Monorepo for Aesthetic.Computer
aesthetic.computer
feat(native): add SRT live streaming to OBS/TikTok over WiFi
Adds an opt-in ac-native-stream systemd service that captures the DRM
framebuffer (kmsgrab) + ALSA audio (via snd_aloop tee) and pushes an
SRT stream to OBS on a Windows host for TikTok Live broadcasting.
- ffmpeg-full with VAAPI hw encode for low-latency h264
- asound.conf tee routes audio to both speakers + loopback
- AC_AUDIO_DEVICE env var in audio.c for clean ALSA routing
- Controlled via /mnt/stream.conf on USB config partition
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
+155
+18
fedac/native/src/audio.c
+18
fedac/native/src/audio.c
···
1053
1053
1054
1054
// Open ALSA — try multiple cards and devices, with retries for race conditions.
1055
1055
// On fast NVMe boots the HDA codec may not be fully probed when we first try.
1056
+
// If AC_AUDIO_DEVICE is set, try it first (used for stream tee via asound.conf).
1056
1057
snd_pcm_t *pcm = NULL;
1057
1058
const char *devices[] = {
1058
1059
"hw:0,0", "hw:1,0", "hw:0,1", "hw:1,1",
···
1062
1063
};
1063
1064
int err = -1;
1064
1065
int card_idx = 0;
1066
+
1067
+
// AC_AUDIO_DEVICE override — try the env var device before the hardcoded list.
1068
+
const char *env_dev = getenv("AC_AUDIO_DEVICE");
1069
+
if (env_dev && env_dev[0]) {
1070
+
err = snd_pcm_open(&pcm, env_dev, SND_PCM_STREAM_PLAYBACK, 0);
1071
+
if (err >= 0) {
1072
+
fprintf(stderr, "[audio] Opened AC_AUDIO_DEVICE=%s\n", env_dev);
1073
+
snprintf(audio->audio_device, sizeof(audio->audio_device), "%s", env_dev);
1074
+
if (sscanf(env_dev, "hw:%d", &card_idx) != 1 &&
1075
+
sscanf(env_dev, "plughw:%d", &card_idx) != 1)
1076
+
card_idx = 0;
1077
+
} else {
1078
+
fprintf(stderr, "[audio] AC_AUDIO_DEVICE=%s failed: %s — falling back\n",
1079
+
env_dev, snd_strerror(err));
1080
+
}
1081
+
}
1082
+
1065
1083
for (int attempt = 0; attempt < 5 && err < 0; attempt++) {
1066
1084
if (attempt > 0) {
1067
1085
fprintf(alog, "[audio] Retry %d/4 — waiting 2s for codec probe...\n", attempt);
+133
fedac/nixos/configuration.nix
+133
fedac/nixos/configuration.nix
···
69
69
dosfstools # mkfs.vfat
70
70
efibootmgr
71
71
parted
72
+
ffmpeg-full # SRT streaming + VAAPI hardware encode
73
+
libva-utils # vainfo for debugging GPU encode
72
74
];
73
75
74
76
# zram swap
···
130
132
echo "No ACDATA partition found; /mnt is temporary"
131
133
${pkgs.util-linux}/bin/lsblk -o NAME,SIZE,TYPE,FSTYPE,LABEL,MOUNTPOINTS || true
132
134
${pkgs.util-linux}/bin/blkid || true
135
+
'';
136
+
};
137
+
};
138
+
139
+
# ALSA tee: "default" sends audio to both physical speakers and the loopback
140
+
# device. The stream service captures from the loopback's read side.
141
+
# snd_aloop is always loaded (see hardware.nix kernelModules).
142
+
environment.etc."asound.conf".text = ''
143
+
# AC Native audio tee — duplicate playback to speakers + ALSA loopback.
144
+
# Loopback capture side (hw:Loopback,1,0) is read by the stream service.
145
+
146
+
pcm.!default {
147
+
type plug
148
+
slave.pcm "ac_tee"
149
+
}
150
+
151
+
pcm.ac_tee {
152
+
type route
153
+
slave.pcm {
154
+
type multi
155
+
slaves {
156
+
a { pcm "plughw:0,0" channels 2 }
157
+
b { pcm "plughw:Loopback,0,0" channels 2 }
158
+
}
159
+
bindings {
160
+
0 { slave a channel 0 }
161
+
1 { slave a channel 1 }
162
+
2 { slave b channel 0 }
163
+
3 { slave b channel 1 }
164
+
}
165
+
}
166
+
ttable.0.0 1
167
+
ttable.1.1 1
168
+
ttable.0.2 1
169
+
ttable.1.3 1
170
+
}
171
+
172
+
ctl.!default {
173
+
type hw
174
+
card 0
175
+
}
176
+
'';
177
+
178
+
# SRT streamer: pushes notepat framebuffer over WiFi to OBS on Windows,
179
+
# which then forwards to TikTok Live.
180
+
#
181
+
# Opt-in: only starts if /mnt/stream.conf exists on the USB config partition.
182
+
# Create /mnt/stream.conf with:
183
+
# HOST=192.168.1.100 # Windows host IP on LAN
184
+
# PORT=9000 # SRT port (OBS Media Source listens here)
185
+
# BITRATE=6M # encode bitrate
186
+
# FRAMERATE=60 # capture fps
187
+
# SRT_LATENCY=40 # ms — lower = less latency, more fragile on bad WiFi
188
+
# WIDTH=1280 # output width (scale from native)
189
+
# HEIGHT=720 # output height
190
+
systemd.services.ac-native-stream = {
191
+
description = "AC Native SRT streamer (to OBS → TikTok)";
192
+
after = [ "ac-native-kiosk.service" "mount-usb-config.service" ];
193
+
wants = [ "ac-native-kiosk.service" ];
194
+
wantedBy = [ "multi-user.target" ];
195
+
196
+
unitConfig = {
197
+
ConditionPathExists = "/mnt/stream.conf";
198
+
};
199
+
200
+
environment = {
201
+
LIBVA_DRIVER_NAME = "iHD";
202
+
ALSA_PLUGIN_DIR = "${pkgs.alsa-plugins}/lib/alsa-lib";
203
+
ALSA_CONFIG_PATH = "${pkgs.alsa-lib}/share/alsa/alsa.conf";
204
+
};
205
+
206
+
serviceConfig = {
207
+
Type = "simple";
208
+
Restart = "on-failure";
209
+
RestartSec = 3;
210
+
EnvironmentFile = "/mnt/stream.conf";
211
+
212
+
ExecStartPre = pkgs.writeShellScript "ac-native-stream-wait" ''
213
+
# Give the kiosk a moment to grab DRM master and start rendering
214
+
sleep 2
215
+
216
+
for _ in $(seq 1 40); do
217
+
ls /dev/dri/card* >/dev/null 2>&1 && break
218
+
sleep 0.25
219
+
done
220
+
221
+
if ! ls /dev/dri/card* >/dev/null 2>&1; then
222
+
echo "[stream] no DRM card found"
223
+
exit 1
224
+
fi
225
+
'';
226
+
227
+
ExecStart = pkgs.writeShellScript "ac-native-stream" ''
228
+
set -u
229
+
230
+
HOST="''${HOST:?HOST not set in /mnt/stream.conf}"
231
+
PORT="''${PORT:-9000}"
232
+
BITRATE="''${BITRATE:-6M}"
233
+
FRAMERATE="''${FRAMERATE:-60}"
234
+
SRT_LATENCY="''${SRT_LATENCY:-40}"
235
+
WIDTH="''${WIDTH:-1280}"
236
+
HEIGHT="''${HEIGHT:-720}"
237
+
238
+
CARD="$(ls /dev/dri/card* 2>/dev/null | head -n1)"
239
+
[ -n "$CARD" ] || { echo "[stream] no DRM card"; exit 1; }
240
+
241
+
URL="srt://''${HOST}:''${PORT}?mode=caller&latency=''${SRT_LATENCY}&pkt_size=1316&tlpktdrop=1"
242
+
echo "[stream] capturing $CARD at ''${FRAMERATE}fps → $URL"
243
+
echo "[stream] encode: h264_vaapi ''${WIDTH}x''${HEIGHT} @ ''${BITRATE}"
244
+
245
+
AUDIO_BITRATE="''${AUDIO_BITRATE:-128k}"
246
+
247
+
exec ${pkgs.ffmpeg-full}/bin/ffmpeg \
248
+
-hide_banner -loglevel warning \
249
+
-threads 2 \
250
+
-fflags nobuffer -flags low_delay \
251
+
-device "$CARD" \
252
+
-framerate "$FRAMERATE" \
253
+
-f kmsgrab -i - \
254
+
-f alsa -thread_queue_size 512 -channels 2 \
255
+
-sample_rate 48000 -audio_buffer_size 10000 \
256
+
-i hw:Loopback,1,0 \
257
+
-vf "hwmap=derive_device=vaapi,scale_vaapi=w=''${WIDTH}:h=''${HEIGHT}:format=nv12" \
258
+
-c:v h264_vaapi \
259
+
-b:v "$BITRATE" -maxrate "$BITRATE" -bufsize "$BITRATE" \
260
+
-g "$FRAMERATE" -bf 0 \
261
+
-quality 1 \
262
+
-compression_level 1 \
263
+
-sei 0 \
264
+
-c:a aac -b:a "$AUDIO_BITRATE" \
265
+
-f mpegts "$URL"
133
266
'';
134
267
};
135
268
};
+1
fedac/nixos/modules/hardware.nix
+1
fedac/nixos/modules/hardware.nix
+3
fedac/nixos/modules/kiosk.nix
+3
fedac/nixos/modules/kiosk.nix
···
151
151
SSL_CERT_FILE = "${pkgs.cacert}/etc/ssl/certs/ca-bundle.crt";
152
152
ALSA_PLUGIN_DIR = "${pkgs.alsa-plugins}/lib/alsa-lib";
153
153
ALSA_CONFIG_PATH = "${pkgs.alsa-lib}/share/alsa/alsa.conf";
154
+
# Route audio through asound.conf tee (speakers + loopback for streaming).
155
+
# Falls back to hw:0,0 automatically if the tee device fails.
156
+
AC_AUDIO_DEVICE = "default";
154
157
};
155
158
156
159
serviceConfig = {