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4
Support - (fb2k) / Re: Custom tag values separators
Last post by 0x4D657373696168 -
You have to set the field "mood" as a multivalue one to let FB
separate the values when it finds the ";".
Preferences -> Advanced -> Display -> Properties dialog -> Multivalue fields

Miracle! Just what i needed, thanks!

One question, please:
how do you add the mood tag? By your judgment? If automatically, how?

Only by myself. Listen to a theme and decide under what kind of mood she's good.
5
Scientific Discussion / Re: Audio Summing Algorithm
Last post by jsdyson -
I believe @ziemek.z misunderstanding of FFT (i.e. the fact that FFT returns a complex function from a real variable) comes from how audio editors often display FFTs. Many - including Audacity - display it as a sequence of buckets, where frequencies of each bucket are painted in a voiceprint. The tools often quitely ignore the Imaginary part of the resulting function, and simply paint the magnitude of the complex value, and ignore the argument, which in that case is phase.
Okay -- that makes sense.  From what I know (and from my previous practical experience), the phase is all important.  When I wrote my prototype compressor/expander, the math operations were done on complex numbers.  Using magnitudes only was just a waste of time and just produced garbage.
Depends. If you have a signal that is even (symmetric at center) in your bucket, the Imaginary part of your FFT of that signal is zero. The magnitude is then only the Real part.
In cases where a voiceprint is displayed (I'm not sure "voiceprint" is the correct term, I've seen it a bunch of times, though), it seems it's /just/ being used for display purposes, mixing anything even when using that display option, doesn't mean the actual FFT of that signal is used, and it seems indeed it almost never (in my experience) is.

If your sample bucket is small enough such that it is manageable, you can move all samples beyond the center, map them into the negative part by duplicating them symmetrically, and then run the FFT on that. The Imaginary part of the signal in that bucket will be zero (or equal to the zero function rather). Using this for anything but display purposes isn't really sensical, though.
Okay -- sorry that I wasn't clear -- not properly handling the phase produced garbage *AUDIO*.  I wasn't really looking at using the FFT for any numerical purpose at that time.  So with audio, I didn't really have much of an opportunity to massage the signal as much as you suggested.

I will tell you one thing though -- I think that my next venture into the time/frequency type transforms will be more likely a complex MDCT instead.  I know that you don't get magic for free -- but when people have had the patience to be a trailblazer using the complex MDCT, they have sometimes gotten good results.   I know that the normal (or a variation) MDCT is often used in audio compression, but the complex MDCT supports more flexibility for signal processing purposes.
The FFT domain is 'old hat' nowadays -- I was drawing FFT and even DCT type butterfly diagrams for undergraduate papers in EE in 1979.  I truly don't remember everything, but over the last year or so I have been reading some of the books that I collected over the years on the subject of DCTs, Lapped transforms, etc (the black DCT book, Malvar's book, and every document that I can find online.)   There aren't a lot of papers on the complex MDCT, but it does seem very interesting.
So much of the really cool stuff requires some concentration and a long startup time (a few weeks), but I am having so much fun with my easy stuff (DolbyA, REALLY GOOD expander/NR project, and a pretty good compressor package.)
I truly hope that I get a chance to work on some new technolgy (for me) before I mentally slow down -- I know that I have at least 1-2 more years to do on the mostly time domain compressor/expander/NR projects, so hope that health holds up!!!

John
6
Scientific Discussion / Re: Audio Summing Algorithm
Last post by ziemek.z -
Thank you for clarifying done very important things before I even started. You saved me from doing useless stuff and completely wasting my time! I think I should learn more about FFT and DSP in general...
7
Support - (fb2k) / Re: Custom tag values separators
Last post by fabiospark -
You have to set the field "mood" as a multivalue one to let FB
separate the values when it finds the ";".

Preferences -> Advanced -> Display -> Properties dialog -> Multivalue fields

There add "mood" and all the fields you want to have more than one value.


One question, please:
how do you add the mood tag? By your judgment? If automatically, how?

Thanks.


Edit: added questions.
9
Scientific Discussion / Re: Audio Summing Algorithm
Last post by polemon -
I believe @ziemek.z misunderstanding of FFT (i.e. the fact that FFT returns a complex function from a real variable) comes from how audio editors often display FFTs. Many - including Audacity - display it as a sequence of buckets, where frequencies of each bucket are painted in a voiceprint. The tools often quitely ignore the Imaginary part of the resulting function, and simply paint the magnitude of the complex value, and ignore the argument, which in that case is phase.
Okay -- that makes sense.  From what I know (and from my previous practical experience), the phase is all important.  When I wrote my prototype compressor/expander, the math operations were done on complex numbers.  Using magnitudes only was just a waste of time and just produced garbage.
Depends. If you have a signal that is even (symmetric at center) in your bucket, the Imaginary part of your FFT of that signal is zero. The magnitude is then only the Real part.
In cases where a voiceprint is displayed (I'm not sure "voiceprint" is the correct term, I've seen it a bunch of times, though), it seems it's /just/ being used for display purposes, mixing anything even when using that display option, doesn't mean the actual FFT of that signal is used, and it seems indeed it almost never (in my experience) is.

If your sample bucket is small enough such that it is manageable, you can move all samples beyond the center, map them into the negative part by duplicating them symmetrically, and then run the FFT on that. The Imaginary part of the signal in that bucket will be zero (or equal to the zero function rather). Using this for anything but display purposes isn't really sensical, though.
10
General Audio / Re: Why wasn't there ever a VHS based consumer audio format?
Last post by polemon -
No, type IV was actually superior. There's a demo of noise/hiss levels in the video I posted (starting at 15:25.) The sound is extremely clean. Back then it sounded very near to the CDs I recorded from. And that's without dolby noise reduction. With dolby, there's virtually zero noise. But a poor deck will always produce crappy results though. A decent deck is needed to get good recording and playback quality.
Yeah, I know Techmoan, but he also made this video:
https://youtu.be/I0beJZaOUYM?t=508 <--- Right where I linked this video (8:30), he explains how Cobalt tape was a 90's era improvement, although I read somewhere, that Cobalt was actually something that was kinda tried before, hence my confusion.

I've been using cassettes in the 90's myself, but I don't remember Cobalt tapes. I still have my collection of tapes, and there are some metal tapes, but no Cobalt tapes. No blank ones, and no pre-recorded ones. Metal particle tape was a 3M improvement from 1979, and as far as *I* know, Cobalt tape was released around 1974. However, Techmoan on the other hand, claims it's an improvement that came around in the 90's, so that's where the confusion comes from.
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