Topic: BASS_StreamPutData and bpm detection

[DS]

Hi all,
I want to analyze the bpm of a 20 second PCM array using Bass FX. Here is what I'm doing:

Code: [Select]

HSTREAM decodingChannel = BASS_StreamCreate(44100, 2, BASS_STREAM_DECODE, STREAMPROC_PUSH, 0);
BASS_StreamPutData(decodingChannel, bytes, bytesWritten);
//bytes is an array of PCM data (44.1khz, stereo, 16bit), obtained using the AVFoundation Framework of the iOS SDK. I'm pretty sure the PCM data is correct, since I can play the stream just fine if I remove the BASS_STREAM_DECODE flag.
//bytesWritten is an integer with the number of bytes contained in the bytes array

float trackBPM = BASS_FX_BPM_DecodeGet(decodingChannel, 5.0, 15.0, 0, BASS_FX_BPM_MULT2 | BASS_FX_FREESOURCE, NULL);
//returns -1 instead of a bpm value

BASS_ErrorGetCode() returns error code 7 BASS_ERROR_POSITION. I've got no idea what this means for me. Can someone please help me figure it out?
I'm using bass 2.4 and bass fx 2.4 on the iOS platform.

Thanks,
Daniel

[gnag]

If you want to get a reliable, realistic BPM Value, dont use that function which is included in BassFx, it relies on the SoundTouch Library and has no settings to finetune/optimize it which is making lots of errors,outputting sometines double/half BPM values, I tested with min/max 50/200 and two pop songs which are from 2011 and got totally wrong values, theres a commercial software which detected the correct,exact values for both songs!

There are tools and algorithms out there which can detect BPM a lot more accurately, I am already playing around for more than 1 week to make myself a working BPM detection, I thought its easy because with manual bpm tapping I could see the correct BPM within seconds, so a computer should be able to do the same even havings lots of more power.

I would be happy if someone implements an alternative BPM detection function, I
a colleague recommendended me to use "Rayshooting", he says its easy to implement/understand and works very well compared to other methods.

Im having a hard time understanding the way this is done, you can take a look at this website where it is explained, it would be awesome if someone finally can port a good bpm detection algorithm from the "C++ World" to C#, sadly Im not good at understanding the mathematic backgrounds.If you want to get a reliable, realistic BPM Value, dont use that function which is included in BassFx, it relies on the SoundTouch Library and has no settings to finetune/optimize it which is making lots of errors,outputting sometines double/half BPM values, I tested with min/max 50/200 and two pop songs which are from 2011 and got totally wrong values, theres a commercial software which detected the correct,exact values for both songs!

There are tools and algorithms out there which can detect BPM a lot more accurately, I am already playing around for more than 1 week to make myself a working BPM detection, I thought its easy because which manual bpm tapping I could see the correct BPM within seconds, so a computer should be able to do the same even havings lots of more power.

I would be happy if someone implements an alternative BPM detection function.
A colleague recommendended me to use If you want to get a reliable, realistic BPM Value, dont use that function which is included in BassFx, it relies on the SoundTouch Library and has no settings to finetune/optimize it which is making lots of errors,outputting sometines double/half BPM values, I tested with min/max 50/200 and two pop songs which are from 2011 and got totally wrong values, theres a commercial software which detected the correct,exact values for both songs!

There are tools and algorithms out there which can detect BPM a lot more accurately, I am already playing around for more than 1 week to make myself a working BPM detection, I thought its easy because with manual bpm tapping I could see the correct BPM within seconds, so a computer should be able to do the same even havings lots of more power.

I would be happy if someone implements an alternative BPM detection function, somone who has more mathematic skills than me.

[DS]

Thanks for your replay. Yes, implementing a bpm detection algorithm myself would be an option. But I'm not sure whether I have the necessary maths skills to do that.
While I try to understand how bpm detection algorithms actually work, does anybody know what's wrong with my code?

[Ian @ un4seen]

Code: [Select]

HSTREAM decodingChannel = BASS_StreamCreate(44100, 2, BASS_STREAM_DECODE, STREAMPROC_PUSH, 0);
BASS_StreamPutData(decodingChannel, bytes, bytesWritten);
//bytes is an array of PCM data (44.1khz, stereo, 16bit), obtained using the AVFoundation Framework of the iOS SDK. I'm pretty sure the PCM data is correct, since I can play the stream just fine if I remove the BASS_STREAM_DECODE flag.
//bytesWritten is an integer with the number of bytes contained in the bytes array

float trackBPM = BASS_FX_BPM_DecodeGet(decodingChannel, 5.0, 15.0, 0, BASS_FX_BPM_MULT2 | BASS_FX_FREESOURCE, NULL);
//returns -1 instead of a bpm value

BASS_ErrorGetCode() returns error code 7 BASS_ERROR_POSITION. I've got no idea what this means for me. Can someone please help me figure it out?

The problem there is that "push" streams don't support seeking, so BASS_FX_BPM_DecodeGet is unable to seek to the start position (5 seconds). Perhaps an option can be added to have BASS_FX_BPM_DecodeGet process the stream from its current position. In the meantime, one way to do that could be to use BASS_FX_BPM_CallbackSet instead. Something like this...

Code: [Select]

float bpm;
BASS_FX_BPM_CallbackSet(decodingChannel, BpmProc, 10, 0, BASS_FX_BPM_MULT2, &bpm); // set BPM processing on the stream
DWORD block=BASS_ChannelSeconds2Bytes(decodingChannel, 1); // process the stream in 1s blocks
BYTE *buf=(BYTE*)malloc(block); // allocate a processing buffer
for (int a=0; a<10; a++) // process 10 blocks/seconds
BASS_ChannelGetData(decodingChannel, buf, block);
free(buf);
BASS_FX_BPM_Free(decodingChannel); // remove BPM processing from the stream
// do something with "bpm" value

...

void CALLBACK BpmProc(DWORD chan, float bpm, void *user)
{
*(float*)user=bpm; // store the BPM value
}