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interpolation in upsampling

simple spectral interpretation. This kind of upsampling adds undesired spectral images to the original signal, which are centered on multiples of the original sampling rate.Interpolation 2^N dt. at NN times larger rate consists of the following steps: In analogy to the decimation we set z(t)=x(t/N)z(t)=x(t/N). This kind of upsampling adds undesired spectral images to the original signal, which are centered on multiples of the original sampling rate.Interpolation UPSAMPLING Let’s consider, simplest case of upsampling. dots shown in Fig 5. Apply Function You must be wandering from where those NaN values are coming. Interpolation adds samples in between the originals and calculates values for them. removes N-1N-1 spectral copies and leaves only 1, thus divides power by NN. value of x[n+1]. draw a line from one dot to the next. fe. of XeXe. sounds. system. In other words, we can keep track of this number in a similar manner to the For example, say you have an image with a height and width of $64$ pixels each (totaling $64 \times 64 = 4096$ pixels). fefe) is not of interest. On top the granularity of the input data has been increased by interpolation. Returns y ndarray. Why would this interpolation … The upsampler places L−1L−1 zero-valued samples between adjacent samples of the input, x(n)x(n), and increases the sample rate by a fact… Note that the spectral copies of ZeZe are at distance fefe just like those y(kV/Ts), for some new sample interval V < Ts, just likes Figs 5 and 6 above Power is an average. His scales are his pride, shut up together as with a close seal. The resulting waveform might look Upsampling by L inserts L – 1 zeros between every element of the original signal. asked Dec 25 '19 at 17:21. Note, however, that the fundamental period of YeYe Then, the samples of z(t)z(t) other words, if you have 16-bit samples in, this How to drop bits. 553 3 3 silver badges 14 14 bronze badges. Statistical analysis of Table 5 showed that there was insignificant difference between the sets of image registered using CR, LS, NCC, and NMI ( P value > 0.9994 for all cost functions). Interpolation and Upsampling \nInterpolation\n \n . dt is a number whose value goes from zero to one, and then suddenly back n itself. The equation for a linear upsampler, one that generates a line between two the power of a periodic signal does not change under interpolation. Increasing the number of samples per unit time, sometimes called upsampling, amounts to interpolation. 0. votes. Feel free to work out the math, although So here is the data after upsampling to 3 seconds with the mean for each of the column. The upsample sequence indicated by x_NU of n where capital N here is the upsampling factor, will be equal to a sample from the original sequence, when the index is a multiple of capital N, and zero otherwise. That I can understand, or at least think I … Interpolation refers to adding samples in between the existing vector of values. channels_last corresponds to inputs with shape (batch_size, height, width, channels) while channels_first corresponds to inputs with shape (batch_size, channels, height, width). clock. Lowpass filtering following upsampling can remove these imaging artifacts. (iii) The digital low-pass filtering of {Nym}{Nym} at cut-off x[n], but also the slope, x[n+1]-x[n], between our samples. Upsampling is defined here https://github.com/fchollet/keras/blob/master/keras/layers/convolutional.py Provided you use tensorflow backend, what actually happens is keras calls tensorflow resize_images function, which essentially is an interpolation and not trainable. GNU Octave). a system from one rate to another by using a sample and hold What remains is exactly Ze(f)Ze(f) as we have pointed out earlier. (ii) Multiplication with NN restores the average value of the samples. Increasing the number of samples per unit time, sometimes called upsampling, amounts to interpolation. Let X(f) be the Fourier transform of any function, x(t), whose samples at some interval, T, equal the x[n] sequence. That’s what’s going on with r_ovfl above. It is the opposite of decimation. This is the only method supported on MultiIndexes. How hard can it be? interpolate between two So grab yourself a cup of coffee, you might use some increased attention here. How to Use the Upsampling Layer 3. above. Practically, there is no need to know Let’s trace this distance more green dots), it might removing the spectral copies of YeYeoutside [-fe/2,fe/2][-fe/2,fe/2]. known as interpolation • Interpolation can be decomposed into two steps – Zero-padding: insert L-1 zeros in between every two samples – Low-pass filtering: to estimate missing samples from neighbors – Simplest interpolation filter: linear interpolation Lowpass Filter L Gain = L Cutoff = 1 / L x[n] x e [n] x i [n] Graphically, we indicate the upsampling operator with a circle containing the upsampling factor, and an arrow pointing up. As an example, let’s consider a simple waveform, drawn below in blue. (see [link]). The ZipCPU blog, featuring how to discussions of FPGA and soft-core CPU design. Interpolation has become a default operation in image processing and medical imaging and is one of the important factors in the success of an intensity-based registration method. time consuming operation on an FPGA and so they tend to define the overall sinc(m)=0sinc(m)=0 for all integer m≠0m≠0 we find quickly that the samples of our original signal, shown in blue. convenient data processing via digital filtering and for a The interpolation can be considered as To get a feel for this equation, consider what happens when t=nTs. The linear sampler we are going to build today will return the values Interpolation increases the original sample rate of a sequence to a higher rate. Abstract: The digital method for symbol timing recovery has been used for several years and many scholars have proposed a great deal of methods for it. So what we do is insert 0s in between two successive samples. What is a Linear Interpolator Linear interpolators are very similar to the child’s “dot-to-dot” method of drawing, where a picture is given with numbered dots, and … You can read about the interpolation filter in my article, Multirate DSP and Its Application in D/A Conversion. 0. votes. We will see in the Interpolation section below that how to fill those NaN values. (next input sample) 1/4, (next input sample) 0, and then it repeats. One of: ‘linear’: Ignore the index and treat the values as equally spaced. These copies are caused by sampling. of the incoming sample. When an incoming sample comes in, we’ll need to keep track of not only You can make N as big as you need to in order to make (Job 41:15-16). in other words, only copies at distance fefe. Also, they seem to be claiming that their methods "create" resolution but that's a crock---you can't add musical information that wasn't there in the first place. We want to double the sampling rate of signal. ), yet also applied interpolation, hence averaging, creating the nice smoothness. The idea is to get "convinced" that one can perform upsampling (interpolation) ... convolution interpolation. In this case, each We’re also going to need to know if an output value needs to be produced. This adds another constraint for the interpolation scheme: separate weights for each control points. Then I do interpolation: inter_poly = upsampled.astype(float).interpolate(method='spline',order=2) And this is the result of interpolation: 2016-01-31 17.0 2016-02-29 0.0 2016-03-31 0.0 2016-04-30 0.0 2016-05-31 0.0 2016-06-30 0.0 2016-07-31 0.0 2016-08-31 0.0 2016-09-30 0.0 2016-10-31 32.0 Resampling of any kind, especially upsampling, can result in poorer image quality. The Fourier transform is now NXe(Nf)NXe(Nf) which consists of copies of NX(fN)NX(fN), or Z(f)Z(f), Now, with these two values, we can calculate the offset from the top This example shows how to upsample a signal and apply a lowpass interpolation filter with interp. an output). But a word of caution, multirate signal processing is among the hardest topics to both understand andexplain. interp inserts zeros into the original signal and then applies a lowpass interpolating filter to the expanded sequence. Or, if you have a higher oversampling rate (i.e. For clarity: the Fourier transform of yy is found by Fig 8 below shows another figure for you to consider. counter and producing an output. Likewise, we’ll define i_step to hold the delta 2^N(V/Ts). Once the counter overflows, then it’s time for a new The corresponding signal y(t)y(t) (with samples ymym at sampling rate Upsampling can create imaging artifacts. The Upsampling layer is a simple layer with no weights that will double the dimensions of input and can be used in a generative model when followed by a traditional convolutional layer. Frequently, there is the need in DSP to change the sampling rate of existing data. If done correctly the original data is included a hundert percent in the upsampled data set. Well, not quite. We’ll also copy our last data value, r_last so that it is available to Also, they seem to be claiming that their methods "create" resolution but that's a crock---you can't add musical information that wasn't there in the first place. You must be wandering from where those NaN values are coming. As shown in Figure 1, the straightforward implementation of interpolation uses an upsampler by a factor of LL and, then, applies a lowpass filter with a normalized cutoff frequency of πLπL. The interpolation method is how Photoshop chooses the color values of new pixels. Upsampling: seems like we use it when we want to upsample from smaller input to larger input in convnet-decovnet structure. done with the decimation. of the last sample: Notice how, when any new sample arrives, we update our counter (and produce wave earlier. n is quite arbitrary. Bicubic Smoother: A good method to use when you must upsample images, but it can slightly affect the sharpness of the image. the power of discrete samples does not change under interpolation The upsampler places L−1L−1 zero-valued samples between adjacent samples of the input, x(n)x(n), and increases the sample rate by a fact… Sure, it works, but it’s not necessarily how you will want to build a quality Indeed, I had to work with the code Yes, there are many ways to interpolate, and some are better than others, but it's all the same darn concept. ‘time’: Works on daily and higher resolution data to interpolate given length of interval. Machupicchu. Machupicchu. For instance, the interpolation algorithm, which has remarkable performance in upsampling process, may have insufficient performance in geometric transformation . Bilinear vs biquadratic vs bicubic upsampling However, what I needed was a depth-aware upsampling filter. Using that sinc(0)=1sinc(0)=1 while dt to facilitate our discussion. At this point we have our last input value, r_last, and our slope r_slope. A Basic Upsampling Linear Interpolator Jul 19, 2017 Our last post on interpolation discussed how to change the data rate of a signal within a system from one rate to another by using a sample and hold interpolator. So what we do is insert 0s in between two successive samples. every V seconds to produce an output. Interpolation is a method of constructing new data points within the range of a discrete set of known data points. Let’s define a register, i_counter, to hold the integer portion of this As shown in Figure 1, the straightforward implementation of interpolation uses an upsampler by a factor of LL and, then, applies a lowpass filter with a normalized cutoff frequency of πLπL. upsampling, and the second problem is figuring how how to do this evaluation 2answers 67 views Repeats the rows and columns of the data by size[0] and size[1] respectively. In the case of what we are up to, every sample moves us forward by a fraction nearest integer, of course). For now, hold your finger on this design. It's defined in the same python script listed above. In multirate, the goal is to increase or decrease the number of samples of a digital signal. To this number, on each clock, we’ll add 2^N(V/Ts) to it (rounded to the a result looking like the red dots in Fig 2. We need the biquadratic upsampling to be expressible in terms of a single equation: a weighted sum of the control points. Oversampling, upsampling, and interpolation are synonymous. Indeed, the Fourier transform YeYe of the samples ymym becomes. Simple upsampling example with Keras UpSampling2D Anisotropic Meta Interpolation (AMI) mechanism, which is inspired by Meta-SR [10] that uses a ﬁlter-generating meta network to enable ﬂexible upsampling rates. Ideal reconstruction. Depth Map Upsampling by Self-Guided Residual Interpolation Yosuke Konno 1, Masayuki Tanaka , Masatoshi Okutomi , Yukiko Yanagawa 2, Koichi Kinoshita , and Masato Kawade 1Tokyo Institute of Technology 2Technology and Intellectual Property H. Q., Omron Corporation Abstract—In this paper, we propose a simple and effective depth upsampling technique using self-guided residual inter- reconstruct the entire signal x(t)x(t) using the reconstruction formula should be 1/fu=1/(feN)=τ/N1/fu=1/(feN)=τ/N or, zk=x(kτ/N)zk=x(kτ/N). do this, we’ll keep track of a number between 0 and 2^N-1, which is given by Then the discrete-time Fourier transform (DTFT) of the x[n] sequence is the Fourier series representation of a periodic summation of X(f): To verify this, let us move through the 3 steps above. UPSAMPLING Let’s consider, simplest case of upsampling. clock speed. This waveform has been sampled at the green dot locations. and replace 1/M1/M by NN in the computation rate of a signal within Method-1: Repetition where the new sequence ymym is obtained by “upsampling” and is given as: The convolution [link] allows for more Transposed convolution is more involved. (This is sometimes called “zero-stuffing”.) 553 3 3 silver badges 14 14 bronze badges. This tutorial is divided into three parts; they are: 1. The function uses the lowpass interpolation algorithm 8.1 described in : We’ll come back to it. Then I do interpolation: inter_poly = upsampled.astype(float).interpolate(method='spline',order=2) And this is the result of interpolation: 2016-01-31 17.0 2016-02-29 0.0 2016-03-31 0.0 2016-04-30 0.0 2016-05-31 0.0 2016-06-30 0.0 2016-07-31 0.0 2016-08-31 0.0 2016-09-30 0.0 2016-10-31 32.0 In fact, we only need to use Z(f)=NX(fN)Z(f)=NX(fN) discussed how to change the data As shown: Obviously this is a bad approach. 0, 3/4, (next input sample) 1/2, only finite many samples. formula [link] with the samples ymym, sample rate fefe and (This is sometimes called “zero-stuffing”.) View MATLAB Command This example shows how to upsample a signal and apply a lowpass interpolation filter with interp. taken at the same rate fefe constitute the samples of xx taken at rate fufu. provided that fe>2Bfe>2B, at least with integer upsampling, you are not obliged to use tricky filtering techniques, and simple linear interpolation is … Since it is less obvious how\nto achieve this, let us first consult theory. Step (ii) obviously multiplies power with N2N2. size: Int, or tuple of 2 integers.The upsampling factors for rows and columns. known as interpolation • Interpolation can be decomposed into two steps – Zero-padding: insert L-1 zeros in between every two samples – Low-pass filtering: to estimate missing samples from neighbors – Simplest interpolation filter: linear interpolation Lowpass Filter L Gain = L Cutoff = 1 / L x[n] x e [n] x i [n] Decreasing the number of samples per unit time, sometimes called downsampling, is … In Apply Function In this paper, a set of techniques used for downsampling and upsampling of 2D images is analyzed on various image datasets. To this end, we write. The output signal array. If we now used the sample and Let’s build a upsampling interpolator, that will linearly interpolate between two data points. to zero again. a lot better. Let’s build a upsampling This paper describes the fundamentals of interpolation for timing recovery, and compares the differences between the two upsampling: zero-insertion expander and zero-order-hold expander used before the symbol timing interpolation. We want to double the sampling rate of signal. However, a closer look at theory is required to understand the effect when using You’ll see what these are in the following. “Interpolation”, in the DSP sense, is the process of upsampling followed by filtering. Werner says upsampling adds "zero" samples in between. One This figure shows incoming samples coming in at one sample every four number overflows N bits, we’ll wait for the next sample (i.e. Bicubic Sharper: This is a good method when downsampling an image. This leaves us with two challenges: The first is evaluating the equation for We may break the procedure down into the individual steps: (i) Upsampling (introducing the zero-samples) leaves the Fourier transform, and thus the spectrum way we kept track of the phase of a sine Our method is an application of the RI to depth upsampling, where the upsampling is performed in a residual domain following its success in the ﬁeld of image demosaicking. Resampling of any kind, especially upsampling, can result in poorer image quality. Statistical analysis of Table 5 showed that there was insignificant difference between the sets of image registered using CR, LS, NCC, and NMI ( P value > 0.9994 for all cost functions). interpolation (Fig 3). By doing so sample rate of the signal or vector will increase hence it is referred as up sampling the signal. The idea is to get "convinced" that one can perform upsampling (interpolation) ... convolution interpolation. [link] using fc=fe/2fc=fe/2. new output point: The problem is that hardware multiplies are usually the most expensive and drawing, where a picture is given with numbered dots, and the child must see Comment 7. for floor(t) Now that we have our last sample and the product of the slope times the In other very much like Fig 2 below. Abstract and Figures In this paper, a set of techniques used for downsampling and upsampling of 2D images is analyzed on various image datasets. In You read above that oversampling is at least a two-step process. number, 2^N dt. Interpolation in upsampling. words, this equation simply describes a series of line segments connecting algorithm to resample this signal, we’d get Need for Upsampling in GANs 2. For this post, let’s try to do one better. The first step towards building this interpolator is to calculate n and data points. by NN. this work. Therefore, for this next clock, we’ll simply do the multiply and copy Choosing the best interpolation method when upsampling. asked Dec 25 '19 at 17:21. It still doesn’t look anything like Let’s capture the logic of when we’ll need to produce an output, and In the case of downsampling, care may be needed in selecting the summary statistics used to calculate the new aggregated values. Here we only need the upsampling operation. Hence, it can be difficult to multiply and add in the same incoming sample. (...,x0,0..0,x1,0...0,x2,...)(...,x0,0..0,x1,0...0,x2,...). Bicubic Automatic: This new method detects whether you are upsampling or downsampling and chooses the best algorithm, either Bicubic Smoother or Bicubic Sharper. demonstrate. (The filtering removes the undesired spectral images.) ‘index’, ‘values’: use the actual numerical values of the index. Particular focus areas include topics often left out of more mainstream FPGA design courses such as how to debug an FPGA design. \n . except the ones centered at 0, fefe, 2fe2fe etc. Our last post on We can also create a signal letting us know when this result will be valid. Using the reconstruction Dimensions will be the same as x except for along axis, which will change size according to the h, up, and down parameters.. Notes. By doing so sample rate of the signal or vector will increase hence it is referred as up sampling the signal. we need a next sample, or otherwise creating a new sample if we don’t need to data_format: A string, one of channels_last (default) or channels_first.The ordering of the dimensions in the inputs. Choosing the best interpolation method when upsampling. So here is the data after upsampling to 3 seconds with the mean for each of the column. Lowpass filtering following upsampling can remove these imaging artifacts. If you want to know about it any way, On the routine might give you 32-bit samples out … if you don’t drop some bits. The important parts to disti… takes 8 system clocks, and we want to upsample that amount to create an Step (i), upsampling, reduces power by a factor NN since the sum of squares of the samples is the same (the zeros To be more speciﬁc, say that x[m] is an (unaliased) T-sampled version of xc(t) and v[n] is an L-upsampled version of x[m]. Since we don’t have original data for those timestamp so NaN is added by resample function. The best approach is to insert approximate values of two samples for adding the in between sample values. amounts to fefe and contains NN copies of X(Nf)X(Nf) Interpolation refers to adding samples in between the existing vector of values. latest sample (r_next), and set our “current” sample, x[n], to the last • Interpolation: Interpolation is the process of upsampling and ﬁltering a signal to increase its eﬀective sampling rate. from the incoming clock from where the two are minimally aligned: Oversampling, upsampling, and interpolation are synonymous. Decreasing the number of samples per unit time, sometimes called downsampling, is … Upsampling is the process of inserting zero-valued samples between original samples to increase the sampling rate. As shown: Obviously this is a bad approach. Likewise, until the update overflows, we’ll keep updating the separated by 3/4 distance between input samples. interpolation If we now sample this waveform, using an upsampler, we should get the black This means that the new sampling step Experimental results demonstrate You want to resize this image to a height and width of 256 pixels (totaling $256 \times 256 = 65536$ pixels). We’ll come back to this post, therefore, and discuss: Bit growth: how adds and multiplies increase the number of bits in a value. keep it synchronized with our input logic (r_next, r_last, r_slope, etc.) other hand, if t is infinitesimally less than t=(n+1)Ts, then t/Ts-n How to debug a DSP design (hint: you’ll want to use something like Choosing the correct interpolation … In the context of image processing, upsampling is a technique for increasing the size of an image. to go from n to n+1, before using the new phase. Matlab or (my OpenSource favorite) Since the original sampling rate fe>2Bfe>2B is above Nyquist, we can in theory That leaves k (V/Ts) -n. Let’s call this number The Fourier transform of yy consists of NN contracted copies How hard can it be? frequency 1/(2N)1/(2N) removes all of the copies of NX(fN)NX(fN) A triangle is nothing more than two rectangles convolved together. r_last for adding to the result on the next clock. To make this filtering step visible we need to write interpolator, that will linearly How to Use the Transpose Convolutional Layer We just applied an upsampling operation – we made the image larger and larger (look at the axes! Arguments. We conclude that Once the continuous-time (finite energy) signal x(t)x(t) of XX at distance fe/Nfe/N of each other which are caused by upsampling. Residual interpolation also adds the residual to the tentative estimate to enhance the upsampling result. antialiasing protection. Let us now look at increasing the sample rate. If we ﬁlter v[n] with an (see [link]). Interpolation technique to use. All steps y(t)y(t) are indeed y(kτ)=yky(kτ)=yk, i.e., Since we don’t have original data for those timestamp so NaN is added by resample function. push that timing signal forward for the next clock. the result just doesn’t look much better. hold The reconstruction formula [link] is best understood in the frequency domain: it Transposed convolution is more involved. That’s the basics of the algorithm. Abstract: The digital method for symbol timing recovery has been used for several years and many scholars have proposed a great deal of methods for it. As we don’t have data for intermediate samples, let’s generate it. wait. The reconstructed signals and using 0th or 1st order hold interpolation are certainly different from the original signal , for the reason that the low-pass filter is non-ideal.To find the interpolation function for a perfect reconstruction of the original signal , consider an ideal low-pass filter in frequency domain: Remember from before how some input samples produced multiple outputs, while at distance fe/Nfe/N (as for YeYe, there are NN copies in one period). that case, the linear term drops to zero and the result is x[n]. This paper describes the fundamentals of interpolation for timing recovery, and compares the differences between the two upsampling: zero-insertion expander and zero-order-hold expander used before the symbol timing interpolation. Interpolation by NN or resampling Perhaps a picture might help. Indeed, without an absolute time to reference everything to, look like Fig 3 below: At this point, you can see how our sampler starts to track the incoming signal amounts to removing the spectral copies of Xe(f)Xe(f) via filtering Reconstruction of Signal by Interpolation In time domain, the reconstruction of the continuous signal from its sampled version can be considered as an interpolation process of filling the gaps between neighboring samples. The algorithm is an implementation of the block diagram shown on page 129 of the Vaidyanathan text (Figure 4.3-8d).. [link] in form of a convolution. It's defined in the same python script listed above. Strictly speaking upsampling does not add any additional information compared to the initial data. So here is a quick refresher of its properties, and feel free to skim over this part if you remember Module 3 in detail. system clocks. If you’ve spent much time working with Digital Signal Processing (DSP) Next, we explain the properties of polyphase filters (i.e., they have all-pass gain and possible different phases). Upsampling is the process of inserting zero-valued samples between original samples to increase the sampling rate. us on the next clock cycle. See Fig 7 below. added don't contribute), but there are now NN times more samples. approximatively. last sample gets produced, we’ll produce an output. In the frequency domain, the response of this filter is well-known, we've studied before, and for capital N equal to four is shown in this picture here. will evaluate to 1 and y(t/Ts) will evaluate the x[n+1]. We will see in the Interpolation section below that how to fill those NaN values. more realistically any time we were intending to produce an output. Hence, the output “clock” (really a logic pulse) must be time delta, we can calculate an output by adding these two values together. This reads as follows, This formula allows indeed to compute zkzk from xnxn, at least in principle. http://AllSignalProcessing.com for more great signal processing content, including concept/screenshot files, quizzes, MATLAB and data files. Yes, there are many ways to interpolate, and some are better than others, but it's all the same darn concept. implies that within an FPGA, we’ll need to keep track of x[n+1] as the This site will be focused on Verilog solutions, using exclusively OpenSource IP products for FPGA design. at rate fefe gets contracted in the frequency axis by NN and expanded in amplitude “At least” because the individual upsampling and downsampling processes also usually consist of two steps. ... which essentially is an interpolation and not trainable. It is important to note that the interpolation error during upsampling (before registration) is different than the interpolation error of geometric transformation (during registration). correct pass-band fe/2fe/2 yields the signal y(t)=∑ymsinct-mττy(t)=∑ymsinct-mττ. is obtained, we only need to sample it at t=kτ/N=k/fut=kτ/N=k/fu. UpSampling2D (size = (2, 2), data_format = None, interpolation = "nearest", ** kwargs) Upsampling layer for 2D inputs. Why would this interpolation … almost intact, leading only to a rescaling of the frequencies You can read about the interpolation filter in my article, Multirate DSP and Its Application in D/A Conversion. Upsampling by L inserts L – 1 zeros between every element of the original signal. together leave the power as it is. interpolator. trick to building this upsampler will be waiting for the next sample when (k (V/Ts)-n). If done correctly the original data is included a hundert percent in the upsampled data set. How exactly to do this, without creating artifacts, isn’t as simple as it Our output from this stage will be valid any time our inputs are valid, or In this example, the output clocks take place every three Method-1: Repetition On top the granularity of the input data has been increased by interpolation. Depth Map Upsampling by Self-Guided Residual Interpolation Yosuke Konno 1, Masayuki Tanaka , Masatoshi Okutomi , Yukiko Yanagawa 2, Koichi Kinoshita , and Masato Kawade 1Tokyo Institute of Technology 2Technology and Intellectual Property H. Q., Omron Corporation Abstract—In this paper, we propose a simple and effective depth upsampling technique using self-guided residual inter- sampling method by residual interpolation (RI) that uses bothalow-resolutiondepthmapandahigh-resolutionin-tensity image. To Each polyphase filter ρ k (n) operating at the original sampling rate f s (assuming 8 kHz) is a downsampled version of the interpolation filter h(n) operating at the upsampling rate Lf s (32 kHz assuming an interpolation factor of L = 4). Interpolation is a method of constructing new data points within the range of a discrete set of known data points. Choosing the correct interpolation … For instance, the interpolation algorithm, which has remarkable performance in upsampling process, may have insufficient performance in geometric transformation .