Sound static when playing content off of laptop to fm transmitter

[Randy Stankey]

Is the Mac in close enough proximity to the fm transmitter that you could plug the aux cord into the headphone jack of the mac rather than the projector's aux out? You'll definitely want to turn the Mac's volume down to about 1/3 if you do this.

That's how I would do it. I would hook the computer directly to the transmitter or processor with a good audio cable.
Start with the computer's output volume at 1/3 to 1/4 of it's maximum value. Then, set your processor/transmitter input gain at default position. Some equipment has a center mark. Some has a "zero" setting as opposed to turning the gain control all the way down to actual zero. If you don't have a default or "zero" mark, start at the lowest setting.

Start your program and slowly creep the gain control up to a level where you get good sound then back off just a smidgen.
If your equipment has a level meter, use that. Turn the gain up until the level meter reads correctly.

If you can't get a good sound level, return the gain control to default, increase the computer's volume output by a few clicks and do it again. Repeat the process until you get good sound.

Whenever you are hooking an "unknown" input to your sound system, you should always start with all your settings at or near their lowest settings then build up from there.

If you don't, you risk blowing out somebody's ears when the sound suddenly starts blaring, you could end up with bad sound like you are talking about or, worse, you could damage speakers and other equipment.

[Marcel Birgelen]

Plenty of non-technicians and audience members would describe a ground loop hum as static. Considering the setup in question: ground loops, gain-staging issues, and interference are all possible here.

Anyone who doesn't know the difference should not be setting up drive ins.

Any possibility it's a lack of decoding of DTS or Dolby encoding?

I can't really imagine a signal path where you're getting a DTS/Dolby bitstream decoded as PCM and still can hear the original audio too, but then again, there's a lot of junky gear out there.

I guess once the projector is eliminated from the signal path and the transmitter has been directly hooked up to the MacBook, the static or whatever it is, will be gone. Luckily, for the time being, Apple still puts headphone jacks onto their MacBooks. Some more recent models even have a hybrid TOSLINK port on there, which could be an alternative for an unbalanced analog signal, if both the Mac and the transmitter support it.

[Dave Macaulay]

It's experience, not bias, that has me avoiding Apple stuff for cinema work. Things that should work... just don't.. Can't explain it. But avoiding macOS avoids lots of problems.
Dolby, Barco, NEC, GDC, Christie have all privately said "please don't use MacOS". IMAX prohibits techs from using Macs, even running bootcamp Windows.

If your image and sound are good with a pc, then just get a pc for the DI and keep the mac for other things.

Direct connection to the headphone jack will be best regardless. HDMI is tricky and d-cinema gear is somewhat flaky with it. When I have had issues, support asks me to try a connecting a normal DVD player... when that works ok they tell me "our stuff is fine, fix your source".

[Marcel Birgelen]

It's experience, not bias, that has me avoiding Apple stuff for cinema work. Things that should work... just don't.. Can't explain it. But avoiding macOS avoids lots of problems.
Dolby, Barco, NEC, GDC, Christie have all privately said "please don't use MacOS". IMAX prohibits techs from using Macs, even running bootcamp Windows.

Can you tell this the Dolby engineers themselves too, as they clearly didn't get that memo.

Dolby Atmos Production Suite is only available for the MacOS version of ProTools.

[Dave Macaulay]

Content creation is a different subject entirely, and Pro Tools is pretty much the standard for audio production. Apple is used almost exclusively in "prosumer" content creation and in a majority of professional studios.
For service work on projectors, servers, etc. ... a PC brings much less trouble.

[Carsten Kurz]

Barco is the only company supplying a dedicated Mac version of communicator. So, in general, of course, using a Mac/OS(X) machine as a cinema tech doesn't make much sense (it does work perfectly well with a bootcamp windows). Most techs will prefer a Windows laptop with a real physical COM Port anyway.

But this topic is not about a cinema tech's notebook, but a video playback machine/VLC.

I use a Macbook Pro for playback and content creation, and I own a WIN7 DELL and WIN XP Dell notebook, both with integrated COM Ports, for cinema tech style work, and the occasional software that is not available for mac OS. I prefer to buy second hand Apple machines, as their price policy in recent years has grown to the absurd.

- Carsten

[Sean McKinnon]

As Mark indicated I have found that when overloading the input to FM transmitters it sounds like "static" like you are not getting a good signal. Try the volume control in VLC or if it has it on the transmitter itself. I ran into this problem when I connected my I-phone to an FM transmitter for testing. I had to turn the phone AND the transmitter way down and then the signal was crystal clear!

[Marcel Birgelen]

Content creation is a different subject entirely, and Pro Tools is pretty much the standard for audio production. Apple is used almost exclusively in "prosumer" content creation and in a majority of professional studios.
For service work on projectors, servers, etc. ... a PC brings much less trouble.

They may have had a competitive advantage for professional content creation, but they lost that years ago, when they decided to become a boutique electronic jewelry company instead of a computer company. Apple has neglected their professional segment for years on end, which lead many shops including us to switch to Windows machines for content creation. For example, Apple totally ignored their MacPro line for years. The only thing they had on offer was the "trashcan" Mac, which had zero expandability, was hopelessly outdated by the time they replaced it and wasn't even officially available in some markets around here.

Macs are still required for Final Cut Studio/Pro and Final Cut X workflows, but Final Cut lost a lot of traction too, due to decisions made by Apple, to abandon a large part of their user base by essentially ending development for their original product and substituting it by something new, that wasn't even compatible with the old stuff.

[Gordon McLeod]

Still no awnser to what is the projector being used since he says the projector aux audio is feeding the FM transmitter and what is the transmitter used

[Marcel Birgelen]

Still no awnser to what is the projector being used since he says the projector aux audio is feeding the FM transmitter and what is the transmitter used

You may check his other topics regarding this, it's not a DCI projector, but something else. Many "hobby" projectors do have AUX outputs, but they should be used with caution and maybe as a last-resort if there's really no other way to get audio out of the thing you're projecting from. There are quite some DVD players, for example, that do not have any form of analog out or other means of splitting audio to a separate HDMI output.

[Van Dalton]

I can't really imagine a signal path where you're getting a DTS/Dolby bitstream decoded as PCM and still can hear the original audio too, but then again, there's a lot of junky gear out there.

Probably not the same thing you're talking about, but I used to have a JVC DVD-Video player (XV-N312 IIRC) that would bleed a little bit of the audio through the coaxial digital audio output. If you connected it to an analogue line-in (like a stereo receiver) and monitored it on headphones you could hear it faintly above the digital hash. I don't know if it was internal crosstalk (poor isolation) or if its DAC was improperly wired, or what.

[David Buckley]

Would help to have an audio sample, record it independently perhaps with your phone, confirm that it is an authentic sample of what you are terming "static".