Dolby Digital Prologic 2 vs Dolby digital 5.1

herolegend

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What's the differences between them? Using either headset turtle beach capable of digital surround 7.1 and or an actual surround system at home that's capable for a 7.1 surround. What's better for games and movies?
 

Pinhedd

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There is no such thing as Dolby Digital Pro Logic, it's Dolby Pro Logic. The reason for this is that Pro Logic is analog, not digital in nature.

Pro Logic is a quadraphonic system in which two additional channels, center and rear, are encoded into the left and right stereo channels. When received by a non Pro Logic receiver, the audio appears to be nothing more than standard stereo audio.

Dolby Digital 5.1 is an encoding and compression scheme. It takes as its input 6 discrete channels, Left, Right, Center, Rear Left, Rear Right, and LFE (Low Frequency Effect, commonly used for a discrete subwoofer). As its output is a single channel bitstream. Unlike Pro Logic, the digital bitstream can only be decoded by a Dolby Digital decoder. When decoded, it will produce the same 6 input channels with only a small amount of loss but a large savings in disk space.

The key word here is "large savings in disk space" as this is really the only reason to use DD5.1. Games use sound rendering engines to create positional audio from single channel sources. Every gunshot, shout, alarm, and environmental noise in a game comes from a single channel source which is positioned in the environment and rendered in real time. If you configure your PC to use 6 speakers, most games will pick up on that and render 6 audio channels. Since the audio channels are sent directly to the speakers, there's no need to save them and thus no need to compress or encode them. The only reason you would want to use DD5.1 in a gaming situation is if you were sending surround audio to an external receiver over an optical connection because the S/PDIF format used for optical audio only supports 2 discrete channels or a digital bitstream (DD/DTS). To do this, you would need to use a software tool called Dolby Digital Live which requires you to have a compatible sound card as well. This will capture the 6 input channels from your PC speakers and compress them in real time into a DD5.1 bitstream.

As for movies on the other hand, the audio is all prerendered. Multiple languages can add a lot of overhead, so it's a good idea to save space when possible. Thus, most DVDs/BluRays use either Dolby Digital or Digital Theater Sound as their audio compression method of choice.

The thing to keep in mind here is that the audio always starts as 6 input channels and ends up as 6 output channels. The question is on whether or not there is an intermediary used for storage.
 

ingtar33

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well both are basically 5.1 surround sound systems... the pro-logic has some nicer features for converting a 2 channel stereo sound into 5.1 surround. otherwise when working with a true 5.1 digital surround signal they're basically identical... some later versions of prologic 2 (prologic 2x) allowed the conversion of 2 channel stereo to 6.1 and 7.1 surround signals as well... however prologic 2 remains a true 5.1 digital surround interface...

neither dolby digital 5.1 or dolby digital prologic 2 are 7.1 surround formats.

Dolby Digital Plus or Dolby Digital HD will support true digital 7.1 surround sound.
 

Pinhedd

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There is no such thing as Dolby Digital Pro Logic, it's Dolby Pro Logic. The reason for this is that Pro Logic is analog, not digital in nature.

Pro Logic is a quadraphonic system in which two additional channels, center and rear, are encoded into the left and right stereo channels. When received by a non Pro Logic receiver, the audio appears to be nothing more than standard stereo audio.

Dolby Digital 5.1 is an encoding and compression scheme. It takes as its input 6 discrete channels, Left, Right, Center, Rear Left, Rear Right, and LFE (Low Frequency Effect, commonly used for a discrete subwoofer). As its output is a single channel bitstream. Unlike Pro Logic, the digital bitstream can only be decoded by a Dolby Digital decoder. When decoded, it will produce the same 6 input channels with only a small amount of loss but a large savings in disk space.

The key word here is "large savings in disk space" as this is really the only reason to use DD5.1. Games use sound rendering engines to create positional audio from single channel sources. Every gunshot, shout, alarm, and environmental noise in a game comes from a single channel source which is positioned in the environment and rendered in real time. If you configure your PC to use 6 speakers, most games will pick up on that and render 6 audio channels. Since the audio channels are sent directly to the speakers, there's no need to save them and thus no need to compress or encode them. The only reason you would want to use DD5.1 in a gaming situation is if you were sending surround audio to an external receiver over an optical connection because the S/PDIF format used for optical audio only supports 2 discrete channels or a digital bitstream (DD/DTS). To do this, you would need to use a software tool called Dolby Digital Live which requires you to have a compatible sound card as well. This will capture the 6 input channels from your PC speakers and compress them in real time into a DD5.1 bitstream.

As for movies on the other hand, the audio is all prerendered. Multiple languages can add a lot of overhead, so it's a good idea to save space when possible. Thus, most DVDs/BluRays use either Dolby Digital or Digital Theater Sound as their audio compression method of choice.

The thing to keep in mind here is that the audio always starts as 6 input channels and ends up as 6 output channels. The question is on whether or not there is an intermediary used for storage.
 

ingtar33

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everything else in your post was spot on. perhaps my understanding of the format is faulty, but from what i know of them Prologic 2 is basically an upgraded version of the original dolby digital 5.1 surround (having come out a year later), with improved analog stereo input to 5.1 surround output emulating features. (and prologic 2x taking it a step further with stereo input to 7.1 suround output).

otherwise it also features true 5.1 digital encoding just like dolby digital
 

Pinhedd

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Pro Logic has very little in common with Dolby Digital and predates it by more than a decade. Pro Logic upmixes two matrix encoded stereo channels into three or more non-discrete surround channels.

Dolby Digital encodes and compresses 6 discrete channels into one digital channel in order to save space and then decodes them back into the same 6 discrete channels during playback.

Pro Logic is designed to take a high quality, specially formatted stereo signal (called Dolby Surround) and extract extra surround channels which have been encoded into the left and right channels. Unlike a Dolby Digital bitstream, Dolby Surround is indistinguishable from a regular stereo signal to unaware stereo playback devices.

Pro Logic can often be found on old VCRs and stereo amplifiers. When an audio source featuring Dolby Surround audio (meaning specially formatted stereo), the Pro Logic decoder would upmix this from two channels into 3 or more. A non Pro Logic device would just play the normal two stereo channels.

In contrast, a receiver that receives a Dolby Digital bitstream without having the appropriate decoding hardware would simply spit out garbled noise.

I believe that newer versions of Pro Logic II can upmix surround audio as well as stereo audio (this may be what you are thinking of), but the audio source for the upmixing is the analog surround channels decoded from the digital bitstream, not the digital bitstream itself.
 

herolegend

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So Dolby prologic 2 is better than dolby digital 5.1? I recently put on The last of us for ps3, and noticed the mute sound even with my headset on, so i went in audio options changed it and it seems to be enabled when i set it to dolby prologic 2, and dolby digital 5.1 I do notice a difference but for the life of me I can't tell what exactly changed, i think prologic 2 was louder? I wonder which is better for a 7.1 headset my headset can do dolby 5.1 and prologic 2 and goes upto 7.1 surround, I can't understand some of your posts dudes, but I think from the sound of it dolby prologic 2 is better than dolby digital 5.1 if your system can do the dolby prologic 2 that would be better to use for say pc, ps3 and xbox360? as it came out later and upmixes to 5.1 and even 7.1 is this correct? I always used to think digital was best sound quality so if its not dolby digital prologic 2 then its just plain dolby prologic 2 vs a digital 5.1 but the latest one my common sense tells me the newest is better, that would make dolby prologic 2 the best.
 

Pinhedd

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Dolby Digital is superior in almost all cases. Newer is just newer, not necessarily better. Pro Logic sounds louder because it has to maintain a high fidelity in order to encode the analog surround channels into the analog stereo channels. Digitally encoded discrete channels have no such requirement and when decoded maintain their individual sharpness whereas Pro Logic will not.

The best solution though would be LPCM. This will work over HDMI, but not over optical.
 

herolegend

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Thanks everyone for your replies I'm understanding a bit better now, so in almost all cases dolby digital 5.1 is better? Your probably right too recently I put on the game, the sound of bullets dropping and reloading weapons in the game "The last of us" sounded better on dolby digital 5.1 settings, but what other cases would Dolby prologic 2X be better at? Music? It's as if the sound of voices and objects are better in dolby digital 5.1 its really sharp and clear.
 

dingo07

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Dolby Digital 5.1 is the first true surround sound - and is still the standard
80% of voice comes through the center speaker in Dolby5.1 - that's why a good center channel is a must for great surround sound

Don't even concern yourself with pro logic mode IMO
 

Pinhedd

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Dolby Digital will only work with a receiver that has a digital input and a Dolby Digital decoder; it will not work on anything else. Dolby Pro Logic will work with any receiver that supports analog inputs, but will only upmix properly if used with a receiver that supports Dolby Pro Logic. Dolby Pro Logic is a rather dated technology that is not widely used anymore.
 

herolegend

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Cool thanks guys, yeah my headset is turtlebeach can do dolby digital 5.1 and dolby prologic 2x I pick dolby all the time now.

Lastly would like to ask should I pick an answer for this topic? and if so which one would you like me to pick or should I not bother?
 

Pinhedd

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I think that I put the most critical information in my first post
 

herolegend

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ok Pinhedd you make a good point! wait its already done for me someone else picked your solution as the best and or most thorough oh well that makes my job easier lol, I must say though I also liked comment from dingo07 who told me straight out not to concern myself with prologic 2x If I have dolby digital 5.1 that is I should use that instead as its better most if not all the time? Am I right?
 

Pinhedd

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Yup, use them in the following order:

6/8 channel LPCM (discrete channels, no encoding or compression) but this is not available over optical audio connections.

Dolby Digital 5.1

Dolby Pro Logic II

Stereo
 

Pinhedd

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LPCM stands for Linear Pulse-Code Modulation. It's a method of representing analog waveforms digitally. When applied to audio, the audio amplitude from a particular source taken at a particular instant in time is called a sample. These samples are stored sequentially without any encoding or compression.

For audio recording, the audio is captured (or sampled) by a microphone at a constant rate. For CD audio, this rate is 44,100 times per second, or 44.1Khz. For DVD quality audio (and for Dolby Digital) this rate is 48,000 times per second, or at 48Khz. Studio quality is anything higher than that, with common rates of 96Khz and 192Khz. However, nothing above 48Khz is perceivable to human ears.

Since human hearing is based off of perceived pressure, there's a massive difference in amplitude between hearing a mouse skitter across a floor, and hearing a space vehicle lift off the launch pad. Thus, in physics we measure sound intensity on a logarithmic scale using real numbers. However, computers have finite storage capabilities and cannot support an infinite range of real numbers so an audio sample must somehow be stored digitally using the two data formats supported by computers, integers and floats. The method of doing this is called linearization and requires two reference amplitudes. The first reference amplitude is zero, or no intensity. The second reference point is a floating "maximum intensity" which is the maximum signal strength as determined by the sound recording or sound playback device. Thus, the real amplitude of any audible sound source can be fitted to a point between zero and the maximum signal strength of the recording device. Digitizing this real amplitude is done by taking the real amplitude as a fraction of the maximum and converting that into a digital fraction of a digital maximum.

Imagine a real sample in real time that is 25% of the maximum perceivable by the recording device. If the device were to use 8 bit digital values to represent that same analog value, then the minimum digital value would be zero (fixed as stated above) and the maximum would be 255 (2^8 - 1). 25% of this would be 64, so the digital value of that particular sample would be 64 if 8 bit samples are used. 255 different intensity levels does not leave a lot of range for values between a mouse and a rocket, so 8 bit audio samples are rather useless and haven't been used for any purpose in decades.

If 16 bit samples are used instead, the minimum digital value would be zero, and the maximum would be 56535. This provides significantly more resolution. The same 25% intensity sample above would take the value 16,384. 16 bit samples are the standard for most recorded audio, but 24 and 32 bit samples may also be used.

This method of waveform replication is exactly what's used in .wav files. A .wav file is nothing more than a header which contains the sample rate, sample resolution (bits per sample), and number of samples, followed by the samples in sequence. This is by far the most "lossless" way of storing audio because everything is stored exactly as it was received from the analog to digital converter in the microphone. If we were so inclined, we could take 6 separate .wav files recorded from 6 different point sources and play them back through 6 different speakers and we would get 6 channel surround sound just like Dolby Digital. However, this isn't a good idea; lets find out why.

Using standard DVD audio specifications of 48Khz/16bps a one minute recording of uncompressed audio will consume:

48,000 samples per second * 16 bits per sample * 60 seconds per minute / 8 bits per byte = 5,760 KiloBytes or 768Kbps

Almost 6 megabytes for one minute of audio on a single channel. If that same method was used to store 6 channels worth of audio for a 90 minute movie, we'd have:

48,000 samples per second * 16 bits per sample * 60 seconds per minute* 90 minutes * 6 channels / 8 bits per byte = 3,110 megabytes or 4.6MBps. That's over 3 gigabytes of uncompressed audio to cram in a 4.7GB DVD.

Encoding those same 6 channels of uncompressed audio into a Dolby Digital bitstream drops the 48Khz/16bps 6 channel maximum bitrate from 4,608Kbps (4.6Mbps mentioned above) to 448Kbps maximum (Dolby Digital specification). That's about a 90% compression rate with minimal loss in quality.

Now, on to answering your question.

The protocol used to send and receive audio over optical connections (Sony / Philips Digital Interchange Format, or S/PDIF) does not allow for more than two LPCM channels to be present at the same time. It does however allow for a Dolby Digital or DTS bitstream to be sent. HDMI has similar features, but allows up to 8 LPCM channels to be present at the same time. So, when connecting a surround system via optical, the source must be in the form of a Dolby Digital or DTS bitstream, either recorded or generated in real time. When connecting a surround system via HDMI no such constraint exists, so the source can be up to 8 channel LPCM, Dolby Digital, or DTS. Most receivers will figure out which it is receiving and handle it appropriately.

The other one that I want to touch on briefly are 3.5mm speaker jacks. Each 3.5mm jack consists of three wires, one common ground and two signal wires that are sent to two separate speakers. Left/Right on one, Rear Left / Rear Right on another, Side Left / Side Right on a third, and Center / Sub on a fourth. The signals sent on these wires are simply the 6/8 LPCM channels discussed above, but converted back to analog through a digital to analog converter.

Hope that long winded explanation helped!
 

herolegend

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err... yeah ^_^; I guess then hdmi is the best one to use if possible then, did you just type that off your head? are you real or did a star fleet captain teleport you to Earth lol? well I must say that was very in depth you are very tech savy and good to know but I'm sure I'll forget what it means tomorrow, had you told me this in real life on the fly I would have asked you to say it in English lol no wait I still don't get how it works but I did understand that the HDMI produces no restraints on the audio so it can use 8 LCPM at the same time thus its the best cable to use for audio and probably for video. Cool thank you very much and to all of you who contributed to this.
 
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