fequency peaks and time

[worldveil]

fequency peaks and time

[srinidhikrs]

can some one clarify on the comments made above
The blog and document talks about storing 2 frequencies and delta time as hash , but in the implementation it seems like delta frequencies and 2 times are stored as hash?
Thanks

[srinidhikrs]

can some one please clarify my questions above

[worldveil]

I don't think so? On line 72, the tuple list is (time, freq, amp). Notice we switch ordering of i and j lists.
https://github.com/worldveil/dejavu/blob/master/dejavu/fingerprint.py#L72

If you are unconvinced, instead look at the maximum values for the i and j lists - are they what you would expect? Specifically, the maximum index into the frequency list should be close to but not exceed

1/2 * WINDOW_SIZE + 1

as per the formulation of the discrete FFT results returned from the spectrogram call - this should be one of the dimensions of the spectrogram matrix.

[srinidhikrs]

Thanks for clarifying. One more thing is why the peaks are not flattened column wise (time segment wise) which will arrange frequency peaks of subsequent time segment next to each other and assist in computing hashes of target zone.
And also if suppose sample frequency peaks are not exactly equal to corpus freq peak but close to the corpus freq peak like for example corpus freq peak is 822 at time x and sample freq peak is 835 at time y and subsequent freq peaks also lie close to the corpus freq peaks in subsequent time segments, how to identify a match in such cases.
Thanks

worldveil [email protected] wrote:

I don't think so? On line 72, the tuple list is (time, freq, amp). Notice we switch ordering of i and j lists.
https://github.com/worldveil/dejavu/blob/master/dejavu/fingerprint.py#L72

If you are unconvinced, instead look at the maximum values for the i and j lists - are they what you would expect? Specifically, the maximum value of the frequency list should be close to but not exceed

1/2 * WINDOW_SIZE + 1

as per the formulation of the discrete FFT results returned from the spectrogram call - this should be one of the dimensions of the spectrogram matrix.

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[worldveil]

We're currently addressing this issue here:

#49