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Topic: MP3 Mono Maximum Bitrate (Read 8146 times) previous topic - next topic
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MP3 Mono Maximum Bitrate

I understand that a single-channel mono MP3 requires only half the bitrate of a stereo MP3 to achieve the same quality.  Thus, a 160kbps mono MP3 should be about the same quality as a 320kbps stereo MP3, right?. 

However, I've noticed that with LAME it is possible to encode a mono MP3 at bitrates even higher than 160kbps.  Is there a point beyond which there is no audible improvement to be gained from using a higher bitrate on a mono file?

I'm asking because I need to create some very high quality mono files, but it seems like it would be pointless to encode a mono file at something as high as 192 or more.  In fact, I've noticed that Sound Forge and Adobe Audition don't even support encoding mono files at bitrates higher than 128k, so I'm wondering if there is any kind of issue with using a higher bitrate than that.  For example, is 128kbps the maximum mono playback bitrate supported by any hardware/software apps?  If not, I think 160kbps CBR is the bitrate I want to use, but I'd appreciate any input.

MP3 Mono Maximum Bitrate

Reply #1 –
Quote
I understand that a single-channel mono MP3 requires only half the bitrate of a stereo MP3 to achieve the same quality. 
[a href="index.php?act=findpost&pid=297084"][{POST_SNAPBACK}][/a]


This assumption is false. Stereo music generally has redundancies between channels, which the encoder can and will exploit.

MP3 Mono Maximum Bitrate

Reply #2 –
Quote
This assumption is false. Stereo music generally has redundancies between channels, which the encoder can and will exploit.
[a href="index.php?act=findpost&pid=297087"][{POST_SNAPBACK}][/a]



Correct me if i'm wrong, but 320kbps is usually not encoded as joint stereo afaik, so apart from the bitrate reservoir being distributed between the two channels, it does not take advantage of the redundancies between channels and hence would be pretty close in quality terms to 160kbps mono?
Veni Vidi Vorbis.

MP3 Mono Maximum Bitrate

Reply #3 –
Quote
Correct me if i'm wrong

You are wrong

MP3 Mono Maximum Bitrate

Reply #4 –
Quote
but 320kbps is usually not encoded as joint stereo afaik


joint -stereo is a mixture of pure stereo and mid-side stereo frames

it should be usually, 320kbps uses more stereo frames and less mid-side stereo frames

as the bitrate goes lower and lower the ratio of mid-side stereo frames to pure stereo frames increases

am i right?

MP3 Mono Maximum Bitrate

Reply #5 –
Do you have a specific reason to use CBR? AFAIK, sufficiently high-quality VBR encoding, like lame 3.90.3 with --alt-preset extreme and lame 3.96.1 with -V 0, should be transparent to nearly all people under nearly all circumstances (see listening tests on mp3-tech forum). It may be interesting to just add the -m flag to this, and let the proven VBR algorithm handle the bitrate.
<offtopic>
About the listening tests, I can't supply you with many links, because I seem to bee too dumb to make proper use of the "search" function (i.e. it never returns what I want, even though I know the thread exists).
</offtopic>
In this case, the only things I could come up with are:
http://www.hydrogenaudio.org/forums/index....showtopic=20715
http://www.hydrogenaudio.org/forums/index....showtopic=32121

Edit: messed with URLs.

MP3 Mono Maximum Bitrate

Reply #6 –
Quote
Quote
Correct me if i'm wrong

You are wrong
[a href="index.php?act=findpost&pid=297161"][{POST_SNAPBACK}][/a]


I think what he means is that when encoding at alt preset insane, the encoder doesn't use many JS frames anyway.

MP3 Mono Maximum Bitrate

Reply #7 –
I thought that above a certain bitrate it used exclusively stereo frames, may'be im confused with a different MP3 encoder or and older LAME version.
Veni Vidi Vorbis.