what are the appearance of aliasing in image and audio processing?

Started by kiki in comp.dsp13 years ago 4 replies

Hi all, I've heard a lot of aliasing. What do they look like in image and audio/speech/music with aliasing? I did not see/hear any real...

Hi all, I've heard a lot of aliasing. What do they look like in image and audio/speech/music with aliasing? I did not see/hear any real aliasing stuff, so the concept of aliasing looks abstract to me, although I know how it occurs in terms of mathematics... I am also wondering about the anti-aliasing filter before downsampling... By filtering, you lose information, right? It is har...


Calculating aliasing components at a particular sampling frequency

Started by Benjamin S. in comp.dsp6 years ago 4 replies

I'm not sure how to calculate aliasing components as I've only dealt with systems that are sampled above fs > = 2B. So if I want to make sure...

I'm not sure how to calculate aliasing components as I've only dealt with systems that are sampled above fs > = 2B. So if I want to make sure that I have aliasing but the components due to aliasing are at most 20dB below the maximum amplitude of the signal I don't know how to do that.


A Basic Aliasing Question

Started by Anonymous in comp.dsp13 years ago 14 replies

Here's something I don't remember about aliasing - someone please verify whether or not this is correct. Assume the sample rate is 2000 Hz for...

Here's something I don't remember about aliasing - someone please verify whether or not this is correct. Assume the sample rate is 2000 Hz for the sake of illustration. Conventional wisdom tells us that a 1200 Hz signal will look like an 800 Hz signal due to aliasing. I say it may look the same on a spectrum analyzer (i.e., its magnitude spectrum may look the same), but it may actually be...


2 tone IMD aliasing on Win Mobile

Started by Kevin T in comp.dsp11 years ago

Looks like Treo and maybe other Windows Mobile based devices have huge (~15% THD) wideband aliasing products when you play any non 44.1 file...

Looks like Treo and maybe other Windows Mobile based devices have huge (~15% THD) wideband aliasing products when you play any non 44.1 file ( MP3 or .Wav) back. Windows resamples all to 44.1 k and seems to have poor anti-aliasing filters. Whats up with that? My Laptop (XP) AC97 is OK on any sample rate. Kevin T


Does an inadequate pixel-density cause spatial aliasing?

Started by Green Xenon [Radium] in comp.dsp9 years ago 12 replies

Hi: Is spatial aliasing caused by an insufficient pixel-density? Also, some video websites say that spatial aliasing causes jaggies, other...

Hi: Is spatial aliasing caused by an insufficient pixel-density? Also, some video websites say that spatial aliasing causes jaggies, other say it causes the Moire effect, still others say it causes pixelation. Who is right? Thanks, Radium


What is the analog equivalent of aliasing?

Started by Green Xenon [Radium] in comp.dsp9 years ago 28 replies

Hi: Aliasing is a digital entity. What is the analog equivalent of aliasing? Thanks, Radium

Hi: Aliasing is a digital entity. What is the analog equivalent of aliasing? Thanks, Radium


Aliasing question

Started by lovejet in comp.dsp8 years ago 4 replies

Hi, I'm junior in the signal processing and I have a question. Can anybody help to answer me? Suppose there's a analog signal bandwidth is B Hz...

Hi, I'm junior in the signal processing and I have a question. Can anybody help to answer me? Suppose there's a analog signal bandwidth is B Hz and with noise. There is no higher frequency componet outside the B Hz but the noise. If I sample and quantize the analog signal by the sampling rate 2*B Hz without aliasing filter. What does the noise happen in the digital domain? Are they aliasing? how? ...


Question about aliasing spectrum in RC filter

Started by fl in comp.dsp12 years ago 1 reply

Hi, For a single carrier system, rooted raised cosine pulse shaping filter is generally used in both transmitting and receiving. I have read...

Hi, For a single carrier system, rooted raised cosine pulse shaping filter is generally used in both transmitting and receiving. I have read a paper which said the FFT bin outside of signal plus excessive bandwidth were set to zero to suppress aliasing signal component. I find that in frequency selective fading channels, suppress aliasing signal component does give better performance for ZF ...


Why use an anti aliasing filter with an energy meter.?

Started by hrh1818 in comp.dsp8 years ago 10 replies

The following document says on page 5 an anti aliasing filter is used on the A/D input channels of an energy meter. Warning the document is 31...

The following document says on page 5 an anti aliasing filter is used on the A/D input channels of an energy meter. Warning the document is 31 pages long, only click on the link if you have a broadband internet connection. http://focus.ti.com/lit/an/slaa409a/slaa409a.pdf. My understanding is you only need an anti aliasing filter if you want to reconstruct the signal or find the frequency c...


Spatial Aliasing and Delay and Sum Beamformer

Started by RIH7777 in comp.dsp4 years ago 6 replies

I'm trying to understand how spatial aliasing will give problems with a simple delay/sum beamformer. I understand the the principle of...

I'm trying to understand how spatial aliasing will give problems with a simple delay/sum beamformer. I understand the the principle of aliasing/Nyquist rate. Lets take simplest case: linear microphone array with 2 mics located d meters apart along the x axis. Sound source is far field and monochromatic with wavelength lambda. Theta is the angle between mic array and sound sour


Anti-Aliasing filter

Started by Anonymous in comp.dsp9 years ago 12 replies

If you are estimating time-delay bewteen two microphones would it be better to use a Bessel filter for anti-aliasing rather than a Butterworth...

If you are estimating time-delay bewteen two microphones would it be better to use a Bessel filter for anti-aliasing rather than a Butterworth due to the approximate linear phase. Wang King


Aliasing in MDCT

Started by Anonymous in comp.dsp9 years ago 16 replies

Why exactly does MDCT introduce time-domain aliasing? From the 2M samples, the MDCT transforms to M samples, before the IMDCT transform back to...

Why exactly does MDCT introduce time-domain aliasing? From the 2M samples, the MDCT transforms to M samples, before the IMDCT transform back to 2M samples. From my understanding going from the frequency domain to the time domain using IMDCT, the original 2M samples are now only represented by M samples. But where exactly does the time-domain aliasing occur in the reconstructed signal, and wh...


aliasing error question

Started by bos1234 in comp.dsp7 years ago 3 replies

Consider the system below. At point B it is graphed. The question is what is the value of the signal at 15Khz. And what is the aliasing error at...

Consider the system below. At point B it is graphed. The question is what is the value of the signal at 15Khz. And what is the aliasing error at this frequency. Why did they minus F_s-f=45 in the solution. And what is the value of the aliasing error mean? [IMG]http://i41.tinypic.com/idbrjm.png[/IMG] at Point A and B respectively [IMG]http://i39.tinypic.com/kas1mp.png[/IMG] [IMG]http...


Time Aliasing Methods of Spectrum Estimation Real Time?

Started by westocl in comp.dsp4 years ago

In a previous thread I had a question about time domain aliasing and you guys helped me out in understanding some. Mr. Lyons gave a really...

In a previous thread I had a question about time domain aliasing and you guys helped me out in understanding some. Mr. Lyons gave a really good explanation. Previous thread: http://www.dsprelated.com/showmessage/209160/1.php I found the a thesis "Time Aliasing Methods of Spectrum Estimation" on some of the topic. Good reading.... But questions just lead to more questions. http://cdm159...


samplig rate conversion

Started by twain in comp.dsp12 years ago 11 replies

I have a large bunch of WAV files sampled at 44.1kHz and at 48kHz, which I would like to convert to 8kHz sampling rate, efficiently/quickly but...

I have a large bunch of WAV files sampled at 44.1kHz and at 48kHz, which I would like to convert to 8kHz sampling rate, efficiently/quickly but professionally & accurately (i.e. no aliasing etc.) Could anyone recommend me a tool for doing that (free software or Matlab)? (For example I know GoldWave is bad for this purpose since its anti-aliasing filter is unprofessional.)


Nice aliasing demonstration.

Started by Eric Jacobsen in comp.dsp6 years ago 2 replies

This vid may be interesting to some for many reasons, but one thing it does is demonstrate aliasing visually pretty well. The camera used must...

This vid may be interesting to some for many reasons, but one thing it does is demonstrate aliasing visually pretty well. The camera used must have had a pretty decent effective shutter speed. http://www.youtube.com/watch?v=QdfO657zHNY Eric Jacobsen Anchor Hill Communications www.anchorhill.com


Perceived aliasing in small ratio SRC

Started by somenoob in comp.dsp11 years ago 15 replies

I'm pretty new to the world of frequency domain as proven by this question: Is there any correlation between the quality of resampler required...

I'm pretty new to the world of frequency domain as proven by this question: Is there any correlation between the quality of resampler required to make aliasing "imperceptible" and the magnitude of sampling rate change? I'm currently playing with various resampling algorithms, running some 44.1kHz content through them (with lots of high and low frequencies) and I noticed increasing the samp...


Interesting example of aliasing...

Started by Eric Jacobsen in comp.dsp10 years ago 10 replies

Got this from a friend, who was mostly interested in it because it looks cool, and we both play an on-line game that includes this type of...

Got this from a friend, who was mostly interested in it because it looks cool, and we both play an on-line game that includes this type of helicopter. http://www.break.com/index/helicopter-blades-stop-moving.html It's a pretty interesting example of visual aliasing. I wonder what the rotation would have looked like if one of the rotors had been painted a different color. Eric Jacobs...


automatic detection of aliasing?

Started by Vista in comp.dsp10 years ago 15 replies

Hi all, I need your help on the following difficulties: I am designing something like "automatic" detection of aliasing,...

Hi all, I need your help on the following difficulties: I am designing something like "automatic" detection of aliasing, programmatically. For a given signal discrete time signal x(n), possibly infinite support, we know its values are all positive, they are absolutely summable, so DTFT exists and we know that the signal die down for large n, and it can be roughly deemed as zero fo...


help regarding impulse invariance method !

Started by nikkogta4 in comp.dsp8 years ago 1 reply

Hi, i hav just studied the impulse invariance method & bilinear transform. In Impulse Invariance there is "many to one mapping" and hence...

Hi, i hav just studied the impulse invariance method & bilinear transform. In Impulse Invariance there is "many to one mapping" and hence aliasing takes place. while in Bilinear Transform there is "one to one mapping" and hence no aliasing. Actually what is the "one to one mapping" & "many to one mapping"? how it is related to aliasing?