Ok, I had a closer look, but will have to get deeper I think, since i did not fully got this.
According to my simulations, using copied samples does sometimes better.
Maybe a question of intelligent filter design.

Regarding Tom's remark:  Using the copied samples also requires no additional multiplcation since the value is already stored and in use (?)

Anyway thanks.
 
Rolf
 
 
Gesendet: Dienstag, 24. Juli 2018 um 18:36 Uhr
Von: "Nigel Redmon" <earle...@earlevel.com>
An: music-dsp@music.columbia.edu
Betreff: Re: [music-dsp] resampling
(Not sure why I didn’t receive Rolf’s email directly…)
 
Hi Rolf,
 
First, I should have pointed to this newer series of articles (of mine), not old ones, earlier in this thread. You’ll get a detailed explanation of why zeroes (and as Alex points out, the zeros can be handled efficiently so it’s a good thing anyway):
 
 
Nigel
 
 
On Jul 24, 2018, at 7:53 AM, Tom O'Hara <tom_i...@ticino.com> wrote:
 

Adding zeros is an advantage as then you don't need to calculate their multiplication, as 0 x coefficient = 0

The filter order will be the same with zeros or repeated samples.

Tom

 
On 7/24/2018 4:37 PM, rolfsassin...@web.de wrote:
Hello Nigel
 
could you please say a word more to what you mean by "2x", "3x"?

Also I am again not sure why in this case, adding zeros is an advantage. I had expected to just copy the samples to have less work to do in filtering. I tested such things in MATLAB and found that feeding zeros needs more filter TAPs to come to the same result.
 
Rolf
 
 
Gesendet: Montag, 23. Juli 2018 um 18:25 Uhr
Von: "Nigel Redmon" <earle...@earlevel.com>
An: music-dsp@music.columbia.edu
Betreff: Re: [music-dsp] resampling
Some articles on my website: http://www.earlevel.com/main/category/digital-audio/sample-rate-conversion/, especially the 2010 articles, but the Amp Sim article might be a helpful overview.
 
48k -> 8k: Filter with a lowpass with cutoff below 4k; keep 1 sample, throw away 5, repeat.
 
8k -> 48k: Use 1 sample, follow it with 5 new samples of 0 value, repeat; filter with a lowpass filter with cutoff below 4k.
 
 
Virus-free. www.avg.com
 
 
 
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