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Discussion Starter · #1 · (Edited)
Hello everyone,

From past research, I was under the belief that uncompressed audio formats could only be transferred across HDMI or multichannel PCM (via several RCA cables). Also, that the digital coaxial & fiber optic cables could only transfer compressed 5.1 formats (regular DTS & DolbyDigital for example).

I recently picked up a cheap Sony 3D blu-ray player (just for the purposes of displaying 3D blu-rays) as I typically use an older Oppo player. My Onkyo receiver is from 2009 (model TX-SR607), and unfortunately the "choke" point is the HDMI ports. The ports are only compliant to HDMI 1.3a, and do NOT support 3D (not enough bandwidth). As such, I could not "daisy chain" the HDMI signal from the player > receiver > TV (to get both surround sound and allow the video to pass through). I was able to hook the HDMI to the TV directly (and get 3D picture), but obviously I didn't want to be restricted to just listening out of the TV's speakers.

So I decided to connect audio to the receiver using the Digital Out from the 3D player box via digital coax. I assumed I would only be able to receive compressed DolbyDigital 5.1 or DTS 5.1, but thought given the rare times I would be watching 3D the audio sacrifice wouldn't be too big of a deal. To my surprise, during the presentation of "Finding Nemo 3D", it sounded like I *WAS* getting uncompressed audio! The "dynamic & pop" was definitely there compared to the compressed 5.1 formats. I was shocked at what I was hearing. When the movie was over, I checked to see what the receiver's and blu-ray player's settings were. The Onkyo was set to "Direct". Using the blu-ray player's remote, I next pressed the audio button to toggle through the various audio formats on the disc (mainly to verify if I was truly listening to one of the uncompressed audio tracks). Sure enough - I was definitely listening to audio track #1 : Dolby True HD (and not only that, the Sony player temporarily displayed some kind of bit rate... which I think was around 5.7 give or take).

So what gives???

How in the world was I able to broadcast UNCOMPRESSED Dolby True HD across a $15 digital coaxial cable? I thought I needed HDMI 1.3 for that!
 

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There's about a 99% chance that you were getting the embedded DD5.1 out of the TrueHD track.
 

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As above. TrueHD tracks have a "hidden" AC3 (standard DD) in them to allow backward compatibility. Although the theoretical bandwidth of the coax / SPDIF (modern versions only) would allow a TrueHD / HD MA and even uncompressed multichannel audio, the chipsets can't do it, as it's not in the SPDIF standard.
 

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Discussion Starter · #4 ·
As above. TrueHD tracks have a "hidden" AC3 (standard DD) in them to allow backward compatibility. Although the theoretical bandwidth of the coax / SPDIF (modern versions only) would allow a TrueHD / HD MA and even uncompressed multichannel audio, the chipsets can't do it, as it's not in the SPDIF standard.
I wonder if the audio track was DTS M.A. if I would have been able to hear anything from that track. I can do some more tests with other movies. I have Gravity (not sure if it's DTHD or DTSMA). I can also run some key scenes from the movie on my 2D Oppo for comparison. This is my first time viewing Finding Nemo on Blu-Ray (and the first go-around was in 3D obviously). But given my previous experience with other films... I can usually tell a subtle difference if the audio is compressed or the more dynamic (and alive "pop") uncompressed version. And to me, the Finding Nemo audio seemed uncompressed to me - as crazy as that sounds.

On a similar subject, I can vouch for other audio tracks not having much difference between uncompressed vs. compressed. Spileberg's Jurassic Park and War of the Worlds, for example, seem to have no discernible difference in audio quality between the two. Compare that to say... Pixar's UP and/or Brave. Check out the lightning storm scene (from Up) or the first bear attack scene (from Brave), and you will definitely hear a big difference between the compressed and uncompressed versions.

It makes sense that Dolby Digital would want to have backwards compatibility. Many novice users start playing a movie (from blu-ray) and would get frustrated when no sound comes out (because they need to change the audio from default high-end to a lower quality version). For similar reasons, expert users would find it frustrating if the disc defaulted to regular DolbyDigital instead of the higher quality tracks (i.e., Batman Begins, and Batman: The Dark Knight do this!!!!!). So it seems the best solution is to have that hidden "easter egg" solution of a standard AC3/DolbyDigital (standard) embedded track.

The best thing for me to do is run a 2D audio test through the oppo (ensuring the receiver says "Dolby True HD" (which, BTW... when running from the 3D player it did NOT say that it just said "Direct").
 

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Discussion Starter · #5 ·
By the way...

How long are those disc-shaped batteries supposed to last? After watching Finding Nemo (close to 2hrs), I did a re-pairing verification and it looked like the batteries were already 70%-80% used up! Do you guys find you need to replace the batteries after 2 or 3 movies? That would be awful.
 

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DTS-HD Master Audio also contains a legacy DTS track for compatibility. I assure you there is not enough bandwidth to support lossless multichannel on the coax/SPDIF input.
 

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Hello everyone,
....How in the world was I able to broadcast UNCOMPRESSED Dolby True HD across a $15 digital coaxial cable? I thought I needed HDMI 1.3 for that!
Just a slight correction. TrueHD and DTS-MA are (lossless) compressed.

DTS-HD Master Audio also contains a legacy DTS track for compatibility. I assure you there is not enough bandwidth to support lossless multichannel on the coax/SPDIF input.
The cable could but S/PDIF is the format standard and it doesn't support the bandwidth of TrueHD, DTS-MA or multi channel LPCM (I believe even 2 channel 96/24 fudges the standard a little).
 

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The cable could but S/PDIF is the format standard and it doesn't support the bandwidth (I believe even 2 channel 96/24 fudges the standard a little) of TrueHD, DTS-MA or multi channel LPCM.
That's what I meant. No real reason to talk about the theoretical cable limit because there isn't a workaround to the imposed standard. ;)
 

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That's what I meant. No real reason to talk about the theoretical cable limit because there isn't a workaround to the imposed standard. ;)
Understand, just didn't want the OP to think that the cable was the bottleneck and he/she could switch to optical and get multi channel lossless formats.;)
 

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Discussion Starter · #10 ·
I'm definitely going to run some tests tonight. It could very well be one superb Dolby Digital / AC-3 track that only gets marginal improvement to the True HD (see the DTS vs. DTS Master Audio for Jurassic Park and War of the Worlds for reference).

I wonder how compressed the lossless tracks are. It was my impression that LPCM was not only lossless, but uncompressed as well. I bet there is not much compression on the lossless formats compared to AC3 & DTS. IMO, regular DTS is generally much better sounding than regular AC3.

Any ideas on the battery time for those 3D glasses?
 

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I'm definitely going to run some tests tonight. It could very well be one superb Dolby Digital / AC-3 track that only gets marginal improvement to the True HD (see the DTS vs. DTS Master Audio for Jurassic Park and War of the Worlds for reference).

I wonder how compressed the lossless tracks are. It was my impression that LPCM was not only lossless, but uncompressed as well. I bet there is not much compression on the lossless formats compared to AC3 & DTS. IMO, regular DTS is generally much better sounding than regular AC3.

Any ideas on the battery time for those 3D glasses?
Lpcm is lossless in the sense that it is the original. Digital recording (mostly) IS LPCM (linear pulse code modulation). The lossless systems save data space but end up, once decoded, exactly the same as the original lpcm. Just like if you zip an excel sheet and email it to yourself. When you open it, it is exactly waht you had before.
 

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I'm definitely going to run some tests tonight. It could very well be one superb Dolby Digital / AC-3 track that only gets marginal improvement to the True HD (see the DTS vs. DTS Master Audio for Jurassic Park and War of the Worlds for reference).

I wonder how compressed the lossless tracks are. It was my impression that LPCM was not only lossless, but uncompressed as well. I bet there is not much compression on the lossless formats compared to AC3 & DTS. IMO, regular DTS is generally much better sounding than regular AC3.

Any ideas on the battery time for those 3D glasses?
Just to add some to what JHAz said. There are 2 types of compression.

Lossy: Which throws away audible information judged to be less important. MP3, DTS and Dolby are this.

Lossless: Only removes info it can replace exactly bit for bit as was. FLAC, ALAC, TrueHD and DTS-MA are this (ZIP files for audio).

LPCM master is what the engineer starts with and it is encoded to a compressed format. You also end with LPCM, but if it's from decoded MP3, DTS or DD it will still be lossy. The information is gone and can't be replaced.

If the decoded (final) LPCM is from FLAC, ALAC, TrueHD or DTS-MA it will be exactly the same as the LPCM master.



Also objectively comparing audio quality of any two (or more) tracks like DD and DTS requires a lot of carful setup and DB testing. You probably can't do this.

To even come close you must level match. In many cases the DD has the DN set -4dB. This can fool even the most golden ear audiophile.
 

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The DD 5.1 track embedded in the TrueHD package is encoded at the maximum bitrate, much higher than the rate used on DVD, and it rivals lossless in quality. The same goes for the DTS core used with dts-MA. So, you really aren't missing anything in terms of audio quality using an S/PDIF connection.
 

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I read some place, S/PDIF and TosLink can send anything other than lossy/lossless audio formats. I have seen my pioneer showing it was decoding DTS-HDMA, but i was using TosLink, so pioneer must lie, or Sony wants me to buy a HDMI cable. I don't know what to believe.
 

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I can usually tell a subtle difference if the audio is compressed or the more dynamic (and alive "pop") uncompressed version. And to me, the Finding Nemo audio seemed uncompressed to me - as crazy as that sounds.
Sounds like you're confusing digital audio compression and dynamic range compression, as crazy as that sounds.
 

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I read some place, S/PDIF and TosLink can send anything other than lossy/lossless audio formats. I have seen my pioneer showing it was decoding DTS-HDMA, but i was using TosLink, so pioneer must lie, or Sony wants me to buy a HDMI cable. I don't know what to believe.
It's not possible to send dts-MA over an optical connection. What did your Pioneer report that leads you to believe it was receiving a lossless codec?
 

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Discussion Starter · #17 ·
It's not possible to send dts-MA over an optical connection. What did your Pioneer report that leads you to believe it was receiving a lossless codec?
Okay, so here are the results...

When I play Spanish or French DolbyDigital 5.1, the player reports back 48Hz @ apx. 500Kbs-600Kbs (the overal quality sounds comparable to the Dolby Digital I'm used to - maybe slightly less).

When I play English Lossless Dolby Digital 7.1, it's the same exact quality as English Dolby Digital 5.1... but the player reports back at 48Hz @ apx. 7.5-9.3 MBs (note it's MEGA and not Kilo). That's a HUGE bit rate number for lossy dolby digital.

In contrast, when I watch Gravity, the audio is shown as DTS Master Audio 48Hz @ 2.5MBs - 3.1MBs (much lower than Finding Nemo).

So... for some reason Dolby Digital can handle the digital coaxial (or perhaps that's just how the blu-ray disc is encoded) much better than Gravity's DTS Master Audio.

As I type, I am now comparing the bit rate for the 2D lossless audio track for Finding Nemo. And the results are (drum roll)...

...

...

25Mbs - 35Mbs!!!!!

The loud/dynamic moments are incredibly close to the Dolby Digital 5.1. Very hard to tell the difference - maybe just slightly more "oomph" (less than 5% difference).

However, some of the softer nuance details did seem a little more pronounced on the 25Mbs-35Mbs track (maybe about 10% at best - but more noticeable).

So at least I feel better now :) But it's good to know there is a true difference between audio through HDMI versus digital coax. It just so happens that Finding Nemo's "standard" Dolby Digital 5.1 / AC3 track is exceptionally good for that format.
 

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To the OP - movie soundtracks are mastered as multichannel PCM, which takes up a lot space on a disc. In order to save space, without sacrificing quality, studios useless lossless data compression - essentially a zipping process. They feed the track into a TrueHD or dts-MA encoder, which squeezes it down to a smaller size. The decoder unsqueezes the file, turning it back into PCM that is bit-for-bit identical to the original soundtrack.

It is not correct to call TrueHD or dts-MA "uncompressed". They are codecs, an acronym meaning COmpressionDECompression. Similarly, it is not correct to call PCM "lossless." Lossless refers to the type of data compression used to reduce the size of the file and there's no data compression involved in a PCM file.
 

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Okay, so here are the results...

When I play Spanish or French DolbyDigital 5.1, the player reports back 48Hz @ apx. 500Kbs-600Kbs (the overal quality sounds comparable to the Dolby Digital I'm used to - maybe slightly less).

When I play English Lossless Dolby Digital 7.1, it's the same exact quality as English Dolby Digital 5.1... but the player reports back at 48Hz @ apx. 7.5-9.3 MBs (note it's MEGA and not Kilo). That's a HUGE bit rate number for lossy dolby digital.

In contrast, when I watch Gravity, the audio is shown as DTS Master Audio 48Hz @ 2.5MBs - 3.1MBs (much lower than Finding Nemo).

So... for some reason Dolby Digital can handle the digital coaxial (or perhaps that's just how the blu-ray disc is encoded) much better than Gravity's DTS Master Audio.

As I type, I am now comparing the bit rate for the 2D lossless audio track for Finding Nemo. And the results are (drum roll)...

...

...

25Mbs - 35Mbs!!!!!

The loud/dynamic moments are incredibly close to the Dolby Digital 5.1. Very hard to tell the difference - maybe just slightly more "oomph" (less than 5% difference).

However, some of the softer nuance details did seem a little more pronounced on the 25Mbs-35Mbs track (maybe about 10% at best - but more noticeable).

So at least I feel better now :) But it's good to know there is a true difference between audio through HDMI versus digital coax. It just so happens that Finding Nemo's "standard" Dolby Digital 5.1 / AC3 track is exceptionally good for that format.
Most players don't report the specs of all possible outputs. When you play a TrueHD track, the player may be processing it for lossless bitstream output, as a lossy source for mixing in secondary audio, as a stereo downmix (using either the lossy or lossless source), and as a lossy bitstream. The stats you see almost certainly refer to the lossless version on the disc, not to the DD 5.1 output over S/PDIF.

Bitrates are not a meaningful spec with lossless encoding, which uses variable bitrates, taking as much or as little bandwidth as is needed at any given moment in the soundtrack.

And, once again, the embedded DD 5.1 track in a TrueHD encode is not exactly "standard". DD 5.1 on DVD is rarely encoded at more than 448kbps, usually less. It's almost always 640k on TrueHD, the maximum rate in the DD 5.1 spec.
 

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Discussion Starter · #20 ·
To the OP - movie soundtracks are mastered as multichannel PCM, which takes up a lot space on a disc. In order to save space, without sacrificing quality, studios useless lossless data compression - essentially a zipping process. They feed the track into a TrueHD or dts-MA encoder, which squeezes it down to a smaller size. The decoder unsqueezes the file, turning it back into PCM that is bit-for-bit identical to the original soundtrack.

It is not correct to call TrueHD or dts-MA "uncompressed". They are codecs, an acronym meaning COmpressionDECompression. Similarly, it is not correct to call PCM "lossless." Lossless refers to the type of data compression used to reduce the size of the file and there's no data compression involved in a PCM file.
Thank you for clarifying this, BIslander.

I like the "zipping" analogy. For instance, I can ZIP (compress) a spreadsheet or word processing document and save 90% of space. But to view the document, I must UNZIP (decompress) to view in its normal "raw" state.

Image files, on the other hand, are already compressed. Well... some of them are :)

Take a JPG image file, for example. I could take a few jpg images... and further compress them with ZIP. I don't save very much additional space at this point (since the image files are already compressed), but more useful is the fact I'm sending ONE "simple" file rather than several. Even so, I usually see a slight reduction in size too - so it is compacting them slightly further.

===

Back to Finding Nemo...

The lossy Dolby Digital track was high in quality @ 7-9 MBps.

The lossless Dolby True HD track was VERY high in quality @ 25-35 MBps.

The lossy DTS track played from the "DTS MA option" (probably the hidden easter egg for backwards compatibility)
was average in quality at 2-3 MBps.

It seems to me there really is no difference in sound quality between DTS-MA, and DtrueHD. Because there is no data compression involved (at all) with LPCM, I wonder if there can be a very slight noticeable difference (even with just a scope or other hardware equipment)... meaning... is it possible there may be some miniscule distortion from the compress / uncompress state? If the audio was analog, I would imagine that would be the case. But since it's digital, probably not. I heard some amazing audio tracks in LPCM that were incredibly BOLD with a lot of punch (i.e., Scorcese's THE DEPARTED for example).

The bottom line is that I was SHOCKED to how spectacular the audio track was from using the digital coaxial (and... hearing Dolby Digital 5.1 even though the audio file chosen was Dolby True HD 7.1/5.1 - lol).
 
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