Thanks Erik - interesting stuff. Apologies Dave if I led things slightly awry there. Certainly shows that that I'm better off using csound and libsamplerate than our expensive proprietary DAW when it comes to some operations anyway - sample rate conversion being one of them... Denis On Sun, Apr 27, 2008 at 9:28 AM, Erik de Castro Lopo wrote: > Denis Crowdy wrote: > > > On Thu, Apr 24, 2008 at 11:22 PM, Dave Seidel wrote: > > > Thanks, Mike. > > > > > > As I mentioned, I normally render to 96/24, and that's what I play in a > > > concert situation. I'm guessing that you recommend 88.2K rather than 96K > > > because dithering it down to 441.1K is simpler (just a divide by 2), > > > correct? > > > > I'm pretty sure the answer to this is no - it is by no means a simple > > divide by 2. The author of libsamplerate (Erik de Castro Lopo) gives > > a series of lectures to my audio engineering students > > I really enjoyed that Denis. Thanks. > > > > and demonstrates > > how important the filtering and conversion process is so that aliasing > > artefacts don't appear after the conversion, > > To expand on this a bit, there are two basic categories of doing sample > rate conversion > > - algorithmically naive and computationally cheap ways > - good algorithms > > When using the first method, yes, downsampling by 2 is better/easier > than downsampling by 960/441. > > However, when using good algorithms (ie the SRC_SINC_* in libsamplerate > and similar converters in other libraires and applications) the > difference in quality between downsampling by 2 over downsampling by > 960/441 is unlikely to be measurable. > > > > (similar to those at http://src.infinitewave.ca/) to demonstrate this. > > Excellent web site. For a little more on what these spectral plots > mean and how they are obtained, see my blog post: > > http://www.mega-nerd.com/erikd/Blog/CodeHacking/SecretRabbitCode/src_compare.html > > A later post > > http://www.mega-nerd.com/erikd/Blog/CodeHacking/SecretRabbitCode/progress.html > http://www.mega-nerd.com/erikd/Blog/CodeHacking/SecretRabbitCode/rel_0_1_3.html > > describes a reworking of the converters I did just recently which put > the best of the libsamplerate converters (with a SNR of 145dB) > extremely close to the best of the commercial converters (160dB SNR or > better). Personally, I think 145dB SNR should be more than sufficient > for any audio application. > > Cheers, > Erik > -- > ----------------------------------------------------------------- > Erik de Castro Lopo > ----------------------------------------------------------------- > With 22,100,000 legitimate businesses in the US alone, > allowing each to send only one UCE per *year* gets every > mailbox 60,547 emails per day. There will either be email > without UCE or there will be no email. > > > > > Send bugs reports to this list. > To unsubscribe, send email sympa@lists.bath.ac.uk with body "unsubscribe csound" > -- Dr Denis Crowdy Department of Contemporary Music Studies, Macquarie University +61 2 9850 6787 http://www.dcms.mq.edu.au http://motekulo.blogspot.com/ http://www.melanesianmusic.org CRICOS Provider No 00002J This message is intended for the addressee named and may contain confidential information. If you are not the intended recipient, please delete it and notify the sender. Views expressed in this message are those of the individual sender, and are not necessarily the views of DCMS or Macquarie University.