Author Topic: Question about BASS_FX beat-related function  (Read 2892 times)

nadia

  • Posts: 302
Hello,   ;D
 
I would like to know which is the theory behind the following parameters of the BASS_FX_BPM_BeatSetParameters function:
- bandwidth
- cutoffreq
- beat_rtime
Is there some reading that would better clarify their use? From the documentation I was not able to understand what they mean and how their change would affect calculation.

Thanks in advance and Kind Regards    ;D

Nadia

radio42

  • Posts: 4576
Re: Question about BASS_FX beat-related function
« Reply #1 on: 11 Dec '07 - 07:14 »
I am also not 100% sure - but as nobody tries, I'll do:

1) beat_rtime: Once a beat is detected, this should be the time in ms after that beat in which no other beat will be detected. The background should be, that often you have kind-of 'double beats' in a drum set. So this param should avoid, that a second (quickly repeated beat) beat

2) cutoffreq: Frequencies below this value should not be concidered when detecting beats.

3) bandwidth: Should normally be the range around a center-frequency to include in the beat detection algo. So I assume there is a fixed center-freq. defined, but here I am also no fully sure.

(: JOBnik! :)

  • Posts: 1065
Re: Question about BASS_FX beat-related function
« Reply #2 on: 11 Dec '07 - 10:31 »
Hi ;D

Currect and one more thing is that it uses a Band Pass Filter:
http://en.wikipedia.org/wiki/Bandpass

nadia

  • Posts: 302
Re: Question about BASS_FX beat-related function
« Reply #3 on: 11 Dec '07 - 11:03 »
Hi ;D

Currect and one more thing is that it uses a Band Pass Filter:
http://en.wikipedia.org/wiki/Bandpass

Thanks JOBnik and radio42 ;D

now I can understand perfectly but I have the doubt that one parameter is missing in this algo: this doubt started trying the beat detection over the song "Barbie girl" of Aqua where, in the first 20 seconds of the song, there is no beat but only a certain music with voices: using the default parameters of the algo there were some beat detected in places where there is absolutely no beat and the music is quite: may be that a parameter determining the minimal beat "energy" should be added? The question is obviously from someone who doesn't have much background so, please, don't laugh about this question.  ;D

Kind Regards

Nadia

radio42

  • Posts: 4576
Re: Question about BASS_FX beat-related function
« Reply #4 on: 14 Dec '07 - 11:13 »
Hi Jobby,

what is your center-frequency for the band pass filter (250Hz)?
And would it make sense to have that also being configurable?

(: JOBnik! :)

  • Posts: 1065
Re: Question about BASS_FX beat-related function
« Reply #5 on: 16 Dec '07 - 08:44 »
Hi ;D

Thanks JOBnik and radio42 ;D

now I can understand perfectly but I have the doubt that one parameter is missing in this algo: this doubt started trying the beat detection over the song "Barbie girl" of Aqua where, in the first 20 seconds of the song, there is no beat but only a certain music with voices: using the default parameters of the algo there were some beat detected in places where there is absolutely no beat and the music is quite: may be that a parameter determining the minimal beat "energy" should be added? The question is obviously from someone who doesn't have much background so, please, don't laugh about this question.  ;D

Kind Regards

Nadia

I see... I'll look into improving the band pass algo :)

Hi Jobby,

what is your center-frequency for the band pass filter (250Hz)?
And would it make sense to have that also being configurable?

Reading your post again, I see that you're not correct about the cutoff freq as it's actually a center-frequency...

Quote
Band Pass Filter
‏‏‏‏‏‏‏‏‏‏‏‏‏‏‏‏
Implements digital band pass filter which have cuttof (central) frequency
(fc) & bandwidth.

If cutoff freq = 250Hz and bandwidth = 10Hz, then algo will use freqs from 240Hz to 260Hz :)

I guess it's confusing, so I'll rename cutofffreq to centerfreq :)
« Last Edit: 16 Dec '07 - 10:11 by (: JOBnik! :) »