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xerxes: add android-webcam tool for using phone as webcam
Uses scrcpy to stream phone camera via v4l2loopback.
Optional --ascii flag enables GPU-accelerated ASCII art filter
via ffmpeg libplacebo shader.
author
lassulus
date
(Jan 16, 2026, 2:39 PM CET)
commit
0965092a
0965092a09e4b4d7a1cbbf3eed799d74a850013f
parent
186740ff
186740fffaf50695b202690a207c168e0457d5ec
+161
+16
2configs/android-webcam.nix
+16
2configs/android-webcam.nix
···
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{ config, pkgs, self, ... }:
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{
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# v4l2loopback with two devices: raw camera and ASCII output
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boot = {
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kernelModules = [ "v4l2loopback" ];
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extraModulePackages = [ config.boot.kernelPackages.v4l2loopback ];
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extraModprobeConfig = ''
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options v4l2loopback devices=2 video_nr=0,1 exclusive_caps=1,1 card_label="Phone Camera","ASCII Webcam"
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'';
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};
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environment.systemPackages = [
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pkgs.android-tools
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self.packages.${pkgs.system}.android-webcam
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];
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}
+1
machines/xerxes/config.nix
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machines/xerxes/config.nix
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tools/android-webcam/android-webcam.sh
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tools/android-webcam/android-webcam.sh
···
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#!/usr/bin/env bash
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SHADER_PATH="@shaderPath@"
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ASCII_MODE=false
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while [[ $# -gt 0 ]]; do
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case $1 in
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--ascii)
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ASCII_MODE=true
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shift
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;;
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*)
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echo "Unknown option: $1" >&2
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echo "Usage: android-webcam [--ascii]" >&2
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exit 1
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;;
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esac
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done
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# Check if v4l2loopback module is loaded
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if ! lsmod | grep -q v4l2loopback; then
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echo "Error: v4l2loopback kernel module is not loaded" >&2
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echo "Make sure you have rebooted after enabling the android-webcam module" >&2
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exit 1
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fi
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if $ASCII_MODE; then
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# ASCII mode needs both devices
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if [[ ! -e /dev/video0 ]] || [[ ! -e /dev/video1 ]]; then
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echo "Error: /dev/video0 and /dev/video1 must exist for ASCII mode" >&2
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echo "v4l2loopback should be configured with devices=2" >&2
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exit 1
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fi
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else
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if [[ ! -e /dev/video0 ]]; then
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echo "Error: /dev/video0 must exist" >&2
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exit 1
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fi
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fi
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cleanup() {
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echo "Stopping..."
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kill $SCRCPY_PID 2>/dev/null || true
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[[ -n "${FFMPEG_PID:-}" ]] && kill $FFMPEG_PID 2>/dev/null || true
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}
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trap cleanup EXIT
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# Start scrcpy to stream phone camera to /dev/video0
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echo "Starting phone camera stream..."
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scrcpy \
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--video-source=camera \
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--camera-facing=back \
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--no-audio \
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--v4l2-sink=/dev/video0 \
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--video-encoder=c2.exynos.h264.encoder \
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--camera-size=1920x1080 &
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SCRCPY_PID=$!
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if $ASCII_MODE; then
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sleep 2
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# Start ffmpeg with ASCII shader to /dev/video1
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echo "Starting ASCII filter pipeline..."
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ffmpeg \
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-f v4l2 -i /dev/video0 \
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-vf "libplacebo=custom_shader_path=${SHADER_PATH}" \
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-f v4l2 -pix_fmt yuv420p /dev/video1 &
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FFMPEG_PID=$!
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echo ""
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echo "Android ASCII webcam running!"
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echo " Raw camera: /dev/video0 (Phone Camera)"
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echo " ASCII output: /dev/video1 (ASCII Webcam)"
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else
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echo ""
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echo "Android webcam running!"
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echo " Camera: /dev/video0 (Phone Camera)"
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fi
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echo ""
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echo "Press Ctrl+C to stop"
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wait
+39
tools/android-webcam/ascii.hook
+39
tools/android-webcam/ascii.hook
···
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//!HOOK MAIN
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//!BIND HOOKED
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//!DESC ASCII art filter
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const int SCALE = 6;
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const bool MONOCHROME = false;
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const vec3 BASE_COLOR = vec3(0.0, 1.0, 0.0);
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float character(int n, vec2 p) {
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p = floor(p * vec2(4.0, 4.0) + 2.5);
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if (clamp(p.x, 0.0, 4.0) == p.x && clamp(p.y, 0.0, 4.0) == p.y) {
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int a = int(round(p.x) + 5.0 * round(p.y));
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if (((n >> a) & 1) == 1) return 1.0;
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}
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return 0.0;
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}
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vec4 hook() {
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vec2 iResolution = HOOKED_size;
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vec2 pix = HOOKED_pos * iResolution;
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vec2 cell = floor(pix / vec2(float(SCALE) * 8.0)) * vec2(float(SCALE) * 8.0);
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vec4 c = HOOKED_texOff((cell - pix) / iResolution * HOOKED_size);
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float gray = 0.3 * c.r + 0.59 * c.g + 0.11 * c.b;
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int n;
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if (gray <= 0.2) n = 4096;
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else if (gray <= 0.3) n = 65600;
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else if (gray <= 0.4) n = 332772;
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else if (gray <= 0.5) n = 15255086;
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else if (gray <= 0.6) n = 23385164;
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else if (gray <= 0.7) n = 15252014;
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else if (gray <= 0.8) n = 13199452;
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else n = 11512810;
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vec2 p = mod(pix / vec2(float(SCALE) * 4.0), vec2(2.0)) - vec2(1.0);
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if (MONOCHROME) c.rgb = BASE_COLOR;
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c.rgb = c.rgb * character(n, p);
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return c;
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}
+22
tools/android-webcam/flake-module.nix
+22
tools/android-webcam/flake-module.nix
···
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{ ... }:
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{
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perSystem =
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{ pkgs, ... }:
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let
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ffmpeg-placebo = pkgs.ffmpeg.override { withPlacebo = true; };
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in
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{
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packages.android-webcam = pkgs.writeShellApplication {
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name = "android-webcam";
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runtimeInputs = [
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pkgs.scrcpy
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ffmpeg-placebo
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pkgs.kmod
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];
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text = builtins.replaceStrings
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[ "@shaderPath@" ]
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[ "${./ascii.hook}" ]
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(builtins.readFile ./android-webcam.sh);
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};
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};
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}