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PCM over HDMI vs Dolby TrueHD over HDMI

post #1 of 61
12/6/06 at 1:37pm
Thread Starter 
I did read this...

"HDMI 1.1 is capable of transporting all HD DVD and Blu-ray audio formats in native form except for losslessly compressed DTS HD Master and Dolby True HD, whose 768kHz frame rates exceed HDMI's 192kHz frame-rate capability, the HDMI licensing organization previously told TWICE."

This could mean that the bandwidth of LPCM over HDMI 1.1, 1.2 and 1.2a is insufficient, and Dolby TrueHD for example has to be down sampled.

It seems like any string of 24 bit numbers at a rate 96khz or less should be able to be transmitted over over HDMI/LPCM with no loss of fidelity. I seem to recall higher bitrates were optional. If the above quote is correct the string of bits from a Dolby TrueHD decoder would have to be downsampled even if both devices could communicate at 192hkz.
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post #2 of 61
12/6/06 at 2:56pm
Packet (or frame) restrictions prevent HDMI 1.1, 1.2, and 1.2a from supporting the output of Dolby Digital Plus, Dolby TrueHD, and DTS-HD MA bitstreams.

Remember, Dolby TrueHD and DTS-HD are the audio equivalent of zip files. There is no "bitness" to the TrueHD or DTS-HD MA stream until it is unpacked, be it in the player or the receiver. Unpacked TrueHD and DTS-HD MA is simply LPCM.

There is no downsampling of any kind necessary.
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post #3 of 61
12/7/06 at 7:35am
Thread Starter 
I found an HDMI spec online. HDMI can handle 4, 96khz IEC 60958 audio streams. Each stream carries two channels. I am not sure if you are supposed to divided by 2 or not to get the channel rate. If you do, channels are 48khz. I believe the word size is 24 bits.

Dolby TrueHD channels, according to what I read, are 96khz (24 bit word) audio streams.

If I understood all that correctly, LPCM over HDMI may only have half the data rate of a decoded TrueHD stream. If that's true, the decoded TrueHD would have to be downsampled to LPCM.

I believe the TrueHD stream is compressed, so it could be sent untampered over an HDMI bitstream (with HDMI 1.3.)

So once again, if I understood all that right, you would gain a higher fidelity from using a bitstream.
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post #4 of 61
12/7/06 at 8:27am
Not sure what an IEC 60958 stream is but the HDMI FAQ says this:

Quote:


Q: Do I need v1.3 HDMI to hear the new Dolby TrueHD and DTS Master HD audio content on HD-DVD or BluRay players?

No. HDMI has the flexibility to transport these new high definition, lossless audio formats in either an uncompressed PCM stream, or as an encoded stream. PCM stands for Pulse-code modulation and it is a standard way to encode digital audio in computers, consumer electronics, CDs, DVDs, etc. Both Dolby Digital Plus and Dolby TrueHD, as well as DTS Master HD bitstreams are transportable over all versions of HDMI as decoded PCM. HDMI supports the highest quality uncompressed PCM audio at 192kHz, 24 bits per sample.

Oh I should add that my Anthem shows six channels of 96kHz when playing TrueHD soundtracks. It doesn't have a word length indicator though I assume it is 24bits.
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post #5 of 61
12/7/06 at 8:36am
Thread Starter 
Yep, I am aware that you don't need HDMI 1.3. The question was whether or not it improved the audio fidelity.

IEC 60958 is the standard for LPCM.

Are you sending LPCM or bitstream to your Anthem?
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post #6 of 61
12/7/06 at 8:50am
Quote:
Originally Posted by MichaelJHuman View Post

The question was whether or not it improved the audio fidelity.

The answer is it wouldn't. Whether you decode a TrueHD bitstream in the player or in the receiver, the end result (the decoded data) will be exactly the same.

Sanjay
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post #7 of 61
12/7/06 at 8:52am
Quote:
Originally Posted by sdurani View Post

The answer is it wouldn't. Whether you decode a TrueHD bitstream in the player or in the receiver, the end result (the decoded data) will be exactly the same.

Sanjay

There it is.
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post #8 of 61
12/7/06 at 9:25am
Quote:
Originally Posted by sdurani View Post

The answer is it wouldn't. Whether you decode a TrueHD bitstream in the player or in the receiver, the end result (the decoded data) will be exactly the same.

Sanjay

Sums it all up, short and sweet.
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post #9 of 61
12/7/06 at 9:28am
Michael,
The new codecs are DESIGNED to work without loss of quality across an HDMI V1.1 link when the player does the decoding. There is no reduction in quality implemented by the player or codec if it discovers the link is V1.1 instead of V1.3. The multiple channels of PCM that come across the V1.1 link are the best the new codecs can produce.

Period.

The only thing that V1.3 adds is the ability to send the original, undecoded bitstream format to the receiver for the receiver to decode. Your ability to actually take advantage of this may be limited however. Discs authored in the "advanced content" mode *MUST* be decoded in the player. Most commercial discs are authored this way. The net result is that even with a V1.3 link, and a new receiver with its own decoder for that codec, the decoding still must happen IN THE PLAYER and what comes across the V1.3 link is identical in quality to what would come across a V1.1 link.

Even if decoding does happen in the receiver, what comes out of the codec itself is still the same quality. This is true even if the receiver has a higher internal sampling rate. Such upsampling (which can be applied just as well to a signal coming across the link as PCM) helps insure quality of subsequent processing inside the receiver, but the information coming out of the codec is identical either way.
--Bob
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post #10 of 61
12/7/06 at 9:31am
Quote:
Originally Posted by Q of BanditZ View Post

Sums it all up, short and sweet.

I still want to see a BD PCM vs a HD-DVD TruHD. (same title of course)
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post #11 of 61
12/7/06 at 9:32am
Quote:
Originally Posted by shamus1099 View Post

I still want to see a BD PCM vs a HD-DVD TruHD. (same title of course)

That would be interesting.
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post #12 of 61
12/7/06 at 9:52am
Quote:
Originally Posted by shamus1099 View Post

I still want to see a BD PCM vs a HD-DVD TruHD.

Why? Both tracks will be bit-for-bit identical. Like comparing a zipped file to the unzipped version. What sort of difference are you expecting?

Sanjay
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post #13 of 61
12/7/06 at 9:55am
Quote:
Originally Posted by sdurani View Post

The answer is it wouldn't. Whether you decode a TrueHD bitstream in the player or in the receiver, the end result (the decoded data) will be exactly the same.

The user experience won't be exactly the same. Unless I'm mistaken, you'll lose dialogue normalisation, dynamic range compression parameters, and Surround and EX flags. So you lose a little bit of behaviour. But the raw audio data comes out pure and clear.
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post #14 of 61
12/7/06 at 9:56am
Quote:
Originally Posted by sdurani View Post

Why? Both tracks will be bit-for-bit identical. Like comparing a zipped file to the unzipped version. What sort of difference are you expecting?

Quite. DTS-HD Master Audio, MLP, Dolby TrueHD and PCM will all sound exactly the same; they're lossless. They can only differ in how much disc space they take up.
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post #15 of 61
12/7/06 at 9:56am
Thread Starter 
I may have misinterpreted the HDMI document then. It probably supports 96khz x 8 channels.

FYI (From the 1.0 spec)
-----------------------------
Basic audio functionality consists of a single IEC 60958 audio stream at sample rates of 32kHz,
44.1kHz or 48kHz. This can accommodate any normal stereo stream. Optionally, HDMI can carry
a single such stream at sample rates up to 192KHz or from two to four such streams (3 to 8 audio
channels) at sample rates up to 96KHz. HDMI can also carry IEC 61937 compressed (e.g.
surround-sound) stream at sample rates up to 192kHz.
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post #16 of 61
12/7/06 at 10:06am
Quote:
Originally Posted by sdurani View Post

Why? Both tracks will be bit-for-bit identical. Like comparing a zipped file to the unzipped version. What sort of difference are you expecting?

Sanjay

I know but still. Just like people like to compare VC-1 to MPEG.
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post #17 of 61
12/7/06 at 10:15am
Well, that's totally different. They're lossy codecs, so the end result will differ.
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post #18 of 61
12/7/06 at 10:17am
Quote:
Originally Posted by KMO View Post

Quite. DTS-HD Master Audio, MLP, Dolby TrueHD and PCM will all sound exactly the same; they're lossless. They can only differ in how much disc space they take up.

This truth needs to be spread far and wide!
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post #19 of 61
12/7/06 at 10:25am
Quote:
Originally Posted by KMO View Post

The user experience won't be exactly the same.

Right, but I was answering the OP's question about "whether or not it improved the audio fidelity".

Sanjay
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post #20 of 61
12/7/06 at 1:51pm
I'm out of my league with the knowledge in this thread, but the information is starting to sink in. I have a 1080P Samsung and am looking at the Panny Blue Ray player. Since most, if not all, HD disc players only have one HDMI out, if one wants to take advantage of the advanced audio codecs, and be able to use one's AVR processing, one must connect the player to the AVR via HDMI. And then to the monitor.

I'm a purist and have always connected the video source directly to my monitor. The above method forces me to run the entire signal, audio and video, through the receiver. While I don't mind doing it, doesn't that force me to select an AVR that is 1080p capable if I want to pass a 1080p signal from the disc player to my Samsung? If I've figured all this out correctly it does. Otherwise I'd have to use the 1080i signal from the disc player, assuming the AVR will pass 1080i and not 1080p, and let my Samsung deinterlace the 1080i signal to 1080p.

My question is an encrypted way of finding out if the Denon 5805 MK 2 will really give me any advantage over the 5805 MK 1. One of the things I've learned here is I'm going to wait for a blue ray player that will decode all the new codecs. That way I don't need to wait for an AVR that is HDMI 1.3 ready. Many thanks to the excellent advice you gentlemen have made available.
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post #21 of 61
12/7/06 at 5:44pm
egrady,
You've figured it out correctly. Blame an industry obsessed with copy protection. To get the best audio you need to use HDMI audio to the receiver and that means you need a receiver that can at least "pass through" 1080p, if not also process it. If you get a receiver that "passes through" video, be sure it actually extracts the audio from the HDMI. Some such receivers will only "pass through" audio as well.
--Bob
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post #22 of 61
1/6/07 at 5:44am
Hi there, while we are on the HDMI subject I would like to ask a question, as I have a dvd player with HDMI output and soon planning to buy a receiver with HDMI input, could I use the HDMI from the player to the receiver to listen to SACD or DVDa ? your reply would be appreciated
Gerry
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post #23 of 61
1/6/07 at 6:07am
Quote:


could I use the HDMI from the player to the receiver to listen to SACD or DVDa ?

Depends on the player. Some Oppos can do that. I have the 970 on order for just that purpose.
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post #24 of 61
1/6/07 at 6:10am
Hi and thank you for the reply, I have a Denon 1920 and hoping to purchase a pioneer AX2 AS not too sure what model number is over there
Gerry
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post #25 of 61
1/6/07 at 6:16am
I believe that those audio formats are only output over the Denon's 5.1 analog jacks.
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post #26 of 61
1/6/07 at 8:46am
Quote:
Originally Posted by Jack Gilvey View Post

I believe that those audio formats are only output over the Denon's 5.1 analog jacks.

Thank you and happy new year

Gerry
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post #27 of 61
1/6/07 at 10:26am
Quote:
Originally Posted by Bob Pariseau View Post

Michael,
.... Discs authored in the "advanced content" mode *MUST* be decoded in the player. Most commercial discs are authored this way. ......


--Bob

Bob,

Are you talking about the AACS or do you truely mean "advanced content" ( which I understand to be things like pip commentaries) ?

Where did you hear this? I have a really hard time believing this to be true, not that it couldn't be.
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post #28 of 61
1/6/07 at 11:40am
Quote:
Originally Posted by jp9 View Post

Bob,

Are you talking about the AACS or do you truely mean "advanced content" ( which I understand to be things like pip commentaries) ?

Where did you hear this? I have a really hard time believing this to be true, not that it couldn't be.


Never mind my question, I found what you are talking about on the dolby web site.
see page 3 of this link

http://www.dolby.com/consumer/techno...HD_avrs_1.html


the dts site doesn't seem to discuss this but their images show a 'mixer' in one case

http://www.dts.com/dts-hd/dtshd-mast...g-receiver.php

http://www.dts.com/dts-hd/dtshd-mast...w-receiver.php



and via the hdmi org site I found a link to an article on this topic

http://www.hdtvmagazine.com/articles...-channel_a.php
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post #29 of 61
1/6/07 at 11:54am
Quote:
Originally Posted by Bob Pariseau View Post

Michael,
The new codecs are DESIGNED to work without loss of quality across an HDMI V1.1 link when the player does the decoding. There is no reduction in quality implemented by the player or codec if it discovers the link is V1.1 instead of V1.3. The multiple channels of PCM that come across the V1.1 link are the best the new codecs can produce.

Period.

The only thing that V1.3 adds is the ability to send the original, undecoded bitstream format to the receiver for the receiver to decode. Your ability to actually take advantage of this may be limited however. Discs authored in the "advanced content" mode *MUST* be decoded in the player. Most commercial discs are authored this way. The net result is that even with a V1.3 link, and a new receiver with its own decoder for that codec, the decoding still must happen IN THE PLAYER and what comes across the V1.3 link is identical in quality to what would come across a V1.1 link.

Even if decoding does happen in the receiver, what comes out of the codec itself is still the same quality. This is true even if the receiver has a higher internal sampling rate. Such upsampling (which can be applied just as well to a signal coming across the link as PCM) helps insure quality of subsequent processing inside the receiver, but the information coming out of the codec is identical either way.
--Bob

so why even put the ability to decode TrueHD or DTS-HD in the receivers?
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post #30 of 61
1/6/07 at 1:05pm
Quote:
Originally Posted by joffer View Post

so why even put the ability to decode TrueHD or DTS-HD in the receivers?


Because some Players don't do the decoding.


Example: The Samsung Blu Ray player does not have decoding for DTS-HD or TRUeHD.
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