# Forum: help

Monitor Forum | Start New Thread
| |

RE: Individual Gabor atoms [ Reply ] By: Jessica Beltran on 2014-02-25 19:15 | [forum:148211] scale question.png (28) downloads |

I found a formula for Gabor atoms in this paper [1] Given the next parameters for a single atom: amp = 0.651673114873373; chirp = 0; freq = 0.117187500000000; lenS = 128; phase = 3.141472727003703; pos = 78648; windowoption= 0; windowtype =9; I convert them to seconds and Hz by using the samplig frequency len in seconds=0.0464; pos in seconds= 1.7834; freq in HZ = 44100*.1171; With this code in MATLAB I'm able to reconstruct a single atom atom =zeros(100000,1); %length of the complete signal for n=1:100000 atom(n,1) = (1/sqrt(len))*exp(-pi*(n/44100-pos)^2/len^2) * cos(2*pi*freq*(n/44100-pos)+phase); end atom = (1/norm(atom)) .* atom; %Normalization factor figure; plot(atom); Using the time shift and scale in number of samples will lead to the same result, just not divide n per 44100. I'm using the frequency in Hz but I'm confused because in the paper it shown 2*pi*w. Also, in the final vector, the atom does not consist of only 128 samples, but the other values are very close to zero. [1]Environmental Sound Recognition With Time–Frequency Audio Features |

RE: Individual Gabor atoms [ Reply ] By: Jessica Beltran on 2014-02-24 22:05 | [forum:148210] |

I'm using MATLAB interface. I obtain these values for a single atom: amp 0.651673114873373 chirp 0 freq 0.117187500000000 len 128 phase 3.141472727003703 pos 78648 windowoption 0 windowtype 9 As I'm using a sampling frequency (fs) of 44100 I can deduce that: freq in Hz = freq*fs = 5.16KHz time = pos/fs = 1.7834sconds I still don't know how use the phase and the scale. As I know, the len parameter give me the number of samples or length of the atom, but this is not enough form me to reconstruct because I don't know how is the mother wavelet suppose to be. |

RE: Individual Gabor atoms [ Reply ] By: Christian Guilleminot on 2014-02-21 19:06 | [forum:148200] |

Instead of a binary book, request a book in XML. But I do not find in what units are the values. For Gabor atoms envelope is a Gaussian curve. The manual does not say which units are the measurements. I asked these questions and I did not answer. If anyone can publish this information would be useful. De même pour des exemples de dictionnaires et leur usage |

Individual Gabor atoms [ Reply ] By: Jessica Beltran on 2014-02-20 21:53 | [forum:148198] |

Hi. Once I have decomposed a signal into atoms, I would like to have acces to the shape of each atom, this way I could calculate the energy or entropy of the atom. Is there a way to extract each gabor wavelet individually? Tks |