Subject:Mono .mp3 files

Posted by: rraud

Date:12/15/2003 11:37:23 AM

My client wants mono .mp3 files @ 320kbs or higher, however SF and BC will only covert mono at a max of 128kbs. The original files are spoken word 44.1/16 mono wave.
Is this an inherent design parameter or an isolated incident?
Thanks for any info on this.
Rick

Subject:RE: Mono .mp3 files

Reply by: farss

Date:12/16/2003 4:15:28 AM

This is interesting as I'm about to tackle a similar project. Can I ask why they want such a hig bitrate if its only speech. Or for that matter would it make any difference if you gave them mono over both channels?

Subject:RE: Mono .mp3 files

Reply by: rraud

Date:12/16/2003 2:31:33 PM

I ask the same question. Well recorded spoken word material converted to 128kbs mono mp3, sounds damn good. But some clients just wants what they wants, no if's and's or but's..
It is true however that mono mp3 files are compressed less than stereo ones, of the same rate, but end up approx. the same file size.

Subject:RE: Mono .mp3 files

Reply by: Chienworks

Date:12/16/2003 7:22:04 PM

A mono 128Kbps file will have more or less the same compression as a 256Kbps stereo file. Surely this is good enough.

Subject:RE: Mono .mp3 files

Reply by: Iacobus

Date:12/18/2003 1:16:25 PM

It may be inherent to the official MP3 spec. (Can anyone confirm?) You can do 320 Kbps stereo but not mono, for example.

Iacobus
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RodelWorks - Original Music for the Unafraid
mD's ACIDplanet Page

Subject:RE: Mono .mp3 files

Reply by: TommyB

Date:2/16/2004 6:41:44 AM

I am trying to figure this out as well.

The knowledge base says that you can do Dual Mono(half bandwidth) or Mono(full bandwidth).

If you select custom and Highest quality VBR, then click the Convert To Mono switch, you end up with a 324K file. It's single mono file. Not two channels. So my questionis,, is it 324K? I say it is, but others argue it is not. Any insight on this?

TB

Subject:RE: Mono .mp3 files

Reply by: rraud

Date:2/16/2004 10:37:30 AM

Dual mono would have the same compression ratio as a stereo file.
As Chien stated a regular MONO 128kbs would have the same compression ratio as a 256kbs STEREO file. But both a mono or stereo 128kbs file would have about same file size. Obviously the mono file would sound a little better. (less compression needed)
It's a little confusing and takes some thought to figure it out.

Subject:RE: Mono .mp3 files

Reply by: Chienworks

Date:2/16/2004 6:59:36 PM

The thing is that the size of the file is determined by the bitrate multiplied by the length of the file. Nothing else (more or less) matters in the slightest. Then again, that's the definition of 'bit rate' ... how many bits are used per unit time. So, a 3 minute (for example) 128Kbps mono file will need 2.8MB while a 3 minute (for example) 128Kbps stereo file will need ... 2.8MB, because both take 131,072 bits per second no matter how many channels they have. In fact, and this is NOT confusing* a 128Kbps mono file will be twice as big as a 64Kbps stereo file.

*Yes, trust me, this really isn't confusing at all. Honest. :)

Subject:RE: Mono .mp3 files

Reply by: Rednroll

Date:2/17/2004 8:37:22 AM

Yep not confusing at all.....I think I need to take some aspirin to keep my head from spinning. I would hate to have to try and explain that one to a client. I'm sure they would just say, give me a mono 320Kbs file or if you can't do it, I will have to go somewhere that can. I've never really understood all the math or how the .MP3 encoding works. I'm with everyone else and really would like to know if this is a limitation of the format or it's just some over engineering on the Sony .mp3 plugin, giving us what they think is best for us, since there's no benefit. I've seen similar discussions in the past and am leaning towards the later explaination. Sure would be nice if someone could give us the answer.