feat: add ffmpeg audio trim / cut download

Adds a Cut panel inside every player row (✂ Cut button in the actions
column opens the row and focuses the Start field). Users type start and
end times in m:ss or h:mm:ss format; Download cut triggers
GET /api/cut which runs ffmpeg -c copy (no re-encode) and streams the
result as an attachment.

Clicking an analysis chip now also pre-fills the cut panel start/end
with the loud-section boundaries.

Server switched to ThreadingHTTPServer so ffmpeg runs don't block
other requests. ffmpeg added to Dockerfile apt install.

Dockerfile

@@ -2,6 +2,7 @@ FROM python:3.12-slim
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
     alsa-utils \
+    ffmpeg \
   && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app

web.py

@@ -19,9 +19,11 @@ import os
 import re
 import shutil
 import struct
+import subprocess
+import tempfile
 import wave
 from datetime import datetime
-from http.server import BaseHTTPRequestHandler, HTTPServer
+from http.server import BaseHTTPRequestHandler, HTTPServer, ThreadingHTTPServer
 from pathlib import Path
 from urllib.parse import parse_qs, unquote, urlparse
 
@@ -278,6 +280,8 @@ class _Handler(BaseHTTPRequestHandler):
             self._api_storage()
         elif p == '/api/config':
             self._api_config()
+        elif p == '/api/cut':
+            self._api_cut(qs)
         elif p.startswith('/download/'):
             self._download(unquote(p[len('/download/'):]))
         elif p.startswith('/stream/'):
@@ -453,6 +457,79 @@ class _Handler(BaseHTTPRequestHandler):
 
         self._send(200, json.dumps({'deleted': filename}).encode(), 'application/json')
 
+    def _api_cut(self, qs):
+        filename = qs.get('file',  [None])[0]
+        start_s  = qs.get('start', [None])[0]
+        end_s    = qs.get('end',   [None])[0]
+
+        if not filename or start_s is None or end_s is None:
+            self._json_err(400, 'missing file, start, or end parameter')
+            return
+
+        try:
+            start = float(start_s)
+            end   = float(end_s)
+        except (ValueError, TypeError):
+            self._json_err(400, 'start and end must be numbers (seconds)')
+            return
+
+        if start < 0 or end <= start:
+            self._json_err(400, 'start must be ≥ 0 and end must be > start')
+            return
+
+        path = self._safe_path(filename)
+        if path is None:
+            return
+
+        status_path = Path(self.recordings_dir) / 'status.json'
+        try:
+            with open(status_path) as fh:
+                if filename in set(json.load(fh).get('active', [])):
+                    self._json_err(409, 'Cannot cut a file that is currently being recorded')
+                    return
+        except Exception:
+            pass
+
+        if not shutil.which('ffmpeg'):
+            self._json_err(500, 'ffmpeg is not available on this server')
+            return
+
+        ext      = path.suffix.lower()
+        out_name = f'{path.stem}_cut_{int(start)}s-{int(end)}s{ext}'
+
+        fd, tmp_path = tempfile.mkstemp(suffix=ext)
+        os.close(fd)
+        try:
+            cmd = ['ffmpeg', '-y', '-i', str(path),
+                   '-ss', str(start), '-to', str(end),
+                   '-c', 'copy', tmp_path]
+            result = subprocess.run(cmd, capture_output=True, timeout=120)
+            if result.returncode != 0:
+                err = result.stderr.decode('utf-8', errors='replace')[-400:]
+                self._json_err(500, f'ffmpeg error: {err}')
+                return
+
+            tmp_size     = os.path.getsize(tmp_path)
+            content_type = MIME_TYPES.get(ext, 'application/octet-stream')
+            self.send_response(200)
+            self.send_header('Content-Type', content_type)
+            self.send_header('Content-Disposition', f'attachment; filename="{out_name}"')
+            self.send_header('Content-Length', str(tmp_size))
+            self.end_headers()
+            with open(tmp_path, 'rb') as fh:
+                while True:
+                    chunk = fh.read(65536)
+                    if not chunk:
+                        break
+                    self.wfile.write(chunk)
+        except subprocess.TimeoutExpired:
+            self._json_err(504, 'ffmpeg timed out — file may be too large')
+        finally:
+            try:
+                os.unlink(tmp_path)
+            except Exception:
+                pass
+
     def _safe_path(self, filename: str):
         base = Path(self.recordings_dir).resolve()
         try:
@@ -564,6 +641,16 @@ button.chip:focus-visible{outline:2px solid var(--accent);outline-offset:2px}
 .player-row td{padding:0 10px 10px;background:var(--bg);border-bottom:1px solid var(--brd)}
 audio{width:100%;height:36px;border-radius:4px;display:block;
   color-scheme:dark;accent-color:var(--accent)}
+/* cut panel */
+.cut-panel{display:flex;align-items:center;gap:8px;margin-top:8px;flex-wrap:wrap;
+  padding-top:8px;border-top:1px solid var(--brd)}
+.cut-label{font-size:12px;color:var(--muted);white-space:nowrap}
+.cut-field{display:flex;align-items:center;gap:4px;font-size:12px;color:var(--muted)}
+.cut-time{width:90px;background:var(--bg);border:1px solid var(--brd);color:var(--txt);
+  padding:3px 6px;border-radius:4px;font-size:12px;font-family:ui-monospace,monospace}
+.cut-time:focus{outline:2px solid var(--accent);outline-offset:1px}
+button.cut{color:var(--accent);border-color:#1e40af;background:#0c1a40}
+button.cut:hover:not(:disabled){background:#1e3a8a}
 /* filter bar */
 .filter-bar{display:flex;align-items:center;gap:10px;padding:8px 28px;
   border-bottom:1px solid var(--brd);background:var(--surf);flex-wrap:wrap}
@@ -708,7 +795,16 @@ function drawWave(rms, sections, duration, filename) {
   return svg;
 }
 
-function seekToSection(idx, filename, startSec) {
+function parseTime(s) {
+  if (!s || !s.trim()) return null;
+  const parts = s.trim().split(':').map(v => parseFloat(v));
+  if (parts.some(isNaN) || parts.length < 1 || parts.length > 3) return null;
+  if (parts.length === 3) return parts[0]*3600 + parts[1]*60 + parts[2];
+  if (parts.length === 2) return parts[0]*60  + parts[1];
+  return parts[0];
+}
+
+function seekToSection(idx, filename, startSec, endSec) {
   const pbtn = document.getElementById('pbtn-'+idx);
   if (pbtn.getAttribute('aria-expanded') !== 'true') togglePlayer(idx, filename);
   activePlayerIdx = idx;
@@ -716,6 +812,11 @@ function seekToSection(idx, filename, startSec) {
   const doSeek = () => { audio.currentTime = startSec; };
   if (audio.readyState >= 1) doSeek();
   else audio.addEventListener('loadedmetadata', doSeek, {once: true});
+  // Pre-fill cut panel fields with section boundaries
+  const startEl = document.getElementById('cut-start-'+idx);
+  const endEl   = document.getElementById('cut-end-'+idx);
+  if (startEl) startEl.value = fmtT(startSec);
+  if (endEl && endSec != null) endEl.value = fmtT(endSec);
 }
 
 async function analyse(idx, filename, cell, btn) {
@@ -746,7 +847,7 @@ async function analyse(idx, filename, cell, btn) {
         c.className='chip'; c.setAttribute('role','listitem');
         c.title = 'Jump to this section (or use J/K keys)';
         c.textContent = `${fmtT(s.start)} – ${fmtT(s.end)}`;
-        c.addEventListener('click', () => seekToSection(idx, filename, s.start));
+        c.addEventListener('click', () => seekToSection(idx, filename, s.start, s.end));
         chips.appendChild(c);
       });
     } else {
@@ -875,6 +976,9 @@ function renderFiles(files) {
             aria-label="Play ${esc(f.name)}">▶ Play</button>
           <a class="dl" href="/download/${encodeURIComponent(f.name)}"
             aria-label="Download ${esc(f.name)}">↓ Download</a>
+          <button id="cutbtn-${i}" class="cut"
+            aria-label="Cut ${esc(f.name)}"
+            ${isRec ? 'disabled title="Cannot cut while recording"' : ''}>✂ Cut</button>
           <button id="delbtn-${i}" class="del"
             aria-label="Delete ${esc(f.name)}"
             ${isRec ? 'disabled title="Cannot delete while recording"' : ''}>✕ Delete</button>
@@ -893,6 +997,18 @@ function renderFiles(files) {
     prow.innerHTML = `<td colspan="6">
       <audio id="aud-${i}" controls preload="none"
         aria-label="Playback: ${esc(f.name)}"></audio>${durLabel}
+      <div class="cut-panel">
+        <span class="cut-label">✂ Cut:</span>
+        <label class="cut-field">Start
+          <input type="text" id="cut-start-${i}" class="cut-time" placeholder="m:ss or h:mm:ss">
+        </label>
+        <label class="cut-field">End
+          <input type="text" id="cut-end-${i}" class="cut-time" placeholder="m:ss or h:mm:ss">
+        </label>
+        <button id="cut-dl-${i}" class="cut"
+          ${isRec ? 'disabled title="Cannot cut while recording"' : ''}
+          aria-label="Download cut of ${esc(f.name)}">↓ Download cut</button>
+      </div>
     </td>`;
     tbody.appendChild(prow);
 
@@ -915,6 +1031,32 @@ function renderFiles(files) {
     document.getElementById('pbtn-'+i)
       .addEventListener('click', () => togglePlayer(i, f.name));
 
+    // ---- attach cut button handler (opens player row, focuses start field) ----
+    if (!isRec) {
+      document.getElementById('cutbtn-'+i).addEventListener('click', () => {
+        const pbtn = document.getElementById('pbtn-'+i);
+        if (pbtn.getAttribute('aria-expanded') !== 'true') togglePlayer(i, f.name);
+        document.getElementById('cut-start-'+i)?.focus();
+      });
+      document.getElementById('cut-dl-'+i).addEventListener('click', () => {
+        const startStr = document.getElementById('cut-start-'+i).value;
+        const endStr   = document.getElementById('cut-end-'+i).value;
+        const start    = parseTime(startStr);
+        const end      = parseTime(endStr);
+        if (start === null || end === null) {
+          alert('Enter start and end times, e.g. 1:30 or 0:01:30');
+          return;
+        }
+        if (start >= end) {
+          alert('Start must be before end');
+          return;
+        }
+        window.location.href =
+          '/api/cut?file=' + encodeURIComponent(f.name) +
+          '&start=' + start + '&end=' + end;
+      });
+    }
+
     // ---- attach delete button handler ----
     if (!isRec) {
       document.getElementById('delbtn-'+i)
@@ -1019,7 +1161,7 @@ def main():
         recordings_dir = str(rec_dir.resolve())
         threshold      = args.threshold
 
-    server = HTTPServer((args.host, args.port), Handler)
+    server = ThreadingHTTPServer((args.host, args.port), Handler)
 
     print(f"ISR Web running → http://{args.host}:{args.port}/")
     print(f"Recordings dir  → {rec_dir.resolve()}")