diff --git a/src/decoder/Client.hxx b/src/decoder/Client.hxx
index f0064fcbb..610c90bb4 100644
--- a/src/decoder/Client.hxx
+++ b/src/decoder/Client.hxx
@@ -21,7 +21,11 @@
 #define MPD_DECODER_CLIENT_HXX
 
 #include "check.h"
+#include "DecoderCommand.hxx"
 #include "Chrono.hxx"
+#include "Compiler.h"
+
+#include <stdint.h>
 
 struct AudioFormat;
 
@@ -42,6 +46,44 @@ public:
 	 */
 	virtual void Ready(AudioFormat audio_format,
 			   bool seekable, SignedSongTime duration) = 0;
+
+	/**
+	 * Determines the pending decoder command.
+	 *
+	 * @return the current command, or DecoderCommand::NONE if there is no
+	 * command pending
+	 */
+	gcc_pure
+	virtual DecoderCommand GetCommand() = 0;
+
+	/**
+	 * Called by the decoder when it has performed the requested command
+	 * (dc->command).  This function resets dc->command and wakes up the
+	 * player thread.
+	 */
+	virtual void CommandFinished() = 0;
+
+	/**
+	 * Call this when you have received the DecoderCommand::SEEK command.
+	 *
+	 * @return the destination position for the seek in milliseconds
+	 */
+	gcc_pure
+	virtual SongTime GetSeekTime() = 0;
+
+	/**
+	 * Call this when you have received the DecoderCommand::SEEK command.
+	 *
+	 * @return the destination position for the seek in frames
+	 */
+	gcc_pure
+	virtual uint64_t GetSeekFrame() = 0;
+
+	/**
+	 * Call this instead of CommandFinished() when seeking has
+	 * failed.
+	 */
+	virtual void SeekError() = 0;
 };
 
 #endif
diff --git a/src/decoder/DecoderAPI.cxx b/src/decoder/DecoderAPI.cxx
index 017edb897..da637a0b1 100644
--- a/src/decoder/DecoderAPI.cxx
+++ b/src/decoder/DecoderAPI.cxx
@@ -164,50 +164,45 @@ decoder_lock_get_virtual_command(DecoderClient &client)
 }
 
 DecoderCommand
-decoder_get_command(DecoderClient &client)
+Decoder::GetCommand()
 {
-	auto &decoder = (Decoder &)client;
-	return decoder_lock_get_virtual_command(decoder);
+	return decoder_lock_get_virtual_command(*this);
 }
 
 void
-decoder_command_finished(DecoderClient &client)
+Decoder::CommandFinished()
 {
-	auto &decoder = (Decoder &)client;
-	DecoderControl &dc = decoder.dc;
-
 	const ScopeLock protect(dc.mutex);
 
-	assert(dc.command != DecoderCommand::NONE ||
-	       decoder.initial_seek_running);
+	assert(dc.command != DecoderCommand::NONE || initial_seek_running);
 	assert(dc.command != DecoderCommand::SEEK ||
-	       decoder.initial_seek_running ||
-	       dc.seek_error || decoder.seeking);
+	       initial_seek_running ||
+	       dc.seek_error || seeking);
 	assert(dc.pipe != nullptr);
 
-	if (decoder.initial_seek_running) {
-		assert(!decoder.seeking);
-		assert(decoder.current_chunk == nullptr);
+	if (initial_seek_running) {
+		assert(!seeking);
+		assert(current_chunk == nullptr);
 		assert(dc.pipe->IsEmpty());
 
-		decoder.initial_seek_running = false;
-		decoder.timestamp = dc.start_time.ToDoubleS();
+		initial_seek_running = false;
+		timestamp = dc.start_time.ToDoubleS();
 		return;
 	}
 
-	if (decoder.seeking) {
-		decoder.seeking = false;
+	if (seeking) {
+		seeking = false;
 
 		/* delete frames from the old song position */
 
-		if (decoder.current_chunk != nullptr) {
-			dc.buffer->Return(decoder.current_chunk);
-			decoder.current_chunk = nullptr;
+		if (current_chunk != nullptr) {
+			dc.buffer->Return(current_chunk);
+			current_chunk = nullptr;
 		}
 
 		dc.pipe->Clear(*dc.buffer);
 
-		decoder.timestamp = dc.seek_time.ToDoubleS();
+		timestamp = dc.seek_time.ToDoubleS();
 	}
 
 	dc.command = DecoderCommand::NONE;
@@ -215,53 +210,44 @@ decoder_command_finished(DecoderClient &client)
 }
 
 SongTime
-decoder_seek_time(DecoderClient &client)
+Decoder::GetSeekTime()
 {
-	auto &decoder = (Decoder &)client;
-	const DecoderControl &dc = decoder.dc;
-
 	assert(dc.pipe != nullptr);
 
-	if (decoder.initial_seek_running)
+	if (initial_seek_running)
 		return dc.start_time;
 
 	assert(dc.command == DecoderCommand::SEEK);
 
-	decoder.seeking = true;
+	seeking = true;
 
 	return dc.seek_time;
 }
 
 uint64_t
-decoder_seek_where_frame(DecoderClient &client)
+Decoder::GetSeekFrame()
 {
-	auto &decoder = (Decoder &)client;
-	const DecoderControl &dc = decoder.dc;
-
-	return decoder_seek_time(decoder).ToScale<uint64_t>(dc.in_audio_format.sample_rate);
+	return GetSeekTime().ToScale<uint64_t>(dc.in_audio_format.sample_rate);
 }
 
 void
-decoder_seek_error(DecoderClient &client)
+Decoder::SeekError()
 {
-	auto &decoder = (Decoder &)client;
-	DecoderControl &dc = decoder.dc;
-
 	assert(dc.pipe != nullptr);
 
-	if (decoder.initial_seek_running) {
+	if (initial_seek_running) {
 		/* d'oh, we can't seek to the sub-song start position,
 		   what now? - no idea, ignoring the problem for now. */
-		decoder.initial_seek_running = false;
+		initial_seek_running = false;
 		return;
 	}
 
 	assert(dc.command == DecoderCommand::SEEK);
 
 	dc.seek_error = true;
-	decoder.seeking = false;
+	seeking = false;
 
-	decoder_command_finished(decoder);
+	CommandFinished();
 }
 
 InputStreamPtr
diff --git a/src/decoder/DecoderAPI.hxx b/src/decoder/DecoderAPI.hxx
index 0f49e832b..5f682e81c 100644
--- a/src/decoder/DecoderAPI.hxx
+++ b/src/decoder/DecoderAPI.hxx
@@ -54,56 +54,6 @@ class DecoderClient;
  */
 class StopDecoder {};
 
-/**
- * Determines the pending decoder command.
- *
- * @param decoder the decoder object
- * @return the current command, or DecoderCommand::NONE if there is no
- * command pending
- */
-gcc_pure
-DecoderCommand
-decoder_get_command(DecoderClient &decoder);
-
-/**
- * Called by the decoder when it has performed the requested command
- * (dc->command).  This function resets dc->command and wakes up the
- * player thread.
- *
- * @param decoder the decoder object
- */
-void
-decoder_command_finished(DecoderClient &decoder);
-
-/**
- * Call this when you have received the DecoderCommand::SEEK command.
- *
- * @param decoder the decoder object
- * @return the destination position for the seek in milliseconds
- */
-gcc_pure
-SongTime
-decoder_seek_time(DecoderClient &decoder);
-
-/**
- * Call this when you have received the DecoderCommand::SEEK command.
- *
- * @param decoder the decoder object
- * @return the destination position for the seek in frames
- */
-gcc_pure
-uint64_t
-decoder_seek_where_frame(DecoderClient &decoder);
-
-/**
- * Call this instead of decoder_command_finished() when seeking has
- * failed.
- *
- * @param decoder the decoder object
- */
-void
-decoder_seek_error(DecoderClient &decoder);
-
 /**
  * Open a new #InputStream and wait until it's ready.
  *
diff --git a/src/decoder/DecoderInternal.hxx b/src/decoder/DecoderInternal.hxx
index 2a6cf1a93..b6801e758 100644
--- a/src/decoder/DecoderInternal.hxx
+++ b/src/decoder/DecoderInternal.hxx
@@ -59,9 +59,8 @@ struct Decoder final : DecoderClient {
 	bool initial_seek_running = false;
 
 	/**
-	 * This flag is set by decoder_seek_time(), and checked by
-	 * decoder_command_finished().  It is used to clean up after
-	 * seeking.
+	 * This flag is set by GetSeekTime(), and checked by
+	 * CommandFinished().  It is used to clean up after seeking.
 	 */
 	bool seeking = false;
 
@@ -120,6 +119,11 @@ struct Decoder final : DecoderClient {
 	/* virtual methods from DecoderClient */
 	void Ready(AudioFormat audio_format,
 		   bool seekable, SignedSongTime duration) override;
+	DecoderCommand GetCommand() override;
+	void CommandFinished() override;
+	SongTime GetSeekTime() override;
+	uint64_t GetSeekFrame() override;
+	void SeekError() override;
 };
 
 #endif
diff --git a/src/decoder/plugins/AudiofileDecoderPlugin.cxx b/src/decoder/plugins/AudiofileDecoderPlugin.cxx
index 7c1cbe289..552116673 100644
--- a/src/decoder/plugins/AudiofileDecoderPlugin.cxx
+++ b/src/decoder/plugins/AudiofileDecoderPlugin.cxx
@@ -228,10 +228,10 @@ audiofile_stream_decode(DecoderClient &client, InputStream &is)
 				   kbit_rate);
 
 		if (cmd == DecoderCommand::SEEK) {
-			AFframecount frame = decoder_seek_where_frame(client);
+			AFframecount frame = client.GetSeekFrame();
 			afSeekFrame(fh, AF_DEFAULT_TRACK, frame);
 
-			decoder_command_finished(client);
+			client.CommandFinished();
 			cmd = DecoderCommand::NONE;
 		}
 	} while (cmd == DecoderCommand::NONE);
diff --git a/src/decoder/plugins/DsdiffDecoderPlugin.cxx b/src/decoder/plugins/DsdiffDecoderPlugin.cxx
index 7af58712d..4f705cc30 100644
--- a/src/decoder/plugins/DsdiffDecoderPlugin.cxx
+++ b/src/decoder/plugins/DsdiffDecoderPlugin.cxx
@@ -372,23 +372,23 @@ dsdiff_decode_chunk(DecoderClient &client, InputStream &is,
 	const unsigned buffer_frames = sizeof(buffer) / frame_size;
 	const size_t buffer_size = buffer_frames * frame_size;
 
-	auto cmd = decoder_get_command(client);
+	auto cmd = client.GetCommand();
 	for (offset_type remaining_bytes = total_bytes;
 	     remaining_bytes >= frame_size && cmd != DecoderCommand::STOP;) {
 		if (cmd == DecoderCommand::SEEK) {
-			uint64_t frame = decoder_seek_where_frame(client);
+			uint64_t frame = client.GetSeekFrame();
 			offset_type offset = FrameToOffset(frame, channels);
 			if (offset >= total_bytes) {
-				decoder_command_finished(client);
+				client.CommandFinished();
 				break;
 			}
 
 			if (dsdlib_skip_to(&client, is,
 					   start_offset + offset)) {
-				decoder_command_finished(client);
+				client.CommandFinished();
 				remaining_bytes = total_bytes - offset;
 			} else
-				decoder_seek_error(client);
+				client.SeekError();
 		}
 
 		/* see how much aligned data from the remaining chunk
diff --git a/src/decoder/plugins/DsfDecoderPlugin.cxx b/src/decoder/plugins/DsfDecoderPlugin.cxx
index 9818d2233..e34144883 100644
--- a/src/decoder/plugins/DsfDecoderPlugin.cxx
+++ b/src/decoder/plugins/DsfDecoderPlugin.cxx
@@ -259,23 +259,23 @@ dsf_decode_chunk(DecoderClient &client, InputStream &is,
 	const size_t block_size = channels * DSF_BLOCK_SIZE;
 	const offset_type start_offset = is.GetOffset();
 
-	auto cmd = decoder_get_command(client);
+	auto cmd = client.GetCommand();
 	for (offset_type i = 0; i < n_blocks && cmd != DecoderCommand::STOP;) {
 		if (cmd == DecoderCommand::SEEK) {
-			uint64_t frame = decoder_seek_where_frame(client);
+			uint64_t frame = client.GetSeekFrame();
 			offset_type block = FrameToBlock(frame);
 			if (block >= n_blocks) {
-				decoder_command_finished(client);
+				client.CommandFinished();
 				break;
 			}
 
 			offset_type offset =
 				start_offset + block * block_size;
 			if (dsdlib_skip_to(&client, is, offset)) {
-				decoder_command_finished(client);
+				client.CommandFinished();
 				i = block;
 			} else
-				decoder_seek_error(client);
+				client.SeekError();
 		}
 
 		/* worst-case buffer size */
diff --git a/src/decoder/plugins/FfmpegDecoderPlugin.cxx b/src/decoder/plugins/FfmpegDecoderPlugin.cxx
index 2fcdeac24..57c86c549 100644
--- a/src/decoder/plugins/FfmpegDecoderPlugin.cxx
+++ b/src/decoder/plugins/FfmpegDecoderPlugin.cxx
@@ -717,11 +717,11 @@ FfmpegDecode(DecoderClient &client, InputStream &input,
 
 	uint64_t min_frame = 0;
 
-	DecoderCommand cmd = decoder_get_command(client);
+	DecoderCommand cmd = client.GetCommand();
 	while (cmd != DecoderCommand::STOP) {
 		if (cmd == DecoderCommand::SEEK) {
 			int64_t where =
-				ToFfmpegTime(decoder_seek_time(client),
+				ToFfmpegTime(client.GetSeekTime(),
 					     av_stream.time_base) +
 				start_time_fallback(av_stream);
 
@@ -730,11 +730,11 @@ FfmpegDecode(DecoderClient &client, InputStream &input,
 			   stamp, not after */
 			if (av_seek_frame(&format_context, audio_stream, where,
 					  AVSEEK_FLAG_ANY|AVSEEK_FLAG_BACKWARD) < 0)
-				decoder_seek_error(client);
+				client.SeekError();
 			else {
 				avcodec_flush_buffers(codec_context);
-				min_frame = decoder_seek_where_frame(client);
-				decoder_command_finished(client);
+				min_frame = client.GetSeekFrame();
+				client.CommandFinished();
 			}
 		}
 
@@ -757,7 +757,7 @@ FfmpegDecode(DecoderClient &client, InputStream &input,
 						 interleaved_buffer);
 			min_frame = 0;
 		} else
-			cmd = decoder_get_command(client);
+			cmd = client.GetCommand();
 
 #if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(56, 25, 100)
 		av_packet_unref(&packet);
diff --git a/src/decoder/plugins/FlacDecoderPlugin.cxx b/src/decoder/plugins/FlacDecoderPlugin.cxx
index b78e98fea..e865fee9d 100644
--- a/src/decoder/plugins/FlacDecoderPlugin.cxx
+++ b/src/decoder/plugins/FlacDecoderPlugin.cxx
@@ -151,16 +151,15 @@ flac_decoder_loop(FlacDecoder *data, FLAC__StreamDecoder *flac_dec)
 					  std::move(data->tag));
 			data->tag.Clear();
 		} else
-			cmd = decoder_get_command(client);
+			cmd = client.GetCommand();
 
 		if (cmd == DecoderCommand::SEEK) {
-			FLAC__uint64 seek_sample =
-				decoder_seek_where_frame(client);
+			FLAC__uint64 seek_sample = client.GetSeekFrame();
 			if (FLAC__stream_decoder_seek_absolute(flac_dec, seek_sample)) {
 				data->position = 0;
-				decoder_command_finished(client);
+				client.CommandFinished();
 			} else
-				decoder_seek_error(client);
+				client.SeekError();
 		} else if (cmd == DecoderCommand::STOP)
 			break;
 
@@ -198,7 +197,7 @@ flac_decoder_loop(FlacDecoder *data, FLAC__StreamDecoder *flac_dec)
 		}
 
 		if (!FLAC__stream_decoder_process_single(flac_dec) &&
-		    decoder_get_command(client) == DecoderCommand::NONE) {
+		    client.GetCommand() == DecoderCommand::NONE) {
 			/* a failure that was not triggered by a
 			   decoder command */
 			flacPrintErroredState(FLAC__stream_decoder_get_state(flac_dec));
diff --git a/src/decoder/plugins/FlacInput.cxx b/src/decoder/plugins/FlacInput.cxx
index e07dbbd12..7cc3c3d96 100644
--- a/src/decoder/plugins/FlacInput.cxx
+++ b/src/decoder/plugins/FlacInput.cxx
@@ -36,7 +36,7 @@ FlacInput::Read(FLAC__byte buffer[], size_t *bytes)
 	if (r == 0) {
 		if (input_stream.LockIsEOF() ||
 		    (client != nullptr &&
-		     decoder_get_command(*client) != DecoderCommand::NONE))
+		     client->GetCommand() != DecoderCommand::NONE))
 			return FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM;
 		else
 			return FLAC__STREAM_DECODER_READ_STATUS_ABORT;
@@ -84,8 +84,8 @@ FLAC__bool
 FlacInput::Eof()
 {
 	return (client != nullptr &&
-		decoder_get_command(*client) != DecoderCommand::NONE &&
-		decoder_get_command(*client) != DecoderCommand::SEEK) ||
+		client->GetCommand() != DecoderCommand::NONE &&
+		client->GetCommand() != DecoderCommand::SEEK) ||
 		input_stream.LockIsEOF();
 }
 
@@ -93,7 +93,7 @@ void
 FlacInput::Error(FLAC__StreamDecoderErrorStatus status)
 {
 	if (client == nullptr ||
-	    decoder_get_command(*client) != DecoderCommand::STOP)
+	    client->GetCommand() != DecoderCommand::STOP)
 		LogWarning(flac_domain,
 			   FLAC__StreamDecoderErrorStatusString[status]);
 }
diff --git a/src/decoder/plugins/GmeDecoderPlugin.cxx b/src/decoder/plugins/GmeDecoderPlugin.cxx
index b3722d754..133e4a628 100644
--- a/src/decoder/plugins/GmeDecoderPlugin.cxx
+++ b/src/decoder/plugins/GmeDecoderPlugin.cxx
@@ -192,13 +192,13 @@ gme_file_decode(DecoderClient &client, Path path_fs)
 
 		cmd = decoder_data(client, nullptr, buf, sizeof(buf), 0);
 		if (cmd == DecoderCommand::SEEK) {
-			unsigned where = decoder_seek_time(client).ToMS();
+			unsigned where = client.GetSeekTime().ToMS();
 			gme_err = gme_seek(emu, where);
 			if (gme_err != nullptr) {
 				LogWarning(gme_domain, gme_err);
-				decoder_seek_error(client);
+				client.SeekError();
 			} else
-				decoder_command_finished(client);
+				client.CommandFinished();
 		}
 
 		if (gme_track_ended(emu))
diff --git a/src/decoder/plugins/MadDecoderPlugin.cxx b/src/decoder/plugins/MadDecoderPlugin.cxx
index 17944d42c..19d462464 100644
--- a/src/decoder/plugins/MadDecoderPlugin.cxx
+++ b/src/decoder/plugins/MadDecoderPlugin.cxx
@@ -985,18 +985,18 @@ MadDecoder::Read()
 		if (cmd == DecoderCommand::SEEK) {
 			assert(input_stream.IsSeekable());
 
-			unsigned long j =
-				TimeToFrame(decoder_seek_time(*client));
+			const auto t = client->GetSeekTime();
+			unsigned long j = TimeToFrame(t);
 			if (j < highest_frame) {
 				if (Seek(frame_offsets[j])) {
 					current_frame = j;
-					decoder_command_finished(*client);
+					client->CommandFinished();
 				} else
-					decoder_seek_error(*client);
+					client->SeekError();
 			} else {
-				seek_time = decoder_seek_time(*client);
+				seek_time = t;
 				mute_frame = MUTEFRAME_SEEK;
-				decoder_command_finished(*client);
+				client->CommandFinished();
 			}
 		} else if (cmd != DecoderCommand::NONE)
 			return false;
@@ -1042,7 +1042,7 @@ mp3_decode(DecoderClient &client, InputStream &input_stream)
 	if (!data.DecodeFirstFrame(&tag)) {
 		delete tag;
 
-		if (decoder_get_command(client) == DecoderCommand::NONE)
+		if (client.GetCommand() == DecoderCommand::NONE)
 			LogError(mad_domain,
 				 "input/Input does not appear to be a mp3 bit stream");
 		return;
diff --git a/src/decoder/plugins/ModplugDecoderPlugin.cxx b/src/decoder/plugins/ModplugDecoderPlugin.cxx
index fe666701c..b7e3e5cc0 100644
--- a/src/decoder/plugins/ModplugDecoderPlugin.cxx
+++ b/src/decoder/plugins/ModplugDecoderPlugin.cxx
@@ -165,8 +165,8 @@ mod_decode(DecoderClient &client, InputStream &is)
 				   0);
 
 		if (cmd == DecoderCommand::SEEK) {
-			ModPlug_Seek(f, decoder_seek_time(client).ToMS());
-			decoder_command_finished(client);
+			ModPlug_Seek(f, client.GetSeekTime().ToMS());
+			client.CommandFinished();
 		}
 
 	} while (cmd != DecoderCommand::STOP);
diff --git a/src/decoder/plugins/MpcdecDecoderPlugin.cxx b/src/decoder/plugins/MpcdecDecoderPlugin.cxx
index 2acb1968d..9bfb1f3f1 100644
--- a/src/decoder/plugins/MpcdecDecoderPlugin.cxx
+++ b/src/decoder/plugins/MpcdecDecoderPlugin.cxx
@@ -152,7 +152,7 @@ mpcdec_decode(DecoderClient &client, InputStream &is)
 
 	mpc_demux *demux = mpc_demux_init(&reader);
 	if (demux == nullptr) {
-		if (decoder_get_command(client) != DecoderCommand::STOP)
+		if (client.GetCommand() != DecoderCommand::STOP)
 			LogWarning(mpcdec_domain,
 				   "Not a valid musepack stream");
 		return;
@@ -180,16 +180,15 @@ mpcdec_decode(DecoderClient &client, InputStream &is)
 	DecoderCommand cmd = DecoderCommand::NONE;
 	do {
 		if (cmd == DecoderCommand::SEEK) {
-			mpc_int64_t where =
-				decoder_seek_where_frame(client);
+			mpc_int64_t where = client.GetSeekFrame();
 			bool success;
 
 			success = mpc_demux_seek_sample(demux, where)
 				== MPC_STATUS_OK;
 			if (success)
-				decoder_command_finished(client);
+				client.CommandFinished();
 			else
-				decoder_seek_error(client);
+				client.SeekError();
 		}
 
 		MPC_SAMPLE_FORMAT sample_buffer[MPC_DECODER_BUFFER_LENGTH];
diff --git a/src/decoder/plugins/Mpg123DecoderPlugin.cxx b/src/decoder/plugins/Mpg123DecoderPlugin.cxx
index 2b81abf74..ffd899dad 100644
--- a/src/decoder/plugins/Mpg123DecoderPlugin.cxx
+++ b/src/decoder/plugins/Mpg123DecoderPlugin.cxx
@@ -260,12 +260,12 @@ mpd_mpg123_file_decode(DecoderClient &client, Path path_fs)
 		cmd = decoder_data(client, nullptr, buffer, nbytes, info.bitrate);
 
 		if (cmd == DecoderCommand::SEEK) {
-			off_t c = decoder_seek_where_frame(client);
+			off_t c = client.GetSeekFrame();
 			c = mpg123_seek(handle, c, SEEK_SET);
 			if (c < 0)
-				decoder_seek_error(client);
+				client.SeekError();
 			else {
-				decoder_command_finished(client);
+				client.CommandFinished();
 				decoder_timestamp(client, c/(double)audio_format.sample_rate);
 			}
 
diff --git a/src/decoder/plugins/OpusDecoderPlugin.cxx b/src/decoder/plugins/OpusDecoderPlugin.cxx
index 6e3e9cf4a..78bacb1db 100644
--- a/src/decoder/plugins/OpusDecoderPlugin.cxx
+++ b/src/decoder/plugins/OpusDecoderPlugin.cxx
@@ -181,7 +181,7 @@ MPDOpusDecoder::OnOggBeginning(const ogg_packet &packet)
 	output_buffer = new opus_int16[opus_output_buffer_frames
 				       * audio_format.channels];
 
-	auto cmd = decoder_get_command(client);
+	auto cmd = client.GetCommand();
 	if (cmd != DecoderCommand::NONE)
 		throw cmd;
 }
@@ -291,10 +291,10 @@ mpd_opus_stream_decode(DecoderClient &client,
 			break;
 		} catch (DecoderCommand cmd) {
 			if (cmd == DecoderCommand::SEEK) {
-				if (d.Seek(decoder_seek_where_frame(client)))
-					decoder_command_finished(client);
+				if (d.Seek(client.GetSeekFrame()))
+					client.CommandFinished();
 				else
-					decoder_seek_error(client);
+					client.SeekError();
 			} else if (cmd != DecoderCommand::NONE)
 				break;
 		}
diff --git a/src/decoder/plugins/PcmDecoderPlugin.cxx b/src/decoder/plugins/PcmDecoderPlugin.cxx
index 4ee9f7435..4215d62ba 100644
--- a/src/decoder/plugins/PcmDecoderPlugin.cxx
+++ b/src/decoder/plugins/PcmDecoderPlugin.cxx
@@ -166,18 +166,18 @@ pcm_stream_decode(DecoderClient &client, InputStream &is)
 
 		cmd = !r.IsEmpty()
 			? decoder_data(client, is, r.data, r.size, 0)
-			: decoder_get_command(client);
+			: client.GetCommand();
 		if (cmd == DecoderCommand::SEEK) {
-			uint64_t frame = decoder_seek_where_frame(client);
+			uint64_t frame = client.GetSeekFrame();
 			offset_type offset = frame * frame_size;
 
 			try {
 				is.LockSeek(offset);
 				buffer.Clear();
-				decoder_command_finished(client);
+				client.CommandFinished();
 			} catch (const std::runtime_error &e) {
 				LogError(e);
-				decoder_seek_error(client);
+				client.SeekError();
 			}
 
 			cmd = DecoderCommand::NONE;
diff --git a/src/decoder/plugins/SidplayDecoderPlugin.cxx b/src/decoder/plugins/SidplayDecoderPlugin.cxx
index 97c0e7c50..53799f6a3 100644
--- a/src/decoder/plugins/SidplayDecoderPlugin.cxx
+++ b/src/decoder/plugins/SidplayDecoderPlugin.cxx
@@ -373,7 +373,7 @@ sidplay_file_decode(DecoderClient &client, Path path_fs)
 		if (cmd == DecoderCommand::SEEK) {
 			unsigned data_time = player.time();
 			unsigned target_time =
-				decoder_seek_time(client).ToScale(timebase);
+				client.GetSeekTime().ToScale(timebase);
 
 			/* can't rewind so return to zero and seek forward */
 			if(target_time<data_time) {
@@ -386,7 +386,7 @@ sidplay_file_decode(DecoderClient &client, Path path_fs)
 			       player.play(buffer, ARRAY_SIZE(buffer)) > 0)
 				data_time = player.time();
 
-			decoder_command_finished(client);
+			client.CommandFinished();
 		}
 
 		if (end > 0 && player.time() >= end)
diff --git a/src/decoder/plugins/SndfileDecoderPlugin.cxx b/src/decoder/plugins/SndfileDecoderPlugin.cxx
index 1d3efc293..1a2b1cc8c 100644
--- a/src/decoder/plugins/SndfileDecoderPlugin.cxx
+++ b/src/decoder/plugins/SndfileDecoderPlugin.cxx
@@ -225,12 +225,12 @@ sndfile_stream_decode(DecoderClient &client, InputStream &is)
 				   buffer, num_frames * frame_size,
 				   0);
 		if (cmd == DecoderCommand::SEEK) {
-			sf_count_t c = decoder_seek_where_frame(client);
+			sf_count_t c = client.GetSeekFrame();
 			c = sf_seek(sf, c, SEEK_SET);
 			if (c < 0)
-				decoder_seek_error(client);
+				client.SeekError();
 			else
-				decoder_command_finished(client);
+				client.CommandFinished();
 			cmd = DecoderCommand::NONE;
 		}
 	} while (cmd == DecoderCommand::NONE);
diff --git a/src/decoder/plugins/VorbisDecoderPlugin.cxx b/src/decoder/plugins/VorbisDecoderPlugin.cxx
index 86a4de9bb..41e13906d 100644
--- a/src/decoder/plugins/VorbisDecoderPlugin.cxx
+++ b/src/decoder/plugins/VorbisDecoderPlugin.cxx
@@ -264,7 +264,7 @@ VorbisDecoder::OnOggPacket(const ogg_packet &_packet)
 		if (vorbis_synthesis(&block, &packet) != 0) {
 			/* ignore bad packets, but give the MPD core a
 			   chance to stop us */
-			auto cmd = decoder_get_command(client);
+			auto cmd = client.GetCommand();
 			if (cmd != DecoderCommand::NONE)
 				throw cmd;
 			return;
@@ -322,10 +322,10 @@ vorbis_stream_decode(DecoderClient &client,
 			break;
 		} catch (DecoderCommand cmd) {
 			if (cmd == DecoderCommand::SEEK) {
-				if (d.Seek(decoder_seek_where_frame(client)))
-					decoder_command_finished(client);
+				if (d.Seek(client.GetSeekFrame()))
+					client.CommandFinished();
 				else
-					decoder_seek_error(client);
+					client.SeekError();
 			} else if (cmd != DecoderCommand::NONE)
 				break;
 		}
diff --git a/src/decoder/plugins/WavpackDecoderPlugin.cxx b/src/decoder/plugins/WavpackDecoderPlugin.cxx
index 3abd9b21c..55d0376c2 100644
--- a/src/decoder/plugins/WavpackDecoderPlugin.cxx
+++ b/src/decoder/plugins/WavpackDecoderPlugin.cxx
@@ -170,19 +170,19 @@ wavpack_decode(DecoderClient &client, WavpackContext *wpc, bool can_seek)
 
 	client.Ready(audio_format, can_seek, total_time);
 
-	DecoderCommand cmd = decoder_get_command(client);
+	DecoderCommand cmd = client.GetCommand();
 	while (cmd != DecoderCommand::STOP) {
 		if (cmd == DecoderCommand::SEEK) {
 			if (can_seek) {
-				auto where = decoder_seek_where_frame(client);
+				auto where = client.GetSeekFrame();
 
 				if (WavpackSeekSample(wpc, where)) {
-					decoder_command_finished(client);
+					client.CommandFinished();
 				} else {
-					decoder_seek_error(client);
+					client.SeekError();
 				}
 			} else {
-				decoder_seek_error(client);
+				client.SeekError();
 			}
 		}
 
diff --git a/src/decoder/plugins/WildmidiDecoderPlugin.cxx b/src/decoder/plugins/WildmidiDecoderPlugin.cxx
index 7e29fdd47..4f3de8018 100644
--- a/src/decoder/plugins/WildmidiDecoderPlugin.cxx
+++ b/src/decoder/plugins/WildmidiDecoderPlugin.cxx
@@ -114,11 +114,10 @@ wildmidi_file_decode(DecoderClient &client, Path path_fs)
 		cmd = wildmidi_output(client, wm);
 
 		if (cmd == DecoderCommand::SEEK) {
-			unsigned long seek_where =
-				decoder_seek_where_frame(client);
+			unsigned long seek_where = client.GetSeekFrame();
 
 			WildMidi_FastSeek(wm, &seek_where);
-			decoder_command_finished(client);
+			client.CommandFinished();
 			cmd = DecoderCommand::NONE;
 		}
 
diff --git a/test/FakeDecoderAPI.cxx b/test/FakeDecoderAPI.cxx
index 8b61ca5d3..ad3d37071 100644
--- a/test/FakeDecoderAPI.cxx
+++ b/test/FakeDecoderAPI.cxx
@@ -46,30 +46,30 @@ FakeDecoder::Ready(const AudioFormat audio_format,
 }
 
 DecoderCommand
-decoder_get_command(gcc_unused DecoderClient &client)
+FakeDecoder::GetCommand()
 {
 	return DecoderCommand::NONE;
 }
 
 void
-decoder_command_finished(gcc_unused DecoderClient &client)
+FakeDecoder::CommandFinished()
 {
 }
 
 SongTime
-decoder_seek_time(gcc_unused DecoderClient &client)
+FakeDecoder::GetSeekTime()
 {
 	return SongTime();
 }
 
 uint64_t
-decoder_seek_where_frame(gcc_unused DecoderClient &client)
+FakeDecoder::GetSeekFrame()
 {
 	return 1;
 }
 
 void
-decoder_seek_error(gcc_unused DecoderClient &client)
+FakeDecoder::SeekError()
 {
 }
 
diff --git a/test/FakeDecoderAPI.hxx b/test/FakeDecoderAPI.hxx
index fadbbb5e8..b05e31404 100644
--- a/test/FakeDecoderAPI.hxx
+++ b/test/FakeDecoderAPI.hxx
@@ -34,6 +34,11 @@ struct FakeDecoder final : DecoderClient {
 	/* virtual methods from DecoderClient */
 	void Ready(AudioFormat audio_format,
 		   bool seekable, SignedSongTime duration) override;
+	DecoderCommand GetCommand() override;
+	void CommandFinished() override;
+	SongTime GetSeekTime() override;
+	uint64_t GetSeekFrame() override;
+	void SeekError() override;
 };
 
 #endif