I want to create a H.264 video out of frames generated by my program in C++. Is there a way to change the video encoding parameters for the VideoWriter object in my code, except the codec (eg. CRF) like we do in FFMpeg?
Thanks for your help
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I coded an encoder using FFMPEG (c++). The requirements for this encoder are:
The output format should be uncompressed avi,
Preferably using RGB24/YUV444 pixel format since we do not want chroma subsampling.
Most standard players should support the format (windows media player (WMP), VLC)
Using the encoder I wrote, I can write a number of file types right now:
Lossless H.264 encoded video using the YUV420p pixel format and AVI container. (Obviously not uncompressed and chroma subsampled, however both WMP and VLC play without any problem.)
MPEG4 encoded video using the YUV420p pixel format and AVI container.(Obviously not uncompressed and chroma subsampled, however both WMP and VLC play without any problem.)
AYUV encoded video using the YUVA444P pixel format. (uncompressed as far as I understand and not chroma subsampled. However, VLC does not play this.)
FFV1 encoded video using the YUV444P pixel format. (lossless, and not chroma subsampled. However, WMP does not play this.)
The above is derived from this very usefull post.
So I am now looking into the RAWVIDEO encoder from FFMPEG. I can't get this to work and neither can I find an example in the FFMPEG documentation on how to use this encoder for writing video. Can somebody point me in the right direction or supply sample code for this?
Also, if there is another direction I should follow to meet my requirements feel free to point me to it.
Thanks in advance
I received some video data via RTP / RTSP / SIP, the data is encoded by H264 and sent by a IP camera. I would like to convert H264 keyframe data into a picture and analyze whether it contains faces. I do not want to use FFMPEG such a huge library, just use libx264 and opencv can do it? How?
Thanks.
No, not possible. X264 can not decode (it is a h264 encoder only). It also can not encode jpeg/png. Ffmpeg is what you need. If it is too large, custom compile including only the features you need. And static link so unused functions are striped out.
The steps I follow for writing a video file in openCV are as follows:
CvVideoWriter *writer =cvCreateVideoWriter(fileName, Codec ID, frameRate, frameSize); // Create Video Writer
cvWriteFrame(writer, frame); // Write frame
cvReleaseVideoWriter(&writer); // Release video writer
The above code snippet writes at a fixed frame rate. I need to write out variable frame rate videos. The approach I had used earlier with libx264 involved writing individual timestamps to each frame.
So, the question is how do I write timestamps to a frame in openCV - what is the specific API ? More generally, how do I create variable frame rate videos ?
I don't think it is possible to do this with OpenCV directly without modifying the code to give access under the hood. You would need to use a different library like libvlc to do so using the imem to get your raw RGB frames in OpenCV into a file. This link provides an example using imem with raw images loaded from OpenCV. You would just need to change the :sout options to save to the file you want using your preferred codec.
I want to create a mpeg4 stream whith the following specs:
Container mp4.mov m4v
Resolution 1920 X 1080
Codec h264 main profile 4.1
I am wondering what CV_FOURCC and file extension should I use?
Any help appreciated.
I am using C++
In general where can find the fourcc for any coded?
If you read a file, you don't need to specify any codec.
If you write to a file, I think you need to specify X264. Full list of FOURCC codes avaliable here.
Some of the common fourCC codes used with OpenCV are mentioned here
http://opencv.willowgarage.com/wiki/documentation/cpp/highgui/VideoWriter
Here is a much longer list of the FOURCC codes of other codecs.
http://www.fourcc.org/codecs.php
Since you want to use H264, you can use H264 or X264 as the FOURCC codes.
I want to read in an .avi video file for a program that I am making. I have the file location saved as a string. Is there any good tutorials on using .avi files in c++ or does anyone know who to read one in? Is it the same as normal files?
I have a previously asked SO question that goes into better detail but here is what I want to do:
I am making a program that will detect faces (though OpenCV) As of now I have been given a video processor program that will detect each face on a frame, and return the frame as a image and the CvRec of the faces. I want to take these faces and test them to validate that they are all actually faces.
After I have all the faces (tested) I want to then take the images and test them together. I test the faces on each frame for size and distance changes. If the faces pass this for a frame length of two seconds, then I want to crop the face and make it the subject of each frame.
After each frame is cropped I then want to save the new video file for the user.
Hopefully that helps. If anyone needs a better explanation please let me know.
First of all, a little background.
What is AVI?
AVI stands for Audio Video Interleave. It is a special case of the RIFF (Resource Interchange File Format). AVI is defined by Microsoft and it is the most common format for audio/video data.
I assume you would want to read a avi file and decode the compressed video frames. AVI file is just like any other normal file and you can use fread()(in C) or iostream(in C++) to open an avi file and read it contents. But the contents of an avi file are video frames in a compressed format. The compression allows video content of bigger sizes to be efficiently packed in less memory space.To make any sense of this compressed data you would have to decode the encoded data format.You will have to study the standard which describes how AVI encoding is done and then extract and decode the frames. this raw video data now when fed to a video device will be displayed in video format.
It seems you are staying within OpenCV so things are easy. If OpenCV is compiled properly it is capable of delegating io/coding/decoding to other libraries. Quicktime and others for example, but best is to use ffmpeg. You open, read and decode everything using the OpenCV API which gives you the video frame by frame.
Make sure your OpenCV is compiled with ffmpeg support and then read the OpenCV tutorial on how to read/write AVI files. It's really easy.
Getting OpenCV to be built with ffmpeg support might be hard though. You might want to switch to an older version of OpenCV if you can't get ffmpeg running with the current one.
Personally i would not spent time trying to read the video by yourself and delegate the task to OpenCV. That's how it is supposed to be used.