Segmented recording problem

[PointyHairedBoss]

I am having a problem with Segmented recording. 
Segmented recording always results in 1 less than the number of segments I  set.  The last segment is twice as long as the rest, wraps around the buffer & erases the first segment.
Sounds like a software problem.  Anyone else experiencing this?

[skronstein]

Is the latest software, v3.1, on the camera? http://forum.krontech.ca/index.php?topic=460
If so, what resolution and trigger delay are being used?

[PointyHairedBoss]

I have v0.3.1
Resolution: 1280x1024 1057 fps
I select 4 segments, 2183 frames each.  Pretrigger 1490, post trigger 693 (behaviour is the same for several different trigger delays I tried)

Started recording & triggered 4 times.
2nd segment is frames 1-2183
3rd segment is frames 2184-4366
4th segment is frames 4367-8732
1st segment is lost - appears to have been overwritten by 4th segment which is twice as long as it should be.

[skronstein]

Subtracting 8-10 frames from the length of each buffer may fix this wraparound issue.  So, with 4 segments, you might try subtracting about 64 to 80 frames from the total Record Length.

[PointyHairedBoss]

Subtracting 8-10 frames from the length of each buffer may fix this wraparound issue.  So, with 4 segments, you might try subtracting about 64 to 80 frames from the total Record Length.

Thanks I will try that when I get the camera back. (It's in the mail)

[PointyHairedBoss]

I tried reducing the frames for each segment with no change in the result.
Resolution 1280/720 - total 12421 frames, 4140 each of 3 segments
I first dropped 30 frames - same problem
Then I dropped more & more ending with 12000 frames, 4000 each segment - same problem:  The second segment records 4000 frames, the third segment records 8000 & the first segment is missing, I assume overwritten by the second half of the third frame.

[skronstein]

I have v0.3.1
Resolution: 1280x1024 1057 fps
I select 4 segments, 2183 frames each.  Pretrigger 1490, post trigger 693 (behaviour is the same for several different trigger delays I tried)

Started recording & triggered 4 times.
2nd segment is frames 1-2183
3rd segment is frames 2184-4366
4th segment is frames 4367-8732
1st segment is lost - appears to have been overwritten by 4th segment which is twice as long as it should be.

What if you press the trigger 1 less time than the number of segments? Even after all the segments are filled, the camera continues to record until the red shutter button on the top of the camera is pressed. If you set the number of segments to 4 and press the trigger 4 times, the camera will overwrite the first segment.  But, pressing it only 3 times, the first will not be overwritten because the recording ends right then. This behavior is probably unintuitive and I'll look into whether it can/should be changed.

Also, how are you checking where each segment ends? The Text Overlay on the save settings window gives useful data about current and total number of segments and frame within the current segment, so it is probably the best way to check.

[PointyHairedBoss]

What if you press the trigger 1 less time than the number of segments?  ...
...  Also, how are you checking where each segment ends? The Text Overlay on the save settings window gives useful data about current and total number of segments and frame within the current segment, so it is probably the best way to check.

Using 1 less segment is the way I've been using this mode.  I've been recording birds landing & taking off at our feeder. I make a mental note if the first segment I record looks expendable then I can make a decision whether to use the final segment if something better happens, not worrying that the first segment will be overwritten.  I find this mode of operation good in this instance because although I have a remote trigger I still have to go to the camera to save when the segments are used up & it takes a while for the birds to come back.

I check the segments on the Play screen & the number of frames match my settings (except for the last segment).

Does your camera behave the same way in Segmented mode?  If so, that would point to the software which I assume would be fixed in future and then I can stop spending time trying to figure this out.

[foobar]

I've often found that the last segment when in segmented recording mode is effectively not usable and this is just due to the way that the camera operates.

When you start recording in segmented mode the video memory is divided into segments and the camera starts saving frames into the first segment. At each application of the trigger signal, the camera starts saving frames into the next segment. When the camera is saving frames to the final segment and it receives a trigger event it loops around and begins overwriting the first segment again. This process continues until you exit recording mode using the red button on the top of the camera, or the "Stop" button.

To summarize, the sequence of events is something like this:

• Press the recording button to begin recording, the camera is now saving frames into segment 1.
• Generate a trigger on the BNC port, the camera terminates segment 1 and is now saving to segment 2.
• Generate a trigger on the BNC port, the camera terminates segment 2 and is now saving to segment 3.
• Generate a trigger on the BNC port, the camera terminates segment 3 and is now saving to segment 4.
• Generate a trigger on the BNC port, the camera terminates segment 4 and is now saving to segment 1, which overwrites the first thing we recorded.
• Press the recording button to exit recording mode, the camera terminates segment 1.

As a workaround, you should be able to use the BNC trigger three times for the first three segments and then use the red trigger button to terminate the fourth segment.

[PointyHairedBoss]

Aha!!
I hadn't thought of that.  Thanks - very good explanation.
I've been playing with gated burst which may actually be better for what I'm trying to do.

[skronstein]

Yes, mine operates the same way. As foobar explained, this is operating as intended.
But, we do want to add an option to disable the ring buffer.  Disabling the ring buffer means the camera will stop recording after the final trigger.

[PointyHairedBoss]

But, we do want to add an option to disable the ring buffer.

Good idea

One more thing regarding Segmented & Gated Burst recording - a software wish list item:
I'm not sure there is enough display real estate but it would be handy to see how much memory has been used in each of these modes. 
In Segmented mode "used of total Segments"
In Gated Burst mode "pct% used" or "seconds used of total Seconds" or a full/empty type gauge.

I would be willing to give up a bit of image space on the display for this feature.

[Fyodor]

Aha!!
I hadn't thought of that.  Thanks - very good explanation.

That explains why one segment is lost.

It doesn't explain, why the last segment is double the frames.

[PointyHairedBoss]

It doesn't explain, why the last segment is double the frames.

I think I have an explanation:
When I did the test, the camera was sitting on my desk & I rotated it after each trigger so that I could see the beginning & end of each segment on playback.  After I triggered the last segment, I didn't change the camera position. As foobar noted above, the camera would immediately start recording the next segment, overwriting the first.  Since I hadn't changed the camera position, the overwritten 1st segment looked the same as the last segment on playback.  I thought it was a double length segment whereas it was really 2 segments of the same still scene.