Playback starts several seconds after start time shown in thumbnail

[bricklayer1807]

I have one of my cameras indoors trained on our catflap so we can keep an eye on our cat's movements, especially at night. In the morning I have a quick look at the thumbnails, which often show his head just emerging from the catflap as he is coming in, and the clock on the thumbnail will say, for example, 04.20.17. If I hover the cursor over the thumbnail I see him come in through the catflap and walk out of the frame, all speeded up of course. If I then click on the thumbnail to watch the recording properly, all I see is the tip of his tail just going out of the frame, and then I noticed that the recording being shown starts at 04.20.21, so there are four seconds missing at the start. Sometimes there will be 5 seconds missing, sometimes 2 seconds, sometimes nothing missing at all, especially if the shot contains very little movement. I have 9 other cameras on the setup and as far as I know they are all playing back without anything missing. Any ideas please?

 

[sebastiantombs]

Set the pre-trigger buffer, located in the Trigger tab of the camera, to two or three seconds.

 

[bricklayer1807]

Set the pre-trigger buffer, located in the Trigger tab of the camera, to two or three seconds.

I've already tried that, it increases RAM and processor load, and I still get 3 or 4 seconds missing from the start of the full-screen playback compared to the thumbnail summary.

 

[sebastiantombs]

Are you using substreams? Are you recording continuously or only on trigger?

 

[mikeynags]

Do you have your key frame intervals set to match your FPS settings on the cameras?

 

[bricklayer1807]

Are you using substreams? Are you recording continuously or only on trigger?

I've viewed this as mainstream direct from the BI program on the dedicated computer we use, and also as a substream on the web interface on a different computer, but the result is the same. We record only on triggar, motion activated. The issue really is why the content of a clip is different on the recording shown in fullscreen compared to that shown on the thumbnail, specifically the fullscreen version has the first few seconds missing.

 

[bricklayer1807]

Ah, maybe it's that - a while back we needed to reduce CPU load so we reduced the frame rates on some of the cameras from 25 FPS to 10 FPS. Do I need to make the same change to the FPS settings within the BI program for those cameras? If I didn't do that, could it cause this problem?

 

[sebastiantombs]

The frame and iframe rates are only set in the camera. BI only receives what is sent to it.

I have 15 cameras running with 24/7 recording. CPU utilization is around 7% using substreams. If I play back a clip it doesn't even get to 10%, whether I play back from the console or through UI3. I never miss motion with pre-triggers set at 3 seconds and post recording set to 5 seconds. Something is funky on your end. Exactly what has me scratching my head.

 

[mikeynags]

Ah, maybe it's that - a while back we needed to reduce CPU load so we reduced the frame rates on some of the cameras from 25 FPS to 10 FPS. Do I need to make the same change to the FPS settings within the BI program for those cameras? If I didn't do that, could it cause this problem?

What is your i-frame or key frame interval set to? if your FPS is set to 10, set it to 10 as well.

 

[bricklayer1807]

What is your i-frame or key frame interval set to? if your FPS is set to 10, set it to 10 as well.

We're recording clips direct to disc, so I believe as this doesn't involve compressing of data, i-frame and key frame settings are not involved. Is this correct?

 

[mikeynags]

We're recording clips direct to disc, so I believe as this doesn't involve compressing of data, i-frame and key frame settings are not involved. Is this correct?

I think it is required when using Direct to Disc - it needs to be a minimum of .5 and it's recommended to be 1.00. Setting the I-frame and FPS to the same # will make it 1.00

 

[bricklayer1807]

Can you tell me where to find the I-frame setting on BI please...

 

[bricklayer1807]

I think you're on to something with the I-frame setting (in the actual camera settings apparently) - I found this on the BI website forums - I'll get to work on it and report back tomorrow after another night of cat comings and goings!

e: Not replaying entire clip

Post by toddgibbs123 » Sat Jan 18, 2020 7:53 am
Looking into this further - it appears most of my cameras are doing this.

Basicaly a camera is triggered and a video recorded. In the preview window i can clearly see an animal (cat, etc) that triggered it. But when I play the video it starts _after_the cat has disappeared and I notice the video is shorter than the preview says it should be.

Does anyone have any ideas?

Thanks
Todd.

toddgibbs123 wrote: ↑
Sat Jan 18, 2020 2:34 pm
Ok, I have tracked it down to the option "Direct-to-disc (H.264/5 IP or hardware encoders only)"

enabling this seems to affect how it replays the clips, reducing their length and missing the first 3-5 seconds.
You need to match your IP camera's frame rate to its i-frame interval in each camera's UI, not in Blue Iris. If the cameras frame rate is set to 20 fps, then the i-frame interval should be set to 20.

The I-frame interval configures the number of partial frames (P-Frames & B-Frames) that occur between full frames (I-Frames) in the video stream. By default, many cameras will generate an I-Frame 2-3 times the frame rate. For example, if your cameras frame rate is 20 fps then the default the I-Frame interval would be between 40-60. This means it will generate a full picture frame (I-Frame) every 40 to 60 frames.

When using Direct-to-disk, Blue Iris will always start recording on the next i-frame and not partial frames. This would cause you to miss 2-3 seconds of every triggered motion event recorded. To avoid this, you should always match the I-Frame Interval to the Frame Rate in each cameras UI configuration, not in Blue Iris. In addition, you can set the "Pre-trigger video buffer" to 3 seconds. You can find this settings in Blue Iris camera settings properties -> record tab.

 

[mikeynags]

It's on the camera itself - attached is pic of one of my Dahua cameras. You can see the I-frame and FPS are both set to 20

 

[bp2008]

The issue really is why the content of a clip is different on the recording shown in fullscreen compared to that shown on the thumbnail, specifically the fullscreen version has the first few seconds missing.

The thumbnail for the clip/alert was being captured before recording had actually begun. This happened because when using direct-to-disc, Blue Iris must always begin recording on an i-frame, and your i-frame interval was too long (in the camera's web interface) and your pre-trigger buffer was too short (in Blue Iris camera properties).

When you mouse over a clip in UI3, the animated preview is just a small set of frames evenly spaced throughout the clip. But while that preview is starting to load, the clip's thumbnail is shown. You therefore mistakenly believed that thumbnail to be part of your recorded video, but it was not. It was just the clip's thumbnail.

 

[bricklayer1807]

So I changed the settings on that camera. The FPS rate was on 10 so I left it on 10. The i-frame was set on 2 so I changed that to 10. Sent the dog and cat in front of that camera, then looked at the previews vs the proper recordings. Now the proper recordings, instead of starting 4 or 5 seconds late, are starting 8 or 9 seconds late compared to the previews!

 

[sebastiantombs]

Glad it's resolved.

 

[bricklayer1807]

It's not resolved, it's worse! I want the proper playback to start at the same moment that the preview does...

 

[bricklayer1807]

I changed the i-frame setting to 1 and I think that's fixed it... Thanks everyone for all the help.

 

[bp2008]

It sounds like your camera wants you to specify the i-frame setting in seconds, so in that case you are correct to set it to 1. You can verify what Blue Iris is getting if you look at the camera properties > general tab in Blue Iris. You should see the frame rate followed by a forward slash and then a number which is the number of i-frames received per second. In your case it should be "1". If you had one i-frame every two seconds (a common default value), you would see "0.5" there.

Hikvision and Dahua and many other cameras make you specify the i-frame interval in frames, not seconds, so be careful not to get these confused.