved?
One easy way to implement this is to export the video to a series of frames, store each frame as a PNG, and then "scrub" by seeing to a PNG at a specific offset. That gives you random access in the image stream at the cost of decoding the entire video first and holding all the data on disk. This would also involve decoding each frame as it is accessed, that would eat up CPU but modern iPhones and iPads can handle it as long as you are not doing too much else.