Audio description / Vision Impaired

[Gronw Roberts]

Hi all, I hope you are well.

Years ago I used to receive films with AD in the naming convention but it changed to VI after a while. I was under the impression that Audio Description and Vision Impaired was the same thing but when we checked our headsets today there was no description, only the film audio. I'm a bit confused! We're playing Wonka at the moment. I've for certain heard description over the headsets in the past.

Any light on the situation would be greatly appreciated.

Thanks.

Gron.

[Marco Giustini]

VI = Visually Impaired. That means you the track will have a description of what is happening on screen as you are unable to see. You need a dedicated track on the CPL to have this.

HI = Hearing Impaired. That means the track is usually L+C+R with a boosted C for those who struggle to hear with surround sound etc. The sound processor is the best source of HI as it has an HI output which is automatically generated with everything that is being played back, including commercials and trailers.

AD should be equivalent to VI.

You can play a "channel ID" CPL which will also have HI and VI. The Dolby one keeps saying "Hearing Impaired" or "Visually Impaired" on those tracks while the 5.1 or 7.1 channels are being identified. Sometimes it's just a mis-configuration of your server/sound processor so having a test clip to check things is useful.

I'm not aware of a place where to download such a test CPL though, but your installer should be able to send you a link.

Hope this helps?

[Gronw Roberts]

Hi Marco.

I tested today with a Dolby 7.1 test DCP that has a VI track but but all I get is the Left, Centre and Right channels in the headset.

[Marco Giustini]

There you go. What server do you have and is your sound system 5.1 or 7.1? And what headset do you have and how are they connected to the system?

Do you have someone looking after your system? If they're familiar with the system it might be faster for them to help

[Harold Hallikainen]

Did this ever work? Or did it just stop working? As Marco suggests, more information about the system would help. Also, as he previously suggested, a lot of theaters use a locally derived HI source, doing an LCR mix in the sound processor. On much (most?) content, there is a studio developed HI track on track 7 ( see pages 15 and 16 at https://ieeexplore.ieee.org/stamp/st...number=9161348 ). However, relying on the presence of this track may result in some content not having HI. Also, alternate content (ads, etc.) may not have an HI track. Therefore, it is most reliable to use the sound processor derived HI track. Some sound processors (USL JSD-100) will check for the presence of audio on the HI track and use it if present, and derived if not.

On VI, as pointed out in the above linked RDD, the DCP has VI on track 8. If the server has 1:1 routing, this will be the second channel of AES/EBU pair 4. The Doremi/Dolby HI/VI system pulls the HI/VI audio directly from pair 4 before it gets to the sound processor. The USL/QSC/MIT system has analog audio inputs on the IR transmitter. These are to be driven by the HI/VI outputs of the sound processor. The Dolby CP750 was originally a 5.1 processor with 8 channels, the last two devoted to HI/VI. As 7.1 became popular, they did a firmware update that allowed 7.1 audio to feed the digital 1 (8 channel) input on four AES/EBU pairs, and the HI/VI audio (again, typically on pair 4) to be sent to another digital audio input to drive the "CH7/CH8" audio outputs. The CH8 output would drive the VI input of a USL/QSC/MIT IR transmitter. You could use the CH7 output to use the studio HI track, or the HI output of the CP750 to use a derived HI.

The USL/QSC JSD-60 was also originally designed for 7.1. It has 8 digital input channels that were for the 5.1 audio plus HI/VI. HI can also be derived on the JSD-60. When the JSD-60 is used in a 7.1 auditorium a separate digital to analog converter is required to drive the VI input of the IR transmitter. A typical DAC for that purpose was the DAT-202 .

As I recall, the Sony HI/VI/CC system has both AES/EBU and analog audio inputs.

Then, you get to the HI/VI receivers. The USL/QSC/MIT headphones are available in a couple models. One model has two channels, and you select one, either HI or VI. The other model lets you mix HI and VI at the headphones. If you are hearing Left, Center, Right, etc., you MAY have the wrong channel selected on the headphones.

So... did it ever work?

Good luck!

Harold

[Gronw Roberts]

The Dolby got swapped out recently and the new one was wired for the HI instead of VI. Problem solved. Thank you all for your help. As much as I don't like problems they are a great learning experience!

[Marco Giustini]

Great! You should still be able to get BOTH HI and VI though!

So when you play your Dolby channel ID, you should be able to hear "hearing impaired" and "visually impaired" depending on what channel you select.

[Gronw Roberts]

My boss is going to bring the appropriate leads tomorrow so we can sort getting both the HI and VI wired into the Sennheiser. The HI/VI has almost never been used since we opened but there's been more call for it recently which has brought the problems to light. It's good to know we can offer a better experience going forward!

[Marco Giustini]

Indeed, it's nice to make sure the system is working and that Dolby CPL is very helpful to check things, it removes quite a lot of variables from the equation when suddenly things stop working and you don't know whether to blame the content or the equipment!

It's also difficult to test with actual content as particularly VI is not there all the time so it's always time consuming to "find a spot" where you have description.

[Harold Hallikainen]

There is also test content at https://hallikainen.org/usl/ftp.usli...ent/index.html that includes HI/VI/CC. It was created for ISDCF.

Harold