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"Dolby Digital 2.0/Dolby Surround", "DPL" and my receiver's indicators (Yamaha)

Discussion in 'AV Receivers & Amplifiers' started by Squirrel God, Feb 18, 2003.

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  1. Squirrel God

    Squirrel God
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    Hi,

    I have indicators on my receiver that light up to show the inputs (labelled 16 in the diagram below):

    [​IMG]

    For 5.1 tracks, the L, C, R, RL, RR, and LFE light up, as you might expect.

    For mono tracks, just the C lights up - again, nothing unusual there.

    But for "Dolby Digital 2.0 / Dolby Surround" tracks (from DVD), I only get the L and R lighting up, whereas I would expect L, C, R and RC to light up, since a Dolby Surround soundtrack has 4 channels :confused: (or does it have 3 channels, L, R and RC - same as Dolby Pro Logic? :confused: )

    I get the same situation with Dolby Pro Logic soundtracks from my TV (connected via the phono inputs on the back of the receiver). Here I would expect L, R and RC to light up, but again just the L and R light up. :confused:

    Now I know that Dolby Surround and Dolby Pro Logic soundtracks actually encode all their channels within just 2 channels (L and R), so this is the only reason I can think of why only L and R light up on my receiver when playing these soundtracks. Am I right in thinking this? Is this normal? Is this what everyone else's receivers do? Or do I have a fault with my receiver's display?

    Thanks in advance :)
     
  2. Jase

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    As long as you get the relevant format indicators lit eg. Dolby PL2. I shouldnt worry too much.:smoke:
     
  3. rjw

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    You probably need to manually set the amp to Prologic as IIRC there is no signal present on the input to indicate it's prologic and not stereo.
     
  4. LV426

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    Are you actually getting any sound from the relevant speakers? If yes, then I'd be inclined to dismiss this as an artefact of the display and the type of input signal - in other words - the display is showing you the source rather than the output - and ignore it.

    On the other hand, if all but the indicated (FR, FL) speakers are actually silent - then you aren't getting a DPL output - which is probably down to the settings you have chosen for stereo sources.
     
  5. nunew33

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    Dolby surround (which is the source sound format for DPL, DPL 2)uses stereo as the input so if they are input indicators L and R would be correct.

    If it was output indicators then you would expect C and RC to light up.

    And dolby digital 2.0 is another way of saying stereo!!
     
  6. adox

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    my display only shows l & r when playing in dpl and dpl2, but it is in the correct sound mode. i don`t know what type of receiver you have squirrell. mine is a marantz. before, i owned a sony receiver, which displayed all speakers in dpl.
    i presume the receiver is reading the source, hence the left and right lighting up only. the main thing is that the output is correct, which it is on my amp, when it says dpl2, it is dpl2, even though only l&r are showing on the display.:smashin:
     
  7. deckard

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    SG

    Dolby surround is still only transmitted as 2 channels only, the decoding/matrixing of the extra channels takes place within the amp (I know this is obvious!).

    Dolby surround/DPL/DPLII are NOT discrete multichannel formats, they are a means of processing a 2 channel signal.

    Therefore such formats will only appear as a L and R channel being inputted .

    The indicators, as you've said, show which channels are being received not which channels are being output.

    Hope that helps.
     
  8. nunew33

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    In the words of peter sellers/inspector Cluseau(however its spelt)

    "zat is wat i sed"

    Was mine written in french?
     
  9. Squirrel God

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    Thanks for all your replies everyone.

    I guess my initial reasoning was correct then! :)

    The DPL/DPLII indicators do light up, but then they also do for all sources (including mono and good old stereo/DD2.0) except DD5.1 and DTS, because my receiver puts everything through DPL/DPLII automatically. So I couldn't really go by that.

    As a consequence, I am getting sound from all speakers, just that I wasn't sure if it's the proper Dolby Surround/Dolby PL source, or whether it's just a stereo signal being transformed into DPLII. I've never heard vanilla DPL or Dolby Surround before, so I'm not sure what it should sound like compared to DPL/Dolby Surround transformed into DPL/DPLII.

    As it seems some of you also just see L & R indicators on your receivers for Dolby Surround/DPL, that's put my mind at rest :)

    The amp is a Yamaha HTR-5540RDS btw.

    Thanks again! :)
     
  10. steev

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    As others may have said the Pro-Logic/II are signal processing systems. The input is stereo and may happen to be encoded that way, in which case you should get some rear speaker action.

    I'm not sure that the processor can actually 'detect' Pro-Logic as I would expect it would need some clever sums. No doubt I will be proved wrong on this.

    I've got the 5540 as well and I see no reason to use Pro-Logic when DPLII is so much better. I use it for all TV and most music.
     
  11. LV426

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    There is no clever 'flag' or other information that indicates, to a DPL processor, whether or not the signal is DPL encoded. All these signals are just 2-channel stereo.

    When 'set' to DPL (or DPL2, or DTS Neo:6 or any other sorround decoding format) the decoder will ALWAYS attempt to generate a surround soundfield from a 2-channel source, using the similarities and differences between the two waveforms (for the 2 channels) to 'decide' how and where to steer the output.

    The extent to which this is successful depends solely on the actual contents of the waveforms. Soundtracks 'encoded' with DPL simply exploit this by 'artificially' altering the phase of various frequencies in the two waveforms.

    For example: any component of the soundtrack that is equal in volume and in phase in both channels will be 'steered' to the centre speaker. any component of the waveform that is equal and out of phase will be steered to the rears. (This is a gross over-simplification, but illustrates the principle).
     
  12. Squirrel God

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    Thanks for your input Nigel - very informative post :)

    What gets me though is that my Sony DVD player 'knows' when a soundtrack is a surround encoded DD2.0 soundtrack and when it's just a plain stereo DD2.0 soundtrack. It displays "Dolby Digital 2.0/Dolby Surround" for the former and "Dolby Digital 2.0" for the latter.

    So if my player knows why can't my receiver? I always thought there was a flag in the encoded bitstream that the player was picking up on. Maybe my player is guessing? I seem to remember someone posting here that their Sony receiver indicated the inputs for surround-encoded sources (DPL and Dolby Surround) but their post seems to have gone :confused: I wonder if their receiver was 'guessing' too and it's a 'Sony thing'...

    Ignoring the DVD input into the receiver, it looks like I have no real way of knowing whether a TV programme is stereo or surround-encoded either (I've an analogue connection from my TV phonos to the receiver's phono - I don't have phonos on my Freeview box).
     
  13. Reiner

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    Some receivers do indeed guess based on the information extracted from the L&R channels.
    Based on that it indicates (suggest) that you can activate DPL processing.
    I guess there is no flag even it's a DD(2.0) stream, else the receiver could also switch to DPL automatically - which IMHO none do.
     
  14. Squirrel God

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    Thanks Reiner.

    I'm going to have to re-examine the MPEG-2 program stream because there must be something in there that the DVD player uses to display the source format, which is then stripped out of the digital audio bitstream that is sent to the receiver. If so, this would explain why the DVD player picks up on it and displays the source, but the receiver doesn't.
     
  15. adox

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    this takes us back to the thread about using the dimmer on your receiver:laugh: :laugh:
     
  16. bob007

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    Stop looking at the pretty lights and watch the movie instead. :p ;)
     
  17. EvilMudge

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    AFAIK - and I might be wrong, there are several flags contained in the DD bitstream to enable all sorts of things, one of which is to enable Pro-Logic on a stereo signal. It can also set Dolby 3Stereo, which is useful for old movies that were recorded with a centre channel, but only 2 channel stereo survives - there are quite a few of these about, and this is the correct option rather than Pro-Logic, which will produce rear effects where none were mixed.

    Reiner, I've seen an old Sherwood reciever which auto switches to Stereo or DPL based on a DD bitstream, so now you know.:)
     
  18. Squirrel God

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    I tried a DD4.0 soundtrack last night.

    My DVD player picked it up as DD4.0.

    The packaging said DD4.0.

    My receiver displayed L, C, R, RL, RR - that's DD5.0 :confused:

    It must've created it's own centre channel or thought the RC was actually RL+RR. Or maybe it was actually 5.0 on the DVD and was incorrectly flagged in the soundtrack.

    If something is not stripped out from the original MPEG-2 multiplexed program bitstream, then maybe the flags are:

    • incorrect
    • often not used, ie flag bit(s) are blank
    • ignored by most receivers because they are inaccurate (e.g. the EX flag doesn't work, but the ES one does)
    • not checked by receivers to save costs

    Either way, the weirdness continues :laugh:

    I guess there's no way at all that a receiver will ever tell you whether an analogue DPL (input through phonos) is actually DPL and not stereo as there are no flags in the analogue signal.
     
  19. EvilMudge

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    SG,
    4.0 Is a Dolby Surround (old :p) soundtrack AFAIK, and there may be identical RL+RR signals coming off the disc, so the reciever powers both but sends them a mono signal.

    It's annoying when content producers do this, because in many cases a straight high bitrate DD2.0 put through DPL2 will sound better.

    Was it Edward Scissorhands R2 BTW?
     
  20. LV426

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    I'm pretty certain that DD4.0 is actually a DD5.1 signal but....

    with the sub channel (x.1) present and silent
    and the two rears both present and identical.

    Which adds up to 4 discrete channels.
     
  21. Squirrel God

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    Yeah, but this is inconsistent isn't it. The indicator lights show inputs, not outputs. The rear channel is mono, so a single mono stream is input to the rears and then output to both rear speakers. The indicator lights should therefore show L, C, R, RC because those are the discrete inputs.

    You can get DD2.0 mono tracks and DD2.0 stereo tracks - I would expect both L & R indicators to light up on both occassions because two discrete tracks are present (it doesn't matter if the mono 2.0 track's L & R channels are identical). I have yet to try a mono 2.0 track, but I will see if I have one and give it a go! No doubt I will find the indicators just as confusing!

    It seems there is lots of inconsistency with Dolby formats and it's about time Dolby got their act together!

    Another problem:

    It says in Dolby's FAQ on their website that Dolby Surround actually multiplexes a centre and rear channel into the L & R channels. So that's 4 channels then. Okay, they're not discrete in the traditional sense because they can't be perfectly recovered when demultiplexed, but they are there. When you look on the back of DVDs that have a Dolby Surround soundtrack, they show the square with 3 dots - indicating 3 channels, not 4 channels.

    No, it was Grand Canyon R2 :)
     
  22. EvilMudge

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    It won't come up as RC - because the EX flag controls the activity of the RC, not the content of the signal - mono rear signals come out as RL+RR. Plus, if you play back 4.0 with EX engaged, the RL&RR are silent.
    Okay, this is my limited understanding of the DD stream.
    You can have up to 5 discrete full range channels. You can then add on an LFE channel.
    You don't have to have more than one full range channel and crucially, it doesn't hve to be the front centre. It can be assigned to all five output channels if so desired (I think it has a string of five flags which can be set on/off, indicating L,R,C,RL,RR). At the encoding stage the channel setting is determined. So it a mono signal can be encoded to come out of the centre from a DD5.1 decoder, or both L&R channels for stereo use, which if then put through a pro-logic matrix comes out of the centre again. It could just as easily however come out of only the left or right channel, which sounds very odd (I do have a disc with this problem but can't remember which it is.)
     
  23. Squirrel God

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    Ok, if both rears are present, then that's L, C, R, RL and RR which makes it five channels that are still encoded. So you're saying Dolby said "We can't call this 5.0 because that implies stereo rear channels, not mono rear channels, so we'll have to call it 4.0"? If that's the case, it's yet another inconsistency with Dolby! Damn them! :(
     
  24. Squirrel God

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    I could swear blind I played back 4.0 with Matrix 6.1 engaged last night and the rears were not silent. Is 'Matrix 6.1' what you meant?

    I'll double check when I get home.

    So the Dolby numbering format refers to the number of discrete full range channels (with the .x referring to the number of LFE channels) and does not correspond to actual speakers at all then?

    If so, it's time they got rid of the "square with dots" notation on the back of DVDs as it's confusing :(
     
  25. EvilMudge

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    Yup, the channels don't have to be assigned in any fixed pattern and each channel can be directed to any number of speakers. So theoretically they could produce discs with identical front and rear channels, in order to give MAXIMUM FIREPOWER:eek: to music in stereo.:D

    As for the square with dots, they're totally incosistent, some show four corners, where others show three across the front and one at the rear, with the same information on the disc.
     
  26. nunew33

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    Im pretty sure most of the answers to these questions can be found in www.dolby.com


    From memory Im pretty sure I have seen something that says that a DD stream can indicate whether its DD2.0, 2.1 etc. Which would mean that a dvd connected via digital linkcould communicate to a reciever what the default decoding should be.

    But I cant remember where it is (when i last looked there were only 10 pdf files on the dolby site now there seems to be millions).

    Im pretty sure though that everything that has been raised will be answered after a little investigation on dolbys website

    There is also a set of definitions for square with dot diagrams
     
  27. Squirrel God

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    So still there is the inconsistency with indicator lights on receivers then because they are supposed to show inputs, not outputs.

    So to summarise the indicators :lesson: :D

    1.0 Mono - C
    2.0 Stereo - L&R
    2.0 Mono - C or maybe L&R - need to check
    2.0 Surround - L&R
    3.0 - dunno, don't think I have a disk with 3.0
    4.0 - L, C, R, LR, RR
    5.0 - L, C, R, LR, RR (i.e. same as 4.0 :rolleyes: )
    5.1 - L, C, R, LR, RR, LFE
    6.1 discrete - L, C, R, LR, RC, RR, LFE
    6.1 matrix - L, C, R, LR, RR, LFE ?

    Conclusion: there are no rules or logic that can be applied to all the above formats consistently - each has to be taken on its own :smashin:

    My head hurts :( :D
     
  28. bob007

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    Might be on the wrong track but see what happens when you are connected via phonos and not digital (optical/coaxial).
     
  29. Squirrel God

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    I have my TV connected by phonos to the receiver and it just shows the L+R indicators all the time and the "Pro Logic/II" light.

    Or do you mean connect my DVD player via phonos to the receiver and see what it does?
     
  30. bob007

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    The TV and the phono connections sound right as only a stereo signal is being received from the broadcasts.

    Try connecting the DVD via phonos, don't forget to disconnect the digital cable if you decide to try it. ;)
     

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