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AJS1
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TiVo Optical Audio Output

My TiVo doesn't output in Dolby Digital sound. I have it connected to my 5.1 surround sound controller from the optical connector on the TiVo. I have checked the TiVo audio settings at Dolby Digital and my sound system is ok.

Thanks

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Rabangus
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Re: TiVo Optical Audio Output

I have hdmi AND optical out going from my Tivo box to my Denon AV receiver (so video and sound go through the receiver). I used this setup on the previous generation Tivo box and the new V6 without any issues. Most HD programmes show as Dolby Digital (except on the BBC - they are just rubbish when it comes to surround sound - only a handful of the content on their HD channels actually has surround sound).

Regards

Rowan

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cybmole
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Re: TiVo Optical Audio Output


AJS1 wrote:
.... Also, as yet I've been unable to find a menu that disables Dolby out, apart from the audio setting obtained through the Help and Settings menu or by pressing info on the remote control ..

that's the setting I was thinking of. I suppose we could resort to RTFM, but I don't know where mine is Smiley Happy

 there's swapping cables to try, but surely with optical it either works or doesn't - there's no half way house ?

 i suggest sharing some specific broadcast titles with Rabangus...  who has a working system, & compare your results with his

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Rabangus
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Re: TiVo Optical Audio Output

Yeah, I'm willing to test something if you can give me a title to check if I'm getting surround sound on it...
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Superuser
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Re: TiVo Optical Audio Output


cybmole wrote:

 


BenMcr wrote:

Dolby Digital doesn't guarantee that there are going to 5.1 channels.

Dolby Digital can quite easily be 2.0 i.e Stereo, just encoded using Dolby Digital AC3 rather than MPEG.


and this is where I get confused. my TV has the optical audio out going to a non-Dolby equipped hifi amp. If i send it anything with Dolby encoding added and it screeches or gives up. so the tv is set to substitute PCM stereo

 I believe that optical out is compressed surround i.e. it's like having 2 wires but with matrix encoded data superimposed on the 2 real channels.. it has to be 2 channel as optical can convert to digital coax & vice versa so only 2 real channels. the receiver decodes the overlay and sends it to surround speakers

 I can't quite get my head around ac3 with zero additional encoding. I know that I can watch ac3 stuff on PC in say VLC player and it handles all that in the background, so PC is fine with just 2 speakers, & if I use TV + plex ( either built in or via a Roku box ) then the plex server / clients sort all that out so I don't have to think about it...


So my understanding is that Digital Optical uses the optical light signal to transmit a fully compressed digital signal. It's not set to 2 channels or anything else. This is why your non-DD system can't interpret the audio as it's getting a format it doesn't understand. PCM is an older format that anything with an optical in should understand, which is why the down-sampling option is there on TiVo - but because it's uncompressed it can only do stereo in the available signal space.

It's slightly similar to HD and 4K both using HDMI. If you set the V6 box (or any other 4K system) to 4K only and then connected it to an HDTV, the TV wouldn't display anything as it's a format it can't process.

All AC3 is is an encoding format, but one that is designed to support audio multiple channels, and do so in a reasonable amount of data space. Similar to MPEG2 or MP3, AAC, FLAC, VP9 or any of the other video and audio formats. So as long as the system you're playing the file on has an decoder for the audio format, and that decoder knows how many speakers are attached, then it'll play back. 

**********************************
I work for Virgin Media - but all opinions posted here are my own
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Superuser
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Re: TiVo Optical Audio Output


AJS1 wrote:

So my controller is interpreting Dolby Digital - English 1 as either Dolby Stereo 2.0, ( and showing stereo) and only  showing Dolby 5.1 if that's how the programme is encoded and transmitted. 

Phew. I finally understand. Thanks very much.


As long as your TiVo box isn't set to down-sample to PCM (which you say you've already checked), then that does seem to be the case than only 'full' Dolby Digital 5.1 shows up as such on your audio system.

**********************************
I work for Virgin Media - but all opinions posted here are my own

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Superuser
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Re: TiVo Optical Audio Output

Not all  programs broadcast in dolby, check with something like planet earth 2






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AJS1
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Re: TiVo Optical Audio Output

Thank you for your prompt reply. Yes, I am aware that a lot of programmes don't have Dolby sound but I'm not getting it with those that do. I used to have a V+HD box which produced Dolby sound, where available. 

My Tivo box is only producing stereo, which my 5.1 controller can convert to Dolby Pro Logic II and not Dolby Digital sound.

 

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AJS1
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Re: TiVo Optical Audio Output

Update on original post.
I'm now getting Dolby Digital output intermittently from my TiVo box. I have assumed that getting Dolby output is dependent on the bit rate of the sound on the programme. If this is not the case then there may be DRM issues with Dolby, which cause the sound output to default to stereo on some programmes and output in Dolby Digital on others.

Before this conclusion, I thought that the problem might have been with the TiVo optical output. So I did try using an hdmi to hdmi and optical switch box but that made no difference to the output.

Obviously, I don't think Virgin will be interested in solving this problem because they've moved on to promoting their new box!

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LittleMick73
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Re: TiVo Optical Audio Output

Hi if you have tv with an optical port plug it directly to that, that is how mine is configurated & it works perfectly, unfortunately the base models of tvs will not have that port so if that's the case not sure what you can do. Regards Micky
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AJS1
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Re: TiVo Optical Audio Output

Hi LittleMick

Thanks for your prompt reply. My tv has an hdmi in and an optical out. However, the tv sound output is only in stereo so I have the sound from it on mute. My TiVo box optical out connects to my Logitech surround sound controller, which is capable of relaying Dolby 5.1, DTS, Dolby ProLogic II as well as stereo.

As stated, I've concluded that the TiVo is only producing an output of Dolby 5.1 intermittantly and over 50% of HD channel programmes have stereo sound output, even though the TiVo sound setting shows Dolby Digital.
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cybmole
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Re: TiVo Optical Audio Output

Any surround sound info going into a tv via hdmi is not allowed out except as 2.0 stereo.

Hollywood rules. Tv makers have to comply. 

 You have to send dolby sound directly to an av receiver which has pass thru to forward the video to the tv.

If the content is in a built in smart tv app or OTA different rules apply

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AJS1
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Re: TiVo Optical Audio Output

Hi cybmole

Thank you for your interesting reply. In my case I'm connecting an hdmi cable from TiVo to my tv for display and an optical cable from TiVo to my surround sound controller. So I should be getting  whatever TiVo is indicating it's transmitting. As previously indicated, a large number of Dolby indicated programmes from TiVo are, in fact being transmitted in stereo from my TiVo. 

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cybmole
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Re: TiVo Optical Audio Output

its possible, likely even. that the tv guide is wrong and that said programs are not broadcast in Dolby to begin with. I am pretty sure that the Tivo faithfully records what it is sent.

there is a preference option somewhere in tivo menus that disables dolby audio out - you may need to check that. it may be a hdmi setting that may / may not also affect optical out. I don't use the Tivo optical port myself, ideally you need to hear from folks who so 

 name some shows where you think 5.1 sound has gone a.w.o.l.

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Rabangus
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Re: TiVo Optical Audio Output

I have hdmi AND optical out going from my Tivo box to my Denon AV receiver (so video and sound go through the receiver). I used this setup on the previous generation Tivo box and the new V6 without any issues. Most HD programmes show as Dolby Digital (except on the BBC - they are just rubbish when it comes to surround sound - only a handful of the content on their HD channels actually has surround sound).

Regards

Rowan

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