bug in opencv ffmpeg wrapper. (Bug #1815)

It seems the new ffmpeg wrapper solved the frame positioning bug. However, it introduces a new bug.
The function VideoCapture::get(CV_CAP_PROP_POS_FRAMES) gives wrong results.
Here's the code producing the problem:

1capture.set(CV_CAP_PROP_POS_FRAMES, i);
2capture >> frame;
3int j = capture.get(CV_CAP_PROP_POS_FRAMES);
4cout<< "get =" << j << "| set:" << i<<endl;

The output is:

get =8| set:2000
get =10| set:1998
get =12| set:1996
get =14| set:1994
get =16| set:1992
get =18| set:1990
get =20| set:1988
get =28| set:1986
get =30| set:1984
get =32| set:1982
get =34| set:1980
get =36| set:1978
get =38| set:1976
get =40| set:1974
get =46| set:1972
get =48| set:1970
get =50| set:1968
get =52| set:1966
get =54| set:1964
get =56| set:1962

The problem could lie in following code. frame_number is also a member of CvCapture.

 1void CvCapture_FFMPEG::seek(int64_t frame_number)
 2{
 3    frame_number = std::min(frame_number, get_total_frames());
 4    int64_t dts = dts_to_frame_number(ic->streams[video_stream]->cur_dts);
 5
 6    if (abs(dts - 2 - frame_number) > 16)
 7    {
 8        double sec = static_cast<double>(frame_number) / static_cast<double>(get_fps());
 9        int64_t time_stamp = ic->streams[video_stream]->start_time;
10        double  time_base  = r2d(ic->streams[video_stream]->time_base);
11        time_stamp += static_cast<int64_t>(sec / time_base);
12        av_seek_frame(ic, video_stream, time_stamp, AVSEEK_FLAG_FRAME | AVSEEK_FLAG_BACKWARD);
13    }
14
15    while(dts - 2 < frame_number)
16    {
17        /* cv::Mat imag = read(); */
18        if (!grabFrame()) break;
19
20        dts = dts_to_frame_number(ic->streams[video_stream]->cur_dts);
21    }
22}