PCM vs Dolby Digital

[venkat_9099]

Nice explanation nineth. Thanks

PS:- welcome to the Forum 🙂

I second that.

Sent from my HTC Incredible S using Tapatalk

 

[Radkrishr]

Nineth, Great explanation! I learned this the hard way too... Such a waste of pure HDMI resources and bandwidth instead of just letting customers know that they should choose PCM over Dolby if they need to connect to their TV directly with HDMI.

 

[sivanbalaji]

Originally Posted by sivanbalaji
The only difference is where the decoding of Dolby is happening. In case of 5.1 PCM output, the decoding is happening at the STB and in the other case its happening at the home theater.

Originally Posted by nineth
his is not true. The place of decoding (digital to analog) depends on how you connect your STB to your receiver. If you connect it via a HDMI cable (some receivers support HDMI input), then digital audio (whether it's PCM or Dolby digital) will be decoded and played by the receiver. If you use a digital coaxial audio cable (connecting the S/PDIF output of your STB to your receiver), then again, your STB sends out digital audio, and the decoding is done at the receiver. However, if you connect the analog out (L/R) outputs of your STB to your receiver or TV, the decoding is done at the STB. Note that in this latter case, you get 2-channel audio, whether or not the original audio was Dolby digital. Since receivers are likely to have superior decoding capability, one should send in digital audio directly from the STB to the receiver (via HDMI or digital coaxial); it will decode and play it back on all your speakers. Perhaps, what you really mean is that, some processing is done at the STB when you select PCM (dolby digital to pcm); yes, but this pcm is 2-channel; so there is a downmix done.

Nineth, You are talking about decoding digital audio into analogue, I'm talking about Dolby Digital decoding. Both can happen at STB or the receiver based on the interfaces we choose and the audio output method we choose in STB. If we choose analogue o/p interface at STB then the digital to analogue as well as Dolby decoding has to be done at STB itself. If we choose digital interface and PCM output at STB then Dolby decoding is happening at STB and digital to analogue is happening at receiver. Similarly if we choose digital interface and Dolby output at STB then both Dolby decoding and digital decoding is happening at receiver.

Originally Posted by Harshal
can someone help me?
i have 5.1 home theater but it is not having any optical / coaxial input..it just has 6 inputs (RCV)....i have Tata Sky HD..how to get 5.1 sound?

I found converters that convert digital coax/optical into L/R RCA analogue output. But not 6 RCAs.

 

[Matad]

>> Originally Posted by manujkansal >>I saw two options under audio settings : PCM and dolby digital. I was wondering which one is better for HD content like world cup. I have >>connected my STB to my LCD using an HDMI cable and STB to my Sony home theater system using an optical cable.I am having Sony EX520 and DAV-DZ510 HT. I have connected LED TV and Tata Sky+ using HDMI. Also ARC of TV to HT via again another HDMI. But i observe that iam getting only 2.1for any HD channels. Settings on HT, TV and tatasyk are as per sony technical person. Is using optical cable is only solution? if yes, what care should be taken to buy any optical cable like brand, standard.. etc

 

[sivanbalaji]

Yes. Using optical cable for 5.1 audio is the way I used and experienced at my friends home theater setup. Its my observation that if you choose dolby digital for audio, you will get only audio for HD channels in TV.Regarding the type of cable, I presume that you are using Tata Sky+ HD and if I remember correctly the STB has both optical as well as coax for digital audio output. If so try using any RCA audio/video cable which you have or came with the STB to make sure that you get 5.1 audio. And then go for purchasing optical or coax cable. IMO any optical cable should work flawlessly for good audio quality. A branded one may last longer. Thats it.

 

[Scorpio02]

Yes. Using optical cable for 5.1 audio is the way I used and experienced at my friends home theater setup. Its my observation that if you choose dolby digital for audio, you will get only audio for HD channels in TV.

Regarding the type of cable, I presume that you are using Tata Sky+ HD and if I remember correctly the STB has both optical as well as coax for digital audio output. If so try using any RCA audio/video cable which you have or came with the STB to make sure that you get 5.1 audio. And then go for purchasing optical or coax cable. IMO any optical cable should work flawlessly for good audio quality. A branded one may last longer. Thats it.

I recently bought a LG home theater system (LG HB806TM) and a Panasonic Plasma TV (VIERA TH-P42X30D). In the HTS, there is one HDMI out port but no HDMI input port. So I have connected HTS with the Plasma TV using HDMI cable and it works great. I have also played Blur-ray discs on the HTS and and the 5.1 audio quality is awesome.

It was all great, but I started facing a problem when I bought Tata SKY HD STB, hoping to enjoy the HD quality viewing and 5.1 channel surround on the HD channels. Tata sky has provided one HDMI cable (along with other cables that they usually provide), which I am using to connect the STB with the Plasma TV. I could anyways not use the HDMI cable to connect to my HTS, as it does not have any HDMI in port.

Now, Tata HD STB does have a S/pdif coaxial out port to give 5.1 audio to an HTS, however, the second problem is that my HTS only has a TOSLINK optical input port. There is no S/pdif coaxial in port in my HTS. I know there are converters available that convert coaxial into optical, but the cost would almost be equal to a new TATA sky HD+ STB (which does have a TOSLINK optical output). Had i Known this, I would have bought the HD+ STB in the first place. I am not sure why would Tata sky have different ports on both the HD boxes.

Now, I though a lot about a convenient solution, but I am not sure if it will work.

The specs for Panasonic VIERA TH-P42X30D, does show that it can play digital Dolby (though it obvious does not have the 5.1 speakers to give the effect). Also, it does have a TOSLNIK optical output. So if i connect my Plasma TV (which is getting Video and Sound input from STB throgh HDMI) to the LG HTS using an optical cable, will it give the same 5.1 channel surround effect, which I would have otherwise got (had i been able to connect by STB with LG HTS directly).

I would really appreciate some help on this.

Regards,

 

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[SasoBTV]

nineth i see you have some knoledge on STB's and dolby digital.I have a problem with STB (DVB-C). All the HD channels with AC3 (coming from satelite) dont play audio.The company that sold us the STB's says that it is a problem with Dolby, that we didn't wanted dolby when we made the order. Can anyone tell me is the dolby a hardware or software change if we want to add it now to the STB?

 

[sivanbalaji]

Yes. Your idea of bringing a TOSLINK to your HTS from STB is right if your TV has a pass through of digital audio which it gets via HDMI. But there is another issue also with the STB that generally STBs are outputting Dolby digital audio via either coax or toslink and NOT via HDMI. The reason because many lower-end TVs don't understand any Dolby audio and people not able to understand this and put their STB's audio output to PCM instead of Dolby and thus complaining not getting audio in their TV via HDMI. This is my assumption. So the actual reason could be different.Having multiple inputs (coax and toslink) option in input device such as HTS may create problem if that device is not having switching option and thus playing all input signals together. But I don't understand why they are not putting coax and toslink together in any output device like STB, DVD player or etc. Cost reduction could be the reason. Thats why the DVR device has both but simple HD does not.

 

[Saravana Kumar]

Airtel HD STB comes with Dolby whereas Dish TV has 5.1 channel output but not Dolby certified. Dish TV has the maximum HD channels of 39. Should I go for Airtel for Dolby or Dish TV for maximum HD channels.

 

[jgvg]

PCM is better quality because its uncompressed. However its only sent 2 speakers.
DolbyD is using a MP3 like (sub FM) compression which is an earlier form of ATRAC. To me DD from my set top box seems dull and boring, so I too prefer to listen to PCM through my poor TV speakers instead of my expensive Samsung Home Theater system.
ATRAC3+ produces a near HiFi CD quality. Better than PCM.
ATRAK+HD produces above HiFi quality. The Sub, Mid and High are recorded, encoded and decoded separately.
Surround Surround already has a separate Sub Woofer. The front 3 speakers could do with separate wires for Mid, High and maybe Low.
The rear probably don't need changing.
I have much nostalgia for my MZ-R91. It has a quality amp and produces crisp loud sound to the in ear headphones.
I used to listen to it on coach rides home from Uni.
I can still remember the smiles I used to get from fellow passengers on the coach as they also used to listen to it on their journey.
The future is going to be different. Its not gonna be dull and boring.

 

[mukulshrm4]

Tata Sky binge and tata sky 4k have the same features but prices are differ alot ,why ?