HDMI to TV to Receiver Issue (H21 Related)

[DaDudster]

This was posted before in the DirecTV section but nobody has addressed in awhile.

I have my xbox 360 and my H21 DirecTV receiver plugged into the back of my Sharp Aquos D85U series via HDMI. I then have the TOSLINK coming out of the TV into my receiver.

The primary reason for doing it this way is to minimize the number of cables in my system. Also, my receiver has a limited number of digital inputs.

I would like to be able to just run this one cable out from my TV and into my receiver and then the audio will just switch when I switch the inputs on my TV.

The weird thing is, I have both the xbox360 and H21 set to output Dolby Digital, but my receiver is only playing 2 channels on these devices.

I know the TV CAN output DD from the TOSLINK because when I goto the ATSC OTA antenna, the audio comes through the TOSLINK in DD.

So it seems to me that either BOTH the xbox360 and the H21 don't output DD through the HDMI OR my D85U is downconverting the DD to 2 channel PCM.

Does anyone have some difinitive (not conjecture) information on which of these is the case?

 

[Kevinw]

Outputs from TV is only stereo. You must go from your Xbox and your H21 to your receiver to get DD. What brand receiver and TV do you have?

 

[DaDudster]

Outputs from TV is only stereo.

This is actually not true. Like I said in my previous post, when I am on the ATSC tuner on my TV, it will output DD from the TOSLINK.

Also, like I said on my previous, my TV is the Sharp Aquos D85U series (52 inch if that matters).

Why would Sharp waste the energy on down converting Dolby Digital signals passed to it via HDMI to 2 channel PCM before sending it out the TOSLINK? It seems like it would take much less processing power on the TV to just pass the AC3 signal straight from the HDMI to the TOSLINK.

Per your other question, I am trying to use the Media Live Diva motherboard from MSI to act as my receiver. Right now the SPDIF in on that motherboard will not accept encoded PCM signals (aka DD) as it is, but that is not really my issue (nor my question).

What I specifically want to know is WHY the D85U series Sharp TV down converts signals passed to it via HDMI into 2 channel PCM before sending it back out the TOSLINK??

 

[Kevinw]

According to page 43 of, the manual the optical only outputs PCM and Dolby digital. PCM is stereo and dolby digital appears to be only outputed when using the antenna. How can you connect it to the HTPC motherboard. I see no inputs for audio.

Seems to me what you want to happen is not going to.

 

[DaDudster]

According to page 43 of, the manual the optical only outputs PCM and Dolby digital. PCM is stereo and dolby digital appears to be only outputed when using the antenna. How can you connect it to the HTPC motherboard. I see no inputs for audio.

Seems to me what you want to happen is not going to.

Actually the only thing I see in the manual relating to passing audio from hdmi to to the optical is on page 13:

Note: Depending on the connected equipment, audio will not output from the DIGITAL AUDIO OUTPUT terminal in HDMI connection. In this case, set the audio formats of the connected equipment to PCM, 32/44.1/48 kHz

I know on this page is also mentions that the port outputs "PCM audio" but I don't know if this really means anything since DD is simply just AC3 wrapped in a PCM stream.

Look, I understand why Sharp may be hesitant to try to just pass the audio signal from an HDMI cable straight to a SPDIF cable. I know that HDMI allows for the transfer of the new audio formats (TrueHD, DTS-HD, etc.) while SPDIF cannot transport those signals. I think that is exactly the context to which the aforementioned "note" was referring. However, when the HDMI is carrying an AC3 signal (as most of them do these days) there is no reason why Sharp couldn't have some sort of "check" that would see if the signal can be passed to SPDIF?

SPDIF PCM 2 channel audio is now an absoultely useless technology with most new input devices providing AC3 or better. I don't understand why Sharp would bring out their "state of the art" TV with such a silly limitation. Please explain to me why the TOSLINK can't handle those devices that still output in stereo as well as the devices that output in AC3? It is obvious that the TOSLINK IS capable of outputting an AC3 signal.

What a waste of processing power to downconvert Dobly Digital to 2 channel PCM if the speakers on the TV are not being used. I'm sorry, but the only thing I can see that would cause a major issue would be IF HDMI didn't pass AC3 signals as wrapped PCM (which is possible), but I haven't seen anything in all the literature I have been reading that would suggest that this is the case.

 

[Kevinw]

If it makes you feel better no brand of TV passes audio through.

 

[DaDudster]

Yah that is kind of what I have been gathering. I guess the technology just isn't there yet (who knows if it ever will be) to have your computer replace ALL of the components of the home home theater system (specifically the receiver). It seems like the only way this is ever going to happen is if a sound card company were to start carrying a hardware decoder chip that will pass the signal directly to a directsound device.

As for the issue of passing through AC3 from the TV...Hopefully one day these companies will get their heads out of their behinds and realize that it is far easier for them to just pass the AC3 stream from the HDMI to SPDIF instead of down converting the signal to stereo. I know the TV is down converting because according to the literature on the H21 DirecTV box, the HDMI out is carrying an AC3 stream.

I did some more research and found this on wikipedia:
Dolby Digital Plus - Wikipedia, the free encyclopedia

According to dolby, DD+ is a derivative of AC3 DD (I am going to assume that TrueHD is as well...but don't quote me on that) and one can VERY easy to strip the AC3 DD stream from a DD+ signal.

So I mention again, why would TV companies want to waste prescious processing power on downmixing audio streams to 2 channe PCM if they don't have to? I understand the need for doing it (so they can output the audio to the built in speakers), but if those speakers are disabled (like in variable mode), why waste the processing power?

 

[Kevinw]

Might be in part to the coming of losless audio. Since optical can't pass through lossless, most people HDMI from STB/BD player to an A/V then to TV.

 

[DaDudster]

I have created a new thread on the AVS Forum to compile all of my knowledge about SPDIF related issues.

The Inconvenient Truth about SPDIF Input! - AVS Forum

It provides a really detailed compiling of everything I have discovered about this issue, and lists the limitations in detail.

Lets move all further discussion related to this issue to that thread.

Also, please circulate the thread. I would like it to become a sticky in that forum subsection (so that people wont waste the hours I have wasted on this issue).

 

[Kevinw]

I have created a new thread on the AVS Forum to compile all of my knowledge about SPDIF related issues.

The Inconvenient Truth about SPDIF Input! - AVS Forum

It provides a really detailed compiling of everything I have discovered about this issue, and lists the limitations in detail.

Lets move all further discussion related to this issue to that thread.

Also, please circulate the thread. I would like it to become a sticky in that forum subsection (so that people wont waste the hours I have wasted on this issue).

Your barking up the wrong tree here. AVS is a competitor. You are mor then welcome to duplicate that thread here.

 

[Ilya]

DaDudster, it's usually ok to link to other forums, but calling to move the discussion to another forum is not cool...

 

[Ilya]

On the subject:

SPDIF PCM 2 channel audio is now an absoultely useless technology with most new input devices providing AC3 or better.

The introduction of Blu-ray and HD DVD players has essentially made AC3 (and S/PDIF) obsolete as well. Basically they are left there for backward compatibility: HDMI offers so much more!

Passing through the unchanged OTA audio stream is important, because the TV set serves as the audio source. However for all other audio components it's much better to connect them directly to A/V receivers via HDMI or even analog component audio cables.