I am reading in video files with openCV, I use the following simple code to do this.
std::string arg = argv[1];
VideoCapture capture(arg); //try to open string, this will attempt to open it as a video file
if (!capture.isOpened()) {
cerr << "Failed to open video file!\n" << endl;
help(argv);
system("Pause");
return 1;
}
I can load and manipulate several videos, but I have problems with others. I imagine this is down to codec issues. I can play the videos using old style win media player, so the codecs are on the system, but I imagine not available in opencv?
Does anyone know what codecs and video format will definitely play on opencv and what is a good option to convert video to these formats?
Many Thanks
Indeed, the supported codec of OpenCV is dependent on your platform and avaible codecs.
This tutorial Creating a video with OpenCV explains the video codec of OpenCV clearly. Though it is meant for writing videos, I think the underlying principle is the same with reading videos.
The function C++: double VideoCapture::get(int propId) can retrieve your loaded video's codec property by setting propId = CV_CAP_PROP_FOURCC. The interpretation of FOURCC can be found on this site. If you have problems with reading .avi videos, it is very likely that the codes is not installed in your platform.
Related
I am trying to encode a video using MediaFoundation on Windows 8.1, the output file should be an avi container, with a raw stream NV12.
The video is generated, and I can play it but when I open it with VLC I get the broken index detected (With options to play as is or fix it temporarly). If I press play as is, it plays ok. But this is generating a problem in other softwares.
I tried to research this and noticed that AVI supports 2 types of indexing
https://msdn.microsoft.com/en-us/library/windows/desktop/dd318189(v=vs.85).aspx
But this is for DirectShow and I am using MediaFoundation and I can't find anything related to this inside MediaFoundation.
Any help or suggestion will be appreciated.
Thanks.
Edit:
This is how I am creating the IMFMediaSink:
hr = MFCreateAttributes(&sinkAttributes, 5);
assert(SUCCEEDED(hr));
sinkAttributes->SetUnknown(MF_SINK_WRITER_ASYNC_CALLBACK, this);
sinkAttributes->SetGUID(MF_TRANSCODE_CONTAINERTYPE, MFTranscodeContainerType_AVI);
if (SUCCEEDED(hr)){
hr = MFCreateSinkWriterFromURL(videoURL, NULL, sinkAttributes, (IMFSinkWriter**)&sinkWriter);
}
I'm trying to compare 3 videos that are encoded by H.264, H.265, and VP9.
All of them are made by a same YUV video.
I want to use OpenCV's function to read each frame of the video and do some comparison:
VideoCapture vCap1, vCap2, vCap3;
vCap1.open("h264.mp4");
vCap2.open("h265.mp4");
vCap3.open("vp9.webm");
Mat frame1, frame2, frame3;
while (vCap1.read(frame1) && vCap2.read(frame2) && vCap3.read(frame3))
{
//do something
}
The vCap1 opened successfully, but vCap2 and vCap3 won't open.
Did I miss something to include to make it work?
Or OpenCV even not support the other 2 formats?
After using google :-) I found that
http://answers.opencv.org/question/10741/videocapture-format-supported-by-opencv/
Especially you have the needed codecs installed on your system. You can visit also
http://www.fourcc.org/codecs.php
for codecs.
The documentation from OpenCV is indeed not very helpful. :-)
What I would try if you are running under linux:
strace -xfo dump
and take a look in the system calls. Maybe you can find some hints of missing codec files, used configuration files and or other failed system function calls. If so, you have a startpoint.
I'm trying to use the opencv librarie to display video files to the screen using sdl-2. I got it to work with smaller files(20.5Mb), but when i tryed using bigger files (100 and 136Mb) it didnt work and i go the message "ERROR: Coudnt load the video < video.avi>".
cv::VideoCapture video;
video.open(videoName);
if (!video.isOpened())
{
SDL_Log("ERROR: Coudnt load the video <%s>", videoName.c_str());
return;
}
I don't know if size was the problem, but that would make the most sense to me. I've not found any documentation on size restrictions thought. Any ideas on how to fix it?
PS: All were .avi files, and the file's name was not the problem. Was able to open them with ffplay if that matters at all. OpenCV version 2.4.8
In OpenCV, I see imread() and VideoCapture() both take a string to a file path of multiple extensions. Is there a way to get a list of extensions that are supported by them? For example, getting a list of "jpg", "png", "mov", "mpg", etc.? I assume this is system dependent and others have needed to query this at runtime.
Furthermore, how is support determined? If have something like the below code and the Mat I get back always seems partially corrupted (I can see a bit of the image). It doesn't seem to change regardless of the frame number I ask for. I can play this video in my video player "totem", but I'm not even sure if totem and OpenCV are even using the same codec for this file.
Mat fromVideo(std::string _videoPath, int frame) {
VideoCapture capture(_videoPath);
Mat f;
for (int i = 0; i < frame; i++) {
capture >> f;
}
return f;
}
For imread() (more info here):
Windows bitmaps - *.bmp, *.dib (always supported)
JPEG files - *.jpeg, *.jpg, *.jpe (see the Notes section)
JPEG 2000 files - *.jp2 (see the Notes section)
Portable Network Graphics - *.png (see the Notes section)
Portable image format - *.pbm, *.pgm, *.ppm (always supported)
Sun rasters - *.sr, *.ras (always supported)
TIFF files - *.tiff, *.tif (see the Notes section)
For VideoCapture():
AVI files - *.avi
It seems that AVI is the only format with decent cross-platform support. See here for more info.
Use the method cv::VideoCapture::isOpened() to make sure that the constructor was successful in initializing the VideoCapture object.
Note that even if it was possible to get a list of supported container formats from OpenCV (AVI, MKV for instance) with their typical filename extensions, you would still need to know the exact list of supported codecs (and even then the exact file you want to open might be corrupted, etc...). So a list of filename extensions is not enough to accurately describe what is internally supported by OpenCV, and the simplest solution at the OpenCV API level is this isOpened() method.
Just update:
cv::VideoCapture cap("D:\\test.mp4")
works for me.
I am trying to write a video processing application using OpenCV 2.4.2 (in Visual C++ 2010 Express on Windows 7) but I am having trouble displaying certain AVI files. Most display correctly, but when I use an AVI file encoded in I420 format all I get is a striped pink image for every frame (it displays correctly in regular media players).
Output displayed: http://i.imgur.com/BOu6c.png?1
Currently, I am using the C++ API, but the same thing happens when I use the C API (code from this page: http://nashruddin.com/how_to_play_avi_files_with_opencv). I find this strange, because in most answers on this site and resources on the web, they explicitly recommend to use the I420 encoding. Does anyone know what could be causing this or how to fix it?
Here is a trimmed down version of the code I am using:
int main(int argc, char** argv){
string fname = "test.avi";
VideoCapture capture(fname);
if(!capture.isOpened()){
cerr << "error opening " << fname << endl;
return -1;
}
Mat frame;
namedWindow("output");
double rate = capture.get(CV_CAP_PROP_FPS);
int delay = 1000/rate;
while(true){
if(!capture.read(frame)) break;
cv::imshow("output", frame);
if(waitKey(delay) >= 0) break;
}
capture.release();
return 0;
}
I am using is the pre-compiled version of OpenCV if that makes a difference (http://sourceforge.net/projects/opencvlibrary/).
Ok, so I managed to test on a few more computers. One just crashed and, on another, the video played fine. It turns out that it was a problem with FFMPEG being enabled in the default OpenCV compilation having problems with the uncompressed AVI. Recompile OpenCV with FFMPEG disabled or just use a different codec to compress the video.