functionality of optical out on TVs, ability to pass 5.1 audio from external sources

correct.


It still true, most tvs will only pass through 2 channel audio. Personally, I have a samsung and a vizio, and the vizio DOES pass through 5.1 audio. Its the only tv i've seen in the past 3 years that does that.

Except for those with Audio Return Channel over HDMI.

I have found that this depends on both the TV, and the source.
My Mits WD-65732 DLP will pass 5.1 on to my AV receiver from my Motorola DVR connected via HDMI. It will not pass 5.1 from Blu-ray or DVD conncected via HDMI.

I also have a JVC 46" LCD LT46-FN97. It will not pass 5.1 from my DVR to the receiver.

Yup. I believe it was developed to provide audio from HDTVs where the tuner was in the HDTV. Beyond that, the HDMI handshaking protocols take over.

Wise choice.

Bringing this thread back to life.

I have a LG 60PV250 and what I found was that Dolby Digital was passed from the TV to the amp when cable TV was selected as input.

However, anything over HDMI was just stereo.

I know we spoke about this but why would cable TV be able to pass dolby digital and not the HDMI inputs? Is there any way around this other than passing the signal straight to the amp?

Many later HDTVs can pass up to 7.1 channels of audio out through the receiver outputs. This feature if present is advertized as "Audio Return Channel". Very few HDTVs manufactured before 2010 have the ARC feature.

The reason for this is that few HDTV manufacturers felt the need to include a more complex and costly multichannel digital audio chipset until people started asking for this feature - then it became a matter of competitive marketing. Inexpensive HDTVs and almost all HDTVs manufactured more than two years ago collapse multichannel sound on the HDMI inputs to vanilla 2.0 stereo output, sometimes 2.1 sound if the HDTV is thicker model and contains a subwoofer.

The optical SPDIF output from the HDTV is different. It passes anything present in the broadcast signal. In the case of the cable input, that is up to the cable company and the cable card they give you to decode the cable signals.

No. ATSC standards (digital tv) use AC-3 as their audio format (discrete 5.1 surround sound). Any audio signal that is generated thru the ATSC tuner (i.e. tv) will be 5.1 which is passed thru the optical cable to the AVR or in stereo if the tv speakers are used. Any other source of audio (HDMI) which passes thru the tv and out optical will be stereo because the tv can't decode the signal and 5.1 is all optical can present. As mentioned, ARC (Audio Return Channel) seems to be the workaround provided that both devices, tv and avr, are ARC-capable. However, there seems to be audio-sync issues at times. For my LG (OTA only), I just use optical out for 5.1 with the tv speakers off. All other audio (DVD-BD, streaming) is handled by the AVR via HDMI.

Correct. But in my experience, HDMI audio/video is always synchronized (It is part of the HDMI specification) whereas optical SPDIF signals often are out of sync with the video. ARC over HDMI eliminates sync issues, but of course you MUST have a more modern HDMI A/V receiver.

^^^^ nice to see another local boy here

The TV will supply the type of digital audio that it accepts. In short, HDMI specifications require all source devices to supply, at minimum, PCM 2.0 audio. All other audio is totally optional. The same specs only require the sync device (TV) to accept the same PCM 2.0 audio and all other audio types are totally optional.

The original chip sets for TVs had two audio decoders, one for the tuner, which would turn Dolby Digital 5.1 into stereo for the internal speaker system and keep it as 5.1 when sent out of the digital audio output of the TV. The other chip set was for the HDMI inputs. HDMI video is non-compressed, and those original chip sets also were designed for non-compressed audio (PCM 2.0). Dolby Digital and all other 5.1 audio formats were originally compressed digital audio signals. The TV, in the EDID handshake, tells the source device what type of signals it can handle and that is what the source device sends to the TV. If the TV cannot handle DD 5.1 via HDMI the source device send ONLY PCM 2.0. The HDMI specifications require the source device to do this.

There is only one type of audio on the HDMI cable at any given time, if the source device is sending PCM to the TV; it is not sending DD at the same time. The TV can only output what it gets and it gets only what it can handle.

Newer chip sets allow the TV to accept DD 5.1 via HDMI and send that out to the AVR or convert it to stereo for the internal speakers. Other types of compress 5.1 - 7.1 audio formats are still rare and even many modern TVs are limited to stereo via HDMI still.

Audio Return Channel is not a guarantee of more than stereo, but it is a good possibility, but not a guarantee.

ARC is not designed to use the TV as an HDMI switching device; it is designed so the TV can send the audio from the TV's internal tuner to the AVR without needing to switch the AVR to a different input. The rest of the HDMI source devices are expected to be connected directly to the AVR and the AVR becomes the switching device.

The current Mitsubishi TVs do accept Dolby Digital 5.1 via HDMI inputs and there are several other brands that do as well but this is still not universal.

^^^Best answer I've seen so far for this Frequently Asked Question!!!