player/Thread: don't send silence if decoder is slow

src/MusicChunk.hxx

@@ -80,14 +80,6 @@ struct MusicChunkInfo {
 	ReplayGainInfo replay_gain_info;
 
 	/**
-	 * A magic value for #replay_gain_serial which omits updating
-	 * the #ReplayGainFilter.  This is used by "silence" chunks
-	 * (see PlayerThread::SendSilence()) so they don't affect the
-	 * replay gain.
-	 */
-	static constexpr unsigned IGNORE_REPLAY_GAIN = ~0u;
-
-	/**
 	 * A serial number for checking if replay gain info has
 	 * changed since the last chunk.  The magic value 0 indicates
 	 * that there is no replay gain info available.

src/output/Source.cxx

@@ -140,8 +140,7 @@ AudioOutputSource::GetChunkData(const MusicChunk &chunk,
 		replay_gain_filter_set_mode(*current_replay_gain_filter,
 					    replay_gain_mode);
 
-		if (chunk.replay_gain_serial != *replay_gain_serial_p &&
-		    chunk.replay_gain_serial != MusicChunk::IGNORE_REPLAY_GAIN) {
+		if (chunk.replay_gain_serial != *replay_gain_serial_p) {
 			replay_gain_filter_set_info(*current_replay_gain_filter,
 						    chunk.replay_gain_serial != 0
 						    ? &chunk.replay_gain_info

src/player/Thread.cxx

@@ -26,13 +26,11 @@
 #include "MusicPipe.hxx"
 #include "MusicBuffer.hxx"
 #include "MusicChunk.hxx"
-#include "pcm/Silence.hxx"
 #include "DetachedSong.hxx"
 #include "CrossFade.hxx"
 #include "Control.hxx"
 #include "tag/Tag.hxx"
 #include "Idle.hxx"
-#include "system/PeriodClock.hxx"
 #include "util/Domain.hxx"
 #include "thread/Name.hxx"
 #include "Log.hxx"
@@ -157,8 +155,6 @@ class Player {
 	 */
 	SongTime pending_seek;
 
-	PeriodClock throttle_silence_log;
-
 public:
 	Player(PlayerControl &_pc, DecoderControl &_dc,
 	       MusicBuffer &_buffer) noexcept
@@ -305,17 +301,6 @@ private:
 	 */
 	bool PlayNextChunk() noexcept;
 
-	/**
-	 * Sends a chunk of silence to the audio outputs.  This is
-	 * called when there is not enough decoded data in the pipe
-	 * yet, to prevent underruns in the hardware buffers.
-	 *
-	 * The player lock is not held.
-	 *
-	 * @return false on error
-	 */
-	bool SendSilence() noexcept;
-
 	unsigned UnlockCheckOutputs() noexcept {
 		const ScopeUnlock unlock(pc.mutex);
 		return pc.outputs.CheckPipe();
@@ -551,48 +536,6 @@ Player::CheckDecoderStartup() noexcept
 }
 
 bool
-Player::SendSilence() noexcept
-{
-	assert(output_open);
-	assert(play_audio_format.IsDefined());
-
-	MusicChunk *chunk = buffer.Allocate();
-	if (chunk == nullptr) {
-		/* this is non-fatal, because this means that the
-		   decoder has filled to buffer completely meanwhile;
-		   by ignoring the error, we work around this race
-		   condition */
-		LogDebug(player_domain, "Failed to allocate silence buffer");
-		return true;
-	}
-
-#ifndef NDEBUG
-	chunk->audio_format = play_audio_format;
-#endif
-
-	const size_t frame_size = play_audio_format.GetFrameSize();
-	/* this formula ensures that we don't send
-	   partial frames */
-	unsigned num_frames = sizeof(chunk->data) / frame_size;
-
-	chunk->bit_rate = 0;
-	chunk->time = SignedSongTime::Negative(); /* undefined time stamp */
-	chunk->length = num_frames * frame_size;
-	chunk->replay_gain_serial = MusicChunk::IGNORE_REPLAY_GAIN;
-	PcmSilence({chunk->data, chunk->length}, play_audio_format.format);
-
-	try {
-		pc.outputs.Play(chunk);
-	} catch (...) {
-		LogError(std::current_exception());
-		buffer.Return(chunk);
-		return false;
-	}
-
-	return true;
-}
-
-bool
 Player::SeekDecoder(SongTime seek_time) noexcept
 {
 	assert(song);
@@ -973,11 +916,8 @@ Player::SongBorder() noexcept
 
 		FormatDefault(player_domain, "played \"%s\"", song->GetURI());
 
-		throttle_silence_log.Reset();
-
 		ReplacePipe(dc.pipe);
 
-
 		pc.outputs.SongBorder();
 	}
 
@@ -1017,15 +957,6 @@ Player::Run() noexcept
 			    !dc.IsIdle()) {
 				/* not enough decoded buffer space yet */
 
-				{
-					const ScopeUnlock unlock(pc.mutex);
-					if (!paused && output_open &&
-					    pc.outputs.CheckPipe() < 4 &&
-					    !SendSilence())
-						break;
-				}
-
-				/* XXX race condition: check decoder again */
 				dc.WaitForDecoder();
 				continue;
 			} else {
@@ -1115,15 +1046,10 @@ Player::Run() noexcept
 			}
 		} else if (output_open) {
 			/* the decoder is too busy and hasn't provided
-			   new PCM data in time: send silence (if the
-			   output pipe is empty) */
-			const ScopeUnlock unlock(pc.mutex);
-
-			if (throttle_silence_log.CheckUpdate(std::chrono::seconds(5)))
-				FormatWarning(player_domain, "Decoder is too slow; playing silence to avoid xrun");
+			   new PCM data in time: wait for the
+			   decoder */
 
-			if (!SendSilence())
-				break;
+			dc.WaitForDecoder();
 		}
 	}