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#1
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AudioSuite Signal Generator not accurate?
Hi there
Strange thing here: I did generate a -18dbFS / 1kHz reference tone of 1 min. length and put it on the timline of a 48kHz/25fps session. Now, both ends of the segment should match with a waveform zero cross point. But only the start does. Why is this? Something seems not accurate here... Any idea? Cheers |
#2
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Re: AudioSuite Signal Generator not accurate?
Why SHOULD both ends be at zero points? If the time of the wavelength does not allow it to cross zero at the 1 minute mark, its simple math(isn't it?).
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HP Z4 workstation, Mbox Studio https://www.facebook.com/search/top/...0sound%20works The better I drink, the more I mix BTW, my name is Dave, but most people call me.........................Dave |
#3
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Re: AudioSuite Signal Generator not accurate?
It should end at a zero crossing; if 1kHz cycles to zero 1000 times a second, then also after 60 seconds.
Same "thing" in PT 11.2; about 4 samples difference at 00:59 minute. Maybe a graphic issue ?
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PT 11.3.2 HD , RME Fireface 800 , Genelec 5.1 , Win7 64bit Professional , i7 3930 Hexcore , 48GB Ram , SSD System + SSD PT Session/Audio + SSD Video (all Samsung 840 Evo) + Spinner 1TB Data , 2x Radeon HD 5450 \\ SD 633 Femto MKH8060 MKH8070 MKH30/MKH40 DPA4060 |
#4
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Re: AudioSuite Signal Generator not accurate?
It's based off the selection and the math will very unlikely add up to be a zero crossing on the end, as there's also going to be sample rounding. Apply a 5 sample fade or so on the end.
Shane
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Pro Tools Power User Editing Give your plug-ins a facelift...and skin 'em! __________________ "Music should be performed by the musician, not by the engineer." Michael Wagener 25th July 2005, 02:59 PM __________________ Pro Tools|HD Native 9.0.1 | Pro Tools|HDX 10.2 | Studio One | REAPER 4.22 | HD OMNI | HoboMac Pro 2.26Ghz Quad-Core | W7 Ultimate 64-bit |
#5
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Re: AudioSuite Signal Generator not accurate?
Yes, I see your point now. Maybe graphics, maybe the 1KHz has a small plus or minus factor on exact frequency....and Shan's comment carries as much validity(or more) than my 2 cents
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HP Z4 workstation, Mbox Studio https://www.facebook.com/search/top/...0sound%20works The better I drink, the more I mix BTW, my name is Dave, but most people call me.........................Dave |
#6
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Re: AudioSuite Signal Generator not accurate?
Quote:
With 48kHz sampling there should be exactly 48 samples in 1/1000 sec = 1kHz, i.e. the waveform should be symmetrical. Why should there be any rounding? My selection is exactly 1 min. (or the timecode grid is wrong). How I did it: I entered 00:58:30:00 in the counter window and added a marker. Then I entered 00:59:30:00 and added another marker. Then I selected the timeline between the two markers. If this wouldn't be sample accurate, I would have had a lot of issues in my postproduction work... |
#7
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Re: AudioSuite Signal Generator not accurate?
1 minute at 48kHz samples of a 1KHz synthesized signal and you see the phase out by *4* samples out the end? How accurate do you think these signal generators are designed to be? I can't possibly imagine why you are even looking at this.
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#8
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Re: AudioSuite Signal Generator not accurate?
Quote:
I see no reason why this plugin shouldn't be designed to be accurate enough for the resolution we have... |
#9
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Re: AudioSuite Signal Generator not accurate?
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And what does the sample rate have to do with it if it's a 1KHz tone? It cycles 1,000/second regardless of the frequency at which you're sampling the signal. Zero crossings will occur twice every 1/1,000th of a second. |
#10
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Re: AudioSuite Signal Generator not accurate?
Quote:
There are 20 waveform cycles, but the 20th cycle does not end with a zero crossing. Even the 1st waveform cycle is "off" by 8 samples. Set Grid to 100msec, deviation is clearly visible. One Grid Line should represent 2 waveform cycles. But the zero crossing is later , about 16 samples , and deteriorates naturally from there on. Does not matter to me a lot practically; but Signal Generator seems not be exact.
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PT 11.3.2 HD , RME Fireface 800 , Genelec 5.1 , Win7 64bit Professional , i7 3930 Hexcore , 48GB Ram , SSD System + SSD PT Session/Audio + SSD Video (all Samsung 840 Evo) + Spinner 1TB Data , 2x Radeon HD 5450 \\ SD 633 Femto MKH8060 MKH8070 MKH30/MKH40 DPA4060 |
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