Dolby Digital/DTS signal to 2.0 PCM? - AVS Forum
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post #1 of 26 Old 09-26-2011, 06:28 AM - Thread Starter
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Anyone know of a device that converts a Dolby Digital/DTS signal to 2.0 PCM?
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post #2 of 26 Old 09-26-2011, 06:32 AM
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A standalone device? What do you want as input and output?
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post #3 of 26 Old 09-26-2011, 11:41 AM
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Many (all?) DVD, Blu-ray, and HD-DVD machines should accomplish this from a suitable disc. I think Gefen makes a box that can do this, but it might be prohibitively expensive.
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post #4 of 26 Old 09-26-2011, 12:11 PM - Thread Starter
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Yes, a stand alone device, if one exists. Input: Dolby Digital/DTS signal. Output: two channel PCM.

Gefen makes a very small device for about $85 where the input is Dolby Digital/DTS and the output is 2 channel analog.
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post #5 of 26 Old 09-26-2011, 12:20 PM
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So you want to output 2-channel audio via SPDIF?

What kind of device do you have that has an optical or coax digital input but can't handle DD?
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post #6 of 26 Old 09-27-2011, 07:51 AM
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Quote:
Originally Posted by MLM View Post

Yes, a stand alone device, if one exists. Input: Dolby Digital/DTS signal. Output: two channel PCM.

Gefen makes a very small device for about $85 where the input is Dolby Digital/DTS and the output is 2 channel analog.

You could use the other Gefen to go from analog to PCM; not that it'd be reasonable. And again, why can't a player satisfy this requirement?
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post #7 of 26 Old 09-28-2011, 11:14 AM - Thread Starter
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Originally Posted by walbert View Post

And again, why can't a player satisfy this requirement?

Output is from a cable box. Is there a preamp you can recommend that will take the DD 5.1 digital and turn it into pretty good analog out, either 5.1 or 2 channels.

I know I will lose something because DD is compressed, but if it is reasonably priced I could go for it.

Thanks.
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post #8 of 26 Old 09-28-2011, 11:57 AM
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Are you sure your cable box doesn't already have a setting that does this, perhaps in its 'Audio' menu?
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post #9 of 26 Old 09-28-2011, 08:34 PM
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It must. Cable companies have to be able to handle customers who don't have equipment with DD 5.1 decoders.
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post #10 of 26 Old 09-28-2011, 08:35 PM
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Well the cable box will have analog red/white outputs.

I still don't understand the need to have 2.0 over SPDIF. Anything with an SPDIF input should be able to handle DD signals.
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post #11 of 26 Old 09-28-2011, 10:28 PM - Thread Starter
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Originally Posted by krabapple View Post

Are you sure your cable box doesn't already have a setting that does this, perhaps in its 'Audio' menu?

For reasons known only to them, Verizon has disabled PCM output from their cable boxes. According to their techs this stupid change was effected by a firmware revision.

I may give up on FIOS eventually for that reason. At the moment though, in the NYC area they are offering great "triple play" deals that Time Warner doesn't come close to. And their picture quality and service is far better.
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post #12 of 26 Old 09-28-2011, 10:34 PM - Thread Starter
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Originally Posted by jonnythan View Post

Well the cable box will have analog red/white outputs.

I still don't understand the need to have 2.0 over SPDIF. Anything with an SPDIF input should be able to handle DD signals.

Yes, the box has analog audio outputs, but their quality leaves much to be desired.

I'm afraid you're wrong about DACs. There are many out there that handle only PCM and they're often of a higher quality intend for two channel audio than those mostly intended for DD, for the PCM is not compressed.
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post #13 of 26 Old 09-28-2011, 10:57 PM
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Quote:
Originally Posted by MLM View Post

Yes, the box has analog audio outputs, but their quality leaves much to be desired.

I'm afraid you're wrong about DACs. There are many out there that handle only PCM and they're often of a higher quality intend for two channel audio than those mostly intended for DD, for the PCM is not compressed.

It sounds like you may have drunk the 'high end' kool aid. Analog out should be fine if it's working right -- what is it about the quality of your cable box's that is subpar? Noise?

And the output of a decoded DD bitstream is...PCM. So the DAC is still converting PCM to analog, as any DAC should. The PCM content is 'lossy' compared to the original signal (i.e., before it was DD-encoded), but DACs don't care. Any decent DAC these days should be able to handle the full audible range with aplomb.
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post #14 of 26 Old 09-29-2011, 08:35 AM
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Quote:
Originally Posted by MLM View Post

Yes, the box has analog audio outputs, but their quality leaves much to be desired.

I'm afraid you're wrong about DACs. There are many out there that handle only PCM and they're often of a higher quality intend for two channel audio than those mostly intended for DD, for the PCM is not compressed.

You can't magically make it lossless by converting AC3 to PCM, its still lossy originally, you are not in any way gaining quality. The cable box has the DAC you want built-in, sounds like a solution to me. As far as the quality statements about DACs - your statements are incorrect and even if they were correct they would still be irrelevant for your purposes; audio from OTA is heavily compressed.
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post #15 of 26 Old 09-29-2011, 11:59 AM - Thread Starter
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Originally Posted by krabapple View Post

It sounds like you may have drunk the 'high end' kool aid. Analog out should be fine if it's working right -- what is it about the quality of your cable box's that is subpar? Noise?

And the output of a decoded DD bitstream is...PCM. So the DAC is still converting PCM to analog, as any DAC should. The PCM content is 'lossy' compared to the original signal (i.e., before it was DD-encoded), but DACs don't care. Any decent DAC these days should be able to handle the full audible range with aplomb.

I always appreciate aspersions from persons who know nothing about me.

What I find lacking in the analog out through 16' or so of analog cable is exactly what we kool aid drinkers seek in high end audio.

The output of the cable box is DD. If I can get a device to convert it to two channel PCM, I understand that would be lossy but I can still feed it to my two channel quite decent DAC. Do you know of such a device?
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post #16 of 26 Old 09-29-2011, 12:00 PM
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Can you elaborate on what the deficiencies of the cable box's analog output are?
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post #17 of 26 Old 09-29-2011, 12:06 PM - Thread Starter
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Quote:
Originally Posted by walbert View Post

You can't magically make it lossless by converting AC3 to PCM, its still lossy originally, you are not in any way gaining quality. The cable box has the DAC you want built-in, sounds like a solution to me. As far as the quality statements about DACs - your statements are incorrect and even if they were correct they would still be irrelevant for your purposes; audio from OTA is heavily compressed.

You're quite right; the cable box analog output maybe my best solution, if not a very good one. We have been told that DD is converted first to "lossy" PCM and then to analog. I though I might find a device that does the conversion to PCM and do the final conversion in my very fine DAC. Also the long connection required would be in optical which travels well.

I found the audio from my OTA set up sent through my DAC to give superb performance when the audio was sent out uncompressed, which is true for much musical programming over PBS, for example.
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post #18 of 26 Old 09-29-2011, 12:11 PM
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The PCM isn't lossy.

You seem a little confused about how it works. The original "lossless" multichannel soundtrack is compressed into "lossy" DD. The DD is then decoded into its uncompressed multichannel form. Turning it into 2.0 combines the channels and of course has to throw some parts away. This digital stream is then converted to analog audio by a DAC.

The chances that there are any audible differences between your cable box's DAC and your expensive standalone DAC are infinitesimal.
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post #19 of 26 Old 09-29-2011, 01:59 PM
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Quote:
Originally Posted by MLM View Post

I always appreciate aspersions from persons who know nothing about me.

What I find lacking in the analog out through 16' or so of analog cable is exactly what we kool aid drinkers seek in high end audio.


The problem there is the distance, not 'analog' or your cable box per se. You could make sure you have cable robust enough to do the job. This should do:

http://www.monoprice.com/products/pr...seq=1&format=2


Though if you want to feel more high-endy, by all means the kool-aid hucksters are ready to accommodate you

http://www.audio-direct.com/p-54199-...200m-pair.aspx
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post #20 of 26 Old 09-29-2011, 02:07 PM
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Quote:
Originally Posted by jonnythan View Post

You seem a little confused about how it works. The original "lossless" multichannel soundtrack is compressed into "lossy" DD.

..which happens during production...

Quote:


The DD is then decoded into its uncompressed multichannel form.

....which happens during playback. The decoded DD is indeed 'lossy' compared to the original lossless multichannel soundtrack supplied to the encoder in the DD mastering studio.

Quote:


The chances that there are any audible differences between your cable box's DAC and your expensive standalone DAC are infinitesimal.

Yup.
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post #21 of 26 Old 09-29-2011, 02:29 PM
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Quote:
Originally Posted by MLM View Post

...when the audio was sent out uncompressed, which is true for much musical programming over PBS, for example.

Interesting. Can you please provide more information about uncompressed audio from a PBS broadcast? As you know, PCM covers a wide range of sampling rates and bit depths, all of which are "uncompressed". Since the digital transition, DD is codec of choice used on the vast majority of broadcasts and I don't recall seeing any music shows on my local PBS station that offer stereo PCM. Do you recall which shows you saw and the audio specs that were used?
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post #22 of 26 Old 09-30-2011, 08:04 PM
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Quote:
Originally Posted by MLM View Post

You're quite right; the cable box analog output maybe my best solution, if not a very good one. We have been told that DD is converted first to "lossy" PCM and then to analog. I though I might find a device that does the conversion to PCM and do the final conversion in my very fine DAC. Also the long connection required would be in optical which travels well.

I found the audio from my OTA set up sent through my DAC to give superb performance when the audio was sent out uncompressed, which is true for much musical programming over PBS, for example.

I don't know of a single device that will get you want you want; if you bought *both* Gefen converter devices you could go from AC3 to PCM, but that seems sort of...silly (not to mention expensive). And that being said, I'm really inclined to say these differences are mostly in your head - unless you're attempting to cover an exceptional distance between hardware - TV audio isn't "great" compared to some other media, and you're unlikely to gain anything using a "very fine DAC" over whatever the cable box includes (which could potentially be a better spec'd chip for all we know).
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post #23 of 26 Old 03-10-2013, 12:04 AM
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Quote:
Originally Posted by jonnythan View Post

The PCM isn't lossy.


You seem a little confused about how it works. The original "lossless" multichannel soundtrack is compressed into "lossy" DD. The DD is then decoded into its uncompressed multichannel form. Turning it into 2.0 combines the channels and of course has to throw some parts away. This digital stream is then converted to analog audio by a DAC.


The chances that there are any audible differences between your cable box's DAC and your expensive standalone DAC are infinitesimal.

I wouldn't necessarily say. Lots of consumer grade stuff is pretty crappy. My ancient discman type portable CD player puts out pretty poor sound on its outs. Believe me analog out is not the same quality from everything under the sun.

Compare a top sound card to motherboard analog out, huge difference.
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post #24 of 26 Old 03-10-2013, 05:28 AM
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Originally Posted by skibum5000 View Post

I wouldn't necessarily say. Lots of consumer grade stuff is pretty crappy. My ancient discman type portable CD player puts out pretty poor sound on its outs. Believe me analog out is not the same quality from everything under the sun.

Compare a top sound card to motherboard analog out, huge difference.

So you searched and dug up a nearly 2 year old thread to state this?eek.gif

Also internal PC analog sound cards can suffer PC generated electrical nose. A PC is a terrible place for an analog signal. If you want to tout analog SQ you might use something like an OPPO BDP-105 as an example.
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post #25 of 26 Old 09-18-2013, 02:30 AM
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My problem is similar but a little different. I have Sennheiser RR840 wireless earphones where the base unit is connected to my Comcast DVR RCA outputs. That works pretty well. I even have a separate set of RCA cables attached to my BlurRay player which I switch to the Sennheiser when i watch DVD disks. (I have to switch the DVR input 3/8' cable end for the Blueray player when I watch DVD disks.) However, when I recently connected my internet cable to my TV in order to access Internet media such as Netflix I lost the sound from the Earphones. Not too surprising since the sound output is then coming from the TV's speakers but not available to the Earphones when I would like to use them because the only audio output is digital and the Panasonic outputs Dolby Digital from ATSC channels and only outputs PCM from NTSC Channels. It appears that since Comcast went totally digital that the output would be Dolby Digital and I would need a DAT that converts Dolby Digital to PCMAnalogue two channel stereo.

I am very much a novice on this subject so any comments as to a solution would be helpful. If I can get a DAT converter (and cable) that will work with my Sennheisers, I can even remove the two RCA cables I am currently using from the DVD and DVR units. Any comments would be very much appreciated.
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post #26 of 26 Old 09-18-2013, 09:46 AM
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Quote:
Originally Posted by William View Post

So you searched and dug up a nearly 2 year old thread to state this?eek.gif

Also internal PC analog sound cards can suffer PC generated electrical nose. A PC is a terrible place for an analog signal. If you want to tout analog SQ you might use something like an OPPO BDP-105 as an example.

A PC *could* do that, but typically doesn't nowadays. If you have measurements to suggest otherwise, I'm all eyes (and ears).

FWIW, I've been streaming my collection from a hard drive through my laptop for years now (using foobar2000 as a player), using both analog and digital outs (though mostly digital) , and PC noise has never been an issue. It's not an issue for my iPod either...

and btw, that ancient discman, if *level matched* and *compared blind* to a modern DAC, might do surprisingly well.
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