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  #41 (permalink)  
Old 31st July, 2004, 09:25 AM
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I'm thinking about getting a PC with a DVD-ROM drive. Will it give me 5.1-channel Dolby Digital?

That depends on the computer's configuration and its DVD/audio card, so check the specifications carefully to be sure you get the audio capability you want.

Most PCs can be connected to external playback equipment ranging from amplified stereo speakers to a full 5.1-channel playback system. The latter include not only full home theater systems, but compact, multichannel PC speaker systems incorporating amplifiers and Dolby Digital and/or Dolby Surround Pro Logic decoding. PCs bundled with stereo amplifiers and speakers may have a built-in two-channel Dolby Digital decoder for the DVD-ROM player that will downmix 5.1-channel soundtracks.

Audio outputs possible on PCs include analog power amplifier outputs, line level outputs for external amplifiers, headphone jacks, and RF carriers. They may also provide conventional PCM digital audio outputs, and/or outputs that provide the undecoded Dolby Digital data stream via S/PDIF (IEC 1937), USB, IEEE 1394, LAN, wireless link, or other format connections.


and i have to correct my last post... they DO say ac-3 is dolby digital....however, they also call dolby pro-logic receivers dolby digital recievers, so which is which is kinda iffy
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  #42 (permalink)  
Old 31st July, 2004, 09:31 AM
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OK. I'm not bothered about the details of AC3 too much. Just another question:

PowerDVD has various audio output options: 2spk/4spkr/6 and SPDIF. I presume choosing the SPDIF out mneans you can have other hardware decode the audio stream from the disc (namely using my 5.1 digital amplifier).

Strange thing is that with my Dad's GF's sound card isntalled, I get a different picture in the control panel showing the appropriate connectors but the SPDIF is greyed out (so it's using the right card, not the onboard one). There is no passthrough option like there is with that card in Windows 98 on her machine.
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  #43 (permalink)  
Old 31st July, 2004, 09:34 AM
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[font=TimesNewRomanPS]
A typical application of the algorithm is shown in Figure 1.1. In this example, a 5.1 channelaudio program is converted from a PCM representation requiring more than 5 Mbps (6 channels× 48 kHz × 18 bits = 5.184 Mbps) into a 384 kbps serial bit stream by the AC-3 encoder.Satellite transmission equipment converts this bit stream to an RF transmission which is directedto a satellite transponder. The amount of bandwidth and power required by the transmission has been reduced by more than a factor of 13 by the AC-3 digital compression. The signal received from the satellite is demodulated back into the 384 kbps serial bit stream, and decoded by theAC-3 decoder. The result is the original 5.1 channel audio program.
excerpt from
ATSC Standard:
Digital Audio Compression (AC-3), Revision A

this talks about encoding 5.1 programs of any variety into ac-3 for transmission via sattelite or airwaves. this is what i base my opinions on.
if you like i can attach the pdf again.
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  #44 (permalink)  
Old 31st July, 2004, 09:37 AM
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what card is that again? you want to chose spdif, but it can be sent via a mono phono connector(usually orange in color on the cards i've seen) or via stereo input + phono. as well, some cards, like the soundblaster live, require that you connect your dvd player directly to the sound card via a 2 wire cable, not the standard 3 wire one. as well, you want to make sure that the audio cable is not connected to your mobo...
the digital signal, whatever the format, can be sent via the ide cable as well, so i'm not too sure why you cannot enable spdif...but you amy want to try going to sounds and audio devices in your control panel and seeing if there is a mute there, or in you sound card OEM software. my sblive card did this.
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  #45 (permalink)  
Old 31st July, 2004, 09:49 AM
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Quote:
Originally Posted by cadaveca
no ac-3 cannot be dts..was just an example...
actually ac-3 CAN be DTS....its just a matter of converting the PCM signal to ac-3, and then having the dts decoder handle the decoded pcm signal. this was even built into ac-3. when the packet header of a ac-3 packe is sent, on of the strings signifies which codec it was mixed in....stereo,dolby surround,dolby digital, other, and reserved. the label of other can be programmed to me dts. All of this changed in 2001.
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  #46 (permalink)  
Old 31st July, 2004, 09:51 AM
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oh, and stigweed..i think you may want to enable 6 channel and then spdif? maybe?
on a final note to confused....
things changed in 2001 when, they decided 100% that the future of broadcast media was going to change. it is law now that all cable providers have to be providing thier signal in hdtv, and by 2012 the current analogue frequencies will be made available for public broadcasting. This is what has brought the major change, as the atsc has decided that all audio will be sent via ac-3. this means that DTS was cut out of the slice. But because the DTS foramt carried more information than the dolby digital signal, they made it nessecary for ac-3 to carry a variety of codecs. if they hadn't, there would be another microsoft case about hostile takeovers and such, becasue believe me, the world of surround is not for pansies. this why i asked you earlier to read everything at the site before you commented. it seems that you did not take my advice.
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  #47 (permalink)  
Old 31st July, 2004, 05:14 PM
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Quote:
Originally Posted by cadaveca
you did not read what i said...
read all the articles there...do some research on that site
i don't know how you get that ac-3 is dolby digital...as dolby surround is sent via ac-3 as well. Dude...keep reading!
besides, how does this affect how stigweed gets his sound to his dreamsystem? It doesn't!
if ya want to argue with me about DD, then start a thread on that so we aren't wasting other peoples time.
why should i read it?? you're the one making the argument.. you're supposed to present the facts not expect me to find them. nor give me a vague response in which i have to go on a freakin treasurehunt to find information that, for all i know, doesn't exist.

what i told you to look at in my previous post (which you seem to be unable to click or read) says, and i quote:
"Do all Dolby Digital programs provide 5.1 channels?
No, Dolby Digital soundtracks can provide anything from mono to full 5.1-channel surround sound. DVD- Video discs of movies can even carry multiple versions of the soundtrack that differ in the number of channels. A disc might contain a 5.1-channel sound mix with the dialogue in one language, a Dolby Surround encoded two-channel mix in another language, and a mono track with the directors' comments or other supplementary information. The default soundtrack will vary from disc to disc, so always check the DVD disc's language menu for the choices offered."

if you got complaints on how they use their trademark.. then bitch to them. in the end, you're treating ac3 as if it has nothing to do with dolby digital when it has everything to do with it. ac3 was designed for dolby digital.

from 11:
"As with Dolby Digital program material, "Dolby Digital" on a component such as a DVD player indicates that it incorporates Dolby Digital decoding, but not the number of channels."
that dolby digital decoding that they speak of.. is ac3.
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  #48 (permalink)  
Old 31st July, 2004, 06:09 PM
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lol dude..you read one article and think you're god..lol read the rest..
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  #49 (permalink)  
Old 31st July, 2004, 06:10 PM
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Quote:
Originally Posted by cadaveca
actually ac-3 CAN be DTS....its just a matter of converting the PCM signal to ac-3, and then having the dts decoder handle the decoded pcm signal. this was even built into ac-3. when the packet header of a ac-3 packe is sent, on of the strings signifies which codec it was mixed in....stereo,dolby surround,dolby digital, other, and reserved. the label of other can be programmed to me dts. All of this changed in 2001.
ac3 signals can be dts just the same as water can be used in place of gasoline.. so why don't you go out to your car and put some water in your gas tank?
you know what the outcome will be.

you understand that ac3 doesn't reconstruct the signal completely, right? the ac3 coder determines which information is unnecessary and removes it. when you put it through the decoder, it just gives you everything that it didn't take away. if you put a dts signal through the ac3 input.. the result isn't dts. the ac3 coder would remove a great deal of information from the signal.. more then likely, the information that the dts decoder recognizes as "dts" would be gone.


no, i read one article that you told me to read that supposedly contained the proof that you argued.
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  #50 (permalink)  
Old 31st July, 2004, 06:27 PM
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i did present the facts in the first pdf...
i ENCODE DTS..I am one a few people in northamerica with the setup to do so. I KNOW WHAT I AM TALKING ABOUT.
the first pdf explains exaclty how the ac-3 standard works, and what you need to do to make YOUR SOUND compatible with ac-3. i did back up my statements, you just didn't read it all.

confused, if your comments had any revelancy to the thread, i might be inclined to make another response,
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  #51 (permalink)  
Old 31st July, 2004, 06:36 PM
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Quote:
Originally Posted by cadaveca
i did present the facts in the first pdf...
i ENCODE DTS..I am one a few people in northamerica with the setup to do so. I KNOW WHAT I AM TALKING ABOUT.
the first pdf explains exaclty how the ac-3 standard works, and what you need to do to make YOUR SOUND compatible with ac-3. i did back up my statements, you just didn't read it all.
the first pdf you gave had nothing to do with that argument.. the first pdf you gave was what you told me to read after you made the assertion that ac3 was based off an algorithm by sony.

so what? you encode dts.. hooray for you. i could go out and buy the equipment to do so too if i so pleased.. doesn't mean that i understand what's going on.

the first pdf explains exactly how ac3 works.. it says how it removes the information and such.. but question, how exactly would it remove information that's truly inaudible to the human ear when what it's getting is an encoded signal?
since you have the setup to do so.. plug in the dts signal to an analog input on your preamp.. what do you hear? noise.. and that's precisely what the ac3 codec will be working with.
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  #52 (permalink)  
Old 31st July, 2004, 08:01 PM
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i said i wouldn't respond, but because you are veering so far from the truth, i can't let you misinform other people.
AC-3 is responsible for taking a PCM stream and COMPRESSING it to a smaller format. How it compresses it affects the way the sound comes out on the other end...like a mp3 encoded @ 64kbps sounds way worse than 192 kbps.
What makes AC-3 so great is that it DOES NOT REMOVE INFORMATION. IT RE-ENCODES IT to a different format....like taking your universal remote and getting it to do 4 commands with one button press.
the first pdf I attached was released by the atsc TELLING EVERYONE HOW THE ENCODING/DECODING WORKS. Now why would they release that information? You would think that Dolby would want their best assest kept secret. Well, they had to release it. They had to tell everyone how to be able to encode THIER OWN SOURCE MATERIAL IN WHATEVER FORMAT into AC-3 so it can be broadcasted by satellite, and to americans homes. It's LAW THAT ALL SOUND THAT WILL BE SENT by satellite WILL BE AC-3! LAW!
SO, with all this in mind, AC-3 HAS to be able to handle a variety of formats. otherwise every single person would need new equipment just so that they could watch tv. Although this would make electronics maufacturers really happy, we all know that it could never happen.
this all started in 1992. now you'll find the dolby label on almost every comsumer electronic out there. AC-3 is THE STANDARD. Dolby did quite a great thing. But they are not the only ones out there. but they all send their signlas via pcm.
what's that?ac-3 takes pcm signals,re-encodes it, and sends it away? Is dts not pcm?
of course you cannot plug a coaxial into a regular analogue jack and hear anything....your feeding a analogue line a digital signal. of course it's just noise. but digital to digital, no matter the format, will work. you can go coaxial/have a inline converter to optical, and have a seperate line for video, and still things will be in sync. why? all digital signals end up in the same place. in a codec soldered to a board. as long as the codec knows what's going on, everything works just right.
although most consumer electronics don't have this plug and play like ability, it's coming. there is no avoiding it now, as it's law. we are only about 18 months from an all-in-one cable that send both audio and video, as well as other data.
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  #53 (permalink)  
Old 31st July, 2004, 11:59 PM
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PCM (pulse code modulation) is a digital scheme for transmitting analog data. The signals in PCM are binary; that is, there are only two possible states, represented by logic 1 (high) and logic 0 (low). This is true no matter how complex the analog waveform happens to be. Using PCM, it is possible to digitize all forms of analog data, including full-motion video, voices, music, telemetry, and virtual reality (VR).
To obtain PCM from an analog waveform at the source (transmitter end) of a communications circuit, the analog signal amplitude is sampled (measured) at regular time intervals. The sampling rate, or number of samples per second, is several times the maximum frequency of the analog waveform in cycles per second or hertz. The instantaneous amplitude of the analog signal at each sampling is rounded off to the nearest of several specific, predetermined levels. This process is called quantization. The number of levels is always a power of 2 -- for example, 8, 16, 32, or 64. These numbers can be represented by three, four, five, or six binary digits (bits) respectively. The output of a pulse code modulator is thus a series of binary numbers, each represented by some power of 2 bits.
At the destination (receiver end) of the communications circuit, a pulse code demodulator converts the binary numbers back into pulses having the same quantum levels as those in the modulator. These pulses are further processed to restore the original analog waveform.
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  #54 (permalink)  
Old 1st August, 2004, 09:55 PM
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Dolby Surround is a two channel matrix encoded sound. The rear channel is encoded by adding an inphase signal to the right channel, and a 180 degree out of phase signal to the left channel. As this is simply a two channel system, no compression is required to transmit it across an SPDIF link. Re-encoding Dolby Surround as AC3 leads to a loss in quality, as the phaseing between channels is highly critical. Lossy compression techniques do not attempt to keep phase coherence very well, which leads to poor performance once the Dolby Surround signal is decoded. Phase coherence is critical in Dolby Surround! Instead, taking the source material and re-encoding it into AC3 leads to a situation where better channel seperation is in place, and no signal steering logic is required to 'anchor' signals to a channel. So, in a toss up between AC3 encoding 4 channels, and Dolby Surround encoding 4 channels, AC3 will win each time around.

The AC3 specification clearly defines both the packet structure and the compression used. The compression technique used is based around psychoacoustic analysis, and works by throwing away parts of the sound that the encoder believes humans will not be able to hear. That's exactly the same technique used by MP3, OGG, ATRAC, DCC, MPEG2 and a whole host of others. That's nothing new, as psychoacoustics has been an expanding field for a good number of years now.

AC3 is definately not a 'container format'. That is, an AC3 stream can only handle AC3 encoding. It cannot handle DTS, MPEG2 or any other varient. Re-encoding DTS, MPEG2 or other compressed source material leads to a loss in sound quality, as the different psychoaccoustic engines regard different things are 'important'. This loss is noticable on high end systems.

Dolby released the details on their encoding system, as they want people to build encoders. Dolby receive royalties for every AC3 encoder built, and for every AC3 decoder built. When your revenue generation stream is built around royalties, you work hard to ensure that everyone knows how your system works.

DTS is 'Digital Theater System' and is the preferred format for use in cinema. Like AC3, it is also a lossy compression system, and transmits the compressed audio. Therefore, DTS cannot be AC3, any more than AC3 can be DTS.

MPEG2 is another commonly used multichannel standard. For digital terrestial, digital satellite and digital cable broadcast, MPEG2 audio is a far more common format than AC3 is.

Encoding a monophonic or stereo track into AC3 would be technically possible, but totally pointless. PCM audio across SPDIF can already handle two channels of uncompressed audio. Encoding those into AC3 merely results in compression and loss of material, that could otherwise have been sent across the link as is, as it fits within the bandwidth budget of the link.
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  #55 (permalink)  
Old 1st August, 2004, 10:13 PM
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Quote:
Originally Posted by Áedán

The AC3 specification clearly defines both the packet structure and the compression used. The compression technique used is based around psychoacoustic analysis, and works by throwing away parts of the sound that the encoder believes humans will not be able to hear. That's exactly the same technique used by MP3, OGG, ATRAC, DCC, MPEG2 and a whole host of others. That's nothing new, as psychoacoustics has been an expanding field for a good number of years now.

AC3 is definately not a 'container format'. That is, an AC3 stream can only handle AC3 encoding. It cannot handle DTS, MPEG2 or any other varient. Re-encoding DTS, MPEG2 or other compressed source material leads to a loss in sound quality, as the different psychoaccoustic engines regard different things are 'important'. This loss is noticable on high end systems.
Although ac-3's current applications are only 5.1/4.1 sound, there ARE other uses...and like you say, re-encoding anything to ac-3 will cause a loss of quality ON HIGH END SYSTEMS. Just because this is the case, just not mean that the only application is what is used currently. AC-3 WAS DESIGNED TO BE A CONTAINER FORMAT. It's just not used that way. Remember, Dolby wanted to be THE SOLE SOUND PROVIDER to satelitte braodcasts. This would be a unsurrmountable edge for them that DTS, THX, MP3, OGG, ACTRAC or anything else could have. It's the loss of quality in these other areas that let these other standards break ground.
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  #56 (permalink)  
Old 1st August, 2004, 10:19 PM
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AC3 is not designed to be a container format. If it were designed to be a container format, it would NOT be tied to a specific encoder. Container formats are deliberately not tied to any format. AC3 is tied to AC3's encoding, ergo it's not a container format.

Encoding anything to AC3 will result in a loss of quality on all systems, in exactly the same way that encoding MP3 will result in a loss of quality on all systems. Such is the problem with lossy compression.
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