What exactly do HDMI to HDMI + audio extractors do ? - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 14 Old 11-03-2013, 01:51 AM - Thread Starter
Member
 
chriscalvert's Avatar
 
Join Date: Dec 2011
Location: New Zealand
Posts: 15
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
When an HDMI to HDMI + audio extractor is queried by a source device what replies as to the state of the sink ?
ie is the sink the final device or the extractor device.
From this follows as to what the source device sees as the audio capabilities of the sink.

I want to feed a TV and an AVR amp from the same 2 output channel HDMI switch. Since the TV interferes with the AVR output I am looking at connecting an HDMI to HDMI + Audio extractor. Extractors I have seen say that 2 channel audio will only be present if it is on the originating HDMI signal. So the extractor will present multi-channel audio since that is what will have been negotiated by the source by querying the AVR (or from the HDMI channel that the extractor is on). Now I have found another extractor or converter that will convert multi-channel digital audio down to 2 channels stereo. So theoretically the HDMI signal from the audio extractor will go to the TV and the audio will come from the audio decoder and I will be a happy boy.

However this wil only work if the HDMI to HDMI + audio doesn't send back any information as to the audio capability of the sink (the TV). Hence my question as to what actually negotiates on the sink end. And I suspect they would sell bucket loads of them.
chriscalvert is offline  
Sponsored Links
Advertisement
 
post #2 of 14 Old 11-04-2013, 12:33 AM
AVS Special Member
 
Colm's Avatar
 
Join Date: Aug 2002
Posts: 4,652
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 87
You are going to have to check the documentation for any product you are considering. There is no industry standard. Monoprice has one that is switch selectable between passing through the audio capabilities of the sink and telling the source that it "supports all audio formats", whatever that really means.
Colm is offline  
post #3 of 14 Old 11-04-2013, 02:16 AM - Thread Starter
Member
 
chriscalvert's Avatar
 
Join Date: Dec 2011
Location: New Zealand
Posts: 15
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
This stuff is so hard to find out the exact functions that they will do. I have found the device you have referred to. It looks like it is product 10251 (called an HD Audio Converter)
In Mode B it tells the source that it handles all audio modes. This is exactly what I want so that it won't confuse the other output channel on my 2 output switch. The other channel goes into a full AVR amp giving me multichannel sound which is also what I want.

Mode B states - The source device is told that all available audio modes are supported. This allows you to select advanced multichannel audio strteams for playback on your home theater audio system AND
Note 2 states - When using Mode B, please ensure that your audio system supports the selected audio output mode. If you select a mode that is not supported you will either hear only noise out of the speakers or will hear nothing at all.

Your can't actually select the audio out put other than by chosing which cable to use. If the right signal isn't coming out of the selected cable (because the input feed from the source will be full multichannel) then I am out of luck. I would have to presume that the Audio Converter will turn the multichannel sound into stereo.

The outputs are -
1. 3.5mm jack with 2 RCA plugs at the end
2. Coaxial
3. Optical

Now optical and coaxial outputs presumably can have multichannel audio on them but are irrelevant to me because I only want stereo output to feed the TV with. So if I use the 3.5mm jack and feed this to the TV does this mean that I will get a stereo signal out ? (Still to check that my TV will let me do this since I am basically then using 2 different inputs).

This next bit below is a quote from a user review -

" I bought this to be able to get 5.1 sound to my receiver even though one of my TVs only supports 2.0 pcm. The a-b switch on the back works great but if I want to watch the TV that doesn't have the receiver and only supports 2.0 it only can receive sound information on channels with 2.0 soundtracks or if I switch it back to A and force a 2.0 output. I ended up buying an optical to analog decoder on amazon as there was no equivalent part available from monoprice. This part could be perfect if there were a second version that included the DD and DTS decoder built-in. "

This is sortof confirming that this user had the same issue as I mention above.

So I probably need 2 adapters (assuming I can access the TV stereo inputs as well as the HDMI for the video). I am starting to think that using HDMI as a method of distributing video/audio around your house isn't a good choice. BUT it may be the only way as end or sink devices are doing away with the older analog connectors and inputs.

What I need is an HDMI to HDMI adapter with an audio downscaler in it. That keeps the source end happy and my sink happy without the two interfering with each other.
chriscalvert is offline  
post #4 of 14 Old 11-04-2013, 03:42 AM
AVS Special Member
 
Joe Fernand's Avatar
 
Join Date: Oct 2001
Location: Scotland, UK
Posts: 1,085
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 60
An audio extractor mostly does what it says on the tin ‘extracts’ the audio as being output by the Source – some will include EDID management to allow you rather than the Sink (TV or Projector) to set the Source.

What you are looking for ’up to’ 5.1 Input via HDMI with ‘up to’ 5.1 HDMI + simultaneous 2.0 RCA Output can be achieved – usually by combining a 1x2 Distribution Amp with an Audio Converter (on one Output of the Distribution Amp).

Is the requirement to sometimes listen via the AVR and at other times to listen via the TV speakers?

Wasn’t too sure what you meant here ‘Since the TV interferes with the AVR output’!

Joe

If I've helped 'Like' me on Facebook - www.facebook.com/Octavainc

Joe Fernand is online now  
post #5 of 14 Old 11-04-2013, 08:52 AM
 
alk3997's Avatar
 
Join Date: Jan 2004
Posts: 3,722
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 87
Quote:
Originally Posted by chriscalvert View Post

This stuff is so hard to find out the exact functions that they will do. I have found the device you have referred to. It looks like it is product 10251 (called an HD Audio Converter)
In Mode B it tells the source that it handles all audio modes. This is exactly what I want so that it won't confuse the other output channel on my 2 output switch. The other channel goes into a full AVR amp giving me multichannel sound which is also what I want.

...

What I need is an HDMI to HDMI adapter with an audio downscaler in it. That keeps the source end happy and my sink happy without the two interfering with each other.

Let me simplify this for you. HDMI can only have one audio stream at a time on the cable. So, if you are trying to have stereo and multichannel at the same time, then you can't do it. If you are thinking of downconverting multichannel to stereo, you will need a device to do this.

So, if you have stereo TV and a multichannel AVR getting the same HDMI signal at the same time, then either 1) the TV will not produce sound but the AVR will get mulitchannel or 2) the AVR will only get stereo. Remember only one type of audio at the same time.

That's why the comments were made.

BTW, the easiest way to send stereo and multichannel at the same time is to start at the source. Most (but not all) sources have the ability to send an analog (or S/PDIF) stereo signal when sending a mulitchannel digital signal. Distribute both as needed and this way you don't worry about stereo on the HDMI signal Of course this then requires that the TV has the ability to use analog audio when displaying an HDMI picture (not all TVs can do that).
alk3997 is offline  
post #6 of 14 Old 11-04-2013, 09:02 AM
AVS Special Member
 
AV_Integrated's Avatar
 
Join Date: Jun 2005
Location: Northern, VA - Washington, DC
Posts: 2,801
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 87 Post(s)
Liked: 253
Chris - It sounds like you want exactly what I am describing in this thread:

http://www.avsforum.com/t/1495839/in-line-hdmi-audio-dsp

Since you can't get simultaneous stereo and multi-channel audio from HDMI (stupid idiots at HDMI!!!), then you need to convert things in-line and you need a DSP (digital signal processor) to do this. It doesn't exist. I don't think the Monoprice HDMI Audio Converter does what I originally believed it to do, which was downmix surround sources to stereo, so it just does EDID spoofing to fool the source into believing that all endpoints are HD audio compatible.

The HDMI audio converter would be totally amazing if it provided a HD audio down conversion to stereo on the HDMI cable as it went through it and also provided a stereo audio analog output. Unfortunately, it does neither from HD audio sources the more I read the specifications.

AV Integrated - Theater, whole house audio, and technology installation in the Washington DC metro area.
AV_Integrated is offline  
post #7 of 14 Old 11-04-2013, 09:55 AM
AVS Special Member
 
Colm's Avatar
 
Join Date: Aug 2002
Posts: 4,652
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 87
Quote:
Originally Posted by AV_Integrated View Post

It doesn't exist.
Sure about that? IIRC Gefen has something that will do the job. Of course, it is expensive.
Colm is offline  
post #8 of 14 Old 11-04-2013, 11:09 AM
AVS Special Member
 
AV_Integrated's Avatar
 
Join Date: Jun 2005
Location: Northern, VA - Washington, DC
Posts: 2,801
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 87 Post(s)
Liked: 253
Quote:
Originally Posted by Colm View Post

Sure about that? IIRC Gefen has something that will do the job. Of course, it is expensive.
Pretty sure about it. Always a changing world out there, but this is one I haven't heard of or seen yet.

This kind of is it, but doesn't handle HD audio DSP...

http://www.gefen.com/kvm/gtv-auddec.jsp?prod_id=8202

It kills me as a complete A/V receiver which does handle pretty much any flavor of HD and standard surround audio can be had for just a few hundred bucks with amplification built in, but receivers don't do in-line HDMI audio conversion.

AV Integrated - Theater, whole house audio, and technology installation in the Washington DC metro area.
AV_Integrated is offline  
post #9 of 14 Old 11-04-2013, 02:35 PM
AVS Special Member
 
budwich's Avatar
 
Join Date: Dec 2002
Location: Kanata, Ontario, Canada
Posts: 1,321
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 21
Hey Chris...

I think you might be in "luck" depending on your actual setup. I use a monoprice 4X2 matrix switch to feed a samsung plasma and an denon avr. The output of the AVR then feds two displays, a projector and samsung dlp rear projection TV. I used this setup because the plasma needed audio while the other two units rely on the avr for sound. This was "interesting" because as you have found / read, that the "negotiation" would cause some audio issues.... sometimes resulting in the avr only seeing incoming "stereo" while at other times, 5.1 audio... note I only distribute a sat feed thru this overall setup (only need 5.1 dd) while bluray is fed directly to the receiver to handle "higher" sound encoding and ultimately video distribution to 2 subtending displays. It took a bit of head scratching to figure out why it worked some time and not others. As you have found if I "shut down" the plasma and repowered up the matrix switch, then I could get 5.1dd from the sat to the avr otherwise the avr indicated that all sat channels were 2 channel. After, some experimenting, I found unplugging the hdmi cable going to the plasma was all that was needed along with the "repowering" of the matrix switch. From there as along as everything stayed powered even in standby, things would be OK. Plasma got sound, AVR got 5.1 for channels sending that and so on.
In our area, power hits happen regularly :-(, so the "unplugging" is a bit of an issue as this might cause port problems so I stuck a manual switch in the plasma hdmi connection which allows me to switch to nothing and then back. That solves the problem of "plug wear"...., everything is happy and so am I.

IF your basic requirement / layout is similar, I suspect you will have similar "success". I am not sure whether this is a monoprice "bug" or an "oops" of HDMI edid management. My guess is that edid management isn't as great as one thinks and that bits / capabilities get kind of "nanded" so to speak so once they are set, they kind of stay set for a given connection. The cost of the setup was $70-80" so not too pricey for a "trial".
budwich is offline  
post #10 of 14 Old 11-05-2013, 08:28 AM
 
alk3997's Avatar
 
Join Date: Jan 2004
Posts: 3,722
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 87
For less than $50, you can take the HD component video output and analog stereo output from the source and convert it to HDMI:
http://www.amazon.com/Component-video-YPbPr-HDMI-Converter/dp/B003U7LKUE

Send that to the TV and it will be independent from the multichannel audio.

I don't know the quality of the component video to HDMI conversion in the above adapter. It only seems to go up to 720p and has a number of bad reviews but the idea is good.


I suppose an analog audio injector into the HDMI signal would also work - haven't had time to research that option. Fox uses (or used) what they call "the splicer" to inject local audio and local graphics into their digital stream without decoding. We basically need the consumer equivalent of that.

Edit: a quick seach produced:
http://www.automatedhome.co.uk/new-products/keene-audio-embedder-injects-digital-audio-into-your-hdmi.html
alk3997 is offline  
post #11 of 14 Old 11-11-2013, 01:52 AM - Thread Starter
Member
 
chriscalvert's Avatar
 
Join Date: Dec 2011
Location: New Zealand
Posts: 15
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
I need to add a little more information here to explain what I want to do and why and some of this is based on stuff I have read since my original post.

Whatever I end up with has to be wife proof. I still haven't managed to get her to hold the Harmony One steady when she turns the system on. Incidentally the remote works much better now that I sequenced power on from the sink back through to the source.

On the HDMI output of my amp which feeds my main TV (50" Plasma) I also have a smaller 24" screen only which is used to navigate audio selection instead of having the plasma turned on (500w per hour). Both these are fed from from a small HDMI splitter. Audio not a problem because my amp provides the sound. Whatever it sends back as a sink doesn't seem to affect the source. Okay with that.

I also want to feed a TV in the kitchen with a stereo version of the audio so that my wife can continue to watch stuff while in the kitchen.

I can see now just how this isn't going to happen with out some creative thinking. I already note that if the TV is left on standby (rather than switched off at the wall) or is on (and therefore telling the source that the lowest common denominator is stereo) my amp promptly switches to stereo. I want 5.1 in the lounge and 2 in the kitchen.

And it is now too late to run additional cables from the lounge to the kitchen.

So leaving aside exotic devices that nobody appears to be 100% sure just how they work or that I see reports saying that such and such a device didn't work quite the way they thought it would I am left with this conclusion.

Somewhere I need a device to convert the HDMI 5.1 down to 2. This can be either at the TV end or the lounge amp end.
If at the TV end I need another amp to feed through video and split out the audio - in this case I don't have a problem with adding a couple of small PC speakers fed both from the TV speakers and from the amp. It can only increase the quality of sound from the TV anyway.
Another way might be to use an HDMI to DVI cable feeding into a DVI + Audio to HDMI adapter and then using the existing HDMI cable to the kitchen TV. I could extract the audio from the pre-amp outputs that my amp has. Just need a way to convert the 5.1 to 2 analog signals and feed this into the DVI to HDMI adapter. I am thinking that this might be a preferred way to go.

I found a device called Delock HDMI Stereo / 5.1 Channel Audio Extractor. The blurb says "the audio signal can be sent digital (S/PDIF) and analog (stereo) to other devices such as headphones or a surround receiver." And it is HDCP compliant. Switchable between stereo and 5.1 channel. If it is HDCP compliant I have to presume that whatever you set the switch to will be reflected back to the source
chriscalvert is offline  
post #12 of 14 Old 11-11-2013, 06:15 AM
 
alk3997's Avatar
 
Join Date: Jan 2004
Posts: 3,722
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 87
Quote:
Originally Posted by chriscalvert View Post

I need to add a little more information here to explain what I want to do and why and some of this is based on stuff I have read since my original post.

Whatever I end up with has to be wife proof. I still haven't managed to get her to hold the Harmony One steady when she turns the system on. Incidentally the remote works much better now that I sequenced power on from the sink back through to the source.

...

I found a device called Delock HDMI Stereo / 5.1 Channel Audio Extractor. The blurb says "the audio signal can be sent digital (S/PDIF) and analog (stereo) to other devices such as headphones or a surround receiver." And it is HDCP compliant. Switchable between stereo and 5.1 channel. If it is HDCP compliant I have to presume that whatever you set the switch to will be reflected back to the source

I'm not sure you are completely understanding what you are trying to do. HDCP has nothing to do with this other than if you aren't HDCP compliant you won't get any signal, video or audio.

The EDID handshake is what sets whether the source sends stereo or 5.1-channel or 7.1-channel. The EDID goes from sink to source. The audio and video signals are sent from the source to the preamp to the sink, but the EDID goes the other way from sink to the preamp (who modifies the audio parameters) then to the source.

But, the most important thing to remember is that you can only have one audio stream at a given time. So, once the source is sending 5.1-channel out, there is no way to also send stereo out.

As you pointed out converting 5.1-channel analog to 2-channel analog is a valid way to add a stereo output. To do that you would have to downmix, using some variety of mixer, all six channels of the 5.1-channel output into stereo. The difficulty of this is that you have to know how much of each channel to add together, although simply adding each channel at the same level can produce a rough approximation of what the stereo stream should be.

I say rough because the Dolby Digital, TrueHD and DTS-HD MA (but not regular DTS) source programs all carry what is called "downmix coefficients". These tell a decoder that if they are converting to stereo to set each channel to these individual levels. One big thing the downmix coefficients do is to prevent clipping (or at least they are supposed to) since combining 3 or 4 channels into one channel can result in a signal that is too loud for the preamp to decode properly. The coefficients also keep the back channels and LFE from being too loud when converted to stereo.

Unfortunately, once you convert to analog those downmix coefficients are lost.

Why not just use the front left and front right channels to send to the other TV? I'll use (strangely enough) NBC Nightly News as an example. When Brian Williams is talking, his microphone is sent over the center channel only. When commercials are played their dialog is usually but not always sent over the left and right front channels with the center just used for effects. So, if you just use the front left and front right, then you would not hear Brian Williams at all but you would hear the commercials in all their glory. So, you do have to mix all 6 channels to get a valid stereo output.

So, you'll need something that mixes the channels together. I have used an old Marantz AV560 pre-amp to do that from a digital signal. So, basically convert the HDMI signal to digital S/PDIF (as you wrote) and then send the S/PDIF signal to another pre-amp to convert to stereo. Then re-combine that audio with the video and send to the stereo TV over HDMI. Hope "like heck" that the audio and video are synced properly since I'm not sure you could fix that if they aren't. The AV560 doesn't exist anymore but many current receivers will downmix S/PDIF into 2-channel.

Your DVI suggestion is interesting. If your stereo TV has an S/PDIF input (some have S/PDIF outputs but not inputs), you could send the S/PDIF output to the TV directly with the video coming by DVI (which is the same video signal as HDMI). If the TV can convert 5.1-channel to stereo, you are set. If not then if your HDMI to S/PDIF converter doesn't change the EDID (most do) to stereo, then you would be set. But you would have to check carefully since many of these adapter do their "downmix" by telling the source to just send stereo when you flip the 5.1-channel switch to stereo. In other words, the device doesn't actually downmix but just tells the source to do it instead. In that case your pre-amp would also see stereo instead of 5.1-channel audio.

The webpage for the device you referenced says, "Switchable between stereo and 5.1 channel". It says nothing about being able to do both simultaneously. It also does not reference TrueHD or DTS-HD MA, which might mean that a Blu-Ray player will only send Dolby Digital or regular DTS if connected to that device. You might want to check with the manufacturer before purchasing to see the limitations.

Of course, if your present pre-amp already downmixes while outputting 5.1-channel audio over the speakers, then all you would have to do is to re-combine (re-inject) the audio into the video signal.

Either way you are looking at more little boxes and probably between $100 and $600 to do this, depending upon your current pre-amps capabilities.

It is still easier (and more cost effective) to do all of this at the sources and then send that as a separate audio signal. Unfortunately I understand that running extra cables can be difficult in many pre-existing installs.

This all goes back to only one audio stream at a time over HDMI.
alk3997 is offline  
post #13 of 14 Old 11-11-2013, 11:12 AM - Thread Starter
Member
 
chriscalvert's Avatar
 
Join Date: Dec 2011
Location: New Zealand
Posts: 15
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
I do understand everything that you have stated above. I maybe hadn'tt phrased things quite the way my mind is thinking. I must admit it did take a while to get my head around only one audio stream at a time. For some reason this part of the design of HDMI I link in my mind to requirements dictated by HDCP to prevent anybody from easily extracting and recording any of the high end video/audio signal. Either way the end results are the same - one stream at a time.

My amp does have a Zone 2 stereo output BUT not if any of the source signal contains digital audio. It does have 5.1 (actually 7.1) preamp out analog signals which won't be affected by HDMI. If I injected this back into an HDMI stream solely going to the TV in the kitchen then I should be okay. I was hoping for a more generic solution than this since it does require the presence of the preamp outputs which may not exist on a future amp.

All my HDMI sources have analog outputs so I could rig up something using this as a source but switching would be a nuisance, plus newer source devices don't have analog anymore.

I take your point about synching but maybe not too much of an issue (as long as it wasn't too far out) because the TV would be a background thing and my wife would be doing other things. As long as she can see the picture to catch up with where the scene is taking place and can hear the audio maybe not an issue.

I also appear to have an optical signal out for using with a DVR but whether this actually outputs audio while playing back an HDMI signal I don't know.

We don't watch TV much anymore so my TV recorder output isn't much of a concern. I first set this up by playing back my media player through both TVs. Since we are only interested in following dialogue stereo wasn't an issue. It did become an issue when I played back Avatar from my BluRay player and first listened to it in the kitchen. Great I had sound. Then went back into the lounge and still had sound but only in stereo. That started all this.

Even a passive mixing of audio via a resistor network into a stereo signal would probably be okay and I have seen these years ago. Just a case of looking now.

Thanks for your help Andy.
chriscalvert is offline  
post #14 of 14 Old 11-11-2013, 12:33 PM
 
alk3997's Avatar
 
Join Date: Jan 2004
Posts: 3,722
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 87
Remember the center and LFE have to be divided between the left and right channels. So, a passive network may be more of a challenge than you think.

Sync can be off by seconds, but it will depend upon the devices you use. Analog devices are shorter delays while digital devices will depend upon how the device works.

I know of only a few sources that don't have analog stereo outputs, such as the latest from Roku. But, there is no mandate to eliminate analog stereo audio outputs. As I said you may find that is the easiest way - particularly with an RF universal remote, where you don't have to point (much).

Good luck - you are definitely doing something that most home owners don't do and so you're going to find that your final solution is probably unique.
alk3997 is offline  
Reply HDMI Q&A - The One Connector World

User Tag List



Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off