Cameras out of sync - frame rate issue?

[encryptededdy]

Hello!

First of all, just want to say I'm loving Viseron. I'm not using any of the AI features and just using it for 24/7 recording, however I love the very low resource consumption and slick web UI in this mode.

I'm currently using Viseron with a variety of relatively modern Axis cameras, recording in H.264 on a Raspberry Pi CM5 to a PCIe SSD.

My config is very basic and looks like this for each camera:

    m3116lve:
      name: Balcony Wide
      host: 192.168.1.xx
      port: 554
      path: /axis-media/media.amp
      username: xxxx
      password: xxxx
      record_only: true
      recorder:
        continuous_recording: true
        continuous:
          max_size:
            gb: 128
      still_image:
        url: http://192.168.1.xx/axis-cgi/jpg/image.cgi
        username: xxxx
        password: xxxx
        authentication: digest

followed by just an entry for each camera under nvr:

The issue I'm having is that during playback, my two outdoor cameras seem to be a bit desynced from the indoor cameras. Hopefully the below screenshot demonstrates the issue.

You can see the top two cameras (indoor) are within 10s of the indicated timestamp in the timeline view based on the camera's OSD. My other indoor cameras are have a similar 0~10s delay.

However, the two outdoor cameras are running 30s~60s ahead! Sync with the timestamp on the timeline view isn't important to me, however sync amongst the cameras is.

I don't think it's an issue with the cameras themselves, as I've tried putting 3 or 4 cameras up on my computer using ffplay and left them running for hours, when I come back they're still within 10s sync of each other.

The main thing that sets the outdoor cameras apart from the indoor ones is I've configured them to drop their shutter speed as low as 1/5s at night, thus also dropping the frame rate to 5fps (down from the normal 30fps in daytime). I'm not sure what assumptions Viseron makes about static frame rate, but perhaps that causes issues?

The other thing is all cameras are configured for dynamic GOP up to 300 frames, so I wonder if the GOP length is getting too long at 5fps for Viseron to handle?

I don't think the host is being overloaded, as noted I'm running with no detectors, and the Pi has <5% CPU usage and <0.2 load. It's also only using ~512MB/8GB of RAM.

Anyway, interested to hear any thoughts anyone may have on what could be the cause of my issue, or anything I could check to help.

[encryptededdy]

Oh yes, so the other consequence of this is that if I just click into a camera's timeline view, I get a "No Segments found in Playlist" error. Instead, I need to rewind a bit (e.g. if the time is currently 12:00:00, I have to select 11:58:30) then leave + re-enter the timeline page.

The thing is due to the mismatch mentioned above, when I have 11:58:30 in the timeline, I'm actually watching video from 11:59:30 per the camera's overlay (which I know is accurate), which makes sense and is the ~30s delay I'd expect when watching using the timeline view.

I assume it isn't working because 12:00:00 on the timeline would be 12:01:00 from the camera, which is in the future (hence the No Segments error). It almost seems like the time of the segments on disk might mismatch the database/timeline? Not sure. And of course, on the indoor cameras (with fixed frame rate) the time more or less lines up fine.

[roflcoopter]

Sorry for the delay on a response on this one.

The dynamic frame rate shouldnt be an issue (dont quote me on that tho) in the mode you are running. If you tried to use any detectors, then it would definitely be a problem since it uses the FPS to do some calculations.

I dont have any good answers, but a guess is that maybe the RPIs wall clock is off? If you open the terminal and type date, does it correspond with the actual time?

[encryptededdy]

Thanks for the reply. The Pi's clock is definitely set correctly (and if it was wrong, wouldn't I expect all cameras to be out of sync?).

I've done some more playing around with settings and I think I have it fixed now - the main change is disabling the Axis Zipstream Storage Profile on the outdoor cameras running at a low frame rate. With this done and a reboot, it seems like everything is +/- 10 seconds in sync.

From their documentation the Storage Profile enables both B-frames in the H.264 encoding and dynamic GOP length (up to 300). I'm not exactly sure why this would cause an issue, but I suppose at the low frame rate plus B-frames and long GOP length might mess with HLS in some way when playing back (probably needs to read forward and backward a segment to decode? not sure)

Anyway, disabling this isn't a big deal (other than a hit to storage efficiency) and it seems like everything is working now. When I have more time I might try edit the GOP settings separately to see if it's the B-frames or the dynamic/long GOP length that's the cause of the issue.