Is PCM Better Or Worse Than Dolby Digital?

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I'm not sure exactly what "PCM" means, but when I choose that setting instead of "Dolby Digital", I get much better results. The audio is louder and the surround sound is more, well, surround. I've been having a bear of a time trying to figure out the settings and getting 5.1 to work right. The main issue is only getting audio out some of the speakers. "PCM" has given the overall best-sounding result and gives audio out of all the speakers. But with "Dolby Digital" I don't get audio from the 2 surround speakers.

So which one is normally better? And what's the actual difference between "PCM" and "Dolby Digital"?
 
Dolby Digital is compressed so PCM is better. Dolby True HD, DTS HD MA, Atmos and DTS X are also lossless, so should be similar quality to PCM.

If the source audio is stereo, it should only be coming from your front left and right speakers unless you use an up mixer.

What amp do you have, and what speaker set up?
 
PCM is the originally recorded digital audio (pulse coded modulation) - all A/V audio is PCM to start with, and all A/V audio will end up as PCM before hitting the DAC. Dolby Digital is lossily compressed PCM. It enables more audio to be stored in the same space and more audio to be transmitted across the same bandwidth. However, as said, DD is lossy. Better therefore is Dolby TrueHD, which is losslessly compressed and hence absolutely identical to the original PCM once decompressed.

The volume and performance (Dolby TrueHD) ought to be identical, however, since the decompression, etc. is being done in a different box, if your equipment has not been calibrated, there may well be differences in the level, or dependent upon the equipment quality even differences in the performance.
 
It depends upon where the PCM digital data is derrived from and how it was encoded. It can technically be better by way of it allowing for higher bitrates, but setting a source device to output PCM rather than allowing it to bitstream the formats the content is encoded with simply results in the source converting other formats to PCM data. The audio you get resulting PCM data in such instances will be no better than the audio you'd have gotten had you bitstreamed the encoded audio the PCM data was derrived from.

In some instances, setting a device to output PCM as opposed to having bitstream the actual format the audio was encoded with can result in you getting audio that is less desirable. Choosing the PCM digital output option onboard a TV for example will in most instances result in 5.1 Dolby and DTS encoded formats being mixed down to just 2 channel PCM. Again, the resulting PCM would simply be the DTS or Dolby Digital audio decoded by the TV and mixed downso no improvwement over what you'd have gotten had you bitstreamed the original format.

The only time that PCM may resilt in better quality is in instances where you get the option of either a discrete PCM soundtrack or a Dolby encoded soundtrack. Even then, the PCM option will have to be encoded in a manner than actually means that the lossless uncompressed PCM data includes as much if not more data than the lossy compressed Dolby Digital audio.

Also note that your AV receiver decodes incoming formatted audio and this results in PCM data. It is this PCM data that is processed by the AV receiver and converted to an analogue signal by its DAC.

Streaming audio already encoded as Dolby Digital will not result in better audio if configuring the source device to decode it and output it as PCM. All you've done is change the device doing the decoding from the AV receiver to the source device.


You may find this informative:

and:




PCM isn't technically an audio format and more a way of conveying digital data. It can convey data associated with audio that has a higher bitrate and sample rate than lossy formats, but only if the media you are accessing the audio from includes a PCM encoded soundtrack encoded with the additional information not present with the lossy compressed Dolby Digital variant of that same soundtrack. Converting the Dolby Dogital variant using the source device will not result in better audio.


You may also find this thread of interest:
 
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It's confusing that there's a few different things that have the word "Dolby" in them. This has all been frustrating. Even when the receiver display shows "Dolby D 5.1", I still don't get audio from the far left & right surround speakers.
 
The devices are:

TV - Vizio M507-G1 (A 50-inch LED TV).
Receiver - Onkyo HT-S3300 (5.1 surround sound)
Cable Box - Unsure, it just says "technicolor" on it.

So does PCM actually give you real 5.1 surround sound, or is just taking a stereo-only signal and sending it to all the speakers?
 
Even when the receiver display shows "Dolby D 5.1", I still don't get audio from the far left & right surround speakers
Are you sure? You might be l listening to a soundtrack where there is not much audio mixed for the surround speakers. Do the test tones play?


So does PCM actually give you real 5.1 surround sound, or is just taking a stereo-only signal and sending it to all the speakers?
If the source audio is PCM 5.1 then it is true surround sound. PCM can also be stereo though, 2.0.
 
Well this receiver doesn't really have test tones. There's a menu setting called Level Cal where you can manually set each speaker anywhere from -12 dB to +12 dB and it plays a white noise type sound rather than test tones. The white noise is very quiet and hard to judge even at +12 dB.
 
Well this receiver doesn't really have test tones. There's a menu setting called Level Cal where you can manually set each speaker anywhere from -12 dB to +12 dB and it plays a white noise type sound rather than test tones. The white noise is very quiet and hard to judge even at +12 dB.
White noise counts as test tones. Put your ear right against the speaker to see if the white noise is emitting from it.
 
Note that if you've cnfigured your Vizio TV to output PCM via its digital audio output then you'll only ever be getting 2 channel PCM via that TV. I'm not familiar with yout cable TV box or how TV channels deal with the audio encoding where you are, but it is common practice to limit the SD channels to 2 channel PCM and you'd ordinarilly only get Dolby Digital via the HD channels. It should be noted that just because the audio is Dolby Digital isn't to say it will be 5.1 in nature! Dolby Digital can be stereo or 5.1 and not all TV programs will include anything more than a 2.0 stereo soundtrack. Even if the channel you are watching uses Dolby Digital, not all of the programs aired via that channel will be 5.1 in nature!
 
Yes, I can hear white noise from all the speakers. So I know they're hooked up and working right.

So I guess even though the receiver may display "Dolby D 5.1", it's possible that you're not really getting 5.1?

Here's something aggravating I had happen. Last night watching the show "The Voice" on local over-the-air TV channel 8, I get no surround audio. But then when I switch to that same channel on the cable box, then I get surround sound out all the speakers, with the same rock band still playing. So what the heck? Can you see my frustration?
 
I can. I think the issue might be the upmixer. It is set to come on with some devices and not others?

I am not familiar with your AVR, but there should be a way to cycle through the upmixing options when stereo audio is playing to create pseudo 5.1.
 
Upmixing is processing applied to a source that creates additional pseudo audio channels. Such upmixing can be used to create audio from stereo sources that would be output via the other speakers present within a setup. Examples of this would be Pro Logic, Neo, Dolby Surround, Neural or Neural:X. Most AV receivers also have an all channel stereo mode that portrays 2 channel stereo sources via all of the speakers present. Note that such a mode can be in effect for different sources and will not necessarily be activated for all of the receivers sources.
 
I'm not sure what an upmixer is, but the Receiver is an Onkyo HT-R380.
Upmixing is where the AVR takes a stereo soundtrack and intelligently processes it to send audio to all of the connected speakers to create a pseudo surround effect. Maybe you could read the manual?
 
Dolby Digital is compressed so PCM is better. Dolby True HD, DTS HD MA, Atmos and DTS X are also lossless, so should be similar quality to PCM.

If the source audio is stereo, it should only be coming from your front left and right speakers unless you use an up mixer.

What amp do you have, and what speaker set up?


I am accually getting better sound using dolby digital than using PCM. Dolby digital is louder and wider sound field on my samsung q90r sound bar.
 
I am accually getting better sound using dolby digital than using PCM. Dolby digital is louder and wider sound field on my samsung q90r sound bar.

If you've configured your TV to output PCM then the output will be mixed down to just 2 channels of PCM data. This is due to the inability of conventional ARC or S/PDIF optical to convey more than just 2 channels of PCM data. Your TV would be decoding the formats it can handle and downmixing the resulting multichannel PCM data into just 2 channels.

Regardless of whether you are bitstreaming an audio format or not, the AV receiver can only process the audio and input it into its DAC if it firct decodes it. After the receiver decodes it the signal is PCM in nature. The only exception to this would be if the receiver is receiving SACD and if the receiver has a DAC that can handle the associated SACD signal directly.

DACs do not and cannot handled undecoded Dolby formatted audio.
 
Im having an issue that really is driving me nuts! using an lg soundbar and setting the tv output to Dolby digital is resulting in a massively boosted signal on the soundbar that means I barely have the volume up which in contrast means the soundbar is extremely loud at around half volume. Strange as I have never had this issue with av receivers.
Selecting pcm output results in what i would consider a more balanced output.
What is happening here, why is the Dolby digital option so much louder?
Kit is Samsung mu7000 with lg Sl8yg
 
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If outputting PCM from a TV then it will be stereo and if the source was multichannel in nature than the PCM output from the TV will be the multichannel audio mixed down into just 2 channels. The LFE channel included with multichannel formats isn't however mixed down into the 2 channel PCM signal and this could be why you are under the impression that the PCM audio is quieter? Dialogue normalisation (Dialnorm) alters the dynamic range associated with the DD audio being played.
 
Thanks Dante, the reason it seems odd to me is that the soundbar is pushing into compression at about half volume. It’s as if the Samsung tv is boosting the Dolby signal. On the LG soundbar around 10/40 is the comfortable listening level, it just doesn’t seem right to me. It’s worse on tv content, YouTube and Netflix isn’t quite as bad but is still seems as if the volume to signal ratio isn’t correct. I would be interested to see if I get the same result from an LG tv.
Example. PCM results in a listening level at about 20 (halfway) on the soundbar which when pushed to max volume we are reaching compression.
Dolby digital results in a comfortable listening level of about 10 at 15 we are running out of headroom. These findings are similar to the comment above which states DD results in a louder wider soundstage, but headroom is significantly reduced on my system.
Edit. After some further reading I’m wondering if this is due to the 5.1 signal being output through a 3.1 system.
Edit 2. After playing around some more it seems the LG is applying the boost only in movie mode, standard mode results in far less boost between DD and pcm.
 
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Thanks Dante, the reason it seems odd to me is that the soundbar is pushing into compression at about half volume. It’s as if the Samsung tv is boosting the Dolby signal. On the LG soundbar around 10/40 is the comfortable listening level, it just doesn’t seem right to me. It’s worse on tv content, YouTube and Netflix isn’t quite as bad but is still seems as if the volume to signal ratio isn’t correct. I would be interested to see if I get the same result from an LG tv.
Example. PCM results in a listening level at about 20 (halfway) on the soundbar which when pushed to max volume we are reaching compression.
Dolby digital results in a comfortable listening level of about 10 at 15 we are running out of headroom. These findings are similar to the comment above which states DD results in a louder wider soundstage, but headroom is significantly reduced on my system.
Edit. After some further reading I’m wondering if this is due to the 5.1 signal being output through a 3.1 system.
Edit 2. After playing around some more it seems the LG is applying the boost only in movie mode, standard mode results in far less boost between DD and pcm.
You may be better off posting your question in the Soundbar Forum.

 
Hi all

Hope someone can help.

So I have a samsung ue55ru7400 tv and a very old Samsung sound bar the hw-f550

This soundbar is only 2.1, now on my TV the audio output whilst in YouTube is PCM and when I watch a bluray or netflix the TV switches automatically to dolby digital

So judging my the comments above is that PCM is actually better

Now comes where I need help, so the hw-f550 is very loud, set the volume to 13 and no higher, gone up to 20 and its extremely loud and not appropriate as I live in a flat. Had this soundbar for over 5yrs and its never failed me.

So decided to upgrade the soundbar as my 4k TV is less than a Yr old and thought its time for an upgrade for sound, so bought the samsung q60t soundbar, arrived and setup it all up by just plugging it in, TV recognised it straight away.

So no settings changed either on the TV or soundbar, went onto YouTube to play so.e music to test the new soundbar and at volume lvl 13 you can't hear anything, have to turn the volume up to 20 for any decent audible sound, spent hours trying to figure out how to get the same volume output as my previous 5yr old soundbar and nothing, samsung tech support went through loads of things and nothing till eventually I disconnected the hdmi cable from the soundbar and connected my galaxy s10 to the soundvar via Bluetooth and the soundbar actually gave me the same volume output as my old soundbar, plugged hdmi back in and back to the terrible sound output.

Am I doing something wrong or could this just be a dud unit, are you supposed to use/set under TV options for the sound to PCM and use this all the time? If so how do you force it to instead of it automatically changing depending on the program/app the TV is running?
 
So judging my the comments above is that PCM is actually better


No, PCM is no better than streaming the actual format the audio was originally encoded as. In some instance the original format will be uncompressed PCM, but this doesn't mean that such audio is or will be supperior to audio that has been formatted and packaged differently.

If accessing audio via YouTube then you'd not get anything but 2 channel PCM regardless of whether you are bitstreaming it or allowing the source device to decode it. The YouTube service only provodes access to audio encoded as 2 channel PCM.

If decoding (inpackaging) the audio prior to the device actually processing the audio and or amplifying it then the only difference will be the device decoding the audio. You cannot derive better PCM from what is basically the same formatted audio. What is being decoded to give you the PCM signal is the same audio data so why would you get better quality PCM data if streaming it from a source as unpackaged PCM data?

If using absolute volume then this isn't standardised and will not result in the same volume at the same setting on different devices. If you need the volume to be greater or louder then turn the volume up on the device amplifying the audio.

Audio levels are not bossted or diminished relative to whether the audio is decoded or not prior to output. The headroom associated with a PCM signal will be the excat same headroom associated with the formatted and packaged audio data it was derrived from. The PCM fata can only ever mirror what was packaged if the source derrives its PCM data from the packaged, formatted source.
 
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If outputting PCM from a TV then it will be stereo and if the source was multichannel in nature than the PCM output from the TV will be the multichannel audio mixed down into just 2 channels. The LFE channel included with multichannel formats isn't however mixed down into the 2 channel PCM signal and this could be why you are under the impression that the PCM audio is quieter? Dialogue normalisation (Dialnorm) alters the dynamic range associated with the DD audio being played.
I don't know why but 'stereo uncompressed" option set on my tv using ARC which I assume is PCM sound better in my Yamaha SR B20A Soundbar than feeding it with a Dolby multichannel . The soundbar itself can do virtual surround from multichannel sources.



What I mean better is that the volume is louder and clarity , surround effect ect are all better. Which I don't understand as stereo is supposed to be flatter or dill than Dolby multichannel?



Can someone explain.
 

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