PCM vs Dolby 5.1 - AVS Forum
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post #1 of 18 Old 06-11-2007, 06:46 PM - Thread Starter
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PCM vs Dolby 5.1

It sounds heaps better, but sometimes I just wonder if its the loudness that tricks me into assuming its better... Why is PCM so much louder than Dolby 5.1?
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post #2 of 18 Old 06-11-2007, 06:51 PM
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Well I take it you're talking about uncompressed PCM. Uncompressed PCM sounds better than DD 5.1 simply because it's uncompressed, it really has nothing to do with the loudness of the soundtrack. Dynamic peaks are clearer and more vibrant, bass has more impact and slam. Your ears are not playing tricks on you, uncompressed PCM is leaps and bounds over DD. Of course everyone's ears are different.

Just my .02

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post #3 of 18 Old 06-11-2007, 06:56 PM
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People used to say that DTS was just louder than DD. Personally, I think a lot has to do with bitrate. But then again, I'm not an audio professional.
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post #4 of 18 Old 06-11-2007, 07:02 PM
 
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I have a friend who bought a DVD-A player and he was telling me how great his DVD-As sounded than his CDs. He said they were clear and clean and had bass and high end that he had never heard before.
Then I went to his house and connected his player so that he could hear something other than Dolby Digital...
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post #5 of 18 Old 06-11-2007, 09:11 PM
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It's the lack of compression and full on dynamic range you are now hearing that is waking you up out of your DD DVD inducing coma.

Welcome to no compression. It's so 1990 I say that because Laserdisc had uncompressed PCM and people kept telling me but DD is so much better. Yeah right.
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post #6 of 18 Old 06-11-2007, 09:34 PM
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How does the full 640k Dolby Digital stand up to PCM / TrueHD?

I haven't had a chance to hear any of the new lossless formats yet.
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post #7 of 18 Old 06-12-2007, 05:26 AM
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When listening to the POTC BRs I noticed that the dolby 5.1 track had more bass than the PCM. Now I assume this is because Im using optical for audio out, but my receiver is detecting the PCM signal and when I switch to the Dolby EX track it shows 6.1 dolby.

Is it possible to get uncompressed PCM over optical? I was wondering why the bass was so poor on both of these movies until I put them in Dolby 5.1 mode. Could this be some setting on my receiver?

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post #8 of 18 Old 06-12-2007, 05:39 AM
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Quote:
Originally Posted by Hayrab View Post

When listening to the POTC BRs I noticed that the dolby 5.1 track had more bass than the PCM. Now I assume this is because Im using optical for audio out, but my receiver is detecting the PCM signal and when I switch to the Dolby EX track it shows 6.1 dolby.

Is it possible to get uncompressed PCM over optical? I was wondering why the bass was so poor on both of these movies until I put them in Dolby 5.1 mode. Could this be some setting on my receiver?

The only way (to the best of my knowledge) to get any advanced audio; this includes Dolby True HD, PCM uncompressed, etc... is to use HDMI or analog cables. You can NOT get uncompressed sound via optical as there is not enough "room" for the large signal to transmit.

Someone feel free to correct me if I am wrong, but this is what my understanding is.

As for the difference in sound... I just watched Dreamgirls (HD DVD) and then Apocalypto (BD) and Batman Begins (HD DVD) and both Batman and Apocalypto DESTROYED Dreamgirls' DD+ soundtrack.

I hadn't really appreciated the difference uncompressed sound offered, but upon watching these discs, it was apparent that Dreamgirls sounded a bit anemic in comparison.

I was disappointed, too; I was expecting a walloping soundtrack on that film, being a musical and all...

Play nice. It's just an online forum :)
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post #9 of 18 Old 06-12-2007, 01:10 PM
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Quote:
Originally Posted by wired1 View Post

The only way (to the best of my knowledge) to get any advanced audio; this includes Dolby True HD, PCM uncompressed, etc... is to use HDMI or analog cables. You can NOT get uncompressed sound via optical as there is not enough "room" for the large signal to transmit.

Someone feel free to correct me if I am wrong, but this is what my understanding is.

As for the difference in sound... I just watched Dreamgirls (HD DVD) and then Apocalypto (BD) and Batman Begins (HD DVD) and both Batman and Apocalypto DESTROYED Dreamgirls' DD+ soundtrack.

I hadn't really appreciated the difference uncompressed sound offered, but upon watching these discs, it was apparent that Dreamgirls sounded a bit anemic in comparison.

I was disappointed, too; I was expecting a walloping soundtrack on that film, being a musical and all...

Through optical and from my PS3 to my receiver you can get 3.1 uncompressed. The center, fronts and sub are all active. It sounds great and on most movies it is 6.9 Kbps which is more than 10 times DD 5.1, but I like the surround sound so until I upgrade my receiver to one that is HDMI, I wil listen in DD 5.1.
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post #10 of 18 Old 06-12-2007, 02:33 PM
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Quote:
Originally Posted by Luke212 View Post

It sounds heaps better, but sometimes I just wonder if its the loudness that tricks me into assuming its better... Why is PCM so much louder than Dolby 5.1?

It's from Dialog Normalization that is used in Dolby Digital. PCM and DTS do not use any form of dialog normalization.
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post #11 of 18 Old 06-12-2007, 02:35 PM
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Quote:
Originally Posted by Hughmc View Post

Through optical and from my PS3 to my receiver you can get 3.1 uncompressed. The center, fronts and sub are all active. It sounds great and on most movies it is 6.9 Kbps which is more than 10 times DD 5.1, but I like the surround sound so until I upgrade my receiver to one that is HDMI, I wil listen in DD 5.1.

how do i go about doing this just to see how it sounds in the front channels?
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post #12 of 18 Old 06-12-2007, 02:51 PM
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Quote:
Originally Posted by Hughmc View Post

Through optical and from my PS3 to my receiver you can get 3.1 uncompressed. The center, fronts and sub are all active. It sounds great and on most movies it is 6.9 Kbps which is more than 10 times DD 5.1, but I like the surround sound so until I upgrade my receiver to one that is HDMI, I wil listen in DD 5.1.

When selecting a 5.1 or 6.1 PCM soundtrack and you play it back through optical on the PS3, a 2ch downmix of the 5.1 or 6.1 pcm is being sent, not a 3.1. And based on your settings on your receiver, it will apply pro-logic decoding on this 2ch downmix which is why you get audio from your center channel and your subwoofer is receiving a bass signal due to your bass management configuration.
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post #13 of 18 Old 06-12-2007, 04:59 PM
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It's from Dialog Normalization that is used in Dolby Digital. PCM and DTS do not use any form of dialog normalization.

It's not that. Dialnorm won't affect this amount of difference on the dynamics. there is clear compression being heard on a DD track.
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post #14 of 18 Old 06-12-2007, 05:48 PM
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Quote:
Originally Posted by Shane Martin View Post

It's not that. Dialnorm won't affect this amount of difference on the dynamics. there is clear compression being heard on a DD track.

True, there is a difference in dynamics, as well as other sound qualities being better on PCM vs DD because of uncompressed vs compressed lossy.

But the volume level or loudness difference that Luke212 was noticing when trying to compare Dolby Digital and PCM would be attributed to Dial Norm. For example, if the Dolby Digital soundtrack he is trying to compare has a dial norm offset of -27, the dolby digital decoder will automatically attenuate the audio by -4db. Now if the PCM or DTS version of the same soundtrack is played, it will play 4db louder compared to the dolby digital track being attenuated by -4db due to dial norm. From what Luke212 wrote, this is what he was experiencing.
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post #15 of 18 Old 06-12-2007, 10:06 PM
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Quote:
Originally Posted by Dwellon View Post

When selecting a 5.1 or 6.1 PCM soundtrack and you play it back through optical on the PS3, a 2ch downmix of the 5.1 or 6.1 pcm is being sent, not a 3.1. And based on your settings on your receiver, it will apply pro-logic decoding on this 2ch downmix which is why you get audio from your center channel and your subwoofer is receiving a bass signal due to your bass management configuration.


My receiver would tell me exactly what it is decoding and or being applied and it is not decoding or applying pro logic. It is DTS Neo 6 PCM without surround sound.
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post #16 of 18 Old 06-12-2007, 10:29 PM
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Quote:
Originally Posted by Hughmc View Post

My receiver would tell me exactly what it is decoding and or being applied and it is not decoding or applying pro logic. It is DTS Neo 6 PCM without surround sound.

1. their is no way your getting more then 2 channel pcm from the ps3 or any high def player. through optical
2. what receiver are you using?

you may think its 3.1 uncompressed but it is not. now is it possible that its taking the uncompressed 2 channel track and turning it into 3.1 i would so and same with taking the 5.1 track and compressing it to 3.1...
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post #17 of 18 Old 06-12-2007, 10:46 PM
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Quote:
Originally Posted by Hughmc View Post

My receiver would tell me exactly what it is decoding and or being applied and it is not decoding or applying pro logic. It is DTS Neo 6 PCM without surround sound.

DTS Neo is DTS's version of Pro-Logic II. Your receiver is applying DTS Neo processing to the 2 channel downmix which is why it seems you are getting more than 2 channels.
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post #18 of 18 Old 05-03-2014, 10:05 AM
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its the opposite on my system. Dolby is much louder than PCM? My problrm ids dolby hiccups - looses "connection" or software requires too much memory? So for audio from my computer to my sound system I just use pcm. Dolby works fine from Blue Ray & TV source. Perhaps because the tv & BR are hdmi pass thru & the computer is sound out thru usb to a sound blaster to yamaha amp via digital optical. I originally went directly from the computer to the yamaha via headphone jack but thought "the sb digital box would perform 5.1 conversion better. Perhaps it does but the signal is unacceptable as dolby output!
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