Dolby Digital Question??? I'm confused

[jayswizz]

Hello again everyone,
If someone can help me out it would really help my confusion. When watching cable television, my reciever will show that Dolby Digital has been decoded but my center channel will not produce any sound. On other stations it will. It is on the same channels all the time that this happens. On other channels sound is produced from the center speaker. Is this my reciever or is this the way the tv channel is broadcast? Also, how come some stations are decoded as Dolby Pro Logic? What is the difference between the two? This has been driving me nuts for a week.

 

[MDS]

There are many flavors of DD broadcast by the cable companies. Movies are usually DD 5.1, but some channels (especially the music choice channels) are DD 2.0.

If the format is DD 2.0, you will only get sound out of the center and surrounds if you engage a matrix decoder like PLII. The receiver will decode the DD but because it only has two channels, it will play in stereo. PLII and other matrix decoders can take that 2 channel signal and turn it into 5.1. Most receivers will remember the last setting, so once you set PLII, it should always use PLII when it gets a DD 2.0 signal. [I leave mine on PLII Music at all times].

Dolby ProLogic is the predecessor of PLII (and IIx). It only works on 2 channel analog signals or 2 channel analog signals that were encoded using the Dolby Surround encoder. It is really 4 channels because the surrounds get the same information (in contrast to PLII where the surrounds are stereo). If your receiver is switching to ProLogic, then that station is probably broadcasting an analog signal - with my cable that is normal as some of the stations are digital (DD or PCM) and some are analog.

PLII will work on analog signals too and you should use that instead of ProLogic if the receiver supports it.

 

[j_garcia]

Yes, it would most likely be the broadcast. Dolby may have anywhere from 2 to 6 channels currently, not including the ".1" (not sure if there is a Dolby mono). What you may receive from those channels might be 4.0 or 4.1 which won't have a center channel in the signal.

When your receiver switches to Dolby Pro Logic or DPLII, most likely you are receiving a stereo or Dolby Surround signal (which is also technically stereo).

The difference is with stereo you only get 2 channels. Dolby Surround is a stereo signal that has information encoded (matrixed) in it that your receiver can decode into surround sound. Dolby Digital and DTS have individual, discrete channels encoded to create what would be considered "true" surround.

 

[jayswizz]

God I love this website. Thanks for the information, now I can stop ripping my hair out.

 

[mtrycrafts]

now I can stop ripping my hair out.

There is always hair transplant

Glad we can help. Keep coming back