Thanks Steve, well spotted and tested, I have checked that in. That
routine is 25 years old btw.
It's solving a 10 x 10 matrix (like 10 equations with 10 unknowns) to
work out the 10 filter coefficients a[i] that describe our speech for
the current 10ms.
It's like working out the LC values for a 10th order analog filter.
The k[i] values were alternate forms of the filter coefficients, in the
past they were often quantised and sent over the channel. E[i] is the
residual energy at each step, it should decrease.
Cheers,
David
On 26/06/14 23:05, Steve Sampson wrote:
The levinson_durbin algorithm in lpc.c has a couple of arrays that are not
used. I changed the code to use just a variable instead. Not a lot of
memory saved, but this routine is called every encode frame (20 or 40 ms).
To check that the algorithm works the same, I used c2enc with hts1a.raw and
checked that the output values were the same. Here's a snippet:
Old algorithm: 1.000000 -1.930401 1.770051 -1.443837 0.961698 -0.523273
0.465262 -0.275403 0.496277 -0.624951
New algorithm: 1.000000 -1.930401 1.770051 -1.443837 0.961698 -0.523273
0.465262 -0.275403 0.496277 -0.624951
Old algorithm: 1.000000 -1.255710 0.800782 -1.023655 0.902301 -0.582309
0.414592 -0.220164 0.191661 -0.027249
New algorithm: 1.000000 -1.255710 0.800782 -1.023655 0.902301 -0.582309
0.414592 -0.220164 0.191661 -0.027249
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------------------------------------------------------------------------------
Open source business process management suite built on Java and Eclipse
Turn processes into business applications with Bonita BPM Community Edition
Quickly connect people, data, and systems into organized workflows
Winner of BOSSIE, CODIE, OW2 and Gartner awards
http://p.sf.net/sfu/Bonitasoft
_______________________________________________
Freetel-codec2 mailing list
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