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erdewit

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1 points·by erdewit·3 jaar geleden·0 comments

Show HN: HiFiScan, a Python app to optimize your loudspeakers

github.com
260 points·by erdewit·4 jaar geleden·103 comments

comments

erdewit
·3 jaar geleden·discuss
Isn't this what's used for military applications like AESA radars? If so how come it's open source?
erdewit
·3 jaar geleden·discuss
> If I had a pair of decent speakers and a microphone hooked up to my PC, how would I go about "tuning" the speakers?

Blatant plug: https://github.com/erdewit/HiFiScan
erdewit
·3 jaar geleden·discuss
How the Germans during their Afrika campaign discovered this bacterium to treat dysentery, which was killing more soldiers then the British troops did.
erdewit
·3 jaar geleden·discuss
Elemental iodine in solution with iodide forms tri-iodide, which is perfectly fine to consume. This is what Lugol's solution is and it has an unlimited shelf life.
erdewit
·4 jaar geleden·discuss
I use root to force a 44.1 kHz sample rate for the audio to avoid resampling of my lossless music, which is all in 44.1 kHz. The difference is noticeable even over Bluetooth with aptx(HD).
erdewit
·4 jaar geleden·discuss
For Linux the list is here: https://git.kernel.org/pub/scm/linux/kernel/git/sforshee/wir...

It also shows the maximum power (in mW or dB) for the channels, which is also key to get a good reception. The dB notation is for example (20), which corresponds to 100 mW. Every 3 dB is a factor 2 in power, so (23) is 200 mW.
erdewit
·4 jaar geleden·discuss
> Does this work in encoded videos?

For older encodings such as MPEG2, as used in DVDs, it does work. For newer codecs with higher compression I can't extract a heartbeat signal anymore when using the tool that I've written for that (*).

(*) https://github.com/erdewit/heartwave
erdewit
·4 jaar geleden·discuss
> because a phase-neutral response created in a room is only valid in one point of the room

Author here. The term "phase-neutral" simply means here that the impulse response is symmetrical and doesn't add a phase shift. It doesn't even try to neutralize the phase characteristics of the room, which is what you may be thinking. In fact the phase information from the measurement is completely discarded. Furthermore, the frequency response is averaged to get a more general and robust (less over-fitted) correction that works pretty well across the room. Try it...
erdewit
·4 jaar geleden·discuss
This is dealt with by smoothing the spectrum in a way to preserves the power density. The constructive and destructive interference then cancel each other out.
erdewit
·4 jaar geleden·discuss
My router uses 8 Watt from the mains, regardless of how much traffic it's handling. It also has an ECO mode that doesn't actually lower the power consumption.
erdewit
·4 jaar geleden·discuss
When playing FLAC music over aptX HD, the next step for improvement is to avoid any resampling. The music is generally at 44.1 kHz and the default for Android is 48 kHz. It requires root to change the audio config file to 44100, and it's also necessary to change the bluetooth settings (in the developer options).

Something similar goes for Linux.

The resampling shouldn't matter much in theory, but in practice it's pretty noticeable. It seems to be optimized for CPU usage instead of audio quality.
erdewit
·4 jaar geleden·discuss
For example, the entire entry for "mass formation" was deleted. The Dutch version still exists:

https://nl.wikipedia.org/wiki/Massavorming
erdewit
·4 jaar geleden·discuss
The first 16 GB will still be dual-channel, only the remainder will be single-channel (flex mode).
erdewit
·4 jaar geleden·discuss
What makes Bitcoin a commodity is that nobody can issue more Bitcoin, other then from mining, just like with physical commodities. The market can still be manipulated by the big players but that is besides the point. When more of an asset can be issued (created from thin air) then it is a security.
erdewit
·4 jaar geleden·discuss
Is the TaskGroup really in the 3.11 release though? It's not to be found anywhere in the Python documentation or release notes: https://docs.python.org/3.11/whatsnew/3.11.html

It has been talked about for a long time, probably 4 years now.
erdewit
·4 jaar geleden·discuss
On the photo of the Moskva I can't really see a missile impact.
erdewit
·4 jaar geleden·discuss
It's that the array access of numpy is surprisingly slow compared to a Python list:

  lst = [0]
  %timeit lst[0] = 1
  33.9 ns ± 0.0415 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
  
  arr = np.empty(1, dtype=int)  
  %timeit arr[0] = 1
  73.4 ns ± 0.306 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
erdewit
·4 jaar geleden·discuss
With that much LED light I would be concerned about the high blue peak around 450 nm, it's damaging the retina.

https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC5313540/

https://duckduckgo.com/?q=white+led+spectrum&atb=v310-1&iax=...
erdewit
·4 jaar geleden·discuss
Another great option is to mount the remote file system with SSHFS.
erdewit
·4 jaar geleden·discuss
Other lossy compression methods generally happen in the frequency domain and, depending on the type of music, can introduce audible distortions.

This preprocessor on the other hand throws away some of least significant bits to save data. This increases the quantization noise but has no other sort of artifacts. The quantization noise can be dithered to fall in the higher frequencies (noise shaping) and is generally not perceptible.