How to reduce latency?

DLVid

Member
Hi all, as we get closer to going back on location I thought I'd do some testing of my TC2E to check its latency to see if it will work for Imag. My testing method is as follows: I have a BMD Ursa Broadcast camera connected to the switcher via SDI. I have a black burst generator connected to the switcher and camera. The camera is set to the same format and frame rate as each session. I have a laptop running a millisecond timer. I am shooting the laptop display with the camera and outputting that signal on my critical monitor. To find latency, I take video of both screens, find a clean frame of both images and do some simple math. The results were surprising. Genlocking the system resulted in significantly higher latency. I then went on to test adjusting the camera lines of timing and the switcher H & V position. The camera lines had an effect but not in the right direction. Switcher H & V had no effect. Below is a table of the results. I'd really like the system to be around 60 - 80ms; thoughts? Your feedback is welcome. Anyone using a TC2E for Imag out there?
SESSIONSOURCE TIMEOUTPUT TIMECAMERA LINESLATENCY (ms)
720P/59.94FREE RUN26.01125.8890122
GENLOCKED36.31836.1260192
1080P/29.97FREE RUN19.96519.7750190
GENLOCKED17.08916.8310258
1080P/59.94FREE RUN42.23442.1090125
GENLOCKED10.36810.2360132
CAMERA LINESLATENCY (ms)
1080P/29.97FREE RUN19.96519.7750190
GENLOCKED7.0076.750257
48.79948.5421257
58.78358.5282255
2.2691.953319
14.59114.3324259
38.62238.3665256
57.72357.469-1254
19.00418.688-2316
4.8954.574-3321
49.69549.374-4321
23.39223.199-5193
28.79928.54310256
2.1411.887-10254
SWITCHER H POS
13.18212.92620%256
16.79616.5450%256
15.35515.180%255
4.4464.19-20%256
5.9515.694-50%257
56.57456.318-80%256
SWITCHER V POS
17.14916.89420%255
5.5995.34150%258
53.72653.4780%256
54.55954.302-20%257
45.79145.535-50%256
55.29255.053-80%239
 

kanep

NewTek SE
Genlock works by delaying signals, it not surprising this would have an effect, it is what genlock does. The main question is, does the output of the TriCaster need to be timed to something else?

Also the critical viewing display likely has a native resolution. When signals are set to it that do not match, it has be adapted which will add some latency, so that can account for some of the timing differences when working with different resolutions.

What you might try is genlock all of the cameras, but not the TriCaster. Then turn off frame syncs on all cameras.

The other aspect is how much of the timing is in the camera (because it isn't zero millisecond from lens to output) and how much is in the TriCaster. You might try is playback of a video clip in the DDR showing timecode, loop back into an input. Then put the DDR source and input into a M/E side by side and do a frame grab.
 

DLVid

Member
Hi all, as we get closer to going back on location I thought I'd do some testing of my TC2E to check its latency to see if it will work for Imag. My testing method is as follows: I have a BMD Ursa Broadcast camera connected to the switcher via SDI. I have a black burst generator connected to the switcher and camera. The camera is set to the same format and frame rate as each session. I have a laptop running a millisecond timer. I am shooting the laptop display with the camera and outputting that signal on my critical monitor. To find latency, I take video of both screens, find a clean frame of both images and do some simple math. The results were surprising. Genlocking the system resulted in significantly higher latency. I then went on to test adjusting the camera lines of timing and the switcher H & V position. The camera lines had an effect but not in the right direction. Switcher H & V had no effect. Below is a table of the results. I'd really like the system to be around 60 - 80ms; thoughts? Your feedback is welcome. Anyone using a TC2E for Imag out there?
SESSIONSOURCE TIMEOUTPUT TIMECAMERA LINESLATENCY (ms)
720P/59.94FREE RUN26.01125.8890122
GENLOCKED36.31836.1260192
1080P/29.97FREE RUN19.96519.7750190
GENLOCKED17.08916.8310258
1080P/59.94FREE RUN42.23442.1090125
GENLOCKED10.36810.2360132
CAMERA LINESLATENCY (ms)
1080P/29.97FREE RUN19.96519.7750190
GENLOCKED7.0076.750257
48.79948.5421257
58.78358.5282255
2.2691.953319
14.59114.3324259
38.62238.3665256
57.72357.469-1254
19.00418.688-2316
4.8954.574-3321
49.69549.374-4321
23.39223.199-5193
28.79928.54310256
2.1411.887-10254
SWITCHER H POS
13.18212.92620%256
16.79616.5450%256
15.35515.180%255
4.4464.19-20%256
5.9515.694-50%257
56.57456.318-80%256
SWITCHER V POS
17.14916.89420%255
5.5995.34150%258
53.72653.4780%256
54.55954.302-20%257
45.79145.535-50%256
55.29255.053-80%239
Good idea. I recorded the millisecond timer in DDR 1 and played it back in an M/E with split screen with DDR 1 on one side and mix 4 (DDR 1) re-entered to input 1.
SESSIONSOURCE TIMEOUTPUT TIMECAMERA LINESLATENCY (ms)DDR 1 RE-ENTRY TEST
1080P/29.97FREE RUN2.3982.334N/A64
GENLOCKED49.66449.559N/A105
 

DLVid

Member
I did some additional research on the Blackmagic Ursa Broadcast cameras and learned that they have 60ms of latency. This tracks with the testing I've done.
 
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