fre, 29 02 2008 kl. 12:03 +0100, skrev Eric Chassande-Mottin: > hi, > > I have rewritten resample.m using a polyphase implementation. > See codes attached to this message. > > With the test resample_test.m, I compare this code to the current version > of resample.m in OctaveForge. The test consists in > resampling sinusoids of various frequencies and evaluate the discrepancy > between the result of the resampling algorithm and > the exact waveform one expects. > > in (a), one sees that the RMS error of > OctaveForge's resample.m is large and this is > due to a spurious phase shift in the resampled > time-series (see (c) red and blue). > > in (b), the rejection of OctaveForge's resample.m > appears to be quite poor. > > I've checked that the polyphase version satisfies the > specifications (rolloff width and rejection in the > stopband) of the antialiasing filter (blue dash lines > in (a) and (b)). > > I suggest to replace resample.m with my code. Other people will have to comment the algorithm as I'm not qualified. I do have a few comments:
1) Your implementation is not documented. I know this is the boring part, but it really needs to be done. Otherwise people can only use the program if they read the actual code. 2) You should add a version number to the GPL license. I would prefer if you chose GPL version 3 (or later) as this is what Octave uses. 3) There is no need to add a semi-colon (;) after 'end*' keywords. So, you don't have to write "endif;", you can just use "endif". The same goes for "endwhile", "endfor", and so on. 4) I didn't read your test program, but it might be nice if this was added as a test or demo in the actual implementation, using "%!test" or "%!demo". Thanks, Søren ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Octave-dev mailing list Octave-dev@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/octave-dev
