correct way of using the optical audio output on LG HDTV - AVS Forum
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post #1 of 7 Old 12-10-2013, 12:33 AM - Thread Starter
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Hello,

I have a 47" LG HDTV from 2011.  Nothing fancy, still just LCD, but it has an optical output via toslink.  The Chromecast plugs into the TV's HDMI.  There's also a receiver under the TV with an toslink optical input that's free.  My problem is the Chromecast's audio plays through the TV's built in speakers, which sounds tiny.  But maybe all along I've had an alternative but just never realized it?

 

If I connect a toslink cable from the TV's optical output to the receiver, will the audio that's coming from the Chromecast's HDMI be forwarded to the optical output of the TV, then into my receiver?  Will this pipe any audio that's playing from the TV straight to my audio receiver?  So, even OTA digital broadcasts?

 

I couldn't find any settings for controlling the optical audio output on the TV.  Is the TV always outputting to the optical link, and just waiting for a toslink cable to be connected?  I'm also wondering if volume control is controlled via the optical link - so whether I'd use the volume control on the TV or the volume control on the receiver?  I obviously don't want the TV speakers on at the same time as the receiver is playing the audio.

 

Also, is there noticable delays with this setup?  I'm imagining that the HDMI audio has to pass through the TV to the TV's optical output, then to the receiver before it gets played on the speakers.  Is this typically OK?

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post #2 of 7 Old 12-10-2013, 03:44 AM
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I don't know that we have the same model but I also have a LG 47" LCD of about the same age.

There is a problem and I am not sure I have it exactly figured out.

For OTA TV, the optical output correctly outputs DD 5.1 if that is what the station broadcasts, otherwise stereo

I have a Roku streamer connected via HDMI. When I use it, the TV's optical link ONLY outputs stereo, no matter what I set up on the Roku. I believe (but I'm no expert) that the TV asserts it only wants stereo, so the Roku only provides it. The Roku model I have does NOT have its own optical output, only HDMI and there seems to be no way to get DD5.1, but the stereo works OK.

I also have a Tivo DVR connected. Through the HDMI output, only stereo goes to the TV (and comes out the optical output of the TV). However, the Tivo has its own optical output. If I connect it separately to my receiver (and mute the TV's speakers), I get full DD5.1.

So my receiver uses one optical input for the TV and another for Tivo. If I switch between these (for something on the Tivo), I don't notice a change in audio delay, just the transition from 2 channel to 5.1. However, if the TV's speakers aren't muted (or volume set to zero) there is a tiny delay difference there. NOTE: The optical output is not controlled by the TV's volume control and has to be controlled at the receiver.

The optical output works, but you may have to settle for stereo when the source arrives only via HDMI. It still sounds better than "tiny stereo" from the TV's speakers.
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post #3 of 7 Old 12-10-2013, 06:36 AM - Thread Starter
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Thanks for the detailed response.

 

My receiver only has one optical input, so I'm hoping I can use the TV as a selector switch for the audio on different HDMI ports.  Besides the chromecast, I also have a small HTPC on HDMI for playing movies.  The HTPC does have an optical output, so it might be nice to connect the HTPC directly to the receiver for zero-delay audio...but if I do that there's no way to get the Chromecast audio onto the receiver, since my receiver only has one optical in.

 

I'm not super picky about video/audio sync - as long as it's not too egregious I won't notice.

 

Stereo is fine with me.  I don't currently have the center and rear speakers connected anyways.  

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post #4 of 7 Old 12-10-2013, 02:21 PM
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We just got a new Vizio M501 50" to replace a dinosaur 30" HD tube with very limited connectivity. I wanted to try to connect all sources via HDMI to our TV and then use the TV optical out to the receiver. My receiver is also a few years old and has no HDMI connections. But we have always used it for audio, never the TV speakers (I hate the TV speakers honestly).

Previously we had the separate sources hooked up to the AVR receiver, and also to the TV, so we had to switch between sources on the TV, and switch between sources on the AVR. A little bit annoying.

With DirecTV hooked up to the TV and then sound coming out the TV optical to the AVR, there was a noticeable audio delay from what was seen on-screen. Direct sources from the TV like Netflix or a video on a USB stick did not have any lag issues. I haven't been able to try a Blu-ray disc yet.

So I think we're going to have to go back to each source connected separately to the TV, and each source also connected separately to the AVR. A little more cumbersome but we'll have to live with it I guess.
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post #5 of 7 Old 12-10-2013, 05:12 PM - Thread Starter
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Interesting that direct TV had more audio delay than netflix or playing video files directly.  Is your direct TV connected to the TV via HDMI?  And is the netflix appliance (roku) connected to the TV via HDMI?  Or is your Netflix being played by a smart TV?  If the files and netflix are being played by the TV directly, without any HDMI input being used, it seems that ANY signal input from your TV causes some slight delay between audio and video.

 

I wonder if this delay is always the same...if there's a setting on the TV itself to delay the video by a certain amount.

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post #6 of 7 Old 12-10-2013, 08:13 PM
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Netflix comes directly from TV thru optical out to AVR.

The TV has a lip sync setting, but it only serves to delay the audio even farther, so that's no help at all.

I have decided to run each video source individually via HDMI to the TV, and individually via optical to the AVR. Works MUCH better now, no lip sync issues, and I get DD surround sound out of DirecTV (only stereo comes out of the TV optical output, which royally sucks).
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post #7 of 7 Old 12-10-2013, 08:24 PM
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FWIW, I have an LG LD520. TV for us is OTA so we use the bulit-in ATSC tumer. The tv speakers are always kept off and we use the optical out to the receiver. The audio is always crystal clear 5.1 when broadcast. All other devices are connected directly to the receiver via HDMI. I don't know if the LG can pass 5.1 from an external source or not. No audio delay at all from OTA tv, blu-ray movies, or the AppleTV.
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