Joint Stereo vs. Normal Stereo

Big Benner · #1 08-23-2005, 02:15 PM

Hey All,

I'm using iTunes to convert tracks to MP3s for recordings and just to listen to and I'm wondering what the difference between Joint Stereo is compared to Normal Stereo?

If you would like to see what I mean go into the Preferences -> Importing -> Settings -> and check out the details.

I understand about bit rate and file size but I most certainly want true stereo for any samples that I might use in a recording.

Trevorus · #2 08-23-2005, 02:17 PM

Joint stereo—Unlike stereo, joint stereo employs real-time bit allocation techniques that dynamically assign bits to the channel and frequency bands that need them most. This results in wider bandwidths and better dynamic range. Joint stereo does manipulate left-right separation and sound stage; however, any spatial blending performed is in frequency bands where the human auditory system would normally blend the stereo signal. Joint stereo defaults to true stereo if enough bits are available. Note that real-world listening tests awarded higher scores to Joint Stereo than to discrete at low bit rates.

Stereo and Dual Mono—From a coding standpoint, these two modes are identical. Half of the total bits available from the transmission line are allocated for the left channel and half the bits are allocated for the right channel. Left is always left, right is always right. No blending, no sound-stage manipulations.

Big Benner · #3 08-23-2005, 02:29 PM

Whow.

Ok, so I probably would not hear a difference with my MP3 player and a really great set of headphones?

If I mixed one of my own tracks with a funky wah guitar part 100% on the left side, burned a CD and then converted that track to a Joint Stereo MP3, when I listened on my MP3 player with a really great set of headphones I woundn't hear a difference and I'd still hear that funky wah guitar part 100% on the left side. Is that right?

Thanks for the help Trevorus,......... and I love your avatar!

Benner

Trevorus · #4 08-23-2005, 02:32 PM

BTW, I searched for that on Google, so I won't take all the credit.

Here's where it came from: http://www.musicamusa.com/techdocs%5CTECHTIP.htm

But, the generaly idea is to not keep two separate channels of sounds that come out of both speakers identically anyways. So, by assigning them to one channel that comes out of noth sides, you have kept the true image of the sound, but have opened up more data to be used for other parts of the soundscape to be able to enhance how it sounds.

Big Benner · #5 08-23-2005, 02:45 PM

Hmmm,... I'll have to look into this a little more. When I listen to really (well?) produced music (John Mayer, Madonna) on a really good set of large headphones the stereo image seems huge and I'm sure I can hear perhaps a ride cymbal or a shaker way over to one side.

I'll try it tonight. I've got that track with the funky wah guitar that I created in Cubase and burned to a CD. I'll convert it to MP3 using both Joint Stereo and Normal Stereo. I'll get back to you.

Benner

Trevorus · #6 08-23-2005, 02:58 PM

Cool. The quality all depends on how well executed the codec is, too. Oversimplification in the codec can give you that washy nasty sound on crash cymbals that you hear with a low quality file. The joint stereo "joins" the two channels where they would appear to anyways, thus allowing more detailed "picture" of what the original recording sounded like.

With digital, every bit is a sample of what the waveform actually looks like, but if you were to inspect very closely, you would notice a stepping action along the wavefrom due to the sampling rate of the hardware. True analog recording used in vinyl cutting is the closest to real that you can get, but with a physical contact read mechanism, dust specs can dramatically reduce the sound quality just like a scratch in a cd. Also, lack of quality read components on a turn table will degrade sound quality as well.

But to get back on subject, all of the digital recording you have heard is basically a very fast sampling of a truly analog signal. This is fast enough that most ears cannot tell the difference. But then when stepping down from CD quality to MP3, the codec has to throw out what it deems uneccesary bits to squeeze that space hungry CD file into a small MP3 file. With joint stereo, it allows itself to throw out bits that appear on both sides and just runs that bit into both channels. It allows for less "uneccessary" bits to be thrown out, and thus increasing the percieved quality of the file.