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Author Topic: BPM calculations are off by 50%  (Read 3853 times)

koreth

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BPM calculations are off by 50%
« on: October 22, 2003, 10:45:34 pm »

It seems like for about 80% of my tracks, MC's calculation of beats per minute is roughly half of what I measure. For songs in 4/4 timing, I can sort of kind of understand it; you can't really tell for certain whether you're hearing quarter notes or eighth notes at half the tempo, etc. But it does it even on songs in 3/4 or 6/8 timing -- if you tap out the calculated beat with the music playing in the background, you end up tapping on the 1, then the 3, then the 2, etc.

For example, Enya's "Caribbean Blue" is about 158 beats per minute, but MC calculates it at 77.

If it were always off by half, I'd just make a derived field to double it and that would be that, but on some tracks (e.g. "Lovefool" by The Cardigans) it's spot on, so that won't work. Is there any way to adjust MC's sensitivity so it picks up the extra beats?
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hit_ny

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Re:BPM calculations are off by 50%
« Reply #1 on: October 23, 2003, 03:12:11 am »

it would be cool if they could test the BPM detection against a drum machine program samples.

Try it for different styles of tempos and beats...and fix accordingly.
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kiwi

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Re:BPM calculations are off by 50%
« Reply #2 on: October 23, 2003, 04:11:28 am »

My guess is that in some situations, half of the beats are not strong enough to register at beats for the calculation.  BPM seems to be a rather hard calculation to automatically make.

kiwi
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KingSparta

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Re:BPM calculations are off by 50%
« Reply #3 on: October 23, 2003, 05:22:30 am »

As matt has said about 5 times since BMP was added back in MJ8 it is not perfict.
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gpvillamil

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Re:BPM calculations are off by 50%
« Reply #4 on: October 23, 2003, 05:36:16 am »

Maybe something like this plugin:

http://www.blacktree.com/apps/index.html?iTunes-LAME/index.html

would solve the problem. It's for iTunes on Mac OSX, and what it basically does is let you tap to the beat while the song is playing. It uses this to inform it's calculation of BPM.
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koreth

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Re:BPM calculations are off by 50%
« Reply #5 on: October 23, 2003, 08:30:29 am »

I wrote a similar little Windows app (standalone, not a plugin) which I've used to work out the BPM for a bunch of my tracks. The problem is that as soon as I do Analyze Audio on a track, my correct BPM value is wiped out and replaced with the low one. Which means I can't just set MC to analyze all of my tracks in one go -- I've done manual BPM counting for hundreds of them.

If there were a way to say "analyze audio, but only fill in the values that aren't already filled in" that'd help.
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hit_ny

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Re:BPM calculations are off by 50%
« Reply #6 on: October 23, 2003, 08:32:07 am »

well u dont need that plugin....u can tap to the beat for 15 seconds and mulitply by 4.

the holy grail is more accurate automatic BPM
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Matt

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Re:BPM calculations are off by 50%
« Reply #7 on: October 23, 2003, 08:51:10 am »

The next build will feature a BPM algorithm that's better tuned to handle songs with BPM in the 140 - 170 range.  (lots of fuzzy math goes into BPM calculation, and right now it's too likely to use the "half BPM" in these cases)

Thanks!
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Matt Ashland, JRiver Media Center

NoCodeUK

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Re:BPM calculations are off by 50%
« Reply #8 on: October 23, 2003, 09:22:17 am »

To give Matt his credit I thought some of my BPMs seemed a little awry so I downloaded one of these tap it in programs and in all the cases I tested (about 50 tracks) MCs calculation was spot on so kudos to Matt!!

Adam
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koreth

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Re:BPM calculations are off by 50%
« Reply #9 on: October 23, 2003, 11:27:54 am »

Just tried the new build and it's better -- it gets "Caribbean Blue" to within 4 BPM of my value. But there are still a bunch of tracks that give me bad values, not all of them near 50%. For example:

Enya - "China Roses" - my BPM 114, MC's 63
4 Non Blonds - "What's Up" - 133 vs. 89
Chris Isaak - "Wicked Game" - 112 vs. 74

This new build *is* an improvement -- it's on target a lot more often now. But a "don't overwrite fields that already have values" option in Analyze Audio would still be swell!
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gpvillamil

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Re:BPM calculations are off by 50%
« Reply #10 on: October 23, 2003, 11:31:54 am »

Just tried the new build and it's better -- it gets "Caribbean Blue" to within 4 BPM of my value. But there are still a bunch of tracks that give me bad values, not all of them near 50%. For example:

Enya - "China Roses" - my BPM 114, MC's 63
4 Non Blonds - "What's Up" - 133 vs. 89
Chris Isaak - "Wicked Game" - 112 vs. 74

This new build *is* an improvement -- it's on target a lot more often now. But a "don't overwrite fields that already have values" option in Analyze Audio would still be swell!

Can't you use a search string where BPM <> 0, then analyze audio on the results of that? Or use the automatic smartlist "Task - Needs Audio Analysis"?
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koreth

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Re:BPM calculations are off by 50%
« Reply #11 on: October 23, 2003, 11:34:44 am »

I still want the ReplayGain and Intensity analysis on tracks with BPMs. There's no way to analyze just those two things without also overwriting BPM.
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Matt

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Re:BPM calculations are off by 50%
« Reply #12 on: October 23, 2003, 12:15:32 pm »

How about this:

1) create a field "My BPM"
2) use "Move / Copy Fields..." to fill it
3) analyze
4) "Move / Copy Fields..." back
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Matt Ashland, JRiver Media Center

koreth

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Re:BPM calculations are off by 50%
« Reply #13 on: October 23, 2003, 12:49:45 pm »

That's a good idea -- I'd tried it initially, but with the whole library, and of course it copied the empty values back too. But I could make a smartlist of tracks with a value in that custom field and only do the copy on those.

Feature request retracted; this procedure should give me what I want. Thanks!
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kiwi

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Re:BPM calculations are off by 50%
« Reply #14 on: October 23, 2003, 02:02:42 pm »

Quote
9.1.288 History
1. Fixed: List controls wouldn't always use the proper background color for the non-item dead area in short lists.
2. Changed: Tuned BPM calculator to be less likely to half the BPM of songs with BPM over 140.
3. Fixed: When changing selections in the panes, sometimes the file list wouldn't be scrolled to the top.
4. Fixed: While analyzing audio, several things in the main interface wouldn't work properly. (typing in searches, mouse wheel, etc.)
5. Fixed: Installation of plugins did't work.

Have you tried it since 9.1.288?
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koreth

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Re:BPM calculations are off by 50%
« Reply #15 on: October 23, 2003, 02:09:09 pm »

Yes, the 9.1.288 build is the "new" one I was referring to.
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Matt

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Re:BPM calculations are off by 50%
« Reply #16 on: October 23, 2003, 02:18:00 pm »

The BPM analyzer will be improved again next build.  Those specific examples were helpful for tuning.

Let us know how it works...
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Matt Ashland, JRiver Media Center
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