Problem of decoding h264 video with ffmpeg (Patch #1223)

try the just released OpenCV 2.3.1. Probably, the problem is solved there.

I just tried SVN version of OpenCV 2.3.2 (Aug 18,2011). The same problem remains. When I roll back to OpenCV 2.2 DLLs, it is fine.

My code:
int main(int argc, char** argv) {
string avipath1("..\\video\\video1.avi");
string avipath2("..\\video\\video2.avi");
VideoCapture cap1(avipath1),cap2(avipath2);
int w1,w2,h1,h2,w,h;
Mat image1,image2,image,subimage;
cap1>>image1;
cap2>>image2;
w1 = image1.cols;
h1 = image1.rows;
w2 = image2.cols;
h2 = image2.rows;
assert(w1==w2 && h1==h2);
w = w1 + w2;
h = h1;
VideoWriter writer("..\\output\\result.avi",CV_FOURCC('M','J','P','G'),30,Size(w,h));
image.create(h,w,CV_8UC3);
while(!image1.empty() && !image2.empty()) {
Mat roi1(image,Rect(0,0,w1,h1));
image1.copyTo(roi1);
Mat roi2(image,Rect(w1,0,w2,h2));
image2.copyTo(roi2);
imshow("Playing...",image);
waitKey(10);
writer << image;
cap1>>image1;
cap2>>image2;
}
cap1.release();
cap2.release();
return 0;
}

I fixed the problem for my case. However I am not sure whether it could cause new problems.

[Simple Explanation]
1) In line 589 of cap_ffmpeg_impl.hpp, change "av_seek_frame(ic, video_stream, ts, flags);" back to "av_seek_frame(ic, video_stream, ts, 0);"
2) Follow instruction of ".\3rdparty\ffmpeg\readme.txt" and recompile the opencv_ffmpeg.dll.

[Detailed Explanation]
1) When I did the grab() for the first time and checked the frame number by using get(CV_CAP_PROP_POS_FRAMES), surprisingly it didn't give me 0 or 1 but a number more than that.
2) I tried to set the frame back to the begining by using set(CV_CAP_PROP_POS_FRAMES,1.0). But it gave me a waining message and failed to seek back.
3) I searched from web and found some similar defects as #1419, #1335 and #120.
4) Someone says the last parameter of av_seek_frame() caused the problems.
5) In line 589 of cap_ffmpeg_impl.hpp (in CvCapture_FFMPEG::open()), changing it to be 0 (as in OpenCV220) fixed the prolem of starting from half way.
6) In line 837 of cap_ffmpeg_impl.hpp (in CvCapture_FFMPEG::setProperty()), changing it to be AVSEEK_FLAG_ANY fixed the prolem of not being able to seek to cerntain position.
7) In order to make the changes effective, It is needed to recompile opencv_ffmpeg.dll by following instruction of ".\3rdparty\ffmpeg\readme.txt".

Good work, you guys!
I have just tried the svn version of #8085. In this version the problem has been fixed. Thank you!
Look forward to the final release of OpenCV2.4.