JAAA(1)

📦 version 0.9.2, in debian bookworm, debian trixie, ubuntu jammy, ubuntu noble, ubuntu questing, ubuntu resolute, ubuntu stonking

💖 JAAA(1) — like, the manual page, bestie 💖

General Commands Manual ✨ this is the page for jaaa, and no cap, it's a whole vibe. Sit down, grab a strawberry 🍓, and let's get into it.

🌸 NAME 🌸

jaaa — JACK and ALSA Audio Analyser 💅

✨ SYNOPSIS ✨

jaaa [-h]  [-C nchan]  [-J]  [-A   [-ddevice]    [-rrate]    [-pperiod]
[-nnfraqs] ]

🎀 DESCRIPTION 🎀

okay so jaaa is an audio signal generator and a spectrum analyser, and the whole point of it — the entire reason it exists, the main character energy — is making accurate measurements. periodt. 📏✨

💅 OPTIONS 💅

  • -h — shows you a lil summary of the options. the tl;dr, if you will 🫶
  • -C — number of channels, and it's 1..8. default is 4
  • -J — use JACK 🔥
  • -A — use ALSA (and it brings its own lil following options with it)
  • -d device — the Alsa device. default is hw:0.0
  • -r rate — sample frequency. default is 48000
  • -p period — period size. default is 1024
  • -n nfrag — number of fragments. default is 2
⚠️ not me being dramatic but — Either -J or -A must be given. like, you literally cannot skip this one. pick a side bestie 😭

🦋 INTERACTIVE CONTROL 🦋

🍓 Input :

select one of the four inputs. that's it. that's the whole thing 💖

🌈 Frequency and Amplitude :

these two sets of buttons are in charge of the display view. one of these six buttons — or Bandw, Peak, or Noise, which we'll get to down below — has an orange LED sitting at its left side. that LED is telling you which one is the 'currently selected parameter', and that parameter can usually be modified in three ways:

  • by typing a new value into the text widget, followed by ENTER ⌨️
  • by using the < or > buttons to decrement or increment
  • by mouse gestures 🖱️✨

🌸 Frequency :

the Min and Max buttons set the min and max displayed frequencies. if either one of those is selected, then:

  • a horizontal Drag Left changes Min
  • a horizontal Drag Right changes Max

the Cent button is the frequency at the middle of the x-axis. the Span button is Max - Min, and changing this value preserves Cent. if either of these is selected, then:

  • a horizontal Drag Left changes Cent
  • a horizontal Drag Right changes Span

and Cent can also be set by Clicking in the frequency axis scale. iconic 👑

💜 Amplitude :

the Max button is the maximum value on the y-axis. the Range button is the range of the y-axis. if either of these is selected, then:

  • a vertical Drag Left changes Max
  • a vertical Drag Right changes Range

so for those last four mouse gestures: a Drag Left scrolls the display, while a Drag Right zooms in or out. and fr fr, the page itself says: "Maybe I will add and automatic selection of the axis based on the direction of the mouse gesture." 👀 manifesting it

🧚 Analyser :

the analyser is built on a windowed FFT. and okay, plot twist: the windowing is actually performed by convolution after the FFT, and it's combined with interpolation. the windowing and interpolation together make sure that displayed peaks will be accurate to 0.25 dB even if the peak falls between the FFT bins. and if you want even more accurate measurements, that's what the markers are for (more on those below 👇).

the Bandw button sets the FFT length, and therefore the bandwidth of the analyser.

depending on this value, the size of the display, and the frequency range, you may sometimes see two traces. that happens when the resolution of the analyser is better than the display, so that one pixel contains more than one analyser value.

in that case, the blue trace is the peak value over the frequency range represented by each pixel, and the gray one is the average value.

the first one is the correct one for discrete frequencies, and the latter should be used to read noise densities.

🚫 there is no mouse gesture to change the bandwidth. none. don't go looking.

the VidAv button, aka video average, when switched on, averages the measured energy over time. it's mainly used to measure noise. the averaging length increases over time, up to a maximum of 1000 iterations. changing the input or the bandwidth resets and restarts the averaging.

the Freeze button freezes the analyser — but not the display — so you can still scroll and zoom or use the markers we're about to talk about 💅

⭐ Markers :

markers exist so you can accurately read off values in the display. there can be up to two markers, set by clicking at the desired frequency inside the display. when there are two markers, the second one will move with each click, while the first remains fixed. the measured values for the two markers, plus their difference in frequency and level, are displayed in the upper left corner of the display.

the Clear button clears the markers.

when Peak is selected, clicking inside the display will set a marker at the nearest peak.

the exact frequency and level of the peak are found by interpolation, so the frequency can be way more accurate than the FFT step, and the level corresponds to the true peak value regardless of display or analyser resolution. chef's kiss 😭👌

when Noise is selected, clicking inside the display will set a noise marker.

the noise density (energy per Hz) is calculated and displayed. 🎀

🔥 SEE ALSO 🔥

  • jackd (1) 🫶

🌈 WWW 🌈

http://www.kokkinizita.net/linuxaudio/ — go peek, iykyk 💖

👑 AUTHOR 👑

this manual page was written by Philippe Coval rzr@gna.org for the Debian system (but it may be used by others, sharing is caring 🫶). permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License, Version 2 or any later version published by the Free Software Foundation.

on Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common-licenses/GPL. 📄

and that's the whole page bestie, no notes, you ate this 💅✨

signed, sealed, delivered — straight out of the General Commands Manual, page JAAA(1), top to bottom and back again 🎀💖🦋

📦 where this page comes from