Surround Sound Example for YouTube (Dolby Pro Logic II)

This video (and full description) answers why some people are able to hear surround sound through YouTube and will hopefully stop the less tech savvy arguing about whether YouTube supports surround sound or not.

This is a STEREO sound file demonstrating how a Pro Logic II decoder connected to a PC will split the sound to different audio channels.

YouTube and Flash do not (at time of writing) support 5.1 audio formats. ANY video on YouTube at present claiming to have 5.1 audio is incorrect.

5.1 audio is what it is. It is 5 UNIQUE audio channels (+1 dedicated to low frequencies output via a subwoofer).

Videos on YouTube are all STEREO however through the way sound is played back it is possible to encode surround information which an appropriate decoder can convert to other channels.

In Stereo Left and Right Channels are discrete (Each channel can play a different sound from the other).
Any identical sound that is played simultaneously in both speakers at the same time is essentially MONO.
Mono sound will appear to emanate between the Left and Right speakers.
If a mono sound is played IN PHASE both speakers will move in and out together.
If a mono sound is played OUT OF PHASE the speakers will oppose (L moves in and R moves out and vice versa).
Normally an out of phase sound appears duller/quieter/displaced as the speakers are trying to cancel each other out.

If using a proper PLII decoder the Left and Right speakers will play back as normal and mono sound will be sent to the centre speaker. In the case of sounds which are out of phase the sound will be sent to the rear speakers (though will be heard as a rear centre channel, not rear left and right as in a true 5.1 system).

Audio results may vary depending in PLII decoding method:
PLII Music
PLII Movie
PLII Game

This WILL work for:
Owners of Home Cinema AVR's (Audio Video Receivers) with a PLII decoder
Owners of a 'surround-sound-in-a-box' type kits that is CAPABLE of PLII decoding
Owners of a sound card that performs PLII decoding before out putting to a multichannel sound system.

This WILL NOT work for:
Owners of stereo speakers (Well the rear and centre channels won't work)
Owners of a 'surround-sound-in-a-box' type kits that is INCAPABLE of PLII decoding.
Owners of a PC incapable of decoding PLII and outputting to a multichannel system.

Category:

Gaming

Tags:

• sound
• audio
• system
• bass
• subwoofer
• 5.1
• speaker
• test
• dolby
• prologic
• II
• pro-logic
• PLII

[mattburkey]

@WolfRayStar I'm not too sure but a work around. Play your AC3 file through PowerDVD's "Dolby Surround Compatible Downmix" mode. Set up some software to record audio from your PC's 'stereo outout' in the sound managers 'recording' tab. The recorded sound will be the matrixed stereo sound. Obviously the matrixed surround sound is inferior to discrete multichannel but it works.

[WolfRayStar]

@mattburkey Ya I recently learned about ac3, thanks so much for all the information. Say, if I have a discrete multichannel mixdown, how would I go about converting that to a matrixed encoding? I imagine theres special software for it. Can you refer me to a good textbook on the subject?

[mattburkey]

@WolfRayStar You will have trouble as everything on the web caters for stereo and relies on matrix encoding (Pro Logic) of sound to achieve a rear surround channel. There are different types of surround sound. Matrixed and Discrete Mulitchannel. Games, DVD's and Blu-rays contain multichannel surround (which will contain a discrete LFE channel).

If you're looking for multichannel audio on the web the file needs to be a *.ac3 or *.dts file. Pretty much everything else will be stereo.

[WolfRayStar]

I have a soundcard that does true surround sound and have it setup exactly as should be. This demonstration is not true surround sound as no information is being sent to the LFE channel. I'm having trouble finding anything on the internet that plays back in true surround sound (not this decoding nonsense).