history of coding

Started by RichD in comp.dsp3 weeks ago 9 replies

Recently I attended a coding seminar. The speaker very briefly reviewed the relevant history; first Hamming codes, ~1960: BCH codes, ~1970:...

Recently I attended a coding seminar. The speaker very briefly reviewed the relevant history; first Hamming codes, ~1960: BCH codes, ~1970: convolutional, 1995: polar, 2002: LDPC Clue me in - what was the advance in each case? I worked on a BCH project once, that seemed fairly efficient, how is it, or other algorithms, deficient? -- Rich


Elwyn Berlekamp RIP

Started by Steve Pope in comp.dsp4 weeks ago 2 replies

A few of us had the great fortune to work with Elwyn Berlekamp during our careers. He passed away on April 9, 2019. The most prolific and...

A few of us had the great fortune to work with Elwyn Berlekamp during our careers. He passed away on April 9, 2019. The most prolific and most genius expert on algebraic coding, Berlekamp also contributed significantly to game theory, cryptology, and quant. He was a member of the USA National Academies of both Engineering and Science, recipient of both the Shannon Award and the Hamming M...


Homodyne complex frequency shift

Started by DSP newbie in comp.dsp1 month ago 5 replies

Hi, the input signal is sin(t), I multiply it with cos(t) to get the I component and sin(t) to get the Q component. So...

Hi, the input signal is sin(t), I multiply it with cos(t) to get the I component and sin(t) to get the Q component. So then I(t)=sin(t)*cos(t)=0.5*sin(2t) Q(t)=sin(t)^2 I would expect only the DC component to persist, but instead I have two quickly wiggling waves. What is missing to shift 1kHz to DC without introducing the mirror frequencies? Thanks in advance!


Multiple PDM mic recording

Started by Qe in comp.dsp2 months ago

How to record multiple PDM mics at 16KHz? What is a recommended soundcard/HW that can be used?

How to record multiple PDM mics at 16KHz? What is a recommended soundcard/HW that can be used?


Threshold of hearing compensation

Started by Anonymous in comp.dsp2 months ago 5 replies

There are several new consumer headphone products on the market that allow you to measure your threshold of hearing using an app on your phone and...

There are several new consumer headphone products on the market that allow you to measure your threshold of hearing using an app on your phone and then auto-adjust an equalizer to boost the areas where your threshold is high (indicating hearing loss at those frequencies). I’m no audiologist but this seems suspicious to me; I don’t think having a high threshold is the


magical Black Hole image

Started by Steve Pope in comp.dsp2 months ago 5 replies

The Event Horizon Telescope team of course deserves a huge amount of credit for their results. But it's interesting how they got there. ...

The Event Horizon Telescope team of course deserves a huge amount of credit for their results. But it's interesting how they got there. Here's an article with some non-technical discussion: https://fivethirtyeight.com/features/forget-the-black-hole-picture-check-out-the-sweet-technolog y-that-made-it-possible/ Their data is too noisy to actually create a black hole image. So they a


short pulse generation with DSK6416

Started by farzinalm in comp.dsp2 months ago 2 replies

Hello, I'm trying to generate short pulses with DSP's 32-bit timer. I'm using the DSK6416 board (@1GHz) . I need to have pulse widths as...

Hello, I'm trying to generate short pulses with DSP's 32-bit timer. I'm using the DSK6416 board (@1GHz) . I need to have pulse widths as short as 10ns-50ns and be able to change the duty-cycle. I try to read the CNT register of the timer and set DATOUT to be driven on TOUT pin of timer when the proper width has reached. The problem is that when I use the TIMER_setDatOut API it is not possible...


5-point stencil or Savitsky-Golay for differences

Started by Anonymous in comp.dsp3 months ago 2 replies

I had some code computing the second difference of a sampled signal as (x(n-1)-2x(n)+x(n+1))/(square of interval) I only needed a crude estimate...

I had some code computing the second difference of a sampled signal as (x(n-1)-2x(n)+x(n+1))/(square of interval) I only needed a crude estimate of the second derivative in this case. Then I came across "five point stencils" By this method, the second difference is (-x(n-2)+16x(n-1)-30n(n)+16x(n+1)-x(n+2))/12/(square of interval) And then 5-sample Savitsky-Golay formula, which seems rath...


Efficiency of Midi->Freq and back

Started by MatthewA in comp.dsp4 months ago 2 replies

I'm writing something with a lot of conversions between midi and frequency in a timing tight situation and I'm wondering about efficiency. (in C)...

I'm writing something with a lot of conversions between midi and frequency in a timing tight situation and I'm wondering about efficiency. (in C) What are the community's experiences with this? Would a 1 or 10 cent interpolated lookup table be more efficient? Is there a way to make the log less expensive? Does caching and comparing the last input and output help? Thanks for any insig...


High-order EMA works great - but why?

Started by Piotr Wyderski in comp.dsp4 months ago 3 replies

I have a classic digital PLL with multiplier-based phase detector, intended to lock at 50Hz. The sampling frequency Fs is 25kHz, the...

I have a classic digital PLL with multiplier-based phase detector, intended to lock at 50Hz. The sampling frequency Fs is 25kHz, the loop filter bandwidth varies between Fc=10Hz to 40Hz, as I am experimenting with different filter structures. The PLL itself works like a charm and my reference filter is a 500th order FIR: fir1(500,Fc/(Fs/2)). To a reasonable degree the loop converges to a ...


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