October 2014
Intermediate to advanced
288 pages
6h 27m
Japanese
Content preview from 実践 機械学習システム
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176
9
章 クラス分類
III
：音楽ジャンル分類
ロックとカントリー音楽のペアなど、他のジャンルのペアにおいては、高精度な分類は難題と言えるで
しょう。さらに、2 つのクラスではなく、全部で6つのクラスに適切に分類することができるようにし
なければなりません。それを考慮すると、これは非常に難しい問題です。
9.3.1
音楽をサイン波に分解する
ここでは、生のサンプリングデータ（先ほど Xという変数に格納しました）から周波数強度を抽出し
て、それを分類器に入力したいと思います。これらの周波数強度は、高速フーリエ変換（Fast Fourier
Transform：FFT）を適用することで求めることができます。FFTの理論については本章の範囲外です
ので、ここではFFTを用いることで、どのようなことができるかだけを見ることにします。これ以降、
FFTを特徴抽出を行うためのブラックボックスのツールとして扱うことにします。
ここでは、例として
sine_a.wav
と
sine_b.wav
の二つのWAVファイルを作成します。その二つ
の
ファイルはそれぞれ、400Hz、3,000Hzのサイン波です。先ほど紹介した“万能ナイフ”であるsox
というツールを用いることで、サイン波を生成することができます。
$ sox --null -r 22050 sine_a.wav synth 0.2 sine 400
$ sox --null -r 22050 sine_b.wav synth 0.2 sine 3000
次に示す図は
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.