# Tagged Questions

This is for reducing the amount of data required to store a signal, whether lossy or lossless.

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### Data reduction for a data collected from micro controller?

I have been given a project where I have to collect data reduce its size and send the data via bluetooth to some other storage. At first I thought it is simple data compression and used zlib and ...
63 views

### What would produce this “hamburger” corruption on images?

I have an image that has gone through an unknown number of jpeg and webp conversions (at least one but more likely 2+). Currently this image is a JPEG and contains corruptions in single color or mild ...
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### Arithmetic coding for compression of sensor data [closed]

I have been trying to compress sensor output and then regenerate it back using PCA method from which i obtained the principal components of the sensor data(sensor data here refers to any data measured ...
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### Compression Ratio in ECG compression using Wavelet Decomposition

I have compressed and reconstructed an ECG signal using Wavelet Coefficient. In compressing part, many of Wavelet Coefficient have set to zero. for example, if in original ECG, 5000 wavelet ...
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### Is DCT (Discrete Cosine Transform) of Type-2 lossless or lossy?

As I know, in general, the DCT is lossless. But I'm not exactly sure about Type-2 of DCT. Is it lossless or lossy?
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### 8*8 block matrix in JPEG image compression?

In standard JPEG format of a image, Discrete Cosine transform is used. But instead of applying the transform on whole image, we first divide the image in 8x8 block and apply transform on each of them. ...
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### Low-rank approximation of the STFT matrix : good audio compression technique?

I recently heard about this interesting math tool: With a matrix $A$, compute the SVD ($A = U \Sigma ^tV$ factorization, where $\Sigma$ is a diagonal matrix containing the "singular values") Keep ...
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### Selective image compression?

Forgive me if this is the wrong site for this question. Here's my problem: I am creating a game where players have to search for a hidden detail within the overall image. I downloaded an 11MB ...
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### Compressed Sensing vs Common Compression Approaches

I have a very basic question regarding common compressing approaches. Often, I have heard something like "The problem in our common way to compress data is, that we have to acquire a huge number of ...
113 views

### Compare between JPEG and JPEG2000

JPEG image compression is Fourier based DCT while modern image compression technique like JPEG2000 is based on more multi-scale technique like Wavelets.I want to know how Fourier and Wavelets are ...
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### Will lossy compression prevent me from performing audio analysis?

I'm starting a project where we will have to analyze bird recordings. We will try to measure the birds activity using the audio. The recordings are really long (around 24 hours each) and recorded in ...
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### Decompose an image into better compressible components

Our team develops an application that, in some feature, connects to a scanner (via TWAIN or WIA) and scans a document, and makes a PDF file out of it. The application is mostly used to process mail or ...
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### Why doesn't JPEG use 1D DCT for image compression?

I know that JPEG uses 2D dct and splits the images in 8x8 blocks. Why doesn't it simply split the image in one-dimensional vectors in $\mathbb{R}^{64}$? Wouldn't it simplify the math? My guess is that ...
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### What does the word Entropy refer to in Entropy encoding

I have come know of Huffman and Arithmatic encoding that try to curtail redundant data and thus compress data. Why are they called Entropy encoding? What does that mean? Why not just call them ...
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### Linear Predictive Coding and Block Size

I'm experimenting with linear predictive coding as a low-complexity audio compression method, and I'm observing something very odd. I'm compressing a 20 MB mono 16-bit PCM song in different block ...
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### Low-Complexity Audio Compression?

What options exist for discrete audio compression that is good quality, moderate compression (e.g. 3+:1), and low complexity (e.g. hundreds of processing cycles to encode each sample without the use ...
112 views

### How is data compression possible for audio?

I understand that compression works by exploiting certain psycho-acoustical characteristics of our auditory perception, but I'm still confused. I mean ultimately, the waveform must be recorded ...
286 views

### Audio compression with STFT

Let STFT[frame, freqbin] be the short-time Fourier transform of some audio data. (here frame is the index in time, and ...
365 views

### Difference between jpg compression and mp3 compression

My understanding of jpg compression is that, if done repeatedly, any image will eventually be reduced to a single flat color, due to the way it deals with neighboring pixels. However, years ago I was ...
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### How is compression ratio related to number of dct coefficients

Lets say we have a picture with 6bits/pixel and we use discrete cosine transform with 8x8 blocks of pixels and each coefficient is 8 bits. We can use 2 8x8 masks, a zonal mask A and a zonal bit ...
182 views

### Compressed/compressive sensing, sensor placement

I have a beam fixed at one end and free at the other. It obviously results in vibrations due to the disturbances in the environment or when induced. This system can be represented using a differential ...
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### Error bounds in signal compression represented by truncated Moore-Penrose biorthogonal bases using von Neumann wavelets

I was reading and trying to reproduce the results in the arXiv preprint of Periodic Gabor Functions with Biorthogonal Exchange: A Highly Accurate and Efficient Method for Signal Compression by Asaf ...
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### Limitations of Arithmetic coding?

I have been working on an assignment for university in which I have to compress an 80K message consisting of only two symbols, 'a' and 'b', having probability values of 0.6 and 0.4. I have ...
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### Recovering eigenvalues from singular values [closed]

I am dealing with a problem similar to principal component analysis. Aka, I have a matrix and i want to recover the 'most efficient basis' to exaplin the matrix variability. With a square matrix these ...
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### Sampling from a distribution with arithmetic coding

I'm struggling to implement a sampling scheme where arithmetic decoding is used to generate the samples. This is based on excercise 6.3 from David MacKay's book, where you compare rejection sampling ...
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### Signal quality metric

I have floating point data signal. I apply lossy control to it and I need some kind of metric to determine its quality. In image processing, there is PSNR (or MSE). I tried to use the same for it, It ...
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### What are some techniques to recover an original image from three different compressed versions?

This question is theoretical. Let's say you have three different highly compressed images of a same source image, each compressed with a different algorithm and thus "lossy" in different ways. What ...
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### Usage of Digital Cosine Transform in lossy compression of images

I was reading about Digital Cosine Transform (DCT Type-I) and it's use in JPEG. I have the following doubt. My teacher offered an explanation which wasn't very convincing. What property of Digital ...
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### How does Golomb-Rice Coding work?

I've read the explanation in http://urchin.earth.li/~twic/Golomb-Rice_Coding.html and http://en.wikipedia.org/wiki/Golomb_coding , however, I still not get the intuition why it is efficient and when ...
490 views

### Audible mp3 artifacts?

What kind of compression artifacts would typically be most noticeable to a non-audiophile listener in a low-bit rate mp3 (MPEG-2 Layer III) compressed audio file? What kind of audio signal might one ...
3k views

### What are some typical lossless compression ratios?

A client was trying to send me 250 GB worth of files. After attempting various ways of sharing the data, he sent me a zipped folder only 4 GB in size. That sounds like too much compression to me--I ...
493 views

### change the frequency component of a spectrum in an audio file

I am working on an audio dynamic range compressor using Matlab. After calculating the FFT of the audio file, I use several bandpass filters to amplify specific bands separately. What I want to do then ...
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### Exam Question - end-to-end delay from video capture to video playout

Hi I'm preparing for my exam tomorrow and I've come across a 17 Mark question which seems trivially easy, so I think I'm missing a key point giving the rest of this exam is fairly difficult. The ...
1k views

### Speech Compression - In LPC how does the linear predictive filter work on a general level?

Hi I'm taking a multimedia systems course and I'm preparing for my exam on tuesday. I'm trying to get my head around LPC compression on a general level, but I'm having trouble with what is going on ...
620 views

### Theory behind Linear Predictive Coding (LPC)

What is the theory behind LPC? Why are(were) certain implementations of LPC said to be more tolerant of transmission or encoding errors quantization than other compressed voice encoding schemes? ...
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### A non-lossy aka lossless codec without patent-restrictions for audio?

The term non-lossy codec means the coding thing having no compression lost, more here. I need such format to process the audio, without destroying the quality. ...
261 views

### Compressing plotted data with variable sample rate?

I'm currently plotting high sample rate data by down-sampling by a factor and averaging. Most of the time this is working ok, but I am aware that at very low zoom levels (zoomed right out) the ...
294 views

### Determining the resulting pixel value before creating a compressed JPEG image

Is it possible to determine the resulting pixel values and modify them before the compressed jpeg image is actually created? For example, I'm at the stage where I already have the quantized DCT ...