HDMI Sound?

sebcobb

Standard Member
Yes I am ignorant and I’m sure I should know but having difficulty finding this out on the web.

With Blu-Ray and HD DVD lossless sound that they will be able to deliver, I have heard that this will only be available via HDMI and not analogue, optical or coax! If so, and if Blu-Ray and/or HD DVD take off, it will render my AVR300 and all current Arcam AVR amps obsolete (assuming everyone who buys an Arcam cares a great deal about the sound quality)!

Is this true? If it is, and I hope it isn’t, do you feel that the bigger Japanese companies are taking the mickey expecting everyone to fork out for a new AMP as well as a new player?

Posted this here as I have an Arcam system although is probably more of a general question.
 

Andy98765

Distinguished Member
If your AV amp has direct 5.1 in (It should do) and you purchase a HD DVD/Blu-Ray player with Direct 5.1 out you can connect the two together and let the DVD player do the decoding. Tosh HD DVD XE1 has direct out.
 

Crustyloafer

Distinguished Member
With your Arcam receiver you will need to use the 5.1 analogue outputs of a player that has that capability. The following description about the HD audio capabilities over HDMI is taken from another website.


New HD lossless audio formats:

In addition to HDMI's current ability to support high-bandwidth uncompressed digital audio and all currently-available compressed formats (such as Dolby Digital and DTS), HDMI 1.3 adds additional support for new lossless compressed digital audio formats Dolby TrueHD and DTS-HD Master Audio.

Perhaps the single most confusing aspect of HDMI 1.3 is its support for high-resolution audio formats such as Dolby Digital Plus, Dolby TrueHD, and DTS-HD, all of which require more bandwidth (and copy protection) than can be transmitted over the old digital coaxial or Toslink optical audio connections that were sufficient for Standard-Def DVD. If using one of those cable types, the HD DVD or Blu-ray player will downconvert the DD+, TrueHD, or DTS-HD signal to standard Dolby Digital or DTS quality. In order to benefit from the full high-resolution quality of these formats, the player must be connected by either HDMI or multi-channel analog. For the purposes of this article, we're obviously going to focus on the HDMI transmission method.

As I sat down to write out a detailed explanation of how the audio formats are handled on both Blu-ray and HD DVD, I realized that I would probably never be able to summarize the situation nearly as concisely or eloquently as this description from AVSForum member Sanjay Durani, which is reprinted here with permission:

First let's clarify some nomenclature. Dolby and DTS have both introduced new audio codecs. The lossy ones are DD+ (Dolby Digital Plus) and DTS-HD (High Definition). The lossless codecs are Dolby TrueHD and DTS-HD MA (Master Audio).

Think of Dolby TrueHD and DTS-HD MA as zipping a computer file to save space. None of the data is discarded, just packed more efficiently to take up less storage space. When you unzip the file, 100% of the data is still there, and you get a bit-for-bit copy of the original.

If you had a zipped document that you wanted to send me on disc, you would have two choices. You could unzip it on your computer before putting it on the disc. Or you could send it to me as a zipped file (would take up less space on the disc) and I could unzip it on my computer. Either way, I end up with the exact same document, down to the last letter.

Likewise, decoding (unpacking) a soundtrack in the player or in the receiver will yield the exact same results. It's not like high end receivers have a special secret version of TrueHD decoding reserved for them that cheap players aren't allowed to have. It's just format decoding. If certain audio data is flagged for the left front channel, then decoding in the worlds most expensive receiver won't place that data somehow "more" into the left front channel than decoding in the world's cheapest player.

Going back to the zipped document analogy. If you wanted to change anything in the document, from simple correction of spelling mistakes to complex re-formatting for a better look, you would first need to unzip that document. You wouldn't be able to manipulate it while it was still zipped.

Similarly, everything a receiver does to the soundtrack, up to and including D/A conversion, requires the soundtrack to be in uncompressed PCM form. In fact, when you send your receiver a DD or DTS bitstream, the first thing it does is decompress the soundtrack to linear PCM. Only then can it apply things like bass management, time alignment, etc.

Soundtracks on HD DVD (and eventually on Blu-ray, when it goes interactive) operate very differently than they do on DVD. With current DVDs, you need entirely separate soundtracks for things like foreign languages and filmmaker's commentary. This is actually a pretty wasteful approach.

With HD DVD, soundtracks can be authored in the 'Advanced' mode, which allows multiple content streams to be live-mixed (mixed in real time). You don't need another soundtrack for foreign languages. Just swap out the English centre channel stream with one of the foreign centre channel streams. You don't need another soundtrack for commentary. Just reduce the level of the main soundtrack and mix in the commentary stream. Same with button sounds and other interactive features, like picture-in-picture.

Just like editing the document requires unzipping the file first, doing any of this live-mixing to the soundtrack requires decoding it to linear PCM first. This is why it has to be done in the player. They're not going to transmit every option to your receiver, just one soundtrack. You choose what you want to hear, it is mixed in the player (i.e. the soundtrack you want to hear is literally built in real time inside the player) and transmitted as a final mix to your receiver.

Current HDMI allows 8 channels of 96/24 PCM to be transmitted (more than enough resolution for any soundtrack), but not the new codecs in their native form. When HDMI 1.3 arrives, it will allow the new codecs mentioned above to be transmitted in their native bitstream, but only if they were authored in 'Basic' mode (no interactivity). If the soundtrack was authored in Advanced mode, then it cannot be transmitted in undecoded form; decoding in the player is mandatory because of live mixing.

So far, all HD DVD soundtracks have been authored in Advanced mode. Which means nothing will change when new receivers arrive on the market. Despite having HDMI 1.3 transmission and decoders built into the receiver, decoding will still have to take place in the player.

Currently, Blu-ray discs are authored in Basic mode, since they haven't gotten interactivity yet. As soon as BD Java is up and working, they'll all be authored in Advanced mode too. At that point, what are the decoders in the receivers going to do? Decode the relatively few BD titles that were released before interactivity? Most of those titles will be re-issued anyway.

Personally, I'm glad that decoding is shifting to the player. I wish it had always been that way. Since receivers need the data in PCM form anyway, that's what every player should be outputting (irrespective of what format is used to store the data on the disc). As mentioned before, when new audio codecs and formats arrive, you'll have to buy a new player. But as long as the players keep outputting the audio in PCM form, current receivers will always remain compatible with anything that shows up in the future. How elegant is that!


Once again, marketing material from the hardware manufacturers is misleading. Onkyo outright claims that their upcoming DV-HD805 HD DVD player offers "streaming of the new lossless surround sound formats, Dolby TrueHD and DTS-HD Master Audio, as well as two 'lossy' formats, Dolby Digital Plus and DTS®-HD High Resolution Audio." Sure, the player will be able to transmit the bitstreams of those formats, but only if the disc is authored in Basic mode, which no HD DVDs are, a fact they conveniently neglect to mention.

So, after all that, what does HDMI 1.3 truly gain the HD DVD or Blu-ray consumer that couldn't be gotten from any of the previous existing versions of HDMI? Frankly, not a lot. 1.3 offers the ability to transmit extended color ranges that don't even exist in the source, and makes available the delivery of raw audio bitstreams that are better off decoded inside the player first anyway, after which they can be (and currently are with great success) transmitted as uncompressed PCM by any version of HDMI. Honestly, the only real innovation that HDMI 1.3 allows for is the enhanced lip sync correction feature, and there's no indication of when or how that might be implemented.

If you were buying a new HDTV or A/V receiver right now and wanted to feel thoroughly future-proofed, it certainly couldn't hurt to make sure that they're HDMI 1.3 compliant, but there's no reason to feel nervous or cheated if they aren't. At the present time, for all practical applications, any version of HDMI is perfectly capable of transmitting the best that Blu-ray or HD DVD offers just as well as any other. Unfortunately, HDMI 1.3 is more hype than substance.
 

Dankeech

Member
Very educational post. Cheers for sharing it with us Crusty:smashin:

Dan.
 

grumps

Active Member
Hey Crusty did you know that you are being quoted from this post on Audiolabs website. Nice one! :)
 

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