change to 16khz, add audio filter, refactor to use DMA

baby_mobile_v2/upload_track.py

@@ -44,12 +44,12 @@ def convert_to_pcm(path: str) -> bytes:
                 sample_rate   = struct.unpack_from("<I", data, 24)[0]
                 bits_per_samp = struct.unpack_from("<H", data, 34)[0]
                 needs_convert = (audio_format != 1 or num_channels != 1
-                                 or sample_rate != 8000 or bits_per_samp != 8)
+                                 or sample_rate != 16000 or bits_per_samp != 8)
             except Exception:
                 needs_convert = True
 
             if not needs_convert:
-                print("WAV is already 8-bit mono 8kHz — stripping header")
+                print("WAV is already 8-bit mono 16kHz — stripping header")
                 return data[44:]
             print("WAV needs resampling — converting via ffmpeg")
         # fall through to ffmpeg conversion
@@ -64,14 +64,14 @@ def convert_to_pcm(path: str) -> bytes:
     print(f"Converting {os.path.basename(path)} via ffmpeg...")
     result = subprocess.run(
         ['ffmpeg', '-y', '-i', path,
-         '-ar', '8000', '-ac', '1', '-f', 'u8', '-acodec', 'pcm_u8', 'pipe:1'],
+         '-ar', '16000', '-ac', '1', '-f', 'u8', '-acodec', 'pcm_u8', 'pipe:1'],
         capture_output=True
     )
     if result.returncode != 0:
         sys.exit(f"ERROR: ffmpeg failed:\n{result.stderr.decode(errors='replace')[-400:]}")
 
     pcm = result.stdout
-    duration = len(pcm) / 8000
+    duration = len(pcm) / 16000
     print(f"  Converted: {len(pcm):,} bytes ({duration:.1f}s)")
     return pcm
 
@@ -133,10 +133,10 @@ def upload(port: str, track_num: int, pcm: bytes) -> None:
             if "at=" in err_line:
                 accepted = int(err_line.split("at=")[1].split()[0])
                 safe = int(accepted * 0.9)  # 10% headroom
-                max_s = safe / 8000
+                max_s = safe / 16000
                 print(f"  LittleFS accepted {accepted} bytes before full.")
                 print(f"  Safe clip length: ~{max_s:.1f}s")
-                print(f"  Trim with:  ffmpeg -i input.mp3 -t {max_s:.0f} -ar 8000 -ac 1 -f u8 out.raw")
+                print(f"  Trim with:  ffmpeg -i input.mp3 -t {max_s:.0f} -ar 16000 -ac 1 -f u8 out.raw")
             sys.exit(1)
 
         # Wait for OK