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Digital video transmitters-latency-interference-etc...


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Starting new project. I was just informed that video going to be all wireless. Systems that i have not worked with before. Either HPvideo or Microlite. 5.8ghz systems. HPvideo claims 1ms latency and Microlite claims 120ms.

Anybody here have real world experience with these systems? 120 ms- seems like enough to warrant a delay.

thanks!

john

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My latency concern is only in relation to people listening via comteks and watching live picture. I agree 120 ms is enough to be of a bother. And adding the potential frame of delay from the monitors themselves is not something i considered.

Is the Behringer shark still the best bet for cheap, DC powered delay? In a pinch i could route the comtek feed thru one channel of 788t and apply delay but ties up an input that i may need for this particular project.

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Marc, 33.33 ms is about 1 frame of delay at 30 fps and 33.37 ms is about 1 frame of delay at 29.97 fps. At 23.98 fps, 1 frame of delay is about 41.7 ms. I sort of made the assumption that John's gig will be at 23.98 FPS since it will doubtless be HD video. Once you get inside 2 or 2 1/2 fps either direction it will be hard to tell what's wrong for the average viewer although some folks will sense something's not quite right. Time delay for frame rate is easy, divide the time (1 second) by the number of frames and move the decimal point in the answer 3 places to the right to express 1 frame of delay in ms.

John, I think they changed the model number of the Shark delay (DSP 110 now?) but it still uses a device specific AC supply.

Best regards,

Jim

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John,

I have used my Shark only once, coincidentally with the last director on the last episode. It was set for 60ms! Enough to bother him, I guess, but no other director. Had bigger delays over the years, but I always ask if they want Comtek to match monitors or "live" actors. Until just now, it's always been live actors. This director said, "If I am watching the actors, I am not wearing headphones. I only wear headphones at the monitors." He is probably my favorite TV director, Michael Lange.

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Does the video hop also carry audio? Send your mix to camera, then attach your comtek transmitter to a feed out of the video reciever or monitor, the delay should be the same as the video, and you don't have to buy another piece of hardware to fix a problem you didn't create.

Just a thought.

That's assuming the live camera output doesn't simply pass audio through without latency. The latency on transmission may or may not be the same for audio/video.

But it's worth a try for sure.

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Does the video hop also carry audio? Send your mix to camera, then attach your comtek transmitter to a feed out of the video reciever or monitor, the delay should be the same as the video, and you don't have to buy another piece of hardware to fix a problem you didn't create. Just a thought.

Tried that once with a Boxx system. It was a disaster. The video was not perfectly rock solid but watchable. This resulted in very long times of audio muting, much longer than the length of time that the video was not stable. Regardless of where the fault actually was occuring- it was considered by the director and producer to be a sound problem.

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This is typical that they would call it a "sound" problem. It's a data problem. I bet the sound was fine going into the system.

I have corrected producers in the past when there's a lip-sync problem in a film or video transfer, and they say, "oh, the sound is out of sync." I've said: "well, the picture and sound are out of sync with each other -- it's hard to say which is at fault. It could be that the picture is a frame early, as opposed to sound being a frame late."

It's always much too easy to point the finger at sound.

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Audio Delay quick wolf guide

SHARK DSP110 a digital delay also called a delay line, the audio delay is set matching the picture delay so that the 2 are in sync on the monitor.

How to save settings

It’s important to leave the DSP110 powered on for several minutes after creating new settings for any function so that they will be saved. When you power it up again the new settings will be remembered and re-appear.

To lock the front panel:

Push and hold the LOW CUT button (till all 5 LEDs above display are on) – the LOW CUT YELLOW LED will blink. Do the reverse to unlock the unit to be reset.

How to increase the speed of UP-DOWN control

This works for any parameter where there is a big numeric difference between minimum and maximum.

Press and hold the UP or DOWN arrow keys, to initiate resetting of numbers.

While holding the UP or DOWN button, press the opposite direction button a couple of times. Each press makes the numbers increase or decrease at a faster rate. Cool -

TO ADJUST LOW CUT

Press low cut button briefly – LED lights up. Hold the DOWN button till you see OFF in display. To count faster hold DOWN and press UP briefly several times. Range of cut off is 150Hz to Off. For speech use I suggest somewhere between 80 and 120 Hz for a roll off. There is no info on the slope of the filter.

TO TURN OFF GATE

Press GATE button briefly – LED lights up.

Do not press and hold Gate button – if led flashes, gate is in learning mode – that’s would activate it.

You do not want it ON at all!

Press DOWN until you see OFF in display.

To count faster hold DOWN and press UP briefly.

To make the gate work

Using the Noise Gate Learn Function

With no program material going through the system (the input turned down at the previous stage), press and hold GATE button until all parameter lights at the top are lit.

The DSP110 will automatically adjust the gate threshold to suppress any unwanted noise.

monitor what you just did so you know what it sounds like!

TO TURN OFF COMPRESSOR

Press COMPRESSOR once.

You see numbers from 0-100.

For density, press and hold DOWN until you see 0.

To count faster, hold DOWN and press UP briefly often.

Press COMPRESSOR a second time – the m sec light above display comes on. This is the attack time adjustment. It should not matter.

Mechanical Controls

Mic input gain pot in the rear with switchable +48 V phantom power for mic.

Digital headroom adjust pot on front left with 5 vertical LED display – automatically keeps output level the same, it only controls digital headroom for maximum S/N. Do not let the red LED come on ever!

Shark Turnoffs:

It may be RF sensitive so keep it away from Comteks, transmitters, etc. The remote power supply has a transformer in it that radiates a magnetic field. It gets pretty warm, ventilate.

It has good sounding 24-bit A/D and D/A converters and XLRs and phono jacks.

It has an awkward-to-adjust compressor and a noise gate with LEARN Mode useful as a total quieting tool only.

List $ 99.99, Street: $ 80.00 what a deal! By Behringer engineered in Germany, made in China, poorly written manual, external power supply on 6 ft. cable. Terrific tech help at Behringer USA 1-425-627-0816 X 141 ask for JH; he has some FAQs to email to you (the useful info is included in this manual).

For sales info http://www.behringer.com/DSP110/index.cfm?lang=ENG can be purchased from many places such as: http://www.bswusa.com/searchresult.asp?searchType=keyword&searchValue=DSP110

http://www.guitarcenter.com/Behringer-Shark-DSP110-182463-i1125202.gc?source=4WFRWXX&CAWELAID=54980068

http://www.fullcompass.com/product/283265.html

In La: Ametron, Guitar Center, Ash music

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  • 3 weeks later...

Following up: We used the HP video transmitters and they worked very well. Very impressive range and picture was really high quality- this is clearly going to be the new standard for HD video assist. It just looked great and camera was able to move very fast with no cables. Scary- because the video at times had better range than my wireless systems. So the capability of camera to pull off really long complicated walk and talks and keep video village happy certainly raised the ante with regard to our capability to hear those actors on those walk and talks......

There were a few instances where they were interfering with wireless boom using a particular combo of Schoeps and UM Transmitters. Weird digital hash. Changing to a Sanken cs-3e or changing to a butt plug worked fine. Also, there are tiny fans on these units but only in the quietest of scenes would i hear them. Usually intimate dialogue with mostly static cameras- so cabling was an option.

Delay was handled to by video assist using a shark. For reasons not quite figured out- the shark( an $80 dollar tool) from time to time had to be adjusted to keep in sync. But video took care of it and it was a non issue. Whew! Being a HD show and me needing to see picture at all times, i was cabled to video assist anyway. We made up a video and audio cable loom and it was done.

MIxing to a delay is no fun. Clearly missed some cues because of it. Only happened a few times and i adjusted.

Thanks to all who contributed to this thread. All good info.

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