Hello all I would need to change the frequencies from 0 � 80 kHz to 0 to 10 kHz, a linear scaling of the frequency. For example if I have an input at 50 kHz it is transformed to 6.25 kHz. Is it possible to do it in real time or near real time?
Compress frequency range to smaller range?
Started by ●November 30, 2011
Reply by ●November 30, 20112011-11-30
Lox wrote:> Hello all > > I would need to change the frequencies from 0 � 80 kHz to 0 to 10 kHz, > a linear scaling of the frequency. > For example if I have an input at 50 kHz it is transformed to 6.25 > kHz. > > Is it possible to do it in real time or near real time?Certainly. A divide-by-8 counter would do that.
Reply by ●November 30, 20112011-11-30
On Wed, 30 Nov 2011 06:28:33 -0800, Lox wrote:> Hello all > > I would need to change the frequencies from 0 – 80 kHz to 0 to 10 kHz, a > linear scaling of the frequency. > For example if I have an input at 50 kHz it is transformed to 6.25 kHz. > > Is it possible to do it in real time or near real time?Why 'would' you need to do this? It is possible, but unless your signal is special all you'll do is hopelessly scramble it. Bandwidth * time is information -- so cutting the bandwidth is compression. You'll have to leave information out to do this, and if its important information then you'll never be able to recover a decent semblance of your original signal. Do you know that the signal contains redundant information, and do you have a way to cut it out? Or do you know a scheme to cut the information that is present but "unimportant"? -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
Reply by ●November 30, 20112011-11-30
chop your signal into 100 ms chunks, discard 7 out 8, add some crossfade to taste and serve while still hot.
Reply by ●November 30, 20112011-11-30
Reply by ●November 30, 20112011-11-30
On 11/30/11 12:54 PM, mnentwig wrote:> http://en.wikipedia.org/wiki/Audio_timescale-pitch_modificationMarkus has the right idea, but pitch shifting down 3 octaves is, how you say, a female canine. -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
Reply by ●November 30, 20112011-11-30
Tim <tim@seemywebsite.please> wrote:> On Wed, 30 Nov 2011 06:28:33 -0800, Lox wrote:>> I would need to change the frequencies from 0 ??? 80 kHz to 0 >> to 10 kHz, a linear scaling of the frequency.(snip)> Why 'would' you need to do this?> It is possible, but unless your signal is special all you'll do is > hopelessly scramble it.> Bandwidth * time is information -- so cutting the bandwidth is > compression. You'll have to leave information out to do this, > and if its important information then you'll never be able to > recover a decent semblance of your original signal.I am not so convinced. Without actually looking it up, I thought it was more like bandwidth * time * S/N. Now, one way to scale the frequency is to also scale the time, but it seems that the OP doesn't want to do that. This does remind me of the old problem of high-speed tape duplication, though it isn't exactly the same. -- glen
Reply by ●November 30, 20112011-11-30
On 11/30/11 1:18 PM, glen herrmannsfeldt wrote:> Tim<tim@seemywebsite.please> wrote: >> >> Bandwidth * time is information -- so cutting the bandwidth is >> compression. You'll have to leave information out to do this, >> and if its important information then you'll never be able to >> recover a decent semblance of your original signal. > > I am not so convinced. Without actually looking it up, I thought > it was more like bandwidth * time * S/N.something like it. information in bits is BW time * integral{ log2( 1 + S(f)/N(f) ) df } 0 -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
Reply by ●November 30, 20112011-11-30
On 30 Nov, 18:58, robert bristow-johnson <r...@audioimagination.com> wrote:> ... is, how you > say, a female canine.??????? Rune
Reply by ●November 30, 20112011-11-30
On Wed, 30 Nov 2011 12:44:18 -0800, Rune Allnor wrote:> On 30 Nov, 18:58, robert bristow-johnson <r...@audioimagination.com> > wrote: > >> ... is, how you >> say, a female canine. > > ???????http://en.wiktionary.org/wiki/bitch. Definition 7. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
