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Dolby 5.1 in stereo
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DocBrass
Suspended due to non-functional email address
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22. April 2004 @ 05:00 |
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I believe this is my first post here, though I've been lurking for a week or two. I was dead in the water concerning what to do to create a backup until I found this forum. Many thinks to all the board members for the info and guides as I'm now starting to feel more confident when burning!
Now, for my question. If I burn a movie encoded with AC3 6channel (Dolby 5.1 right?) will it play on a stereo setup that does not have DD? I believe it is backwards compatible, but I wanted to pick your collective brains, so to speak.
I'm wanting to burn in 5.1 for a future home theater but still want it to play on my current two speaker setup.
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Senior Member
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24. April 2004 @ 11:56 |
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This should not be a probem at all, as long as the original file has the metadata correctly written which describes how the downmix should be done on a stereo setup.
Normally, the centre channel will be at either 0.707 or 0.5 of the original surround version, and the surrounds will be -3dB quieter, or around 50% less when downmixed.
This is done to ensure that the effect of folding 5 channels into 2 will not cause overload of your stereo system.
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Motomatt
Senior Member
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24. April 2004 @ 12:22 |
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I like to read explanations from Wilkes..Always a interesting read. Haven't seen you around in awhile.. I was wondering why the sound really sucked when doing that type of downmix. Thanks for the info again.
Matt
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AfterDawn Addict
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24. April 2004 @ 15:59 |
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The sound sucks? If you are using a DVD with AC3 6 channel encoded sound on board, and you only have a stereo set-up, the system will only play in stereo mode. It will be backwards compatible, i dont know of any DVD that has 5.1 on board that will not play on a 2 channel system. It should sound exactly the same as if viewing a 2 channel AC3.
The only problems you tend to get with sound formats on DVD's are if you use a DTS 5.1/6.1 format and try to use a DVD player that doesnt support DTS. However, you can use a DTS format DVD on a 2 channel system, as long as the decoder (probably a DVD player) can decode it....
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Motomatt
Senior Member
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24. April 2004 @ 16:38 |
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Yeah, it sucks.. I play a 5.1 surround disk on my other DVD player upstairs. It seems like I can't turn up the volume enough to hear what they are saying. Sounds muffled or something.. Sometimes it's loud and then sometimes really quiet. Maybe just crappy tv speakers or something?
Matt
This message has been edited since posting. Last time this message was edited on 24. April 2004 @ 16:39
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AfterDawn Addict
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24. April 2004 @ 18:33 |
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Thats actually very strange. Does it only happen on one system or on all 2 channel (stereo) systems. An AC3 6 channel mode carries the necessary signal to produce stereo, just front left/right. Have a look at the Dolby explanation of AC3 6 channel for more info - though u may get bored reading it:
http://www.dolby.co.uk/tech/ac-3mult.html
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Senior Member
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25. April 2004 @ 02:07 |
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It really does sound as if the Metadata is not written correctly. This is exactly what happens when certain flags are not set properly.
Oriphus is right - there should be the necessary information to play back in stereo, but to be honest it depends on who encoded the source material.
According to the Dolby Document "Metadaata Guide", there can be al sorts of Chaos if things are not flagged correctly.
BTW - how is the sound hooked up - via RF mode (using the aerial connection?) or by analogue stereo, or using SCART?
If using RF, then the DRC compression profile is always active and if dialnorm has not been set right this will shift the bass & high frequencies into the wrong bands, so sound that should be compressed is not and other sound that should be left alone is compressed. For example - if the DRC is set to Music Standard, then you get a completely different profile to, say, Film standard. Plus there are also light versions of these two with no early cut range.
Also, when the signal is passed through the RF line then the output is invariably Mono.
It really does get insanely complex at first, as when downmix coefficients are brought into play there is so much that can cause problems. How is the signal getting from the DVD player to the TV is perhaps the info needed right now.
If you can let me know this, I will try to suggest the correct way to get the audio out.
Although if the original metadata is all to hell, then we are fighting a losing battle.
Can you send me an extract of the Audio so I can see how the flags are set?
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AfterDawn Addict
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25. April 2004 @ 06:22 |
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Hey Wilkes good seing you about - sure your still busy as hell even with these new legislations ;-)
Most likely its a scart connection. Its very rare to find the metadata incorrectly written on any DVD Movie produced by a big company. Do you come across them at all Wilkes and if so, who are the ones that do it most?
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Motomatt
Senior Member
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25. April 2004 @ 09:36 |
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See what I mean about wilkes and his posts.. The player and TV that I am speaking of is nothing more than a spare bedroom setup. It's connected to the TV through RCA cables. I usually watch them on my big setup with no problems. I just happen to notice it upstairs and always wondered about but never asked.. Thanks Wilkes and Oriphus for the tips
Matt
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AfterDawn Addict
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25. April 2004 @ 10:34 |
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No problem, i hoped we helped you. Wilkes will be able to further help you, though im at the end of my contribution ;-)
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Senior Member
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26. April 2004 @ 01:57 |
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Never yet seen a badly coded studio release. Probably because to carry the Dolby Logo, they need to send the finished audio to Dolby Labs, who will then check it to ensure it is properly compliant.
I thought that it could be a badly coded private version though - it does show all the symptoms.
However - dodgy SCART is well likely. In my experience about 30-40% of these are U/S straight out of the shop.
If something is dry jointed, or shorting internally, then everything could well be going a bit strange.
Last one I had like this was confusing the heck out of a canopus ADVC300 - it thought it was getting both Analogue & digital input at the same time. Changed the SCART, and the problem went away.
Still well worth checking how the set top player is set up to handle DRC though.
All DD files are heavily dependant on metadata, and the user changeable part is the DRC.
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andymunro
Junior Member
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26. April 2004 @ 13:43 |
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you understand much of that doc? i didnt get much, but its alright guys, dont have to make it simple for me, im just browsing the forums.
Ive got a little query though. I make music, and i like to sample speach from films. When listening to a dvd on my 5.1 soundsystem (dvd player/tv not computer) i hear the main speach comes through the centre channel and left right front and rear seem to be all the rest of the sound.
My question is this - is there a program i can digitaly sample just that centre channel creating a wav file?I dont have a 5.1 sound card in my computer, cos im not wanting 5.1 playback, just the ability to grab wavs of the centre channel. These would usually only be a couple seconds as someone talks, its so i dont get so much background noise goin on.
Id appreciate any help
ta
a site built by clubbers for clubbers
www.boshed.com
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AfterDawn Addict
1 product review
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18. June 2004 @ 16:48 |
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The problem isn't whether or not 5:1 surround will play on a two channel stereo system because it will. The problem is that the sound or multiple channels are likely to be out of phase and out of balance with each other on a two channel system. There is a difference in how surround sound and stereo mixes are done.
Surround sound mixes are done with the idea that some of the sound will becoming from either the right, left, or center of the room or from the back of the room for rear channels. Stero mixes are done with the assumption that the sound is to be aimed directly at the listener who is sitting in front of and facing the speakers. With the use of Panning, reverbs, and digital time delays and other means of manipulating sound, stereo sound is mixed to confuse the listeners ears.
For instance delaying a particular recorded instrument by a couple of milliseconds (BTW human hearing can detect phase discrimination to as close as 1/10 of 1 millisecond) can gives the impression that the musician is a couple of feet farther back on the stage. Delay it by six milliseconds and the instrument sounds even farther to the back of the stage. Adjust the Pan (balance) controls and you can place the musician to the right or left of the stage and farther to the back.
The point is that because we can hear a multichannel playback on a two channel system doesn't equal being compatible. There are just too many variables of amplitude, balance, and phase that have an enmormous effect on what we hear. For the sound to work well on a two channel system, it has to have been mixed on a two channel system.
BTW, your DVD player should be capable of doing an andequate job of playing 2 channels.
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" Please Read!!! Post your questions only in This Thread or they will go unanswered:
Help with development of BD RB: Donations at: http://www.jdobbs.com/. This message has been edited since posting. Last time this message was edited on 18. June 2004 @ 17:24
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Senior Member
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19. June 2004 @ 00:56 |
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Wise words sir.
There are also other considerations as to why automatic downmixing does not always work as well as you might think.
There are different ways of surrounsd mixing, as you said.
Dolby Digital uses discreet channels. That is, the mix actually uses 5 separate channels with full control over each channel, and when this is multiplexed the metadata settings decide how it sounds in stereo.
Dolby Surround is different. It uses LCRS, with the surrounds being a single mono channel split across both. It is a matrixed format, which uses the delay & phase tricks you mention.
One of the really cool things about DVD-A is that with PGC control, you can now embed a dedicated stereo version in with the surround version, and eliminate downmixing altogether. Both versions multiplex together, AFAIK, and the player will pick up whatever stream it is set up to play.
I am going to be playing aroubndwith this next week - I have 4 surround & stereo mixes to do and another to tidy up. I've always hated using downmix for the reasons you gave, and embedded stereo seems like a prayer answered.
I'll post back with the results.....
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AfterDawn Addict
1 product review
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19. June 2004 @ 05:25 |
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wilkes
I'll be looking forward to hearing your results.
" Please Read!!! Post your questions only in This Thread or they will go unanswered:
Help with development of BD RB: Donations at: http://www.jdobbs.com/. |
