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» Film-Tech Forum   » Operations   » Digital Cinema Forum   » Sony STW-C140GI HI/VI problem

   
Author Topic: Sony STW-C140GI HI/VI problem
Bob Ezra
Film Handler

Posts: 67
From: Carbondale, CO, USA
Registered: Apr 2001


 - posted 12-19-2013 06:34 PM      Profile for Bob Ezra   Email Bob Ezra   Send New Private Message       Edit/Delete Post 
Glasses work fine but HI/VI (receiver with headphones) drops out consistently

Placed the transmitter in the auditorium with antenna down/ up and in between. Placed transmitter at every conceivable angle in the booth and auditorium. Tried every channel (there are 14 to choose from) multiple times

Moving around the auditorium ,with receiver and headset, sound consistently drops out. Cannot sit anywhere in the auditorium without waving the receiver all over to get reception or get rid of static (like a portable FM radio).Even when standing close to the transmitter in the booth the sound is erratic.

We used a wifi sniffing app and found 6 or 7 devices on the 2.4ghz frequency wave in our building (a multi-use 1900's structure).

At this point Sony has no solution and in a last ditch effort I thought maybe someone here might have some insight or a possible solution.

Thanks

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Ken Lackner
Phenomenal Film Handler

Posts: 1876
From: Atlanta, GA, USA
Registered: Sep 2001


 - posted 12-20-2013 09:47 AM      Profile for Ken Lackner   Email Ken Lackner   Send New Private Message       Edit/Delete Post 
Bob,

Is this a single screen theater? If not, I would try swapping the transmitter with another auditorium. Have you tried more than one receiver?

The recommended placement of the transmitter is parallel to the ground, antenna side facing the screen, with the antennas folded IN so that the antennas are parallel to the screen. Have you tried this orientation? Also, how are you holding the receiver? The receivers should be supplied with lanyards, which must be attached so that the receiver can be worn around the neck. It, too, must be parallel to the screen for optimum reception; placing it in a pocket or cup holder will diminish the reception.

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Bob Ezra
Film Handler

Posts: 67
From: Carbondale, CO, USA
Registered: Apr 2001


 - posted 12-20-2013 12:26 PM      Profile for Bob Ezra   Email Bob Ezra   Send New Private Message       Edit/Delete Post 
Ken

Thanks for the reply.

Single screen.
Interesting tips but not sure they will help since , other than the lanyard idea, I tried the others.

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Harold Hallikainen
Jedi Master Film Handler

Posts: 738
From: Denver, CO, USA
Registered: Aug 2009


 - posted 12-20-2013 12:49 PM      Profile for Harold Hallikainen   Author's Homepage   Email Harold Hallikainen   Send New Private Message       Edit/Delete Post 
Good luck with this! Because of FCC requirements, license-free transmitters have to use very low power. Further, license-free systems have no protection against interference from other users of the same spectrum (which may be your issue, since you're seeing several Wi-Fi signals). Since you have a spectrum analyzer showing you the Wi-Fi signals, can you watch for the Sony transmitter on the spectrum analyzer and choose the Sony RF channel that lands between the Wi-Fi signals? I think you've said that you've tried all the channels, and none of them is great, but this might be a way of finding the best channel you can.

It's interesting that the closed captioning is working and that it is the HI with the issue. Closed captioning, of course, uses a substantially lower data rate, giving more time for retransmission of the data. Sony uses a protocol that is very similar to that which USL uses for closed captions over IR. The information about the next caption (text, time in, time out, etc.) is transmitted repeatedly from the TimeIn of the previous caption until the TimeIn of the current caption. So, captions are transmitted one caption in advance and are transmitted several times (as much as time allows). So, even with marginal reception, at least one of the caption packets gets through. For audio, however, there is not the bandwidth to transmit the audio repeatedly and doing so would also add excessive latency to the audio. So, the audio transmission is more fragile.

Even with reliable coverage, there can be issues with the use of RF in these applications. Because of the limited number of channels, multiplex theaters face channel re-use issues. Users or theater staff have to configure the receiver such that the audience member hears the appropriate HI or VI-N audio, not one from another auditorium. Infrared systems do not face these issues since the signal is confined to the auditorium.

Because the Sony closed captioning and HI/VI-N system is relatively new (it's only been manufactured for a couple years), perhaps the theater has an existing IR system (emitter and headphones) that could be used for HI/VI-N and keep the Sony system to handle the closed captioning. Or, if not, USL would be happy to provide an IR system (of course).

Good luck!

Harold

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Bob Ezra
Film Handler

Posts: 67
From: Carbondale, CO, USA
Registered: Apr 2001


 - posted 12-20-2013 01:05 PM      Profile for Bob Ezra   Email Bob Ezra   Send New Private Message       Edit/Delete Post 
Harold

I was hoping you would weigh in on this.

The HI/VI is the most requested. None yet for the glasses.

They are cool and expensive.

Thanks for your analysis its kind of how I was thinking/learning about it.

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Marco Giustini
Film God

Posts: 2539
From: Reading, UK
Registered: Nov 2007


 - posted 12-20-2013 01:35 PM      Profile for Marco Giustini   Email Marco Giustini   Send New Private Message       Edit/Delete Post 
What Harold says is solid. My limited experience with those glasses is that I've never heard a glitch in sound or a drop in subtitles no matter where I was in the auditorium. Sound and subtitles were always spot on anywhere, even outside of the auditorium.

Do you have the same problem if you walk by the emitter?

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Bob Ezra
Film Handler

Posts: 67
From: Carbondale, CO, USA
Registered: Apr 2001


 - posted 12-20-2013 01:40 PM      Profile for Bob Ezra   Email Bob Ezra   Send New Private Message       Edit/Delete Post 
sound is poor when close to emitter ( transmitter)

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Gordon McLeod
Film God

Posts: 9449
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 12-20-2013 02:56 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
we still have not been able to get rid of the loud static on the USL VI channel at one location

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Harold Hallikainen
Jedi Master Film Handler

Posts: 738
From: Denver, CO, USA
Registered: Aug 2009


 - posted 12-20-2013 03:29 PM      Profile for Harold Hallikainen   Author's Homepage   Email Harold Hallikainen   Send New Private Message       Edit/Delete Post 
Gordon, sorry to hear about the issue! Since I designed the system, it's my fault! Anyway, the system does not bring up the carriers until there is audio. It holds the carrier up until 30 minutes after audio is last detected.

We transmit HI at 2.3MHz, VI-N at 2.8MHz, and closed captioning as FSK at 1.8MHz. An FM receiver, of course, normally has a hissing sound when no RF is present. If we have the HI carrier up and the captioning carrier up (with a difference of 500kHz), there is a low level intermodulation product generated at 2.3MHz PLUS 500kHz, which lands on 2.8MHz. The intermod product is generated anywhere a circuit is not perfectly linear (and nothing is perfectly linear). The better the linearity, the lower the intermod product. So, a very low level signal is generated by the nonlinearity of the emitter and the nonlinearity of the receiver. IF there is the normal 2.8MHz carrier present, it is much stronger than this intermod product, so there is no problem. But, if there is no VI-N audio (such as during trailers), no carrier is brought up, and the receiver instead gives you this intermod product (and the captioning data sounds fun in your headphones).

I suspect you have IRH-230 headphones. Give us a call about trading them for IRH-280 headphones. These headphones have better selectivity (use of ceramic filters instead of LC networks), have a 1.8MHz trap to attenuate the captioning carrier, AND have a squelch. So, in the absence of carrier, the headphones are silent. In my tests, the headphones remain silent if you are on the VI-N channel, captioning is running, and the VI-N carrier is not up. If you get real close to the emitter, the headphones can still get overloaded, and the sound comes back. But, in most cases, I believe the IRH-280 will solve the problem. Give us a call about a swap!

Harold

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Gordon McLeod
Film God

Posts: 9449
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 12-20-2013 03:35 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
We had already done the swap but to no effect what is odd is that these units reproduce nothing on the VI channel and we had tried swapping the vi and hi inputs
after the chaos of the holidays we are going to get back to that location and delve into it

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Harold Hallikainen
Jedi Master Film Handler

Posts: 738
From: Denver, CO, USA
Registered: Aug 2009


 - posted 12-20-2013 04:28 PM      Profile for Harold Hallikainen   Author's Homepage   Email Harold Hallikainen   Send New Private Message       Edit/Delete Post 
Thanks Gordon! Please give me a call when you're ready so we can solve the issue.

Harold

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12134
From: Annapolis, MD
Registered: Dec 1999


 - posted 12-20-2013 04:34 PM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
My experiences with the UPC-28c have been mixed.

First off...I've found, using the CP750 as the source, that the VI-N input on the UPC-28c has to be turned down all of the way (1V) on the higher sensitivity setting and forget about using compression or you'll boost the noise.

The other thing is that, as Harold states, you can overload things if you get too close...as in the back rows. I have one theatre where I pointed the panel at the side wall of the theatre to knock it down...still have plenty of coverage in the far corner of the theatre...the IRH-280s are quite sensitive. I was even wondering if there is a way to turn down the intensity of the LEDs for smaller rooms so they draw less current, less heat, last longer and don't overload the system.

In other theatres we mounted the panels in the booth to knock the signal down a bit.

Oddly enough, for the HI track, we take that off of a processors HI output, not from the DCP track...there we turn the compression up to 3:1 (max) and set the sensitivity to .2V since at .3 we have had the carrier not turn on in some locations, depending on the volume setting of the processor and the program material.

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Marco Giustini
Film God

Posts: 2539
From: Reading, UK
Registered: Nov 2007


 - posted 12-20-2013 07:25 PM      Profile for Marco Giustini   Email Marco Giustini   Send New Private Message       Edit/Delete Post 
Bob,

I'm a bit puzzled that you have poor sound when you are by the emitter as well. As you sure the noise is not coming from the source? The SONY has an unbalanced input, it may catch some noise over the cable? Can you try a different source - an ipod, a DVD player, whatever - to double check?

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Bob Ezra
Film Handler

Posts: 67
From: Carbondale, CO, USA
Registered: Apr 2001


 - posted 12-20-2013 11:08 PM      Profile for Bob Ezra   Email Bob Ezra   Send New Private Message       Edit/Delete Post 
I will look into that...

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