Merge pull request #42 from r9y9/mc2e

Add mc2e

NEWS.md

@@ -2,6 +2,7 @@
 
 ## v0.1.6
 
+- Add `mc2e`. [#42]
 - Add `sp2mc` and `mc2sp`. [#41]
 
 ## v0.1.5
@@ -59,3 +60,4 @@
 [#35]: https://github.com/r9y9/pysptk/pull/35
 [#39]: https://github.com/r9y9/pysptk/pull/39
 [#41]: https://github.com/r9y9/pysptk/pull/41
+[#42]: https://github.com/r9y9/pysptk/pull/42

pysptk/__init__.py

@@ -43,5 +43,5 @@
 from .sptk import *  # pylint: disable=wildcard-import
 
 from . import synthesis
-from .conversion import mgc2b, sp2mc, mc2sp
+from .conversion import mgc2b, sp2mc, mc2sp, mc2e
 from . import util

pysptk/conversion.py

@@ -9,14 +9,14 @@
     mgc2b
     sp2mc
     mc2sp
-
+    mc2e
 """
 
 from __future__ import division, print_function, absolute_import
 
 import numpy as np
 
-from pysptk.sptk import mc2b, gnorm, freqt
+from pysptk.sptk import mc2b, gnorm, freqt, c2ir
 
 
 def mgc2b(mgc, alpha=0.35, gamma=0.0):
@@ -141,3 +141,33 @@ def mc2sp(mc, alpha, fftlen):
     # back to power spectrum
     # c(m) -> log(|X(ω)|²) -> |X(ω)|²
     return np.exp(np.fft.rfft(symc).real)
+
+
+def mc2e(mc, alpha=0.35, irlen=256):
+    """Compute energy from mel-cepstrum
+
+    Inspired from hts_engine
+
+    Parameters
+    ----------
+    mc : array
+        Mel-spectrum
+
+    alpha : float
+        All-pass constant.
+
+    irlen : int
+        IIR filter length
+
+    Returns
+    -------
+    energy : floating point, scalar
+        frame energy
+    """
+    # back to linear frequency domain
+    c = freqt(mc, irlen - 1, -alpha)
+
+    # compute impule response from cepsturm
+    ir = c2ir(c, irlen)
+
+    return np.sum(np.abs(ir * ir))

tests/test_conversions.py

@@ -282,3 +282,9 @@ def __test(order, alpha, fftlen):
         for alpha in [0.35, 0.41]:
             for fftlen in [512, 1024, 2048]:
                 yield __test, order, alpha, fftlen
+
+
+def test_mc2b():
+    x = windowed_dummy_data(1024)
+    mc = pysptk.mcep(x)
+    assert pysptk.mc2e(mc) > 0