问题
I'm trying to obtain playback video streams from some Axis and Hikvision cameras, using Onvif. I'm doing this in a C# application, and the resulted stream is played in VLC.
Using the FindRecordings/GetRecordingSearchResult calls and then GetReplayUri I can obtain the playback stream (RTSP/H264), but here I have this problem: this behaves like a live stream - I can only use play and pause. I cannot use the time cursor to seek, cannot play in reverse.
So I find this unusable for a playback application - you have to watch the entire recording (days or hours of recording!) in order to see a specific event in time. And once you play it, you cannot go back 1 minute to see it again.
This seems quite stupid to me, so I believe that I'm doing something wrong in my code. Maybe I'm missing some configuration in order to obtain a 'true' playback stream.
My question is: is this playback stream behavior the 'standard' one, and I cannot expect more on this? Or some of you have this working ok (seek, reverse, frame by frame stepping), so I will know it can be done.
Thank you.
回答1:
Reverse playback is possible, but it is not easy. First, the reverse replay is initiated using the Scale header field with a negative value. As an example:
PLAY rtsp://192.168.0.1/path/to/recording RTSP/1.0
Cseq: 123
Session: 12345678
Require: onvif-replay
Range: clock=20090615T114900.440Z-
Rate-Control: no
Scale: -1.0
After the stream is initialized, you will get GOPs in reverse order, not just reversed frames. I don't know if VLC supports this way of operating.
Be aware that only devices with the ReversePlayback capability support reverse playback.
Please refer to the streaming specification for further details.
回答2:
This is not a real solution to the problem above, but maybe it would help others to deal with this situation.
Some cameras with which I worked were continuously recording on the same video file (so the time range was not known) and they were reporting (via RTSP) the available time interval like this:
range:npt=0-
Due to this, VLC was not displaying any time interval in the time slider, so it was not allowing for seek. In my case, it was a requirement to use VLC, so I had to find a workaround to the problem. This was a module which was acting like a proxy, and it sit between VLC and the RTSP source (camera). So all RTSP traffic between VLC and camera was going via this module which I controlled, so I could easily change the responses from camera in a way which was ok for VLC, so I got the seek capability available in VLC.
来源：https://stackoverflow.com/questions/49025449/onvif-playback-stream-cannot-seek