Meaning of output (Diff and Offset)

[worldveil]

Meaning of output (Diff and Offset)

[worldveil]

From the constants in the fingerprinting module, you can derive it yourself.
https://github.com/worldveil/dejavu/blob/master/dejavu/fingerprint.py#L14

In the case of the ones that are in the current master, it would be:
1 sec / 44100 * 4096 * 0.5 = 46.4399 ms per offset

[wangzhengyi]

offset_seconds means the match begin time? anybody who can tell me how to get the match begin time??

[worldveil]

diff is the offset from the beginning of the audio file in WINDOW_SIZE chunks.

Here only 2 hashes matched in alignment, meaning whatever you were looking for likely wasn't in the file you had dejavu listen to.

You only get negative diffs with erroneous hash alignments - thus whenever the diff is negative, there was no match in your database for the song you fingerprinted.

This isn't a bug, this is just how the library operates.

[edwinmugendi]

Thanks for the clarification.
I've run another test and I've go Diff is 14472 with 5 offset-aligned matches", Is there an exact number of the diff and offset that when you get guarantees there was a match?

[worldveil]

No, there is no exact number.

The diff is simply the time offset into the song in which the matched audio was found. The number of offset-aligned matches is a measure of confidence, the higher the better.

[edwinmugendi]

I've googled for window_size and cannot find good material on it.

What are the units of measuring WINDOW_SIZE and how can I convert them to seconds so that I can know where the matches begin?

Also, kindly point me to good material on WINDOW_SIZE.

Thanks in advance

[worldveil]

Yes, offset_seconds is the number of seconds before the recognized clip starts.