set mp3 kbps for mono to half of stereo to get same quality?

[dev]

@steve

@dev

(what were you using to get them? I use win occasionally, but don’t know enough to use a command line tool)

I’m on Linux (Debian).
I used “MediaInfo”, which is a cross platform program (MediaInfo - Download). I don’t often recommend it these days because the Windows installer includes “bundleware” (MediaInfo). The Linux version doesn’t, and it’s a good program. I don’t know about the Mac version.

okay, with bundles maybe not. Mac, I looked into it and it asks me to download itunes first (I have itunes) - later.

@Gale Andrews

@dev

thanks for the metadata, they don’t say whether constant or variable bit rate, do they

Yes, “Overall bit rate mode = Constant”.


Gale

missed that. So exiftool is for the photographers. I’ll look into MediaInfo : )

[dev]

@kozikowski

Those of us who used and loved QuickTime 7 were relieved when, in the face of forcing everyone to use QuickTime X, Apple quietly made QuickTime 7 available as a Utility.

Enclosed, the same music file in the two different media inspectors. The darker one is QuickTime X. Please also note that QT7 has barely visible spectral sound meters to the right.

Koz

ok, quicktime shows the actual (average, probably) bit rate of a vbr export, that is useful. I kept the QT7.1.1 player too, seems to work on Mavericks and Mountain Lion.

[dev]

@steve

@Gale Andrews

@steve

When using VBR (variable bit rate) “joint stereo” mode, where both channels are the same, the file size will be not much more (perhaps 10 to 15% larger) than if it were a mono track.

So I think that means that if you halve the bit rate for a “joint stereo” file that you made mono, you will almost certainly make it sound worse.

Yes, though how noticeable that will be depends on the audio and what other settings were used.

@steve

@Gale Andrews

On the other hand, if you have a stereo track and export it as stereo or joint stereo at a given bit rate or quality, then make the track mono and export that at the same bit rate or quality, the mono version will have better quality than the stereo or joint stereo export.

For a given bit-rate yes.
For a given VBR quality setting, converting a stereo track to mono will reduce the bit-rate and hence the file size but the sound quality should be about the same.

so if my original is VBR and Joint Stereo, then I can’t just take half the bit rate.

checking it out:
Original CBR Joint Stereo 96 kbps, 45 MB, exported as
VBR quality 8 Stereo is 94.2 kbps, 43 MB, about the same, so I used VBR quality 8. (9 is definitely not good)
VBR quality 8 Joint Stereo is 75.5 kbps, 35 MB, sounds good.

Tracks > Stereo to mono, then Export as
VBR quality 8 is 47.4 kbps, 22 MB, sounds good but less than Joint Stereo.
VBR quality 9 is 37.1 kbps, 17 MB, does not sound good at all.

I see what VBR Joint Stereo does. It sounds nice, also the very quiet voices.

[dev]

@Gale Andrews

@dev

@kozikowski

wrote:Head-Banging Rock tends to benefit less from Variable than Classical with lots of silences does.

I thought VBR would destroy the quiet parts by disregarding it as “almost nothing”.

In my experience, Koz’s statement (with reference to file size reduction) and your concern (about quality) are both correct. VBR is not kind to extremely quiet but complex sounds like pianissimo strings unless you use a high quality setting. If you only want a small to moderate size file, CBR may actually be better for classical material with extreme dynamic range.

checked it above, even though this is not music, but very quiet words are not destroyed by VBR. The difference to Mono is much more noticeable, mono makes it less understandable. VBR Joint Stereo sounds like a good option, even if they are bigger.

I also found that each recording reacts a little differently. Probably a consequence of working at such low bit rates.

regarding Steve’s test, even if it is not music here - I do normalize everything to -1 dB before exporting.