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Discussion Starter · #1 ·
I'm in the middle of assembling a surround sound system. I'm a bit new to the surround sound world so I'm confused about a few things.


I have an HTPC plugged into a surround processor (Cary Cinema 11) via optical spdif. I've done some reading about the various codecs on this site's FAQ, etc.


What I was HOPING to do was use my HTPC to do the decoding, bass management, etc, and have the surround processor act as a glorified multichannel DAC & audio source selector.


My confusion boils down to: Where is the decoding happening? If I can do all my decoding at the HTPC I can avoid having the Cary become obsolete (it already is as it doesn't do TrueHD or DTS-MA). This way it would just send a bitstream (which I think just means the decoded raw digital audio tracks), I think? I'm not sure of the difference between bitstream & LPCM...


Any help would be much appreciated.


Thanks in advance,

Jason


EDIT:


After doing some more reading, it seems that you need HDMI 1.3 to send uncompressed 5.1 audio to your receiver as optical doesn't have the bandwidth. Wish I knew that ! (doh)


Anyone want to buy a Cary Cinema 11?
 

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As you've discovered, the S/PDIF protocol used for optical is limited to stereo PCM. HDMI 1.1 is all you need to send multichannel PCM. 1.3 is required if you want to bitstream lossless codecs (TrueHD and DTS-HD Master Audio).


PCM (Pulse Code Modulation) is the digital audio format used with nearly all home entertainment equipment. Digital processing such as bass management and room correction are done when the audio is PCM. DACS are designed to convert PCM to analog.


CDs are recorded as stereo PCM. Movies are mastered as multichannel PCM. But, a multichannel PCM soundtrack takes up a lot of space. So, compression codecs such as DD 5.1, DTS, and their new lossless cousins were created for the sole purpose of saving space. They are really just zip files. The PCM track is fed into an encoder, which compresses it to a much smaller size for storage on a disc. The decoder decompressed it back into PCM. With lossless codecs, the decoded PCM is an exact match to the original. With lossy codecs, there's so much data compression that some of the original cannot be restored. Just like you can't "read" a zip file, audio processors don't "play" encoded Dolby Digital or DTS tracks. They have to decode them back into PCM and that's what gets processed.


Bitstream neans the encoded track is sent to the receiver for decoding and processing. PCM means the player does the decoding. But, even when doing the decoding, most players do not do any other processing. They send the PCM to the receiver, which does bass management, distance adjustments, room correction, and the application of DSPs such as PLII to modify the sound. The only time players do digital processing tasks such as bass management is when they are also doing the digital-analog conversion.
 

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Discussion Starter · #3 ·
BIslander, thanks for confirming all of that info.


The question now becomes, is there a way to buy a 1.3a receiver and make it "futureproof" if all I want to use it for is sound?


For example:

Can you output HDMI 1.4 from say an HTPC to some sort of splitter to send the signal to a TV & receiver simultaneously? The problem being that the receiver can only pass through 1.3a.


Is there a workaround for this? I just want to bitstream 5.1 to my receiver from my HTPC and not have to worry about the next HDMI upgrade since I could care less about video processing.


Thanks,

Jason
 

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Quote:
After doing some more reading, it seems that you need HDMI 1.3 to send uncompressed 5.1 audio to your receiver as optical doesn't have the bandwidth. Wish I knew that ! (doh)

Multi-channel (5.1/7.1) analog is another option. You would do decoding and bass management on your PC and send the signal through 6/8 cables. You would need multi-channel analog inputs on your receiver/amp.


This would also let you connect your HDMI cable to the TV directly.


This assumes that you have good DACs on your sound card (are they generally pretty good these days?)
 

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Quote:
Originally Posted by rockguitardude /forum/post/19553206


BIslander, thanks for confirming all of that info.


The question now becomes, is there a way to buy a 1.3a receiver and make it "futureproof" if all I want to use it for is sound?


For example:

Can you output HDMI 1.4 from say an HTPC to some sort of splitter to send the signal to a TV & receiver simultaneously? The problem being that the receiver can only pass through 1.3a.


Is there a workaround for this? I just want to bitstream 5.1 to my receiver from my HTPC and not have to worry about the next HDMI upgrade since I could care less about video processing.

If all you want is the ability to bitstream lossless audio from your HTPC to a receiver for decoding, then an AVR with 1.3 functionality is all you will ever need. HDMI 1.4 has video upgrades and optional ethernet support, but no new audio functionality beyond the Audio Return Channel, which you don't need.


If you end up needing 1.4 features, get a 1.4 card with dual HDMI outputs. You can run a video output with 1.4 direct to your display and do a 1.3 audio connection to your receiver. Dual HDMI outputs are showing up on 3D players for just that reason.
 

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Discussion Starter · #6 ·
Thanks again for all the info.


This got me wondering, is there anything on the horizon in the audio world that's going to be worth having?


What I'm getting at is it seems like 1.3a is the end of the line for major audio upgrades. What else can they do if they give you 24-bit/192kHz which is equivalent to the studio master track?


If I can use one HDMI output from my HTPC to bitstream to the receiver & one output to my TV I'd be pretty set it seems. Part of why I love audio is that unlike say, computers, you can invest in something and have it last. I'm trying to stay true to this.
 

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Very informative thread, thanks.


I'm nearing the completion of my new listening room that will include a 7.1 setup. I cant wait to enjoy the experiences you guys are familiar with.


But for now, I use an older XP computer and receiver (pre-HDMI). I listen to FLACs with Foobar via optical to the receiver.


I'm still not clear on which DACs, the motherboard's or the Receiver's, are doing my decoding.


With my current setup are the Motherboard's DACs converting the FLAC files to PCM, and the Receiver's DACs converting the PCM signal to analog?


When I do finish building my new computer, which will have an HDMI output ....


Will the HDMI cable be transferring PCM or bitstreaming lossless codecs?


Will I no longer need an optical connection to the receiver for anything?


Will there be any sonic advantage in bitstreaming via Ethernet vs HDMI?


Is there any reason I should invest in a nice soundcard with multi-channel analog outs ..... and an AVR with Multi-Channel analog inputs?
 

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Quote:
Originally Posted by Flacjunky /forum/post/19578939


I'm still not clear on which DACs, the motherboard's or the Receiver's, are doing my decoding.

You're mixing terms here. Decoding is not the same as doing the digital-analog conversion. Decoding takes a compressed file such as DD 5.1 or FLAC and decompresses it back into PCM. A digital-analog converter takes a digital source and converts it to analog.

Quote:
With my current setup are the Motherboard's DACs converting the FLAC files to PCM, and the Receiver's DACs converting the PCM signal to analog?

Your motherboard's DACs would only be involved if you were outputting analog, not digital. Your PC software is likely decoding the FLAC to produce PCM. Then, yes, your receiver's DACs are producing the analog output.

Quote:
When I do finish building my new computer, which will have an HDMI output ....


Will the HDMI cable be transferring PCM or bitstreaming lossless codecs?

It can do either, depending how you configure it and the capabilities of your receiver. You can decode in the computer and send multichannel PCM to the receiver. Or, if your new computer and receiver support lossless bitstreams, you can send the files that way. With FLAC, you would need to decode in the computer since receivers generally don't support that codec.

Quote:
Will I no longer need an optical connection to the receiver for anything?

Probably not.

Quote:
Will there be any sonic advantage in bitstreaming via Ethernet vs HDMI?

Can't help there.

Quote:
Is there any reason I should invest in a nice soundcard with multi-channel analog outs ..... and an AVR with Multi-Channel analog inputs?

No. You'd be hardpressed to match the processing power and DACs of a good AVR. With digital, your AVR can do room correction, bass management, and apply DSPs such as PLIIx to expand 5.1 sources to 7.1. With analog, your AVR is just an amp. All processing would have to be done in the PC prior to the digital-analog conversion.
 

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Well, things didn't work out exactly as I had planned. Instead of building a new PC with HDMI output, and getting a new AVR with HDMI inputs, I had to move into my New Room with the older hardware. (Sony STR-DE698)


I did however upgrade my on-board sound, (AC97 codec 16/48 max) to a newer, but cheap, sound card. A Diamond (C-media 8768+ based) extreme sound 24bit 7.1 PCI card w/ Dobly Digital Live capability.


Now at least, for the first time ever, I've been able to make the AVRs blue light come on.



I have a small collection of 24/96 and multi-channel music files, and after tweaking the AVR I was able to get all 8 speakers rocking over Optical SPDIF.


But my question here revolves around listening to the vast majority of my music collection which is 16/44 Flacs.


If I want my surrounds to work during playback of these files I have to set the Sound Cards output to DDL. There's a noticeable difference switching between DDL and 2 channel 48 or 96, but I'm having a hard time discerning which one sounds "better". They both sound very good.


What I'm really asking is, am I losing the Lossless qualities of my files if I always leave the Sound Card set to DDL? Its certainly easier to leave it there than it is to change it several times a day depending on whether I'm using it for games, movies, DTSWAV or DVD-A files, or standard 2 channel Flacs.

It can't possibly be sending 6 channels of lossless data over the optical cable can it?


Does Dolby Digital Live down-convert it to Lossy?
 
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