SDK Exported video sync problem for couple cameras

MIP
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1

Hi,

I am using couple cameras and NTP time server to sync time, in the Smart Client when playback all cameras videos are sync, but when in the SDK selecting the same time and videos exported, all cameras become not sync.

For example selected export start time 17:44:50, in the Smart Client when looking there all videos are sync and can see the same laser position from the different angles, but then video exported, laser is in the different positions for all cameras at the start time.

Also video is exports about 0.6 second earlier. For example selected start time 17:44:50.39, but it exports from 17:44:49.844 time.

2

Please tell me, if you do the export using the Smart Client’s regular support functionality. Do you see the same issue in playback then? -or is the issue only there when using MIP SDK to export?

3

Hi Bo,

Thank you for your answer.

When using regular support functionality, default Smart Client export, the cameras seems to be in sync, but the exported video starts about 0.6 second before the start time.

I am using SKD 2017 R3 version.

VideoOS.Platform.Data.IExporter _exporter;

bool started = _exporter.StartExport(startTime, endTime);

The issue with cameras sync is only in the MIP SDK export and export starts 0.6 seconds earlier than selected start time.

Kind Regards

Dainora

4

In general exports will start with the beginning of the GOP when using MPEG4, H264 or similar, this might explain why the exports starts at another time than what you ask for. This is the expected behavior.

Could you please test with the newest MIP SDK? (2017R3 is old)

5

As ‘In general exports will start with the beginning of the GOP’, Could you let me know will it always do this, or it can this be configured to use another way?

6

Hi Bo,

Thank you for your answer, I just tried 2018 R2 version, it is the same issue as in the 2017 R3.

1
1853×480 80.5 KB

Cameras are in sync.

2

Selecting the same time for two cameras to export.

3
3805×480 73 KB

It exported before the time is selected.

4
4720×405 69 KB

It exported before the time is selected for another camera as well, but the start time is even different for both cameras.

The same issue applies in the MIP SDK export.

I will try 2019 R1 version as well.

7

Assuming cameras is using H.264 or similar, the video contains GOP and Milestone per default will have a GOP length of one second.

When Milestone exports video the export will always starts with the key frame at the beginning of the GOP.

This means that the video from two exported cameras will always starts with a time different between 0 and 1 second.

https://en.wikipedia.org/wiki/Group_of_pictures

8

Hi Rie,

Thank you for your answer.

Could you let me know is it possible to configure cameras that export would start at precise time?

9

It is impossible unfortunately. However when you use MJPEG for camera codec it could improve the gap. This is because in MJPEG every frame is a key frame .