diff --git a/src/decoder/Client.hxx b/src/decoder/Client.hxx
index 610c90bb4..15710a3ca 100644
--- a/src/decoder/Client.hxx
+++ b/src/decoder/Client.hxx
@@ -28,6 +28,10 @@
 #include <stdint.h>
 
 struct AudioFormat;
+struct Tag;
+struct ReplayGainInfo;
+class MixRampInfo;
+class InputStream;
 
 /**
  * An interface between the decoder plugin and the MPD core.
@@ -84,6 +88,64 @@ public:
 	 * failed.
 	 */
 	virtual void SeekError() = 0;
+
+	/**
+	 * Sets the time stamp for the next data chunk [seconds].  The MPD
+	 * core automatically counts it up, and a decoder plugin only needs to
+	 * use this function if it thinks that adding to the time stamp based
+	 * on the buffer size won't work.
+	 */
+	virtual void SubmitTimestamp(double t) = 0;
+
+	/**
+	 * This function is called by the decoder plugin when it has
+	 * successfully decoded block of input data.
+	 *
+	 * @param is an input stream which is buffering while we are waiting
+	 * for the player
+	 * @param data the source buffer
+	 * @param length the number of bytes in the buffer
+	 * @return the current command, or DecoderCommand::NONE if there is no
+	 * command pending
+	 */
+	virtual DecoderCommand SubmitData(InputStream *is,
+					  const void *data, size_t length,
+					  uint16_t kbit_rate) = 0;
+
+	DecoderCommand SubmitData(InputStream &is,
+				  const void *data, size_t length,
+				  uint16_t kbit_rate) {
+		return SubmitData(&is, data, length, kbit_rate);
+	}
+
+	/**
+	 * This function is called by the decoder plugin when it has
+	 * successfully decoded a tag.
+	 *
+	 * @param is an input stream which is buffering while we are waiting
+	 * for the player
+	 * @param tag the tag to send
+	 * @return the current command, or DecoderCommand::NONE if there is no
+	 * command pending
+	 */
+	virtual DecoderCommand SubmitTag(InputStream *is, Tag &&tag) = 0 ;
+
+	DecoderCommand SubmitTag(InputStream &is, Tag &&tag) {
+		return SubmitTag(&is, std::move(tag));
+	}
+
+	/**
+	 * Set replay gain values for the following chunks.
+	 *
+	 * @param replay_gain_info the replay_gain_info object; may be nullptr
+	 * to invalidate the previous replay gain values
+	 */
+	virtual void SubmitReplayGain(const ReplayGainInfo *replay_gain_info) = 0;
+
+	/**
+	 * Store MixRamp tags.
+	 */
+	virtual void SubmitMixRamp(MixRampInfo &&mix_ramp) = 0;
 };
 
 #endif
diff --git a/src/decoder/DecoderAPI.cxx b/src/decoder/DecoderAPI.cxx
index da637a0b1..362df4e03 100644
--- a/src/decoder/DecoderAPI.cxx
+++ b/src/decoder/DecoderAPI.cxx
@@ -382,12 +382,11 @@ decoder_skip(DecoderClient *client, InputStream &is, size_t size)
 }
 
 void
-decoder_timestamp(DecoderClient &client, double t)
+Decoder::SubmitTimestamp(double t)
 {
 	assert(t >= 0);
 
-	auto &decoder = (Decoder &)client;
-	decoder.timestamp = t;
+	timestamp = t;
 }
 
 /**
@@ -446,56 +445,52 @@ update_stream_tag(DecoderClient &client, InputStream *is)
 }
 
 DecoderCommand
-decoder_data(DecoderClient &client,
-	     InputStream *is,
-	     const void *data, size_t length,
-	     uint16_t kbit_rate)
+Decoder::SubmitData(InputStream *is,
+		    const void *data, size_t length,
+		    uint16_t kbit_rate)
 {
-	auto &decoder = (Decoder &)client;
-	DecoderControl &dc = decoder.dc;
-
 	assert(dc.state == DecoderState::DECODE);
 	assert(dc.pipe != nullptr);
 	assert(length % dc.in_audio_format.GetFrameSize() == 0);
 
-	DecoderCommand cmd = decoder_lock_get_virtual_command(decoder);
+	DecoderCommand cmd = decoder_lock_get_virtual_command(*this);
 
 	if (cmd == DecoderCommand::STOP || cmd == DecoderCommand::SEEK ||
 	    length == 0)
 		return cmd;
 
-	assert(!decoder.initial_seek_pending);
-	assert(!decoder.initial_seek_running);
+	assert(!initial_seek_pending);
+	assert(!initial_seek_running);
 
 	/* send stream tags */
 
-	if (update_stream_tag(decoder, is)) {
-		if (decoder.decoder_tag != nullptr) {
+	if (update_stream_tag(*this, is)) {
+		if (decoder_tag != nullptr) {
 			/* merge with tag from decoder plugin */
-			Tag *tag = Tag::Merge(*decoder.decoder_tag,
-					      *decoder.stream_tag);
-			cmd = do_send_tag(decoder, *tag);
+			Tag *tag = Tag::Merge(*decoder_tag,
+					      *stream_tag);
+			cmd = do_send_tag(*this, *tag);
 			delete tag;
 		} else
 			/* send only the stream tag */
-			cmd = do_send_tag(decoder, *decoder.stream_tag);
+			cmd = do_send_tag(*this, *stream_tag);
 
 		if (cmd != DecoderCommand::NONE)
 			return cmd;
 	}
 
-	if (decoder.convert != nullptr) {
+	if (convert != nullptr) {
 		assert(dc.in_audio_format != dc.out_audio_format);
 
 		try {
-			auto result = decoder.convert->Convert({data, length});
+			auto result = convert->Convert({data, length});
 			data = result.data;
 			length = result.size;
 		} catch (const std::runtime_error &e) {
 			/* the PCM conversion has failed - stop
 			   playback, since we have no better way to
 			   bail out */
-			decoder.error = std::current_exception();
+			error = std::current_exception();
 			return DecoderCommand::STOP;
 		}
 	} else {
@@ -503,10 +498,9 @@ decoder_data(DecoderClient &client,
 	}
 
 	while (length > 0) {
-		MusicChunk *chunk;
 		bool full;
 
-		chunk = decoder.GetChunk();
+		auto *chunk = GetChunk();
 		if (chunk == nullptr) {
 			assert(dc.command != DecoderCommand::NONE);
 			return dc.command;
@@ -514,12 +508,12 @@ decoder_data(DecoderClient &client,
 
 		const auto dest =
 			chunk->Write(dc.out_audio_format,
-				     SongTime::FromS(decoder.timestamp) -
+				     SongTime::FromS(timestamp) -
 				     dc.song->GetStartTime(),
 				     kbit_rate);
 		if (dest.IsEmpty()) {
 			/* the chunk is full, flush it */
-			decoder.FlushChunk();
+			FlushChunk();
 			continue;
 		}
 
@@ -534,17 +528,17 @@ decoder_data(DecoderClient &client,
 		full = chunk->Expand(dc.out_audio_format, nbytes);
 		if (full) {
 			/* the chunk is full, flush it */
-			decoder.FlushChunk();
+			FlushChunk();
 		}
 
 		data = (const uint8_t *)data + nbytes;
 		length -= nbytes;
 
-		decoder.timestamp += (double)nbytes /
+		timestamp += (double)nbytes /
 			dc.out_audio_format.GetTimeToSize();
 
 		if (dc.end_time.IsPositive() &&
-		    decoder.timestamp >= dc.end_time.ToDoubleS())
+		    timestamp >= dc.end_time.ToDoubleS())
 			/* the end of this range has been reached:
 			   stop decoding */
 			return DecoderCommand::STOP;
@@ -554,11 +548,8 @@ decoder_data(DecoderClient &client,
 }
 
 DecoderCommand
-decoder_tag(DecoderClient &client, InputStream *is,
-	    Tag &&tag)
+Decoder::SubmitTag(InputStream *is, Tag &&tag)
 {
-	auto &decoder = (Decoder &)client;
-	gcc_unused const DecoderControl &dc = decoder.dc;
 	DecoderCommand cmd;
 
 	assert(dc.state == DecoderState::DECODE);
@@ -566,16 +557,16 @@ decoder_tag(DecoderClient &client, InputStream *is,
 
 	/* save the tag */
 
-	delete decoder.decoder_tag;
-	decoder.decoder_tag = new Tag(std::move(tag));
+	delete decoder_tag;
+	decoder_tag = new Tag(std::move(tag));
 
 	/* check for a new stream tag */
 
-	update_stream_tag(decoder, is);
+	update_stream_tag(*this, is);
 
 	/* check if we're seeking */
 
-	if (decoder_prepare_initial_seek(decoder))
+	if (decoder_prepare_initial_seek(*this))
 		/* during initial seek, no music chunk must be created
 		   until seeking is finished; skip the rest of the
 		   function here */
@@ -583,28 +574,24 @@ decoder_tag(DecoderClient &client, InputStream *is,
 
 	/* send tag to music pipe */
 
-	if (decoder.stream_tag != nullptr) {
+	if (stream_tag != nullptr) {
 		/* merge with tag from input stream */
 		Tag *merged;
 
-		merged = Tag::Merge(*decoder.stream_tag,
-				    *decoder.decoder_tag);
-		cmd = do_send_tag(decoder, *merged);
+		merged = Tag::Merge(*stream_tag, *decoder_tag);
+		cmd = do_send_tag(*this, *merged);
 		delete merged;
 	} else
 		/* send only the decoder tag */
-		cmd = do_send_tag(decoder, *decoder.decoder_tag);
+		cmd = do_send_tag(*this, *decoder_tag);
 
 	return cmd;
 }
 
 void
-decoder_replay_gain(DecoderClient &client,
-		    const ReplayGainInfo *replay_gain_info)
+Decoder::SubmitReplayGain(const ReplayGainInfo *new_replay_gain_info)
 {
-	auto &decoder = (Decoder &)client;
-
-	if (replay_gain_info != nullptr) {
+	if (new_replay_gain_info != nullptr) {
 		static unsigned serial;
 		if (++serial == 0)
 			serial = 1;
@@ -614,32 +601,29 @@ decoder_replay_gain(DecoderClient &client,
 			if (rgm != REPLAY_GAIN_ALBUM)
 				rgm = REPLAY_GAIN_TRACK;
 
-			const auto &tuple = replay_gain_info->tuples[rgm];
+			const auto &tuple = new_replay_gain_info->tuples[rgm];
 			const auto scale =
 				tuple.CalculateScale(replay_gain_preamp,
 						     replay_gain_missing_preamp,
 						     replay_gain_limit);
-			decoder.dc.replay_gain_db = 20.0 * log10f(scale);
+			dc.replay_gain_db = 20.0 * log10f(scale);
 		}
 
-		decoder.replay_gain_info = *replay_gain_info;
-		decoder.replay_gain_serial = serial;
+		replay_gain_info = *new_replay_gain_info;
+		replay_gain_serial = serial;
 
-		if (decoder.current_chunk != nullptr) {
+		if (current_chunk != nullptr) {
 			/* flush the current chunk because the new
 			   replay gain values affect the following
 			   samples */
-			decoder.FlushChunk();
+			FlushChunk();
 		}
 	} else
-		decoder.replay_gain_serial = 0;
+		replay_gain_serial = 0;
 }
 
 void
-decoder_mixramp(DecoderClient &client, MixRampInfo &&mix_ramp)
+Decoder::SubmitMixRamp(MixRampInfo &&mix_ramp)
 {
-	auto &decoder = (Decoder &)client;
-	DecoderControl &dc = decoder.dc;
-
 	dc.SetMixRamp(std::move(mix_ramp));
 }
diff --git a/src/decoder/DecoderAPI.hxx b/src/decoder/DecoderAPI.hxx
index 5f682e81c..f2d010c16 100644
--- a/src/decoder/DecoderAPI.hxx
+++ b/src/decoder/DecoderAPI.hxx
@@ -104,73 +104,4 @@ decoder_read_full(DecoderClient *decoder, InputStream &is,
 bool
 decoder_skip(DecoderClient *decoder, InputStream &is, size_t size);
 
-/**
- * Sets the time stamp for the next data chunk [seconds].  The MPD
- * core automatically counts it up, and a decoder plugin only needs to
- * use this function if it thinks that adding to the time stamp based
- * on the buffer size won't work.
- */
-void
-decoder_timestamp(DecoderClient &decoder, double t);
-
-/**
- * This function is called by the decoder plugin when it has
- * successfully decoded block of input data.
- *
- * @param decoder the decoder object
- * @param is an input stream which is buffering while we are waiting
- * for the player
- * @param data the source buffer
- * @param length the number of bytes in the buffer
- * @return the current command, or DecoderCommand::NONE if there is no
- * command pending
- */
-DecoderCommand
-decoder_data(DecoderClient &decoder, InputStream *is,
-	     const void *data, size_t length,
-	     uint16_t kbit_rate);
-
-static inline DecoderCommand
-decoder_data(DecoderClient &decoder, InputStream &is,
-	     const void *data, size_t length,
-	     uint16_t kbit_rate)
-{
-	return decoder_data(decoder, &is, data, length, kbit_rate);
-}
-
-/**
- * This function is called by the decoder plugin when it has
- * successfully decoded a tag.
- *
- * @param is an input stream which is buffering while we are waiting
- * for the player
- * @param tag the tag to send
- * @return the current command, or DecoderCommand::NONE if there is no
- * command pending
- */
-DecoderCommand
-decoder_tag(DecoderClient &decoder, InputStream *is, Tag &&tag);
-
-static inline DecoderCommand
-decoder_tag(DecoderClient &decoder, InputStream &is, Tag &&tag)
-{
-	return decoder_tag(decoder, &is, std::move(tag));
-}
-
-/**
- * Set replay gain values for the following chunks.
- *
- * @param replay_gain_info the replay_gain_info object; may be nullptr
- * to invalidate the previous replay gain values
- */
-void
-decoder_replay_gain(DecoderClient &decoder,
-		    const ReplayGainInfo *replay_gain_info);
-
-/**
- * Store MixRamp tags.
- */
-void
-decoder_mixramp(DecoderClient &decoder, MixRampInfo &&mix_ramp);
-
 #endif
diff --git a/src/decoder/DecoderInternal.hxx b/src/decoder/DecoderInternal.hxx
index b6801e758..61576bd32 100644
--- a/src/decoder/DecoderInternal.hxx
+++ b/src/decoder/DecoderInternal.hxx
@@ -124,6 +124,13 @@ struct Decoder final : DecoderClient {
 	SongTime GetSeekTime() override;
 	uint64_t GetSeekFrame() override;
 	void SeekError() override;
+	void SubmitTimestamp(double t) override;
+	DecoderCommand SubmitData(InputStream *is,
+				  const void *data, size_t length,
+				  uint16_t kbit_rate) override;
+	DecoderCommand SubmitTag(InputStream *is, Tag &&tag) override ;
+	void SubmitReplayGain(const ReplayGainInfo *replay_gain_info) override;
+	void SubmitMixRamp(MixRampInfo &&mix_ramp) override;
 };
 
 #endif
diff --git a/src/decoder/DecoderThread.cxx b/src/decoder/DecoderThread.cxx
index 61c02f558..2d42c5763 100644
--- a/src/decoder/DecoderThread.cxx
+++ b/src/decoder/DecoderThread.cxx
@@ -245,14 +245,14 @@ decoder_run_stream_fallback(Decoder &decoder, InputStream &is)
 
 /**
  * Attempt to load replay gain data, and pass it to
- * decoder_replay_gain().
+ * DecoderClient::SubmitReplayGain().
  */
 static void
-LoadReplayGain(Decoder &decoder, InputStream &is)
+LoadReplayGain(DecoderClient &client, InputStream &is)
 {
 	ReplayGainInfo info;
 	if (replay_gain_ape_read(is, info))
-		decoder_replay_gain(decoder, &info);
+		client.SubmitReplayGain(&info);
 }
 
 /**
diff --git a/src/decoder/plugins/AdPlugDecoderPlugin.cxx b/src/decoder/plugins/AdPlugDecoderPlugin.cxx
index d3077ce5e..4a43cc64b 100644
--- a/src/decoder/plugins/AdPlugDecoderPlugin.cxx
+++ b/src/decoder/plugins/AdPlugDecoderPlugin.cxx
@@ -73,9 +73,9 @@ adplug_file_decode(DecoderClient &client, Path path_fs)
 		int16_t buffer[2048];
 		constexpr unsigned frames_per_buffer = ARRAY_SIZE(buffer) / 2;
 		opl.update(buffer, frames_per_buffer);
-		cmd = decoder_data(client, nullptr,
-				   buffer, sizeof(buffer),
-				   0);
+		cmd = client.SubmitData(nullptr,
+					buffer, sizeof(buffer),
+					0);
 	} while (cmd == DecoderCommand::NONE);
 
 	delete player;
diff --git a/src/decoder/plugins/AudiofileDecoderPlugin.cxx b/src/decoder/plugins/AudiofileDecoderPlugin.cxx
index 552116673..d664fa6e0 100644
--- a/src/decoder/plugins/AudiofileDecoderPlugin.cxx
+++ b/src/decoder/plugins/AudiofileDecoderPlugin.cxx
@@ -223,9 +223,9 @@ audiofile_stream_decode(DecoderClient &client, InputStream &is)
 		if (nframes <= 0)
 			break;
 
-		cmd = decoder_data(client, nullptr,
-				   chunk, nframes * frame_size,
-				   kbit_rate);
+		cmd = client.SubmitData(nullptr,
+					chunk, nframes * frame_size,
+					kbit_rate);
 
 		if (cmd == DecoderCommand::SEEK) {
 			AFframecount frame = client.GetSeekFrame();
diff --git a/src/decoder/plugins/DsdiffDecoderPlugin.cxx b/src/decoder/plugins/DsdiffDecoderPlugin.cxx
index 4f705cc30..615b0010c 100644
--- a/src/decoder/plugins/DsdiffDecoderPlugin.cxx
+++ b/src/decoder/plugins/DsdiffDecoderPlugin.cxx
@@ -408,8 +408,8 @@ dsdiff_decode_chunk(DecoderClient &client, InputStream &is,
 		if (lsbitfirst)
 			bit_reverse_buffer(buffer, buffer + nbytes);
 
-		cmd = decoder_data(client, is, buffer, nbytes,
-				   sample_rate / 1000);
+		cmd = client.SubmitData(is, buffer, nbytes,
+					sample_rate / 1000);
 	}
 
 	return true;
diff --git a/src/decoder/plugins/DsfDecoderPlugin.cxx b/src/decoder/plugins/DsfDecoderPlugin.cxx
index e34144883..02d67ca05 100644
--- a/src/decoder/plugins/DsfDecoderPlugin.cxx
+++ b/src/decoder/plugins/DsfDecoderPlugin.cxx
@@ -289,9 +289,9 @@ dsf_decode_chunk(DecoderClient &client, InputStream &is,
 		uint8_t interleaved_buffer[MAX_CHANNELS * DSF_BLOCK_SIZE];
 		InterleaveDsfBlock(interleaved_buffer, buffer, channels);
 
-		cmd = decoder_data(client, is,
-				   interleaved_buffer, block_size,
-				   sample_rate / 1000);
+		cmd = client.SubmitData(is,
+					interleaved_buffer, block_size,
+					sample_rate / 1000);
 		++i;
 	}
 
diff --git a/src/decoder/plugins/FaadDecoderPlugin.cxx b/src/decoder/plugins/FaadDecoderPlugin.cxx
index 8dc0d2d95..236b260f3 100644
--- a/src/decoder/plugins/FaadDecoderPlugin.cxx
+++ b/src/decoder/plugins/FaadDecoderPlugin.cxx
@@ -393,9 +393,9 @@ faad_stream_decode(DecoderClient &client, InputStream &is,
 
 		/* send PCM samples to MPD */
 
-		cmd = decoder_data(client, is, decoded,
-				   (size_t)frame_info.samples * 2,
-				   bit_rate);
+		cmd = client.SubmitData(is, decoded,
+					(size_t)frame_info.samples * 2,
+					bit_rate);
 	} while (cmd != DecoderCommand::STOP);
 }
 
diff --git a/src/decoder/plugins/FfmpegDecoderPlugin.cxx b/src/decoder/plugins/FfmpegDecoderPlugin.cxx
index 57c86c549..d6f8f5e72 100644
--- a/src/decoder/plugins/FfmpegDecoderPlugin.cxx
+++ b/src/decoder/plugins/FfmpegDecoderPlugin.cxx
@@ -218,7 +218,8 @@ PtsToPcmFrame(uint64_t pts, const AVStream &stream,
 }
 
 /**
- * Invoke decoder_data() with the contents of an #AVFrame.
+ * Invoke DecoderClient::SubmitData() with the contents of an
+ * #AVFrame.
  */
 static DecoderCommand
 FfmpegSendFrame(DecoderClient &client, InputStream &is,
@@ -250,9 +251,9 @@ FfmpegSendFrame(DecoderClient &client, InputStream &is,
 		skip_bytes = 0;
 	}
 
-	return decoder_data(client, is,
-			    output_buffer.data, output_buffer.size,
-			    codec_context.bit_rate / 1000);
+	return client.SubmitData(is,
+				 output_buffer.data, output_buffer.size,
+				 codec_context.bit_rate / 1000);
 }
 
 #if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(57, 37, 0)
@@ -330,9 +331,8 @@ ffmpeg_send_packet(DecoderClient &client, InputStream &is,
 			if (cur_frame < min_frame)
 				skip_bytes = pcm_frame_size * (min_frame - cur_frame);
 		} else
-			decoder_timestamp(client,
-					  FfmpegTimeToDouble(pts,
-							     stream.time_base));
+			client.SubmitTimestamp(FfmpegTimeToDouble(pts,
+								  stream.time_base));
 	}
 
 #if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(57, 37, 0)
@@ -540,10 +540,10 @@ FfmpegParseMetaData(DecoderClient &client,
 	FfmpegParseMetaData(format_context, audio_stream, rg, mr);
 
 	if (rg.IsDefined())
-		decoder_replay_gain(client, &rg);
+		client.SubmitReplayGain(&rg);
 
 	if (mr.IsDefined())
-		decoder_mixramp(client, std::move(mr));
+		client.SubmitMixRamp(std::move(mr));
 }
 
 static void
@@ -576,7 +576,7 @@ FfmpegScanTag(const AVFormatContext &format_context, int audio_stream,
 
 /**
  * Check if a new stream tag was received and pass it to
- * decoder_tag().
+ * DecoderClient::SubmitTag().
  */
 static void
 FfmpegCheckTag(DecoderClient &client, InputStream &is,
@@ -593,7 +593,7 @@ FfmpegCheckTag(DecoderClient &client, InputStream &is,
 	TagBuilder tag;
 	FfmpegScanTag(format_context, audio_stream, tag);
 	if (!tag.IsEmpty())
-		decoder_tag(client, is, tag.Commit());
+		client.SubmitTag(is, tag.Commit());
 }
 
 #endif
diff --git a/src/decoder/plugins/FlacCommon.cxx b/src/decoder/plugins/FlacCommon.cxx
index 59d160e65..024a1c8f8 100644
--- a/src/decoder/plugins/FlacCommon.cxx
+++ b/src/decoder/plugins/FlacCommon.cxx
@@ -77,9 +77,9 @@ FlacDecoder::OnVorbisComment(const FLAC__StreamMetadata_VorbisComment &vc)
 {
 	ReplayGainInfo rgi;
 	if (flac_parse_replay_gain(rgi, vc))
-		decoder_replay_gain(*GetClient(), &rgi);
+		GetClient()->SubmitReplayGain(&rgi);
 
-	decoder_mixramp(*GetClient(), flac_parse_mixramp(vc));
+	GetClient()->SubmitMixRamp(flac_parse_mixramp(vc));
 
 	tag = flac_vorbis_comments_to_tag(&vc);
 }
@@ -148,9 +148,9 @@ FlacDecoder::OnWrite(const FLAC__Frame &frame,
 	unsigned bit_rate = nbytes * 8 * frame.header.sample_rate /
 		(1000 * frame.header.blocksize);
 
-	auto cmd = decoder_data(*GetClient(), GetInputStream(),
-				data.data, data.size,
-				bit_rate);
+	auto cmd = GetClient()->SubmitData(GetInputStream(),
+					   data.data, data.size,
+					   bit_rate);
 	switch (cmd) {
 	case DecoderCommand::NONE:
 	case DecoderCommand::START:
diff --git a/src/decoder/plugins/FlacDecoderPlugin.cxx b/src/decoder/plugins/FlacDecoderPlugin.cxx
index e865fee9d..ae3b14e48 100644
--- a/src/decoder/plugins/FlacDecoderPlugin.cxx
+++ b/src/decoder/plugins/FlacDecoderPlugin.cxx
@@ -147,8 +147,8 @@ flac_decoder_loop(FlacDecoder *data, FLAC__StreamDecoder *flac_dec)
 	while (true) {
 		DecoderCommand cmd;
 		if (!data->tag.IsEmpty()) {
-			cmd = decoder_tag(client, data->GetInputStream(),
-					  std::move(data->tag));
+			cmd = client.SubmitTag(data->GetInputStream(),
+					       std::move(data->tag));
 			data->tag.Clear();
 		} else
 			cmd = client.GetCommand();
diff --git a/src/decoder/plugins/FluidsynthDecoderPlugin.cxx b/src/decoder/plugins/FluidsynthDecoderPlugin.cxx
index 9a64a8013..51330ae21 100644
--- a/src/decoder/plugins/FluidsynthDecoderPlugin.cxx
+++ b/src/decoder/plugins/FluidsynthDecoderPlugin.cxx
@@ -176,8 +176,7 @@ fluidsynth_file_decode(DecoderClient &client, Path path_fs)
 		if (ret != 0)
 			break;
 
-		cmd = decoder_data(client, nullptr, buffer, sizeof(buffer),
-				   0);
+		cmd = client.SubmitData(nullptr, buffer, sizeof(buffer), 0);
 		if (cmd != DecoderCommand::NONE)
 			break;
 	}
diff --git a/src/decoder/plugins/GmeDecoderPlugin.cxx b/src/decoder/plugins/GmeDecoderPlugin.cxx
index 133e4a628..dd7d58a73 100644
--- a/src/decoder/plugins/GmeDecoderPlugin.cxx
+++ b/src/decoder/plugins/GmeDecoderPlugin.cxx
@@ -190,7 +190,7 @@ gme_file_decode(DecoderClient &client, Path path_fs)
 			return;
 		}
 
-		cmd = decoder_data(client, nullptr, buf, sizeof(buf), 0);
+		cmd = client.SubmitData(nullptr, buf, sizeof(buf), 0);
 		if (cmd == DecoderCommand::SEEK) {
 			unsigned where = client.GetSeekTime().ToMS();
 			gme_err = gme_seek(emu, where);
diff --git a/src/decoder/plugins/MadDecoderPlugin.cxx b/src/decoder/plugins/MadDecoderPlugin.cxx
index 19d462464..729decb37 100644
--- a/src/decoder/plugins/MadDecoderPlugin.cxx
+++ b/src/decoder/plugins/MadDecoderPlugin.cxx
@@ -182,13 +182,14 @@ struct MadDecoder {
 	void UpdateTimerNextFrame();
 
 	/**
-	 * Sends the synthesized current frame via decoder_data().
+	 * Sends the synthesized current frame via
+	 * DecoderClient::SubmitData().
 	 */
 	DecoderCommand SendPCM(unsigned i, unsigned pcm_length);
 
 	/**
 	 * Synthesize the current frame and send it via
-	 * decoder_data().
+	 * DecoderClient::SubmitData().
 	 */
 	DecoderCommand SyncAndSend();
 
@@ -361,11 +362,11 @@ MadDecoder::ParseId3(size_t tagsize, Tag **mpd_tag)
 		ReplayGainInfo rgi;
 
 		if (parse_id3_replay_gain_info(rgi, id3_tag)) {
-			decoder_replay_gain(*client, &rgi);
+			client->SubmitReplayGain(&rgi);
 			found_replay_gain = true;
 		}
 
-		decoder_mixramp(*client, parse_id3_mixramp(id3_tag));
+		client->SubmitMixRamp(parse_id3_mixramp(id3_tag));
 	}
 
 	id3_tag_delete(id3_tag);
@@ -806,7 +807,7 @@ MadDecoder::DecodeFirstFrame(Tag **tag)
 				rgi.Clear();
 				rgi.tuples[REPLAY_GAIN_TRACK].gain = lame.track_gain;
 				rgi.tuples[REPLAY_GAIN_TRACK].peak = lame.peak;
-				decoder_replay_gain(*client, &rgi);
+				client->SubmitReplayGain(&rgi);
 			}
 		}
 	}
@@ -903,9 +904,9 @@ MadDecoder::SendPCM(unsigned i, unsigned pcm_length)
 				       MAD_NCHANNELS(&frame.header));
 		num_samples *= MAD_NCHANNELS(&frame.header);
 
-		auto cmd = decoder_data(*client, input_stream, output_buffer,
-					sizeof(output_buffer[0]) * num_samples,
-					bit_rate / 1000);
+		auto cmd = client->SubmitData(input_stream, output_buffer,
+					      sizeof(output_buffer[0]) * num_samples,
+					      bit_rate / 1000);
 		if (cmd != DecoderCommand::NONE)
 			return cmd;
 	}
@@ -1010,8 +1011,8 @@ MadDecoder::Read()
 			ret = DecodeNextFrameHeader(&tag);
 
 			if (tag != nullptr) {
-				decoder_tag(*client, input_stream,
-					    std::move(*tag));
+				client->SubmitTag(input_stream,
+						  std::move(*tag));
 				delete tag;
 			}
 		} while (ret == DECODE_CONT);
@@ -1057,7 +1058,7 @@ mp3_decode(DecoderClient &client, InputStream &input_stream)
 		     data.total_time);
 
 	if (tag != nullptr) {
-		decoder_tag(client, input_stream, std::move(*tag));
+		client.SubmitTag(input_stream, std::move(*tag));
 		delete tag;
 	}
 
diff --git a/src/decoder/plugins/MikmodDecoderPlugin.cxx b/src/decoder/plugins/MikmodDecoderPlugin.cxx
index f91be1726..c01408ccf 100644
--- a/src/decoder/plugins/MikmodDecoderPlugin.cxx
+++ b/src/decoder/plugins/MikmodDecoderPlugin.cxx
@@ -177,7 +177,7 @@ mikmod_decoder_file_decode(DecoderClient &client, Path path_fs)
 	DecoderCommand cmd = DecoderCommand::NONE;
 	while (cmd == DecoderCommand::NONE && Player_Active()) {
 		ret = VC_WriteBytes(buffer, sizeof(buffer));
-		cmd = decoder_data(client, nullptr, buffer, ret, 0);
+		cmd = client.SubmitData(nullptr, buffer, ret, 0);
 	}
 
 	Player_Stop();
diff --git a/src/decoder/plugins/ModplugDecoderPlugin.cxx b/src/decoder/plugins/ModplugDecoderPlugin.cxx
index b7e3e5cc0..7e114c05a 100644
--- a/src/decoder/plugins/ModplugDecoderPlugin.cxx
+++ b/src/decoder/plugins/ModplugDecoderPlugin.cxx
@@ -160,9 +160,9 @@ mod_decode(DecoderClient &client, InputStream &is)
 		if (ret <= 0)
 			break;
 
-		cmd = decoder_data(client, nullptr,
-				   audio_buffer, ret,
-				   0);
+		cmd = client.SubmitData(nullptr,
+					audio_buffer, ret,
+					0);
 
 		if (cmd == DecoderCommand::SEEK) {
 			ModPlug_Seek(f, client.GetSeekTime().ToMS());
diff --git a/src/decoder/plugins/MpcdecDecoderPlugin.cxx b/src/decoder/plugins/MpcdecDecoderPlugin.cxx
index 9bfb1f3f1..2922daca9 100644
--- a/src/decoder/plugins/MpcdecDecoderPlugin.cxx
+++ b/src/decoder/plugins/MpcdecDecoderPlugin.cxx
@@ -172,7 +172,7 @@ mpcdec_decode(DecoderClient &client, InputStream &is)
 	rgi.tuples[REPLAY_GAIN_TRACK].gain = MPC_OLD_GAIN_REF  - (info.gain_title  / 256.);
 	rgi.tuples[REPLAY_GAIN_TRACK].peak = pow(10, info.peak_title / 256. / 20) / 32767;
 
-	decoder_replay_gain(client, &rgi);
+	client.SubmitReplayGain(&rgi);
 
 	client.Ready(audio_format, is.IsSeekable(),
 		     SongTime::FromS(mpc_streaminfo_get_length(&info)));
@@ -213,9 +213,9 @@ mpcdec_decode(DecoderClient &client, InputStream &is)
 		long bit_rate = unsigned(frame.bits) * audio_format.sample_rate
 			/ (1000 * frame.samples);
 
-		cmd = decoder_data(client, is,
-				   chunk, ret * sizeof(chunk[0]),
-				   bit_rate);
+		cmd = client.SubmitData(is,
+					chunk, ret * sizeof(chunk[0]),
+					bit_rate);
 	} while (cmd != DecoderCommand::STOP);
 
 	mpc_demux_exit(demux);
diff --git a/src/decoder/plugins/Mpg123DecoderPlugin.cxx b/src/decoder/plugins/Mpg123DecoderPlugin.cxx
index ffd899dad..ddfcb153e 100644
--- a/src/decoder/plugins/Mpg123DecoderPlugin.cxx
+++ b/src/decoder/plugins/Mpg123DecoderPlugin.cxx
@@ -129,7 +129,7 @@ mpd_mpg123_id3v2_tag(DecoderClient &client, const mpg123_id3v2 &id3v2)
 	for (size_t i = 0, n = id3v2.comments; i < n; ++i)
 		AddTagItem(tag, TAG_COMMENT, id3v2.comment_list[i].text);
 
-	decoder_tag(client, nullptr, tag.Commit());
+	client.SubmitTag(nullptr, tag.Commit());
 }
 
 static void
@@ -154,10 +154,10 @@ mpd_mpg123_id3v2_extras(DecoderClient &client, const mpg123_id3v2 &id3v2)
 	}
 
 	if (found_replay_gain)
-		decoder_replay_gain(client, &replay_gain);
+		client.SubmitReplayGain(&replay_gain);
 
 	if (found_mixramp)
-		decoder_mixramp(client, std::move(mix_ramp));
+		client.SubmitMixRamp(std::move(mix_ramp));
 }
 
 static void
@@ -257,7 +257,7 @@ mpd_mpg123_file_decode(DecoderClient &client, Path path_fs)
 
 		/* send to MPD */
 
-		cmd = decoder_data(client, nullptr, buffer, nbytes, info.bitrate);
+		cmd = client.SubmitData(nullptr, buffer, nbytes, info.bitrate);
 
 		if (cmd == DecoderCommand::SEEK) {
 			off_t c = client.GetSeekFrame();
@@ -266,7 +266,7 @@ mpd_mpg123_file_decode(DecoderClient &client, Path path_fs)
 				client.SeekError();
 			else {
 				client.CommandFinished();
-				decoder_timestamp(client, c/(double)audio_format.sample_rate);
+				client.SubmitTimestamp(c / (double)audio_format.sample_rate);
 			}
 
 			cmd = DecoderCommand::NONE;
diff --git a/src/decoder/plugins/OpusDecoderPlugin.cxx b/src/decoder/plugins/OpusDecoderPlugin.cxx
index 78bacb1db..0f8dcc2a2 100644
--- a/src/decoder/plugins/OpusDecoderPlugin.cxx
+++ b/src/decoder/plugins/OpusDecoderPlugin.cxx
@@ -212,10 +212,10 @@ MPDOpusDecoder::HandleTags(const ogg_packet &packet)
 			 &rgi,
 			 add_tag_handler, &tag_builder) &&
 	    !tag_builder.IsEmpty()) {
-		decoder_replay_gain(client, &rgi);
+		client.SubmitReplayGain(&rgi);
 
 		Tag tag = tag_builder.Commit();
-		auto cmd = decoder_tag(client, input_stream, std::move(tag));
+		auto cmd = client.SubmitTag(input_stream, std::move(tag));
 		if (cmd != DecoderCommand::NONE)
 			throw cmd;
 	}
@@ -237,16 +237,15 @@ MPDOpusDecoder::HandleAudio(const ogg_packet &packet)
 
 	if (nframes > 0) {
 		const size_t nbytes = nframes * frame_size;
-		auto cmd = decoder_data(client, input_stream,
-					output_buffer, nbytes,
-					0);
+		auto cmd = client.SubmitData(input_stream,
+					     output_buffer, nbytes,
+					     0);
 		if (cmd != DecoderCommand::NONE)
 			throw cmd;
 
 		if (packet.granulepos > 0)
-			decoder_timestamp(client,
-					  double(packet.granulepos)
-					  / opus_sample_rate);
+			client.SubmitTimestamp(double(packet.granulepos)
+					       / opus_sample_rate);
 	}
 }
 
diff --git a/src/decoder/plugins/PcmDecoderPlugin.cxx b/src/decoder/plugins/PcmDecoderPlugin.cxx
index 4215d62ba..7c93b87fb 100644
--- a/src/decoder/plugins/PcmDecoderPlugin.cxx
+++ b/src/decoder/plugins/PcmDecoderPlugin.cxx
@@ -154,7 +154,8 @@ pcm_stream_decode(DecoderClient &client, InputStream &is)
 
 		auto r = buffer.Read();
 		/* round down to the nearest frame size, because we
-		   must not pass partial frames to decoder_data() */
+		   must not pass partial frames to
+		   DecoderClient::SubmitData() */
 		r.size -= r.size % frame_size;
 		buffer.Consume(r.size);
 
@@ -165,7 +166,7 @@ pcm_stream_decode(DecoderClient &client, InputStream &is)
 					 (uint16_t *)(r.data + r.size));
 
 		cmd = !r.IsEmpty()
-			? decoder_data(client, is, r.data, r.size, 0)
+			? client.SubmitData(is, r.data, r.size, 0)
 			: client.GetCommand();
 		if (cmd == DecoderCommand::SEEK) {
 			uint64_t frame = client.GetSeekFrame();
diff --git a/src/decoder/plugins/SidplayDecoderPlugin.cxx b/src/decoder/plugins/SidplayDecoderPlugin.cxx
index 53799f6a3..b3b122ac3 100644
--- a/src/decoder/plugins/SidplayDecoderPlugin.cxx
+++ b/src/decoder/plugins/SidplayDecoderPlugin.cxx
@@ -366,9 +366,9 @@ sidplay_file_decode(DecoderClient &client, Path path_fs)
 		const size_t nbytes = result;
 #endif
 
-		decoder_timestamp(client, (double)player.time() / timebase);
+		client.SubmitTimestamp((double)player.time() / timebase);
 
-		cmd = decoder_data(client, nullptr, buffer, nbytes, 0);
+		cmd = client.SubmitData(nullptr, buffer, nbytes, 0);
 
 		if (cmd == DecoderCommand::SEEK) {
 			unsigned data_time = player.time();
diff --git a/src/decoder/plugins/SndfileDecoderPlugin.cxx b/src/decoder/plugins/SndfileDecoderPlugin.cxx
index 1a2b1cc8c..674573227 100644
--- a/src/decoder/plugins/SndfileDecoderPlugin.cxx
+++ b/src/decoder/plugins/SndfileDecoderPlugin.cxx
@@ -221,9 +221,9 @@ sndfile_stream_decode(DecoderClient &client, InputStream &is)
 		if (num_frames <= 0)
 			break;
 
-		cmd = decoder_data(client, is,
-				   buffer, num_frames * frame_size,
-				   0);
+		cmd = client.SubmitData(is,
+					buffer, num_frames * frame_size,
+					0);
 		if (cmd == DecoderCommand::SEEK) {
 			sf_count_t c = client.GetSeekFrame();
 			c = sf_seek(sf, c, SEEK_SET);
diff --git a/src/decoder/plugins/VorbisDecoderPlugin.cxx b/src/decoder/plugins/VorbisDecoderPlugin.cxx
index 41e13906d..a73f0e995 100644
--- a/src/decoder/plugins/VorbisDecoderPlugin.cxx
+++ b/src/decoder/plugins/VorbisDecoderPlugin.cxx
@@ -156,7 +156,7 @@ vorbis_send_comments(DecoderClient &client, InputStream &is,
 	if (!tag)
 		return;
 
-	decoder_tag(client, is, std::move(*tag));
+	client.SubmitTag(is, std::move(*tag));
 	delete tag;
 }
 
@@ -211,9 +211,9 @@ VorbisDecoder::SubmitSomePcm()
 	vorbis_synthesis_read(&dsp, n_frames);
 
 	const size_t nbytes = n_frames * frame_size;
-	auto cmd = decoder_data(client, input_stream,
-				buffer, nbytes,
-				0);
+	auto cmd = client.SubmitData(input_stream,
+				     buffer, nbytes,
+				     0);
 	if (cmd != DecoderCommand::NONE)
 		throw cmd;
 
@@ -252,7 +252,7 @@ VorbisDecoder::OnOggPacket(const ogg_packet &_packet)
 
 		ReplayGainInfo rgi;
 		if (vorbis_comments_to_replay_gain(rgi, vc.user_comments))
-			decoder_replay_gain(client, &rgi);
+			client.SubmitReplayGain(&rgi);
 	} else {
 		if (!dsp_initialized) {
 			dsp_initialized = true;
@@ -277,8 +277,7 @@ VorbisDecoder::OnOggPacket(const ogg_packet &_packet)
 
 #ifndef HAVE_TREMOR
 		if (packet.granulepos > 0)
-			decoder_timestamp(client,
-					  vorbis_granule_time(&dsp, packet.granulepos));
+			client.SubmitTimestamp(vorbis_granule_time(&dsp, packet.granulepos));
 #endif
 	}
 }
diff --git a/src/decoder/plugins/WavpackDecoderPlugin.cxx b/src/decoder/plugins/WavpackDecoderPlugin.cxx
index 55d0376c2..685c1b66d 100644
--- a/src/decoder/plugins/WavpackDecoderPlugin.cxx
+++ b/src/decoder/plugins/WavpackDecoderPlugin.cxx
@@ -196,9 +196,9 @@ wavpack_decode(DecoderClient &client, WavpackContext *wpc, bool can_seek)
 		format_samples(bytes_per_sample, chunk,
 			       samples_got * audio_format.channels);
 
-		cmd = decoder_data(client, nullptr, chunk,
-				   samples_got * output_sample_size,
-				   bitrate);
+		cmd = client.SubmitData(nullptr, chunk,
+					samples_got * output_sample_size,
+					bitrate);
 	}
 }
 
@@ -563,7 +563,7 @@ wavpack_filedecode(DecoderClient &client, Path path_fs)
 
 	ReplayGainInfo rgi;
 	if (wavpack_replaygain(rgi, wpc))
-		decoder_replay_gain(client, &rgi);
+		client.SubmitReplayGain(&rgi);
 
 	wavpack_decode(client, wpc, true);
 
diff --git a/src/decoder/plugins/WildmidiDecoderPlugin.cxx b/src/decoder/plugins/WildmidiDecoderPlugin.cxx
index 4f3de8018..a8db10dec 100644
--- a/src/decoder/plugins/WildmidiDecoderPlugin.cxx
+++ b/src/decoder/plugins/WildmidiDecoderPlugin.cxx
@@ -75,7 +75,7 @@ wildmidi_output(DecoderClient &client, midi *wm)
 	if (length <= 0)
 		return DecoderCommand::STOP;
 
-	return decoder_data(client, nullptr, buffer, length, 0);
+	return client.SubmitData(nullptr, buffer, length, 0);
 }
 
 static void
diff --git a/test/FakeDecoderAPI.cxx b/test/FakeDecoderAPI.cxx
index ad3d37071..3c4539af1 100644
--- a/test/FakeDecoderAPI.cxx
+++ b/test/FakeDecoderAPI.cxx
@@ -127,16 +127,14 @@ decoder_skip(DecoderClient *client, InputStream &is, size_t size)
 }
 
 void
-decoder_timestamp(gcc_unused DecoderClient &client,
-		  gcc_unused double t)
+FakeDecoder::SubmitTimestamp(gcc_unused double t)
 {
 }
 
 DecoderCommand
-decoder_data(gcc_unused DecoderClient &client,
-	     gcc_unused InputStream *is,
-	     const void *data, size_t datalen,
-	     gcc_unused uint16_t kbit_rate)
+FakeDecoder::SubmitData(gcc_unused InputStream *is,
+			const void *data, size_t datalen,
+			gcc_unused uint16_t kbit_rate)
 {
 	static uint16_t prev_kbit_rate;
 	if (kbit_rate != prev_kbit_rate) {
@@ -149,9 +147,8 @@ decoder_data(gcc_unused DecoderClient &client,
 }
 
 DecoderCommand
-decoder_tag(gcc_unused DecoderClient &client,
-	    gcc_unused InputStream *is,
-	    Tag &&tag)
+FakeDecoder::SubmitTag(gcc_unused InputStream *is,
+		       Tag &&tag)
 {
 	fprintf(stderr, "TAG: duration=%f\n", tag.duration.ToDoubleS());
 
@@ -162,8 +159,7 @@ decoder_tag(gcc_unused DecoderClient &client,
 }
 
 void
-decoder_replay_gain(gcc_unused DecoderClient &client,
-		    const ReplayGainInfo *rgi)
+FakeDecoder::SubmitReplayGain(const ReplayGainInfo *rgi)
 {
 	const ReplayGainTuple *tuple = &rgi->tuples[REPLAY_GAIN_ALBUM];
 	if (tuple->IsDefined())
@@ -177,7 +173,7 @@ decoder_replay_gain(gcc_unused DecoderClient &client,
 }
 
 void
-decoder_mixramp(gcc_unused DecoderClient &client, gcc_unused MixRampInfo &&mix_ramp)
+FakeDecoder::SubmitMixRamp(gcc_unused MixRampInfo &&mix_ramp)
 {
 	fprintf(stderr, "MixRamp: start='%s' end='%s'\n",
 		mix_ramp.GetStart(), mix_ramp.GetEnd());
diff --git a/test/FakeDecoderAPI.hxx b/test/FakeDecoderAPI.hxx
index b05e31404..d21d1615d 100644
--- a/test/FakeDecoderAPI.hxx
+++ b/test/FakeDecoderAPI.hxx
@@ -39,6 +39,13 @@ struct FakeDecoder final : DecoderClient {
 	SongTime GetSeekTime() override;
 	uint64_t GetSeekFrame() override;
 	void SeekError() override;
+	void SubmitTimestamp(double t) override;
+	DecoderCommand SubmitData(InputStream *is,
+				  const void *data, size_t length,
+				  uint16_t kbit_rate) override;
+	DecoderCommand SubmitTag(InputStream *is, Tag &&tag) override ;
+	void SubmitReplayGain(const ReplayGainInfo *replay_gain_info) override;
+	void SubmitMixRamp(MixRampInfo &&mix_ramp) override;
 };
 
 #endif