ewan-xu/LibrosaCpp

Output mel spectrograms for python and CPP don't match

Opened this issue · 4 comments

sahi1422 commented

Python Code

samples = np.full(16_000 * 5, 0.2)
mel_spec = librosa.feature.melspectrogram(y=samples, sr=16_000, n_fft=1024, hop_length=512, n_mels=128)

print('shape: ', mel_spec.shape)
print('sum: ', mel_spec.sum())
print('min: ', mel_spec.min())
print('max: ', mel_spec.max())

Python Output

shape:  (128, 157)
sum:  11806.58392107923
min:  7.865755998623591e-34
max:  89.1440147017634

CPP Code

    int sr = 16000;
    int n_fft = 1024;
    int n_hop = 512;
    int n_mel = 128;
    int fmin = 0.0;
    int fmax = sr / 2.0;

    std::vector<float> x(sr * 5, 0.2);

    std::vector<std::vector<float>> mels = librosa::Feature::melspectrogram(x, sr, n_fft, n_hop, "hann", true,
                                                                            "reflect",
                                                                            2.f, n_mel, fmin, fmax);

    std::cout << "shape: [" << mels.size() << "," << mels[0].size() << "]" << std::endl;

    double sums = 0;
    float maxi = -INT_MAX, mini = INT_MAX;
    for(auto &arr: mels) {
        for(auto k: arr) {
            sums += k;
            maxi = max(maxi, k);
            mini = min(mini, k);
        }
    }
    cout << "sums: " << sums << "\n";
    cout << "mini: " << mini << "\n";
    cout << "maxi: " << maxi << "\n";

CPP output

shape: [157,128]
sums: 11761.6
mini: 5.23758e-16
maxi: 74.9149
shreks7 commented

I have the same issue, the outputs don't match.

abdr17 commented

Can you tell me some resources to study basics of audio signal processing like concepts of STFT, MelSpectrogram, etc(code oriented).

xiehengye commented

Python Code

samples = np.full(16_000 * 5, 0.2)
mel_spec = librosa.feature.melspectrogram(y=samples, sr=16_000, n_fft=1024, hop_length=512, n_mels=128)

print('shape: ', mel_spec.shape)
print('sum: ', mel_spec.sum())
print('min: ', mel_spec.min())
print('max: ', mel_spec.max())

Python Output

shape:  (128, 157)
sum:  11806.58392107923
min:  7.865755998623591e-34
max:  89.1440147017634

CPP Code

    int sr = 16000;
    int n_fft = 1024;
    int n_hop = 512;
    int n_mel = 128;
    int fmin = 0.0;
    int fmax = sr / 2.0;

    std::vector<float> x(sr * 5, 0.2);

    std::vector<std::vector<float>> mels = librosa::Feature::melspectrogram(x, sr, n_fft, n_hop, "hann", true,
                                                                            "reflect",
                                                                            2.f, n_mel, fmin, fmax);

    std::cout << "shape: [" << mels.size() << "," << mels[0].size() << "]" << std::endl;

    double sums = 0;
    float maxi = -INT_MAX, mini = INT_MAX;
    for(auto &arr: mels) {
        for(auto k: arr) {
            sums += k;
            maxi = max(maxi, k);
            mini = min(mini, k);
        }
    }
    cout << "sums: " << sums << "\n";
    cout << "mini: " << mini << "\n";
    cout << "maxi: " << maxi << "\n";

CPP output

shape: [157,128]
sums: 11761.6
mini: 5.23758e-16
maxi: 74.9149

I found the same problem, did you solve it?

ewan-xu commented

setting pad_mode = "reflect" in python code like this:

samples = np.full(16000 * 5, 0.2)
mel_spec = librosa.feature.melspectrogram(y=samples, sr=16000, n_fft=1024, hop_length=512, n_mels=128,pad_mode='reflect')

print(mel_spec.T)
print('shape: ', mel_spec.shape)
print('sum: ', mel_spec.sum())
print('min: ', mel_spec.min())
print('max: ', mel_spec.max())

python output:

shape:  (128, 157)
sum:  11761.64503417969
min:  1.1692227111050498e-33
max:  74.91493652343752
  • 👍1