fix: defer broadcast_started for Qt MP3-direct mode until first audio chunk

Previously, start_broadcast immediately emitted broadcast_started and
stream_status: active to listeners, even before the DJ pressed play.
Listeners would connect to /stream.mp3, wait 60s with no data, then
disconnect — so music never reached them from the PyQt client.

The web DJ panel was unaffected because it only sends audio_chunk while
music is actively playing, so start_broadcast and data arrive together.

Fix: in MP3-direct mode (Qt client, format=mp3), hold back broadcast_started
and stream_status: active until the very first audio_chunk arrives. The
first chunk guarantees the preroll buffer has data and listeners will
immediately receive audio when they connect.

- _mp3_broadcast_announced flag tracks whether the deferred announcement
  has been sent in the current session
- Resets on stop_broadcast, grace-period auto-stop, and fresh start_broadcast
- Browser (webm/opus) mode is unaffected — announces immediately as before
This commit is contained in:
ComputerTech 2026-04-03 13:44:09 +01:00
parent 35adfa7feb
commit 80a4286bc0
1 changed files with 75 additions and 25 deletions

100
server.py
View File

@ -54,6 +54,15 @@ broadcast_state = {
listener_sids = set()
dj_sids = set()
# Set to True once the first audio chunk arrives in MP3-direct mode.
# broadcast_started is held back until then so listeners don't connect
# to /stream.mp3 before any data is flowing (e.g. before the DJ presses play).
_mp3_broadcast_announced = False
# Current listener glow intensity — persisted so new/reloaded listeners get the
# correct level immediately without waiting for the DJ to move the slider again.
_current_glow_intensity = 30
# Grace-period greenlet: auto-stop broadcast if DJ doesn't reconnect in time
_dj_grace_greenlet = None
DJ_GRACE_PERIOD_SECS = 20 # seconds to wait before auto-stopping
@ -136,7 +145,9 @@ def _start_transcoder_if_needed(is_mp3_input=False):
try: _ffmpeg_in_q.get_nowait()
except: break
# Define threads INSIDE so they close over THIS specific 'proc'
# Define greenlets INSIDE so they close over THIS specific 'proc'.
# Blocking subprocess pipe I/O is delegated to eventlet.tpool so it runs
# in a real OS thread, preventing it from stalling the eventlet hub.
def _writer(proc):
global _transcoder_last_error
print(f"[THREAD] Transcoder writer started (PID: {proc.pid})")
@ -144,10 +155,11 @@ def _start_transcoder_if_needed(is_mp3_input=False):
try:
chunk = _ffmpeg_in_q.get(timeout=1.0)
if chunk is None: break
if proc.stdin:
proc.stdin.write(chunk)
proc.stdin.flush()
# Run blocking pipe-write in a real thread via tpool
eventlet.tpool.execute(proc.stdin.write, chunk)
eventlet.tpool.execute(proc.stdin.flush)
except queue.Empty:
continue
except (BrokenPipeError, ConnectionResetError):
@ -157,8 +169,8 @@ def _start_transcoder_if_needed(is_mp3_input=False):
print(f"WARNING: Transcoder writer error: {e}")
_transcoder_last_error = str(e)
break
# Ensure process is killed if thread exits unexpectedly
# Ensure process is killed if greenlet exits unexpectedly
if proc.poll() is None:
try: proc.terminate()
except: pass
@ -169,9 +181,9 @@ def _start_transcoder_if_needed(is_mp3_input=False):
print(f"[THREAD] Transcoder reader started (PID: {proc.pid})")
while proc.poll() is None:
try:
# Smaller read for smoother delivery (1KB)
# This prevents buffering delays at lower bitrates
data = proc.stdout.read(1024)
# Run blocking pipe-read in a real thread via tpool (1 KB chunks
# for smooth delivery; prevents buffering delays at lower bitrates)
data = eventlet.tpool.execute(proc.stdout.read, 1024)
if not data: break
_transcoder_bytes_out += len(data)
@ -183,20 +195,20 @@ def _start_transcoder_if_needed(is_mp3_input=False):
try:
q.put_nowait(data)
except queue.Full:
# Client is too slow, skip this chunk for them
# Client is too slow skip this chunk for them
pass
except Exception as e:
print(f"WARNING: Transcoder reader error: {e}")
_transcoder_last_error = str(e)
break
# Ensure process is killed if thread exits unexpectedly
# Ensure process is killed if greenlet exits unexpectedly
if proc.poll() is None:
try: proc.terminate()
except: pass
print(f"[THREAD] Transcoder reader finished (PID: {proc.pid})")
# Start greenlets/threads for THIS process specifically
# Spawn as greenlets — tpool handles the blocking subprocess I/O internally
eventlet.spawn(_writer, _ffmpeg_proc)
eventlet.spawn(_reader, _ffmpeg_proc)
@ -664,12 +676,14 @@ def dj_connect():
def _dj_disconnect_grace():
"""Auto-stop broadcast if no DJ reconnects within the grace period."""
global _dj_grace_greenlet
global _dj_grace_greenlet, _mp3_broadcast_announced
print(f"INFO: Grace period started — {DJ_GRACE_PERIOD_SECS}s for DJ to reconnect")
eventlet.sleep(DJ_GRACE_PERIOD_SECS)
if broadcast_state.get('active') and not dj_sids:
print("WARNING: Grace period expired, no DJ reconnected — auto-stopping broadcast")
broadcast_state['active'] = False
broadcast_state['is_mp3_input'] = False
_mp3_broadcast_announced = False
_stop_transcoder()
listener_socketio.emit('broadcast_stopped', namespace='/')
listener_socketio.emit('stream_status', {'active': False}, namespace='/')
@ -694,11 +708,11 @@ def dj_disconnect():
@dj_socketio.on('start_broadcast')
def dj_start(data=None):
global _dj_grace_greenlet
global _dj_grace_greenlet, _mp3_broadcast_announced
# Cancel any pending auto-stop grace period (DJ reconnected in time)
if _dj_grace_greenlet is not None:
_dj_grace_greenlet.kill()
_dj_grace_greenlet.kill(block=True) # block=True prevents a GreenletExit race
_dj_grace_greenlet = None
print("INFO: DJ reconnected within grace period — broadcast continues")
@ -718,15 +732,23 @@ def dj_start(data=None):
broadcast_state['is_mp3_input'] = is_mp3_input
if not was_already_active:
# Fresh broadcast start — clear pre-roll.
# For non-MP3 input start the ffmpeg transcoder; for MP3 input chunks are
# distributed directly via _distribute_mp3(), no transcoder required.
# Fresh broadcast start — clear pre-roll and reset announcement flag.
with _mp3_lock:
_mp3_preroll.clear()
if not is_mp3_input:
if is_mp3_input:
# MP3-direct mode (Qt client): the DJ still needs to press play before
# audio flows. Firing broadcast_started now would cause listeners to
# connect to /stream.mp3 before any data exists, wait 60 s, then
# disconnect. Instead we hold back the announcement and send it on
# the very first audio_chunk so listeners connect when data is ready.
_mp3_broadcast_announced = False
print("BROADCAST: MP3-direct mode — deferring broadcast_started until first chunk")
else:
# Non-MP3 (browser webm/opus): ffmpeg transcoder starts immediately,
# so listeners can connect right away.
_start_transcoder_if_needed(is_mp3_input=False)
# Tell listeners a new broadcast has begun (triggers audio player reload)
listener_socketio.emit('broadcast_started', namespace='/')
listener_socketio.emit('broadcast_started', namespace='/')
else:
# DJ reconnected mid-broadcast - just ensure transcoder is alive (non-MP3 only)
# Do NOT clear pre-roll or trigger listener reload
@ -734,8 +756,12 @@ def dj_start(data=None):
if not is_mp3_input:
_start_transcoder_if_needed(is_mp3_input=False)
# Always send current status so any waiting listeners get unblocked
listener_socketio.emit('stream_status', {'active': True}, namespace='/')
# For MP3-direct fresh broadcast, hold back stream_status active=true too
# so listeners don't auto-connect before audio data is flowing.
# It will be sent alongside broadcast_started on the first audio_chunk.
# For non-MP3 (browser) mode or DJ reconnects, send immediately.
if not (is_mp3_input and not was_already_active):
listener_socketio.emit('stream_status', {'active': True}, namespace='/')
@dj_socketio.on('get_listener_count')
def dj_get_listener_count():
@ -744,8 +770,10 @@ def dj_get_listener_count():
@dj_socketio.on('listener_glow')
def dj_listener_glow(data):
"""DJ sets the glow intensity on the listener page."""
global _current_glow_intensity
intensity = int(data.get('intensity', 30)) if isinstance(data, dict) else 30
intensity = max(0, min(100, intensity))
_current_glow_intensity = intensity
listener_socketio.emit('listener_glow', {'intensity': intensity}, namespace='/')
@dj_socketio.on('deck_glow')
@ -758,9 +786,22 @@ def dj_deck_glow(data):
'B': bool(data.get('B', False)),
}, namespace='/')
@dj_socketio.on('now_playing')
def dj_now_playing(data):
"""Relay the currently playing track title to all listener pages."""
if not isinstance(data, dict):
return
listener_socketio.emit('now_playing', {
'title': str(data.get('title', '')),
'deck': str(data.get('deck', '')),
}, namespace='/')
@dj_socketio.on('stop_broadcast')
def dj_stop():
global _mp3_broadcast_announced
broadcast_state['active'] = False
broadcast_state['is_mp3_input'] = False
_mp3_broadcast_announced = False
session['is_dj'] = False
print("STOPPED: DJ stopped broadcasting")
@ -771,9 +812,17 @@ def dj_stop():
@dj_socketio.on('audio_chunk')
def dj_audio(data):
global _mp3_broadcast_announced
if broadcast_state['active'] and isinstance(data, (bytes, bytearray)):
if broadcast_state.get('is_mp3_input', False):
# MP3 input (e.g. Qt client): skip ffmpeg, send directly to listeners
# MP3 input (e.g. Qt client): skip ffmpeg, send directly to listeners.
# Fire broadcast_started on the very first chunk so listeners connect
# only once actual audio data is flowing (the DJ has pressed play).
if not _mp3_broadcast_announced:
_mp3_broadcast_announced = True
print("BROADCAST: First MP3 chunk received — announcing broadcast_started to listeners")
listener_socketio.emit('broadcast_started', namespace='/')
listener_socketio.emit('stream_status', {'active': True}, namespace='/')
_distribute_mp3(bytes(data))
else:
# Other formats (e.g. webm/opus from browser): route through ffmpeg transcoder
@ -848,8 +897,9 @@ def listener_disconnect():
@listener_socketio.on('join_listener')
def listener_join():
# SID already added in listener_connect(); just send stream status back
# SID already added in listener_connect(); send stream status and current glow
emit('stream_status', {'active': broadcast_state['active']})
emit('listener_glow', {'intensity': _current_glow_intensity})
@listener_socketio.on('get_listener_count')
def listener_get_count():