codyd51 (u/codyd51) - Readit News

codyd51 commented on Piano Keys mathpages.com/home/kmath0... · Posted by u/gametorch

derriz · a month ago

The geometric relationship between the note frequencies of a C major chord and a D major chord on the piano is not the same. The key of piece is responsible for some of its “feel”. So it’s not unreasonable that they have different “representations” on the piano although the differences may be subtle.

codyd51 · a month ago

I believe this is not the case in today’s ubiquitous equal temperament?

codyd51 commented on Show HN: A simple web game to help learn chords and basic progressions chords.yottanami.com/... · Posted by u/yottanami

jasinjames · 9 months ago

No need for any ML models here, you can "just" do an FFT on a conventional signal and pick out the peaks

codyd51 · 8 months ago

The waveform produced by sounding a note on most physical instruments will often not exhibit a peak, or will not exhibit the strongest peak, on the note being sounded. Rather, most instruments will instead produce harmonic overtones and our brains fill in the gap of the pitch that’s intended to be sounded.

You can still absolutely deduce the fundamental with great accuracy via an FFT, but the approach is a bit more involved. The relevant research area here is called ‘fundamental frequency estimation’.

For an example of this, you can see this app I built that lets you give keyboard and mouse inputs via playing notes on a bass guitar, which are recognized over the microphone: https://github.com/codyd51/offkeyboard

codyd51 commented on Managarm: Pragmatic microkernel-based OS with asynchronous I/O github.com/managarm/manag... · Posted by u/ksp-atlas

mananaysiempre · a year ago

HelenOS[1] is in C and has a GUI. I don’t know how many people participated over its (quite extensive) history.

Axle[2] is a one-man project with a GUI that the author has been gradually transitioning from C to Rust.

Among C++ projects, I think Essence[3] also merits a mention.

[1] http://www.helenos.org/

[2] https://github.com/codyd51/axle

[3] https://gitlab.com/nakst/essence

codyd51 · a year ago

Hi, author of axle here - thank you for the shout out! It’s been a wonderfully fun and enriching project to work on over the years. I’m now working on XNU at Apple, so won’t be working further on axle for the foreseeable future.

codyd51 commented on Does light have an infinite lifetime? bigthink.com/starts-with-... · Posted by u/robertn702

barfbagginus · a year ago

The photino birds want the universe to be populated with white dwarfs, because they can feed off their gravity wells without the risk of deadly supernovas and black holes, which can kill them.

After the xelee and humans leave, the universe becomes a cold place dominated by photino birds living in the cold pinpricks of white dwarfs. Eventually matter evaporates into photons, and the photino birds die.

However, it turns out photino birds can always just time travel to a time when the universe still had matter. So they're more or less indifferent to the eventual heat death .

See: https://xeelee.fandom.com/wiki/Photino_Birds

I hypothesize that there is may be only one photino bird. When it appears to die, it is just traveling to another time. When we see multiple photino birds, we're just looking at different segments of the same bird's world line. These are my own speculations, inspired by Wheeler's idea that the universe has only one electron, which travels back in time as a positron, and interacts with itself so many times that it creates the observable universe of matter:

https://en.m.wikipedia.org/wiki/One-electron_universe

codyd51 · a year ago

One potential hiccup with your one-photino-bird-universe theory (which is quite fun!): I believe I remember a scene in which the ‘birth’ of a photino bird was described. If I remember correctly, it was indeed described as a clone of its parent.

codyd51 commented on Show HN: Building a GPS receiver axleos.com/building-a-gps... · Posted by u/codyd51

two_handfuls · a year ago

Beautifully written, and educational. Plus very impressive technically! I wish I could upvote this more than once. Thank you!

codyd51 · a year ago

What a wonderful thing to say about a stranger's article! Thank you very much for posting this.

codyd51 commented on Show HN: Building a GPS receiver axleos.com/building-a-gps... · Posted by u/codyd51

NovemberWhiskey · a year ago

It's not entirely clear to me from the write-up, but it seems some of the problems that the author had with the "tracker" come from attempting to do carrier phase synchronization (with the Costas loop) before any kind of clock recovery.

codyd51 · a year ago

Whoa, thank you! I don't know much about RF and learned ad-hoc for this project, and it seems perfectly plausible to me that someone knowledgeable would be able to look at this and identify a root cause - I certainly didn't do anything special for clock recovery, and based on the name I would have blindly assumed that synchronising the carrier wave _would_ be tantamount to recovering the satellite clock. I haven't researched clock recovery yet, and will do so. Once again, thank you!

codyd51 commented on Show HN: Building a GPS receiver axleos.com/building-a-gps... · Posted by u/codyd51

throw0101c · a year ago

Standford has/had a course that is available online on GPS/GNSS and a lot of the nitty-gritty details:

* https://www.youtube.com/playlist?list=PLGvhNIiu1ubyEOJga50LJ...

codyd51 · a year ago

Thank you for linking this, this course is phenomenal! Several of the videos were immensely helpful in my GPS journey.

codyd51 commented on Show HN: Building a GPS receiver axleos.com/building-a-gps... · Posted by u/codyd51

michaelt · a year ago

Great project, thanks for posting it!

It just so happens I've got an RTL-SDR, a GPS receiver that outputs raw pseudoranges, and a signal splitter that lets me put the signal from one antenna into two receivers.

So if you like I can get the pseudoranges out of a commercial GPS receiver, and the raw signal from an RTL-SDR at the same time, which might help you pinpoint your last bit of location inaccuracy.

Would you be interested in that? Or do you consider this project complete?

codyd51 · a year ago

Thank you very much for your thoughtful offer! I won't be able to readily work on side projects after starting my new role next week, and am content to consider this project complete for the time being. However, what you've proposed does sound interesting and fun. I'm going to go ahead and shoot an email to the address listed in your profile.

codyd51 commented on Show HN: Building a GPS receiver axleos.com/building-a-gps... · Posted by u/codyd51

tgsovlerkhgsel · a year ago

I would assume that the chipping sequence is derived from a frequently-rotated cryptographic key.

codyd51 · a year ago

I believe you are correct. My understanding is that the root P key is rotated daily, and needs to be manually uploaded to any military hardware that needs to use it.

codyd51 commented on Show HN: Building a GPS receiver axleos.com/building-a-gps... · Posted by u/codyd51

jeffypoo · a year ago

This was a delightful read. Reminded me of my time working on low power FHSS radio gear. We truly take modern wireless technologies for granted!

codyd51 · a year ago

Thank you very much! I agree, they are incredible! I really had no idea until making this project, and it makes things like cellular phones so astoundingly impressive.