Questions tagged [compression]
This is for reducing the amount of data required to store a signal, whether lossy or lossless.
122 questions
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Does Stereo mode use the bandwidth more effectively than Dual Channel mode in SBC codec?
If an earbuds can accept a maximum of 1 Mbps bandwidth connection for audio, can Stereo mode (not Joint Stereo) use the bandwidth more effectively and produce higher audio quality than Dual Channel ...
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How does the first step of vocoding actually compress the vocals?
I only recently learned of the use of the vocoder as a vocal signal compression technique. However, I'm having trouble understanding how it actually reduces the size of whatever goes in. If I think of ...
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Optimalty of Gaussian Information Bottleneck under linear transformations
I have a question regarding the solution of the Information Bottleneck (IB) method in the Gaussian setting.
Suppose $(X, Y)$ is a pair of random variables jointly distributed according to a ...
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How to decode the source coding, like Shannon Coding, Shannon-Fano coding, Huffman coding?
I would like to ask you guys how to decode the source coding in telecommunication? I learned that at the Transmitter side, the Transmitter will use the source coding such as Shannon coding, Shannon-...
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Why does the DCT-II have better energy compaction than DCT-I?
I have some code to take coefficients of a signal with one of the DCT variants, then reconstruct with the inverse transform in this notebook.
I'm seeing I can reconstruct a signal with better fidelity ...
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Will open, edit, store from/to lossy audio format significantly degrade quality?
Say I have files only available as "ogg vorbis", 44.1kHz at 128 kbps vbr - which are meant for archival, but not much storage for lossless was available at the time.
These are to be kept for ...
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Is there a computable operation that minimizes entropy?
I have recently experimentally learned that decorrelation does not necessarily imply good compression, but good compressions have the effect of data decorrelation.
Since I cannot use autocorrelation ...
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How should I go about completely decorrelating a digital signal?
So I'm working on real time signal compression, and I need to come up with the best convolution to minimize the entropy of incoming data (which I will then compress), which I understand is achieved by ...
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What exactly is transmitted in the channel in lossy compression?
Consider the problem of lossily compressing a memoryless binary source $X
\sim \operatorname{Bernoulli}\left(\frac{1}{2}\right)$ at target Hamming distortion $D < \frac{1}{2}$. According to the ...
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Distortion-Rate function for standard Gaussian signals quantized with a uniform alphabet
Let's say $X \sim N(0, 1)$ is a standard Gaussian input signal and $Y \sim U\{y_1, y_2, \cdots, y_{16}\}$ follows a discrete uniform distribution (in fact, $\{y_1, y_2, \cdots, y_{16}\}$ is a ...
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implement gradient descent with sparsification algorithm
I am trying to implement the algorithm in this paper for finding a sparse vector x that minimizes the square error $\lVert y − \Phi x\rVert_2^2$ where $\Phi$ need to satisfy the restricted isometry ...
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Compress filter coeficients?
if we have a FIR with 100 coefficients, is there a method to "compress" the length? so for example, have a similar response with 50 coefficients?
I am ok with the response degrading within ...
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OFDM complex symbols have dynamic phase shift after the fft-block & before the BPSK demodulator at the receiver ,
I have transmitted and received an OFDM-signal using the same ADALM-Pluto-SDR's Tx/Rx Antenna.
I have used BPSK baseband modulation with symbol freq=312.5 KHz, L (length of ifft)=64, fsampling=fsym*L=...
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What is the rationale for division by 8 during ADPCM audio compression?
I am studying ADPCM and while I understand the concept I cannot find an explanation for some of the calculations in available implementations such as the one outlined here:
...
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Can JPEG XR be used for compressing binary images?
I am trying to compress some binary images i.e. images with bit depth equal to 1. For JPEG-XR encoder I used jxrlib but it is not able to compress the image. I am using specified format bmp.
Even ...
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DCT - Measures of energy compaction gain achieved using DCT over FFT
The discrete cosine transform(DCT) is a popular choice for spectral analysis in audio, video, image compression algorithms. This is primarily due its efficient "spectral compaction" property ...
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Why does MP3 use modified DCT?
I read on Wikipedia MP3 that the MP3 standard uses a modified discrete cosine transform.
Why does it use a modified transform and not the original DCT like the JPEG standard? Are there reasons ...
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Lower bound on information or entropy?
Inspired by this question: Does a simple photograph contain more information than a complex painting?
Say that I have a discrete representation of some physical object - eg an image file. What is the ...
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What are some approaches / algorithms for reducing size of numerical data of large size with redundancies?
I'm dealing with bunch of .asc(ascii) files that are the output of continous monitoring of various electronic equipments for certification purposes. We monitor various parameters of the equipments ...
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Huffman coding of a non-dyadic probability distribution
Wikipedia:
Huffman coding is optimal among all methods in any case where each input symbol is a known independent and identically distributed random variable having a probability that is dyadic. ...
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How is this Huffman tree converted into electric voltages?
This is the Huffman tree for word "stackexchange":
How is this Huffman tree converted into electric voltages?
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What happens when you read and save the same JPEG image again over and over?
This question is mostly related to jpeg compression and expected results when you read and save the same jpeg file several times.
Let's say you have read an uncompressed image (originally it has never ...
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How to build the measurement matrix used for compressive sensing
I have a sparse vector $x \in \mathbb{R}^{N \times 1}$, it's real and positive, the non-zeros values are maximum $N/2$ values. It means, I have at least $N/2$ zeros values in $x$.
My question, is it ...
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Evaluate two lossy compression algorithms
I am trying to evaluate several methods to compress some 2D data points. The algorithm itself is not relevant, but from the output, I can compute the MSE and the number of points (which can be used to ...
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Are common formats and encoders of lossy audio compression idempotent?
That an action is “idempotent” means if you do it several times, the effect is the same as if you do only once.
Lossy audio compression by definition loses information. Even if you convert it back to ...
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How use of small blocks allows in description of high frequencies with less cosine terms?
I am studying mpeg compression.
Sources-:
https://homepages.inf.ed.ac.uk/rbf/CVonline/LOCAL_COPIES/AV0506/s0561282.pdf
https://fdocuments.net/document/video-compression-techniques-55849f2b11fba.html
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Arithmetic Coding for Blocks of Images
I try to understand that how to use arithmetic coding on images. For this, I code on MATLAB. I tell my understanding for arithmetic coding. If I misunderstood to this algorithm, please correct me. ...
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do audio compression algorithms encode channels in parralel?
I'm looking to compress multiple mono sound tracks together, as one track (with loads of channels), however, I was wondering if this is stupid - because I may lose out on real compression, as these ...
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Which Audio Codec/Bitrate Relationship delivers best Audio Quality: 128 kbit/s MP3 vs. 192 kbit/s AAC vs. 64 kbit/s OPUS?
Assumed we have those three audio streams available for listening to:
MP3 with a bitrate of 128 kbit/s
...
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using Huffman coding to understand an daily incident
Yesterday, I went hiking with friends who are all studying the same electronic engineering degree with me. During the hike, we talked about female classmates within our degree. Since there are only ...
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Input data for compression algorithm
I want to implement the algorithm from the paper DhyaaAlrahman Latef Thajel1, Kadhim Mahdi Hashim1 - A New Technique for Data Compression. However in section 3.1.1, it says that it needs a binary ...
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Where is truncated-SVD image compression actually used?
What are some instances of real-world sensors, cameras, filetypes, or datasets whose image compression method is (at least mostly-based on) the truncated-SVD?
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Audio, estimate codec's compression ratio only by content
I am about music audios.
These can be compressed by different formats with different degree.
(I.e. I don't mean the dynamic compression).
After being compressed by a large degree (say 96kbps mp3)
the ...
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Reduce signal length while maintaining properties?
I am new to DSP.
So I have a noisy signal with some high-frequency components. I was able to characterize the statistical properties of this signal through a gaussian distribution. My aim is to run a ...
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What is the relationship between image entropy and LZMA compression?
I've got some pictures which i want to compress by using LZMA algorithm in Python. I'm using this implementation.
I've tried to measure the entropy of an image by using skimage.measure.shannon_entropy
...
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What is facebook's image compression algorithm?
For a project I'm working on (master thesis), I need to figure out what is facebook's image compression algorithm.
The goal: to be able to mimic facebook's image compression locally (using python).
...
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Why do we use compression for discrete siganls?
Time compression/expansion (also called dilation) maps the input discrete signal
$x$ to the output discrete signal $y$ as given by :
$$
y[n]=x[\alpha n]
$$
When $\alpha>1$, the signal experiences ...
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Sparse CWT matrix-shape data lossless compression
Is there a specialized lossless compressor for sparse matrices, i.e. large fraction (>40%) of values == 0? LZ4 worked well on 1D signals, but now whether I feed a sparse 2D or an all-zeros array ...
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Karhunen-Loeve Matlab code
I am trying to learn about KL Transform. I found this code. I am struggling to understand how does [v{m},d{m}]=eig(img_covariance); differ from ...
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Preserve specific information in compressed sensing
I have a signal that isn't perfectly sparse and I would like to apply compressed sensing on it for lossy compression. However I would like to preserve specific section of the signal so that this "...
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Arithmetic coding of images
How does arithmetic coding work with images? I understand how it works with textual messages but I don't understand how it works with images.
So with textual data, we use the probabilities of the ...
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Discrete Cosine Transform
Is this piece of text (written by me) true about Discrete Cosine Transform ?
Discrete Cosine Transform (DCT) is a lossy data compression algorithm that is used in many compressed image and video ...
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Matching input buffer size to opus frame size
I am working on an audio effect that passes it's input though the opus codec. I want the effect to be a VST, so I don't have control of the input buffer size and the sample rate. However, opus ...
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How is loop information encoded in FLAC files?
I'm trying to convert .wav files (samples for a sampled instrument) into FLAC format. The .wav files have loop information in ...
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audio reprocessing for machine learning
I have a bunch of phone interviews where there is large sound volume difference between two voices in some of the interview audios, because they were recorded only on one side of the phone. May I ask ...
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image compression versus image denoising
Wavelet based image denoising may be performed by thresholding (selecting a threshold value, and discarding all values below the threshold. Wavelet-based image compression may also be performed by a ...
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How to Downsample The Chrominance Components
So I am doing an image compression project for college and am trying to create a visual demonstration of how downsampling chrominance components can reduce the amount of digital information while ...
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What is the exact compression that is happening from the first sequence of raw audio waveform data to the second sequence? [closed]
The first sequence of audio samples is recorded in JavaScript from the browser in mono, PCM format, 32-bit, and 96,000 Hz.
I wrote this audio file as a blob to a server through a JavaScript FormData ...
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Is there something as self-completing data transfer, like Sudoku?
I would like to know, since I am not that knowledgeable in this subject, if this idea is feasible or widely implemented:
If a data package is sent, I know parity-bytes are used to detect errors. ...
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What algorithm generates these "bucket coloring" artifacts?
Context: This is picture (taken with a smartphone*) of a copy of school test. The original answers were in black pencil and the professor made check marks in red.
However, the parts of the answer ...
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