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YouTube DOESN'T do 5.1 Digial - MYTHBUSTED (2017)



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I've been following some of the internet

traffic on YouTube and 5.1 audio whether

indeed YouTube does deliver 5.1 Digital

to the end-user or not there seems to be

arguments going both ways

but as I have a little bit of a

background in cinema sound and working

with people like Dolby I thought I'd

have a dig around and find out what's

going on if your normal mortal watching

YouTube on your cell phone or your

laptop the simple answer is YouTube does

not deliver 5.1 Digital I think we're

looking at some specific TVs and

possibly the ps4 where things may be

different and the jury's out on what's

happening there but it does look as

though there's some interesting

developments in those very specialized

to the V networks but for the general

user doesn't happen so before those

people who are convinced that they do

hear 5.1 on their computer systems start

getting a bit annoyed I'd like to go to

a little bit of a history of cinema

sound because haven't tell us exactly

what's going on for most of my stereo

started in the 1970s with introduction

of Dolby stereo Dolby stereo use

Pittsville first created for

quadrophonic sound on LP which put two

channels of fonts a at the front and

stereo at the back and use a Maitre

singh system which is an electronic

combining process to put the via tongues

onto the front songs together that with

a phase relationship so that you could

put them on a two channel carrier that

is stereo LP when you played the LP the

matrix in system decoded those signals

and puts the audio back on them back to

channels but because you'd make stuff up

you can't really perfectly unmix it so

the system was less than perfect but did

work

now what don't we did was to put a twist

on this idea instead of having stereo

front and stereo bag they put three or

four channels of the front a left-center

lies and put one or someone else around

but they still use some matrix in system

to put it on a two channel carrier which

was yoked Hawk dragged down the side of

the film so what are those fun for you

Tom Sam C Carrie well left center like

Carrie a spread of the music and the

sound effects in the atmosphere all the

dialogue was really place and still is

on the center channel a cap put dialogue

moving around as people move across the

screen but it sort of really feels a bit

odd when you actually see it so most of

the time when you watch a movie the

dialogue is this place dead center so

now we move on to the 90s with the

introduction of digital cinema sound now

if that's most notably Dolby Digital but

there was also SD the s and DTS and a

couple of obscure ones such as CBS that

fell by the wayside now they all what

more or less the same they all encoded

channels into it a optically recorded

bit stream down the side of the film and

they all carried a 5.1 audio as a

minimum now 5.1 means left-center light

that's firstly but stereo surrounds the

point one is a sub base now that carries

audio that's only up to about a hundred

Hertz of news for all the big bang

effects and the big explosions all the

things that really make an exciting big

movie even bigger the advantage of

having a separate track is that you can

then feed that to dedicated sub both

speakers behind the screen without

amplifiers you don't have to build

everything huge you've got things that

were just built to generate those low

frequency bands

what's often left unsaid about the

insertion of digital cinema sound is

something that is very obvious but worth

saying which is it also introduced five

discrete channels the five tongues were

completely separate they weren't mixed

together as they were with Dolby stereo

so anything you place will always be in

exactly the same position this is great

there's one slight downside with that

which is to deliver this you do need a

five channel carrier whereas with Dolby

stereo you can get away with delivering

it just on two tongues and still get

some impact so what did YouTube do with

your audio because your video with its

nice 5.1 Digital and you upload it it

seems that YouTube hangs on to a master

coffee of that which it may be using to

deliver to these specialized delivery

systems like the ps4 but for the normal

user it produces rear-ended versions at

varying quality levels so for your

computer which is fiber connection it'll

deliver a high bitrate high quality

version and for your cell phone it'll

produce a low bitrate much lower quality

version but all the appropriate the

device you're looking at it also

reprocesses the audio and it repurchases

it down to two channels now in the good

old days I'd 2012 them before YouTube

did something very very crude is simply

stripped out all of the view information

sub-base so anything on the back just

disappeared off the face of the earth

now after 2012 they went a bit more

sophisticated and used down mixing down

mixing is something that's done all the

time when you're watching a movie that

starts in life and 5.1 on your desktop

or laptop or phone

there's dan.mason process is applied to

take those 5.1 times and deliver them in

stereo now

what's happening there is the center

channel has been spread across left and

white when the V returns are then

transcoded onto the fund but with a

phase difference so you can hear

everything that's going on apart from

the point one that's always thrown away

but if you think about it what you're

getting with down mixing is effectively

Dolby stereo you get in a signal 30s

cold front left and white with a sense

of spread on it and the veers added to

it but in a phase relationship so you

could accept them and this is exactly

what's happening with YouTube the audio

being delivered is to channel but it

does contain some information about

what's happening at the rear so if

you're wonderful watching videos with

5.1 on your YouTube and being convinced

that you're here in surround you're not

mad you're not delusional what's

happening is that the YouTube player is

kicking intimated expose and using Dolby

stereo type system to extract some

surround onto their speakers and you're

going to get an effect that relates to

what was serviced and Lee and that's

gonna be something good won't be perfect

or certainly won't be digital 5.1 but

it's giving you some of what was there

and original now if you disagree with

what I've said feel free to pass

comments if you like what I said even if

you didn't like what I said feel free to

subscribe it's going to be a lot more of

this sort of information about cinema

sound and audio in general certainly a

lot of antique audio coming out and

we'll be able to cover some more things

for you in the not-too-distant future

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