Rename crt → osc throughout

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/osc/audio.nim

@@ -0,0 +1,107 @@
+## Audio capture: tries ffmpeg (PulseAudio monitor) → parec → demo signal.
+
+import osproc, streams, strutils, math
+import scope
+
+type
+  AudioMode* = enum
+    amLive   ## Capturing real audio via ffmpeg/parec
+    amDemo   ## Built-in synthesized waveforms
+
+  AudioCapture* = object
+    mode*: AudioMode
+    process: Process
+    stream: Stream
+    phase: float
+    demoFreqL*, demoFreqR*: float
+    demoPreset*: int
+
+proc findMonitorSource(): string =
+  ## Find the PulseAudio monitor for the default audio sink.
+  try:
+    let inspect = execProcess("wpctl",
+      args = ["inspect", "@DEFAULT_AUDIO_SINK@"],
+      options = {poUsePath, poStdErrToStdOut})
+    for line in inspect.splitLines():
+      if "node.name" in line:
+        let eq = line.find("=")
+        if eq >= 0:
+          return line[eq+1..^1].strip().strip(chars = {'"', ' '}) & ".monitor"
+  except: discard
+  ""
+
+proc startAudio*(): AudioCapture =
+  ## Try real audio capture, fall back to demo.
+  let monitor = findMonitorSource()
+  if monitor.len > 0:
+    try:
+      let p = startProcess("ffmpeg",
+        args = ["-f", "pulse", "-i", monitor,
+                "-f", "s16le", "-ac", "2", "-ar", "44100",
+                "-flush_packets", "1", "-fflags", "nobuffer",
+                "-loglevel", "quiet", "pipe:1"],
+        options = {poUsePath})
+      return AudioCapture(mode: amLive, process: p, stream: p.outputStream,
+                          demoFreqL: 440.0, demoFreqR: 330.0)
+    except OSError: discard
+
+  try:
+    let p = startProcess("parec",
+      args = ["--format=s16le", "--channels=2", "--rate=44100",
+              "--latency-msec=20"],
+      options = {poUsePath})
+    return AudioCapture(mode: amLive, process: p, stream: p.outputStream,
+                        demoFreqL: 440.0, demoFreqR: 330.0)
+  except OSError: discard
+
+  AudioCapture(mode: amDemo, demoFreqL: 440.0, demoFreqR: 330.0)
+
+proc stop*(cap: var AudioCapture) =
+  if cap.mode == amLive:
+    cap.process.terminate()
+    cap.process.close()
+
+proc sourceLabel*(cap: AudioCapture): string =
+  if cap.mode == amLive: "LIVE" else: "DEMO"
+
+proc cyclePreset*(cap: var AudioCapture) =
+  ## Cycle through demo frequency ratios for interesting Lissajous patterns.
+  if cap.mode != amDemo: return
+  cap.demoPreset = (cap.demoPreset + 1) mod 4
+  case cap.demoPreset
+  of 0: cap.demoFreqL = 440.0; cap.demoFreqR = 330.0   # 4:3
+  of 1: cap.demoFreqL = 440.0; cap.demoFreqR = 440.0   # 1:1
+  of 2: cap.demoFreqL = 440.0; cap.demoFreqR = 220.0   # 2:1
+  of 3: cap.demoFreqL = 440.0; cap.demoFreqR = 293.3   # 3:2
+  else: discard
+
+proc readSamples*(cap: var AudioCapture, scope: var Scope) =
+  case cap.mode
+  of amLive:
+    const frameSize = 4  # 2 channels × 16-bit
+    const maxFrames = 2048
+    var buf: array[maxFrames * frameSize, uint8]
+    let bytesRead = cap.stream.readData(addr buf[0], maxFrames * frameSize)
+    if bytesRead <= 0: return
+    scope.sampleCount = min(bytesRead div frameSize, scope.samplesL.len)
+    for i in 0..<scope.sampleCount:
+      let off = i * frameSize
+      let left = cast[int16]((buf[off + 1].uint16 shl 8) or buf[off].uint16)
+      let right = cast[int16]((buf[off + 3].uint16 shl 8) or buf[off + 2].uint16)
+      scope.samplesL[i] = left.float / 32768.0
+      scope.samplesR[i] = right.float / 32768.0
+
+  of amDemo:
+    scope.sampleCount = scope.samplesL.len
+    let cycles = 3.0 / scope.timeDiv
+    let drift = sin(cap.phase * 0.3) * 0.1
+    let rL = cap.demoFreqL / 440.0
+    let rR = cap.demoFreqR / 440.0
+    for i in 0..<scope.sampleCount:
+      let t = cap.phase + (i.float / scope.sampleCount.float) * cycles * 2.0 * PI
+      scope.samplesL[i] = sin(t * rL) * 0.7 +
+                           sin(t * rL * 2.0) * 0.15 +
+                           sin(t * rL * 3.0 + drift) * 0.08
+      scope.samplesR[i] = sin(t * rR + 0.5) * 0.7 +
+                           sin(t * rR * 2.0 + 0.3) * 0.2
+    cap.phase += 0.05