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#1
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90degree phase shifts
I'm guessing you all probably know why I need to create one of the above - to trick a Pro Logic Surround decoder.
Problem is, I know what a 90 - and 180 - deg phase shift looks like on a pure sinewave, but how to I achieve 90 degrees phase shift on "real world" material - a clip of ducks quacking or a 1890s locomotive roaring by? There is no simple wave - ducks, trains, and of course music - are anything but simple! |
#2
Posted to rec.audio.pro
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90degree phase shifts
субота, 28. јул 2012. 01.45.20 UTC+2, је написао/ла:
I'm guessing you all probably know why I need to create one of the above - to trick a Pro Logic Surround decoder. Problem is, I know what a 90 - and 180 - deg phase shift looks like on a pure sinewave, but how to I achieve 90 degrees phase shift on "real world" material - a clip of ducks quacking or a 1890s locomotive roaring by? There is no simple wave - ducks, trains, and of course music - are anything but simple! Pass it through capacitor. Not exactly 90deg, and different at freqs, but ...., or just delay it a ms, or so. Phase shift is meaningless on one isolated signal. You have to have at least two to experience the effect. In digital plug ins, you can try passing it through some old EQ, or something. |
#3
Posted to rec.audio.pro
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90degree phase shifts
wrote:
I'm guessing you all probably know why I need to create one of the above - = to trick a Pro Logic Surround decoder. Why not use a pro logic encoder, then? Problem is, I know what a 90 - and 180 - deg phase shift looks like on a pu= re sinewave, but how to I achieve 90 degrees phase shift on "real world" ma= terial - a clip of ducks quacking or a 1890s locomotive roaring by? There = is no simple wave - ducks, trains, and of course music - are anything but s= imple! All-pass networks are discussed extensively in the Audio Cyclopedia. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#4
Posted to rec.audio.pro
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90degree phase shifts
On 07/27/2012 05:44 PM, Scott Dorsey wrote:
All-pass networks are discussed extensively in the Audio Cyclopedia. --scott You'll need a bunch like a graphic EQ has bands for a range where each all-pass is effective. -- -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: When cryptography is outlawed, bayl bhgynjf jvgu unir cevinpl iEYEARECAAYFAlATOL4ACgkQlZadkQh/RmEn7gCgycbmIKSgZwu83YbIv8Z9rg+c WIYAoL4KipNKDyYFXZkc9F/I73XGfYib =JF8o -----END PGP SIGNATURE----- |
#5
Posted to rec.audio.pro
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90degree phase shifts
You'll need a bunch like a graphic EQ
Phase is purely time-related. You can create a phasey effect by combing the eq channels but it's not the desired result. |
#6
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90degree phase shifts
"David Gravereaux" wrote nothing in message
... Do you think you could post using one of our Earth newsreaders? |
#7
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90degree phase shifts
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#8
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90degree phase shifts
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#9
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90degree phase shifts
On 07/27/2012 07:00 PM, None wrote:
"David Gravereaux" wrote nothing in message ... Do you think you could post using one of our Earth newsreaders? Looks fine from https://groups.google.com/d/msg/rec....I/4Tlb479N8M4J -- -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: When cryptography is outlawed, bayl bhgynjf jvgu unir cevinpl iEYEARECAAYFAlATWWMACgkQlZadkQh/RmFdgwCgqnOLywlw1ikwJMRigoPZGr5o IZ0AoMEtspZXcO4Fb2lpK1WmfoNi5yIN =PUYV -----END PGP SIGNATURE----- |
#10
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90degree phase shifts
On 07/27/2012 06:23 PM, wrote:
You'll need a bunch like a graphic EQ Phase is purely time-related. You can create a phasey effect by combing the eq channels but it's not the desired result. See section 16.7 @ http://www.ti.com/lit/ml/sloa088/sloa088.pdf -- -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: When cryptography is outlawed, bayl bhgynjf jvgu unir cevinpl iEYEARECAAYFAlATW2IACgkQlZadkQh/RmF27gCgzFMBMvB6Pa9BcpMH4DWO9+Dr m4kAniDts6GvCcQiXoKNx+iAG6x8JCjg =UG18 -----END PGP SIGNATURE----- |
#11
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90degree phase shifts
None wrote:
"David Gravereaux" wrote nothing in message ... Do you think you could post using one of our Earth newsreaders? He cannot. And hence, via my own newsreader he might as well be miming. I gave up on his attitude about this a long time ago. -- shut up and play your guitar * http://hankalrich.com/ http://www.youtube.com/walkinaymusic http://www.sonicbids.com/HankandShaidri |
#13
Posted to rec.audio.pro
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90degree phase shifts
Les Cargill wrote:
I have no idea how you do it in analog or in real time. But a Hilbert Transform will provide a very good 90 degree phase shift. It will. Unfortunately when you run it through a Dolby CP-50 which uses an all-pass filter (which is NOT a very good 90 degree phase shift), it doesn't sound so good. You need to use filters on the encoding side which are more or less the opposite of the ones on the decoding side. I think that there are real time and analog versions of them; I only know how to do to in the not-real time way. As to the surround decoder - turn that off and do it stereo. People still know how to do that. Go to film-tech.com. Download the Dolby CP-50 manual. Look at the phase shift networks on the Cat 146/150 card. Build the same networks in reverse for encoding. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#14
Posted to rec.audio.pro
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90degree phase shifts
"David Gravereaux" didn't write in message
... That's not a newsreader. It's an abomination. |
#15
Posted to rec.audio.pro
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90degree phase shifts
Les Cargill wrote:
hank alrich wrote: Les Cargill wrote: wrote: I'm guessing you all probably know why I need to create one of the above - to trick a Pro Logic Surround decoder. Problem is, I know what a 90 - and 180 - deg phase shift looks like on a pure sinewave, but how to I achieve 90 degrees phase shift on "real world" material - a clip of ducks quacking or a 1890s locomotive roaring by? There is no simple wave - ducks, trains, and of course music - are anything but simple! I have no idea how you do it in analog or in real time. But a Hilbert Transform will provide a very good 90 degree phase shift. I think that there are real time and analog versions of them; I only know how to do to in the not-real time way. As to the surround decoder - turn that off and do it stereo. People still know how to do that. I'm wondering why one would want to trick a Dolby PLS decoder. I tried real hard not to think about that. Sorry I mentioned it. -- shut up and play your guitar * http://hankalrich.com/ http://www.youtube.com/walkinaymusic http://www.sonicbids.com/HankandShaidri |
#16
Posted to rec.audio.pro
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90degree phase shifts
Scott Dorsey wrote:
Les Cargill wrote: I have no idea how you do it in analog or in real time. But a Hilbert Transform will provide a very good 90 degree phase shift. It will. Unfortunately when you run it through a Dolby CP-50 which uses an all-pass filter (which is NOT a very good 90 degree phase shift), it doesn't sound so good. You need to use filters on the encoding side which are more or less the opposite of the ones on the decoding side. I think that there are real time and analog versions of them; I only know how to do to in the not-real time way. As to the surround decoder - turn that off and do it stereo. People still know how to do that. Go to film-tech.com. Download the Dolby CP-50 manual. Look at the phase shift networks on the Cat 146/150 card. Build the same networks in reverse for encoding. Sounds tricky. -- shut up and play your guitar * http://hankalrich.com/ http://www.youtube.com/walkinaymusic http://www.sonicbids.com/HankandShaidri |
#17
Posted to rec.audio.pro
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90degree phase shifts
hank alrich wrote:
Les Cargill wrote: wrote: I'm guessing you all probably know why I need to create one of the above - to trick a Pro Logic Surround decoder. Problem is, I know what a 90 - and 180 - deg phase shift looks like on a pure sinewave, but how to I achieve 90 degrees phase shift on "real world" material - a clip of ducks quacking or a 1890s locomotive roaring by? There is no simple wave - ducks, trains, and of course music - are anything but simple! I have no idea how you do it in analog or in real time. But a Hilbert Transform will provide a very good 90 degree phase shift. I think that there are real time and analog versions of them; I only know how to do to in the not-real time way. As to the surround decoder - turn that off and do it stereo. People still know how to do that. I'm wondering why one would want to trick a Dolby PLS decoder. I tried real hard not to think about that. -- Les Cargill |
#18
Posted to rec.audio.pro
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90degree phase shifts
Hank
"- show quoted text - I'm wondering why one would want to trick a Dolby PLS decoder. - show quoted text - " Because it's THERE. THAT's why. |
#19
Posted to rec.audio.pro
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90degree phase shifts
hank alrich wrote:
Les Cargill wrote: hank alrich wrote: Les Cargill wrote: wrote: I'm guessing you all probably know why I need to create one of the above - to trick a Pro Logic Surround decoder. Problem is, I know what a 90 - and 180 - deg phase shift looks like on a pure sinewave, but how to I achieve 90 degrees phase shift on "real world" material - a clip of ducks quacking or a 1890s locomotive roaring by? There is no simple wave - ducks, trains, and of course music - are anything but simple! I have no idea how you do it in analog or in real time. But a Hilbert Transform will provide a very good 90 degree phase shift. I think that there are real time and analog versions of them; I only know how to do to in the not-real time way. As to the surround decoder - turn that off and do it stereo. People still know how to do that. I'm wondering why one would want to trick a Dolby PLS decoder. I tried real hard not to think about that. Sorry I mentioned it. Mentioned what? -- Les Cargill |
#20
Posted to rec.audio.pro
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90degree phase shifts
Les Cargill wrote:
I have no idea how you do it in analog or in real time. But a Hilbert Transform will provide a very good 90 degree phase shift. It will. *Unfortunately when you run it through a Dolby CP-50 which uses an all-pass filter (which is NOT a very good 90 degree phase shift), it do Go to film-tech.com. *Download the Dolby CP-50 manual. *Look at the phase shift networks on the Cat 146/150 card. * Build the same networks in reverse for encoding. - show quoted text - Sorry Scott - Resource not found! Actually the filters are just below 100Hz and above 7kHz. I can do that in Audacity. |
#21
Posted to rec.audio.pro
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90degree phase shifts
hank alrich wrote:
Scott Dorsey wrote: Les Cargill wrote: I have no idea how you do it in analog or in real time. But a Hilbert Transform will provide a very good 90 degree phase shift. It will. Unfortunately when you run it through a Dolby CP-50 which uses an all-pass filter (which is NOT a very good 90 degree phase shift), it doesn't sound so good. You need to use filters on the encoding side which are more or less the opposite of the ones on the decoding side. I think that there are real time and analog versions of them; I only know how to do to in the not-real time way. As to the surround decoder - turn that off and do it stereo. People still know how to do that. Go to film-tech.com. Download the Dolby CP-50 manual. Look at the phase shift networks on the Cat 146/150 card. Build the same networks in reverse for encoding. Sounds tricky. Y'know, if I'd practiced more, maybe I would have had to know all this. That's what I keep telling myself anyway. -- Les Cargill |
#22
Posted to rec.audio.pro
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90degree phase shifts
On 07/27/2012 06:23 PM, wrote:
You'll need a bunch like a graphic EQ Phase is purely time-related. You can create a phasey effect by combing the eq channels but it's not the desired result. Here's a rough assemblage in SPICE. Grab LTSpice from http://www.linear.com/designtools/software/ to view it. Obviously the summing overlaps improperly, but this is a rough idea based on octave bands. maintains a 90 shift between 300-6k or so. -- -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: When cryptography is outlawed, bayl bhgynjf jvgu unir cevinpl iEYEARECAAYFAlATaWAACgkQlZadkQh/RmGQNgCg4+FstbSCWyIDZ73wXGozljSm emkAnj/JvFyiaQrKyddOMZN6FBzaNCwc =v3PQ -----END PGP SIGNATURE----- |
#23
Posted to rec.audio.pro
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90degree phase shifts
You need two all-pass filters. One produces a phase shift of phi. The other
producers phi+90 or phi-90. It is impossible to produce a fixed 90 degree phase shift over a wide frequency range and have flat response at the same time. You have to create the 90-degree shift as the difference between two filters' phase responses. Trust me. |
#24
Posted to rec.audio.pro
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90degree phase shifts
wrote:
Hank "- show quoted text - I'm wondering why one would want to trick a Dolby PLS decoder. - show quoted text - " Because it's THERE. THAT's why. It's a fine line between clever and stupid. I think you've crossed it. -- shut up and play your guitar * http://hankalrich.com/ http://www.youtube.com/walkinaymusic http://www.sonicbids.com/HankandShaidri |
#25
Posted to rec.audio.pro
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90degree phase shifts
hank alrich:
"It's a fine line between clever and stupid. I think you've crossed it. " - show quoted text - Keep your closed-minded remarks to yourself! At least others here have suggested ways to accomplish it or emulate it. |
#26
Posted to rec.audio.pro
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90degree phase shifts
Les Cargill wrote:
hank alrich wrote: Scott Dorsey wrote: Go to film-tech.com. Download the Dolby CP-50 manual. Look at the phase shift networks on the Cat 146/150 card. Build the same networks in reverse for encoding. Sounds tricky. Y'know, if I'd practiced more, maybe I would have had to know all this. In the late eighties this sort of thing was all the rage. Everybody wanted to make their own matrix surround tracks and nobody wanted to pay Dolby the licensing fee for the encoder. There were lots of aftermarket fake Dolby encoders sold, and a lot of homebrews. But now we have 5.1 and nobody much bothers with any of that junk except as an afterthought for the occasional film optical track. So, it's sort of like the Phil Collins Drum Sound in that regard... --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#27
Posted to rec.audio.pro
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90degree phase shifts
William Sommerwerck wrote:
You need two all-pass filters. One produces a phase shift of phi. The other producers phi+90 or phi-90. It is impossible to produce a fixed 90 degree phase shift over a wide frequency range and have flat response at the same time. You have to create the 90-degree shift as the difference between two filters' phase responses. Yes. This is also discussed in Tremaine's Audio Cyclopedia which is the first reference I recommended in this thread. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#28
Posted to rec.audio.pro
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90degree phase shifts
wrote:
Go to film-tech.com. =A0Download the Dolby CP-50 manual. =A0Look at the=20 phase shift networks on the Cat 146/150 card. =A0 Build the same networks= =20 in reverse for encoding.=20 - show quoted text - Sorry Scott - Resource not found! Actually the filters are just below 100H= z and above 7kHz. I can do that in Audacity. Okay, class! Everybody pick up your keyboard and go to this url! Yes, you have to start the browser and type it in on the top line. Type http://www.film-tech.com all the way. Yes, you have to type it all out. Now, wait for the page to load and click on WAREHOUSE up at the top. Do you see WAREHOUSE? Now, click on MANUALS... does everybody see MANUALS? That's where the manuals are stored... --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#29
Posted to rec.audio.pro
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90degree phase shifts
SD:
So, it's sort of like the Phil Collins Drum Sound in that regard... --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." ___ And what issues do you have with Phil's drumming? |
#30
Posted to rec.audio.pro
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90degree phase shifts
On 7/27/2012 10:00 PM, None wrote:
"David Gravereaux" wrote nothing in message ... Do you think you could post using one of our Earth newsreaders? Perhaps you need a real Earth newsreader. But he did put an attachment in the posting which I didn't expect would come through in rec.audio.pro. What he said, less the attachment, was: Here's a rough assemblage in SPICE. Grab LTSpice from http://www.linear.com/designtools/software/ to view it. Obviously the summing overlaps improperly, but this is a rough idea based on octave bands. maintains a 90 shift between 300-6k or so. Or maybe you can find a surround encoder to pass your recording through. -- "Today's production equipment is IT based and cannot be operated without a passing knowledge of computing, although it seems that it can be operated without a passing knowledge of audio." - John Watkinson http://mikeriversaudio.wordpress.com - useful and interesting audio stuff |
#31
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90degree phase shifts
"Mike Rivers" wrote in message
... On 7/27/2012 10:00 PM, None wrote: "David Gravereaux" wrote nothing in message ... Do you think you could post using one of our Earth newsreaders? Perhaps you need a real Earth newsreader. whooooosh! |
#32
Posted to rec.audio.pro
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90degree phase shifts
wrote in message
... hank alrich: "It's a fine line between clever and stupid. I think you've crossed it. " - show quoted text - Keep your closed-minded remarks to yourself! At least others here have suggested ways to accomplish it or emulate it. Q. Why would anyone want to reinvent the wheel? A. Because it's fun, and you can learn something from it. Sticking with the example, think for a minute about how you would go about making a wheel if you were in the woods with nothing but an axe. Sean |
#33
Posted to rec.audio.pro
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90degree phase shifts
William Sommerwerck wrote:
You need two all-pass filters. One produces a phase shift of phi. The other producers phi+90 or phi-90. It is impossible to produce a fixed 90 degree phase shift over a wide frequency range and have flat response at the same time. You have to create the 90-degree shift as the difference between two filters' phase responses. Trust me. So I just did an experiment which produced a fixed 90 degree phase shift over the audio range. I have some 'C' source which produces a Hilbert transform of an audio file ( using libsndfile and FFTW plus some code of my own, er code I pretty much swiped off the Internet . When I run this twice*, I get perfect** cancellation *Assume files A,B and C. B = Hilbert(A), C = Hilbert(B). ** to the limit of my ability to measure it. I can provide details on request. What am I missing? -- Les Cargill |
#34
Posted to rec.audio.pro
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90degree phase shifts
On Sat, 28 Jul 2012 06:01:33 -0700, Scott Dorsey wrote
(in article ): In the late eighties this sort of thing was all the rage. Everybody wanted to make their own matrix surround tracks and nobody wanted to pay Dolby the licensing fee for the encoder. There were lots of aftermarket fake Dolby encoders sold, and a lot of homebrews. But now we have 5.1 and nobody much bothers with any of that junk except as an afterthought for the occasional film optical track. ------------------------------snip------------------------------ Yes, this brings back memories of the 1980s with Ultra-Stereo, which I believe was Jack Cashin's attempt to get around Dolby's patents and creating a compatible (and much cheaper) matrixed surround system with a similar noise-reduction encoding. I believe engineer John Mosely was also a consultant for the company; Mosely had previously worked on Quintaphonic sound in the mid-1970s. Interestingly, Dolby could not patent the surround encoding itself, but did patent the noise reduction encoding (either Type A or Type B, depending on the release format), which Ultra Stereo had to mimic for their release prints. I used Ultra Stereo a few times in mastering, and it actually worked OK. To the o.p.: lots of books have the information necessary in order to simulate a matrix surround mix. Dolby's own white paper is he http://www.dolby.com/uploadedFiles/zz- _Shared_Assets/English_PDFs/Professional/214_Mixing%20with%20Dolby%20Pro%20Log ic%20II%20Technology.pdf Tom Holman's book SURROUND SOUND: UP AND RUNNING also covers this in detail: http://www.amazon.com/Surround-Sound-Second-Up- running/dp/0240808290/ref=sr_1_2?s=books&ie=UTF8&qid=1343514433&sr=1-2 But in general, I agree with Scott -- I don't think matrix surround has any point today, in the face of so many ways of discrete surround mixing and digital release formats. Many DVD and Blu-ray releases are "upmixed" or "unwrapped" in advance to take old 2-channel mixes and convert them to 5.1. Done skillfully and with care, these can actually sound much better than any of the old Dolby Matrix releases. http://www.sersc.org/journals/IJSIP/vol2_no4/7.pdf --MFW |
#35
Posted to rec.audio.pro
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90degree phase shifts
субота, 28. јул 2012. 21.57.27 UTC+2, Les Cargill је написао/ла:
William Sommerwerck wrote: You need two all-pass filters. One produces a phase shift of phi. The other producers phi+90 or phi-90. It is impossible to produce a fixed 90 degree phase shift over a wide frequency range and have flat response at the same time. You have to create the 90-degree shift as the difference between two filters' phase responses. Trust me. So I just did an experiment which produced a fixed 90 degree phase shift over the audio range. I have some 'C' source which produces a Hilbert transform of an audio file ( using libsndfile and FFTW plus some code of my own, er code I pretty much swiped off the Internet . When I run this twice*, I get perfect** cancellation *Assume files A,B and C. B = Hilbert(A), C = Hilbert(B). ** to the limit of my ability to measure it. I can provide details on request. What am I missing? -- Les Cargill If you run make 4. one D=hilbert(C) does it, D, cancell out with B? |
#36
Posted to rec.audio.pro
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90degree phase shifts
Luxey wrote:
субота, 28. јул 2012. 21.57.27 UTC+2, Les Cargill је написао/ла: William Sommerwerck wrote: You need two all-pass filters. One produces a phase shift of phi. The other producers phi+90 or phi-90. It is impossible to produce a fixed 90 degree phase shift over a wide frequency range and have flat response at the same time. You have to create the 90-degree shift as the difference between two filters' phase responses. Trust me. So I just did an experiment which produced a fixed 90 degree phase shift over the audio range. I have some 'C' source which produces a Hilbert transform of an audio file ( using libsndfile and FFTW plus some code of my own, er code I pretty much swiped off the Internet . When I run this twice*, I get perfect** cancellation *Assume files A,B and C. B = Hilbert(A), C = Hilbert(B). ** to the limit of my ability to measure it. I can provide details on request. What am I missing? -- Les Cargill If you run make 4. one D=hilbert(C) does it, D, cancell out with B? Yes, as you would suspect. -- Les Cargill |
#37
Posted to rec.audio.pro
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90degree phase shifts
недеља, 29. јул 2012. 01.17.46 UTC+2, Les Cargill је написао/ла:
Luxey wrote: субота, 28. јул 2012. 21.57.27 UTC+2, Les Cargill је написао/ла: William Sommerwerck wrote: You need two all-pass filters. One produces a phase shift of phi. The other producers phi+90 or phi-90. It is impossible to produce a fixed 90 degree phase shift over a wide frequency range and have flat response at the same time. You have to create the 90-degree shift as the difference between two filters' phase responses. Trust me. So I just did an experiment which produced a fixed 90 degree phase shift over the audio range. I have some 'C' source which produces a Hilbert transform of an audio file ( using libsndfile and FFTW plus some code of my own, er code I pretty much swiped off the Internet . When I run this twice*, I get perfect** cancellation *Assume files A,B and C. B = Hilbert(A), C = Hilbert(B). ** to the limit of my ability to measure it. I can provide details on request. What am I missing? -- Les Cargill If you run make 4. one D=hilbert(C) does it, D, cancell out with B? Yes, as you would suspect. -- Les Cargill I think it should not be so. B should be 90deg shift, while D should be 270deg shift. They should not cancel out, if complex signal. If sine wave, it shoud cancel except for the first 1/4 of the first cycle and the last 1/4 of the last cycle. That's what I think. Very often I'm wrong. |
#38
Posted to rec.audio.pro
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90degree phase shifts
To clarify my thinking, seams if you apply function twice it does nos shift signal in phase for 180deg, but rather reverses it.
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#39
Posted to rec.audio.pro
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90degree phase shifts
Luxey wrote:
To clarify my thinking, seams if you apply function twice it does nos shift signal in phase for 180deg, but rather reverses it. When the Hilbert transform is applied twice in succession to a function u, the result is negative u: H(H(u))(t) = -u(t), provided the integrals defining both iterations converge in a suitable sense. In particular, the inverse transform is H. http://en.wikipedia.org/wiki/Hilbert_transform -- Les Cargill |
#40
Posted to rec.audio.pro
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90degree phase shifts
Les Cargill wrote:
William Sommerwerck wrote: You need two all-pass filters. One produces a phase shift of phi. The other producers phi+90 or phi-90. It is impossible to produce a fixed 90 degree phase shift over a wide frequency range and have flat response at the same time. You have to create the 90-degree shift as the difference between two filters' phase responses. Trust me. I have some 'C' source which produces a Hilbert transform of an audio file ( using libsndfile and FFTW plus some code of my own, er code I pretty much swiped off the Internet . When I run this twice*, I get perfect** cancellation What am I missing? You can't do a Hilbert transform directly in the analogue domain. You can only use some functions that approximate it, made with Ls and Cs. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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