[linux-audio-user] Stretching with very high accuracy

[Nick Copeland]

>From: Paul Winkler <pw_lists at slinkp.com>
>Reply-To: A list for linux audio users 
><linux-audio-user at music.columbia.edu>
>To: linux-audio-user at music.columbia.edu
>Subject: Re: [linux-audio-user] Stretching with very high accuracy
>Date: Thu, 8 Jun 2006 17:42:36 -0400
>
>On Thu, Jun 08, 2006 at 11:15:03PM +0200, Nick Copeland wrote:
> > What is the format of the files? Raw audio, WAV, etc? What is the rough
> > content - if the signal is constant than sample insertion is not easy 
>since
> > you may not have periods of silence. If the signal does have silent 
>periods
> > then the solution may be a noise gate that inserts samples - this would 
>be
> > all but inaudible. There is no reason why this should not work from file 
>to
> > file with 'cat oldfile | <program> > newfile so should not need to have 
>the
> > lot in memory.
>
>Given the very small amount of drift (53 ms / hour), we're talking about
>inserting maybe 1 sample per 30000.  I submit that nobody will notice
>if you just insert a copy of an adjacent sample, and if you
>want better than that, interpolation between two adjacent
>samples would be even smoother.
>

You dont think that there may be issues with sample insertion at regular 
locations? They can become noticable as they are cyclic - I tried it with 
SLab, and for a while with bristol before deciding it needed resampling. 
Perhaps going half way would be to duplicate a sample at zero crossing 
rather than during silence. This would be a little more random and hence 
less noticable.

Perhaps somebody should just fix sox - its such a cool tool that a fix might 
be in order. Is it still maintained? I also thinks sox had a few different 
options for resampling (binary/quadrature?), perhaps it just needs a 
different option for the algorithm?

Nick

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