1

This issue relates to Mac Book Pro's and hdmi audio functionality.

I am trying to resolve an issue for a community hall. The hall has a light projector (BenQ) with small internal speaks, and a Home Theater box with surround sound system (Sony BDV-E290).

All hdmi ports and cables are hdmi 1.4.

Normally, a single HDMI cable connects the light projector to the hdmi (incl ARC - Audio Return Channel) port on the back of the Home Theater unit.

The Home Theater unit has the surround sound speakers connected to it.

One can play a video file put on a usb thumb drive and plugging it into the Home Theater unit. Both video on light projector and sound via surround sound speakers plays.

Connect MacBookPro mid 2012 Retina laptop, so as to play video using internet on this system using the hdmi port. Connect MBP via hdmi cable to a powered hdmi splitter. This is to enable one hdmi cable out of the splitter to go to the light projector, while a second hdmi cable plugged into the hdmi port of the home theater unit so it can play the hdmi delivered digital sound data.

With this set up there is no sound from the home theater unit speakers, only video on the light projector.

Despite checking all home theater, and MBP settings, reading manuals, and lots of net research re Mac hdmi, hdmi sound, hdmi standards, etc. I am very puzzled.

The below diagram illustrates this set up.

The question is, should I expect this to work?

Alternatively, am I missing some technical understanding of the hdmi and sound capability of the macbook pro, hdmi port, or hdmi splitter, or concept of hdmi delivered ARC return?

After several hours of research I do not understand what the problem is conceptually, or in practice.

I have confirmed that the audio data output via the MBP hdmi port is active, and all hdmi cables are working. I have confirmed the surround sound speakers are working. I have read (several times) the home theater instruction manuals and tried all settings to my understanding, and played with any other setting I could think of value.

One experienced mac person's solution is that I need to use an hdmi switcher, rather than an hdmi splitter, and use an hdmi audio extractor to stream off the audio data from the laptops hdmi cable. Then rather than the audio data being supplied to the home theater box via its hdmi port, input the audio data via a fibre Tosink audio cable into the audio fibre port available on the theatre box for 5.1 surround sound.

This I think should work. However, I am puzzled and questioning that I should need to do this. Surely such a simple first solution should work. Yet, it does not.

Some relevant links: HDMI ARC functionality Confirms my understanding and use of ARC via hdmi. Apple MBP hdmi port audio functionality Confirms MBP hdmi port includes hdmi 1.4 and 5.1 surround sound consistent with home theatre box.

System set up diagram below.

  • Yes. Have achieved sound to light projector from laptop via hdmi splitter. Sound/audio only not porting or playing on home theatre box. From another forum and feedback the issue could be the technical aspects of ARC, to which the hdmi port in the back of the home theatre box handles audio ARC input only. Beyond this possibility, no clear confirmed understanding of why the above arrangement does not supply the respective video and audio data to the respective devices. Splitter vs switcher is another possibility as to the problem, though I do not see why. – Cam_Aust Mar 8 '17 at 13:09
  • The only time I did get sound from the laptop, is from the light projector and via the splitter. I suspect though this would have worked without the splitter with the light projector, so hdmi cable direct from light projector into laptop, if I had of earlier had better understanding of the audio set up settings. So the answer to your question is not quite definitive. Direct connnection of MBP to home theater box via hdmi cable does not produce sound. – Cam_Aust Mar 8 '17 at 13:31
  • Allan, yes right you are. Understand I have not met home theater systems before, have been learning everything as I go, and its not at my home, but in a Hall were I need key access to rethink and retest new thoughts like you suggest, as I put all the relationships together in my mind and think of such logical tests. I have also been told many different solutions or even there is no problem. Your logic is spot on. I am about to post a key part of the answer to this puzzle. – Cam_Aust Mar 9 '17 at 1:27
  • @Allan I am thinking to delete my comments now that the problem seems solved to keep things tidy. If you think they add to the understanding, and the solution, I can leave them? – Cam_Aust Mar 9 '17 at 5:50
1

The below solution has now been implemented. It did work.

Can now plug in a laptop, access internet, play video, and have sound play via home theatre system.


This technical information is key to why this set up does not work.

HDMI-ARC uses two pins on the hdmi cable an unused one and the hot detect pin, it is not part of the normal data stream and does not use the normal pins. It's basically a coax spdif connection in reverse.

The confusion has arisen it would appear, when the home theatre box manual mentions ARC return feature associated with the HDMI port in a way suggestive of it being essentially a two way hdmi port.

It would seem ARC does not deliver audio data by the standard way of hdmi video/audio data streaming protocols, or even by the same internal physical pins.

A TV set will return ARC signal, as it is designed to use this different standard for the return audio.

Apparently, ARC is part of the hdmi standard though, as was commented on another site.

ARC is part of the hdmi standard .... it was an addition to HDMI to allow a TV to return audio back to an AVR., to replace a spdif coax or optical cable.

This missing technical understanding re ARC explains why a suggested solution was to add to the hdmi cable from the laptop at the theater box end, an hdmi audio extractor box, with a audio fibre Toslink (for 5.1 surround sound) or RCA for stereo sound, input to those available audio input connections on the back of the home theater unit.

The situation has been confusing. It would seem reasonable to assume the connection functionality of the home theater box would be inclusive of plugging in a laptop device, one accessing the internet for various audio visual media. Hence, when not working, the natural assumption is that there was something wrong with the numerous setting options, which is where I began, or the functional capacity of the hdmi laptop port or laptop settings.

However, it seems not so. The danger of unconscious assumptions!

A second part of the problem is that it the hdmi splitter should be an hdmi switcher, so that the hdmi video data can be selected as coming from the theater box or the laptop.

Diagram of expected solution set up below.

Credit and thanks to the guys on the Whirlpool site, as well as those commenting here.

Expected solution, will confirm.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .