cent 音分
semitone/half step/half tone 半音
whole tone 全音
accidental 變音記號
1 semitone = 100 cents
octave 八度音
一個八度音 = 12個半音 = 5個全音 + 2個半音
Twelve-tone equal temperament (十二平均律)
- divide an octave into 12 equal parts
Number of Semitones between Two Frequencies (兩個頻率間相差的半音數):
n = abs(log2(f1/f2)/log2(2(1/12))) = abs(12log2(f1/f2))
Reference
How to find the number of semitones between two frequencies?
2017/05/13
2017/04/06
Matlab: Draw a grayscale
>> a = [0 40 80 120 160 200 220 255];
>> b = [a;a;a;a;a;a;a;a];
>> colormap('gray');
>> imagesc(b)
Result:
>> b = [a;a;a;a;a;a;a;a];
>> colormap('gray');
>> imagesc(b)
Result:
2017/04/03
Modulation terms 調變相關名詞
modulation 調變
modulator 調變器
demodulator 解調器/解調變器
amplitude modulation (AM) 振幅調變/調幅
angle modulation 角度調變
- frequency modulation (FM) 頻率調變/調頻
- phase modulation (PM) 相位調變/調相
modulation index 調變指數
Reference
S. Haykin, Communication Systems, 4th Edition, Wiley, pp106
國家教育研究院雙語詞彙、學術名詞暨辭書資訊網
modulator 調變器
demodulator 解調器/解調變器
amplitude modulation (AM) 振幅調變/調幅
angle modulation 角度調變
- frequency modulation (FM) 頻率調變/調頻
- phase modulation (PM) 相位調變/調相
modulation index 調變指數
Reference
S. Haykin, Communication Systems, 4th Edition, Wiley, pp106
國家教育研究院雙語詞彙、學術名詞暨辭書資訊網
2017/03/18
2017/03/13
Matlab: Length and Size of a Vector/Matrix
Given that
>> a = [1 2 3;4 5 6]
>> b = 1:5
Length
>> length(a)
ans =
3
>> length(b)
ans =
5
Size
>> size(a)
ans =
2 3
>> size(b)
ans =
1 5
>> a = [1 2 3;4 5 6]
>> b = 1:5
>> length(a)
ans =
3
>> length(b)
ans =
5
Size
>> size(a)
ans =
2 3
>> size(b)
ans =
1 5
Matlab: How to use Quantiz with partition and codebook
The Quantiz function requires the Communications System Toolbox.
This quantization function requires at least an input signal and a partition vector.
Partition
The example below shows an input signal between 1 and 10. The partition vector equals [2 5 7]. When the signal is quantized, values become:
y = 0 if x <= 2
y = 1 if x <= 5
y = 2 if x <= 7
y = 3 if x > 7
>> x = 1:10
x =
1 2 3 4 5 6 7 8 9 10
>> partition = [2 5 7]
partition =
2 5 7
>> y = quantiz(x, partition)
y =
0 0 1 1 1 2 2 3 3 3
Codebook
Using the same input signal x and partition above, add a codebook as:
>> codebook = [-4 0 2 4]
Insert the codebook as the third parameter in the Quantiz function. The index and quantized value quants are output:
>> [index,quants] = quantiz(x,partition,codebook)
index =
0 0 1 1 1 2 2 3 3 3
quants =
-4 -4 0 0 0 2 2 4 4 4
Reference
Quantization (MathWorks)
This quantization function requires at least an input signal and a partition vector.
Partition
The example below shows an input signal between 1 and 10. The partition vector equals [2 5 7]. When the signal is quantized, values become:
y = 0 if x <= 2
y = 1 if x <= 5
y = 2 if x <= 7
y = 3 if x > 7
>> x = 1:10
x =
1 2 3 4 5 6 7 8 9 10
>> partition = [2 5 7]
partition =
2 5 7
>> y = quantiz(x, partition)
y =
0 0 1 1 1 2 2 3 3 3
Codebook
Using the same input signal x and partition above, add a codebook as:
>> codebook = [-4 0 2 4]
Insert the codebook as the third parameter in the Quantiz function. The index and quantized value quants are output:
>> [index,quants] = quantiz(x,partition,codebook)
index =
0 0 1 1 1 2 2 3 3 3
quants =
-4 -4 0 0 0 2 2 4 4 4
Reference
Quantization (MathWorks)
2017/03/12
PCM, DPCM, ADPCM
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