Page 1 of Built in Digital Decoder..Advantages?

Hi all,

I am trying to find out the advantages of a built in decoder on a dvd player WITHOUT the six outputs. Ok,WITH the outputs you can connect to an amplifier such as the videologic LC speaker system but with only an optical or coax out what can I connect it to which takes advantage of my built in decoder?
Is this some sort of selling point for a feature which seems to be totally useless as it looks like I still have to buy an external decoder which outputs the six channels!

Any help would be much appreciated.



Thanks,

Tom.

The option of an on-board digital decoder on a DVD player is really for those few people who have old-school Pro-Logic amps that accept the six inputs (not many, I hasten to add - does anyone know the brands ?)

However, you are correct in stating that every DVD player has either an optical and/or coaxial output to hook up to, yup you got it, a Dolby Digital amp (and preferably one with DTS encoding on it too).

On board decoders are fairly superfluous if you already have a DD/DTS amp, because you would never dream of hooking the player up the old six-output way because (a) it`s an analogue signal and thus poorer quality than the digital signal you`d get from a digital connection and (b) who wants six phono-phono plugs all over the floor !

Really the six outputs are only of use to amps/receivers that can`t decode Dolby Digital (and/or DTS depending on whether the DVD can decode that too) for themselves and as I said these are pretty few and far between.

Hope this helps

Thanks clayts but I don`t think this answers my question.I was asking what advantage is a built in decoder that does NOT have the six outputs of which there are many i.e SCAN. I can see at least some advantage if the decoder has six outputs as you can connect it directly ( without purchasing an external decoder) to an amplifier that has the six inputs.

The reason I ask this is that I was told by Videologic that the SC2000 has NOT got a dolby digital decoder built in as it does not have the six outputs. So again what advantage is the digital decoder in the scan without the six outputs.

Sorry to go on about this but I would just like to satisfy my curiosity.

Thanks again

There is no point in having a Dolby Digital Decoder in a DVD player without having the six outputs. The reason for the decoder in the first place is to decode the digital signal to analogue. Then, each of the six channels of sound is piped into an amplifer before going onto the speakers.

Having a DD Decoder in a DVD player without six outputs is about as useful as a chocolate teapot.

Gilesy
DVD Reviewer

> Having a DD Decoder in a DVD player without six outputs . . .

Agreed, I don`t think such a thing exists. If it doesn`t have the six analogue outputs then it will just be a digital out (coax/optical). In which case no decoding is taking place!

Not quite so...

If your DVD player did not have a Dolby Digital (DD) decoder then you would hear no sound from your DVDs at all. Dolby Digital refers to the combined digital bitstream that represents a number of (possibly) seperate audio channels within, these channels are compressed (lossy) and combined in a DD encoder and it is the job of the DD decoder to uncompress & split them out again. How this output is presented is dependant on the facilities the decoder has available...eg If it has the full 6 analogue outputs then it can present each of the six encoded audio channels (L,C,R,LS,RS,LFE) on it`s respective output. If (as per Scan) you only have 2 analogue outputs then you have to combine a 5.1 (6 channel) mix down to 2. This is done in 2 ways, the difference being what is done with LS&RS...

1) LO/RO where L output = L + C*0.707 + LS, Routput = R + C*0.707 + RS
2) Lt/Rt where L output = L + C*0.707 + LS, Routput = R + C*0.707 - RS

LO/RO just adds everything together (with a 3db loss on the centre channel because your reproducing this from two loudspeakers)

Lt/Rt puts the two surround channels out of phase and hence emulates the action of a Dolby Surround encoder ready to be decoded by a Dolby Surround (or better Dolby Surround Pro-Logic) decoder. HOWEVER this emulated surround mix is NOT as the director intended which is why you should really use the `Dolby Surround` soundtrack on the DVD rather than the Dolby 5.1 `downmix` (The Dolby Surround mix is actually a matrixed L + C + R + S down to 2 channels..there`s a bit of Dolby B type noise reduction in there as well...for fun! But it`s still stored in a Dolby Digital format...confused? Now you know why they have so much fun labelling your DVD case!)

Both methods lose the LFE (Low Frequency Effects) channel.

The DD data stream also includes data about the audio such as it`s level, this `meta-data` is used to implement the `dynamic range compression` (or late night mode) such that loudness peaks can be controlled. There are 2 modes for this also, RF mode & Line mode. RF mode compresses quite a bit harder than Line mode but is suitable if you plan to feed the audio through an RF modulated link (eg via your video modulator around the house)...your bedroom telly is unlikely to be able to cope too well with the extremes of `near silence` & then `spaceship crash lands in New York` but your Hi-Fi (Line mode) probably can!

So to sum up....there is no advantage to having a 2 channel output rather than 6 channel. Now that was the long way round huh :-)

Hope that helps

This item was edited on Wednesday, 21st March 2001, 19:55

Thanks, great answer and I believe I understand now. It seems to me that it has some advantage to people who have a Prologic TV.

Cheers.

Kevin,

I bow to your superior knowledge. Yes, you are correct. The DD Decoder does not necessarily have to decode 5.1.

Wow, where do you work? Dolby???

Gilesy.
DVD Reviewer

No need to bow! All the info is available on the Dolby web-site (lots of long PDF files) which is where I got it from.

I work for HP in computer support, but part time in TV as `sound engineer` (whatever that means) hence an `awareness` of digital sound techniques and an interest in how DD & DTS work and Surround vs Stereo vs Mono compatibility.

As an addition to my previous post, I`d also like to point out that the `bedroom telly` scenario is also likely to be listening in mono, so those seperate L & R get combined to `M`. The net effect of this, whether listening to a DD5.1 downmix (in Lt/Rt mode) or a true Dolby Surround mix is that ALL the surround channel gets removed....and think of all those films broadcast on TV where people are still listening in mono. The film sound balancer has a tremendous challenge in making his mix sound as good as possible in a variety of listening conditions!

Regards

Kevin