clean up a bunch of obselete audio code

22 files changed, 61 insertions, 822 deletions

diff --git a/src/audio/include/audio_backend.hpp b/src/audio/include/audio_backend.hpp
deleted file mode 100644
index 86d90d25..00000000
--- a/src/audio/include/audio_backend.hpp
+++ /dev/null
@@ -1,26 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <cstdint>
-namespace drivers {
-
-class IAudioBackend {
- public:
-  virtual ~IAudioBackend() {}
-
-  enum SampleRate {};
-  enum BitDepth {};
-
-  virtual auto Configure(SampleRate sample_rate, BitDepth bit_depth)
-      -> bool = 0;
-  virtual auto WritePcmData(uint8_t* data, size_t length) -> bool = 0;
-
-  virtual auto SetVolume(uint8_t percent) -> void = 0;
-};
-
-}  // namespace drivers
diff --git a/src/audio/include/audio_decoder.hpp b/src/audio/include/audio_decoder.hpp
deleted file mode 100644
index e8da415e..00000000
--- a/src/audio/include/audio_decoder.hpp
+++ /dev/null
@@ -1,51 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <cstddef>
-#include <cstdint>
-#include <memory>
-#include <vector>
-
-#include "chunk.hpp"
-#include "ff.h"
-#include "span.hpp"
-
-#include "audio_element.hpp"
-#include "codec.hpp"
-#include "stream_info.hpp"
-
-namespace audio {
-
-/*
- * An audio element that accepts various kinds of encoded audio streams as
- * input, and converts them to uncompressed PCM output.
- */
-class AudioDecoder {
- public:
-  AudioDecoder();
-  ~AudioDecoder();
-
-  auto Process(const InputStream& input, OutputStream* output) -> void;
-
-  AudioDecoder(const AudioDecoder&) = delete;
-  AudioDecoder& operator=(const AudioDecoder&) = delete;
-
- private:
-  std::unique_ptr<codecs::ICodec> current_codec_;
-  std::optional<StreamInfo::Encoded> current_input_format_;
-  std::optional<StreamInfo::Format> current_output_format_;
-  std::optional<std::size_t> duration_seconds_from_decoder_;
-  std::optional<std::size_t> seek_to_sample_;
-  bool has_prepared_output_;
-  bool has_samples_to_send_;
-  bool has_input_remaining_;
-
-  auto ProcessStreamInfo(const StreamInfo& info) -> bool;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/audio_element.hpp b/src/audio/include/audio_element.hpp
deleted file mode 100644
index 7e3d9d7d..00000000
--- a/src/audio/include/audio_element.hpp
+++ /dev/null
@@ -1,56 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <atomic>
-#include <cstdint>
-#include <deque>
-#include <memory>
-#include <vector>
-
-#include "freertos/FreeRTOS.h"
-
-#include "chunk.hpp"
-#include "freertos/message_buffer.h"
-#include "freertos/portmacro.h"
-#include "result.hpp"
-#include "span.hpp"
-
-#include "stream_buffer.hpp"
-#include "stream_event.hpp"
-#include "stream_info.hpp"
-#include "types.hpp"
-
-namespace audio {
-
-static const size_t kEventQueueSize = 8;
-
-/*
- * One indepedentent part of an audio pipeline. Each element has an input and
- * output message stream, and is responsible for taking data from the input
- * stream, applying some kind of transformation to it, then sending the result
- * out via the output stream. All communication with an element should be done
- * over these streams, as an element's methods are only safe to call from the
- * task that owns it.
- *
- * Each element implementation will have its input stream automatically parsed
- * by its owning task, and its various Process* methods will be invoked
- * accordingly. Element implementations are responsible for managing their own
- * writes to their output streams.
- */
-class IAudioElement {
- public:
-  IAudioElement() {}
-  virtual ~IAudioElement() {}
-
-  virtual auto NeedsToProcess() const -> bool = 0;
-
-  virtual auto Process(const std::vector<InputStream>& inputs,
-                       OutputStream* output) -> void = 0;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/audio_events.hpp b/src/audio/include/audio_events.hpp
index 9c945f33..28e29863 100644
--- a/src/audio/include/audio_events.hpp
+++ b/src/audio/include/audio_events.hpp
@@ -6,7 +6,6 @@
 
 #pragma once
 
-#include <stdint.h>
 #include <cstdint>
 #include <string>
 
diff --git a/src/audio/include/audio_fsm.hpp b/src/audio/include/audio_fsm.hpp
index 5d44fcda..cb307e68 100644
--- a/src/audio/include/audio_fsm.hpp
+++ b/src/audio/include/audio_fsm.hpp
@@ -10,6 +10,8 @@
 #include <memory>
 #include <vector>
 
+#include "tinyfsm.hpp"
+
 #include "audio_events.hpp"
 #include "audio_task.hpp"
 #include "bt_audio_output.hpp"
@@ -20,11 +22,9 @@
 #include "i2s_audio_output.hpp"
 #include "i2s_dac.hpp"
 #include "storage.hpp"
+#include "system_events.hpp"
 #include "tag_parser.hpp"
-#include "tinyfsm.hpp"
 #include "track.hpp"
-
-#include "system_events.hpp"
 #include "track_queue.hpp"
 
 namespace audio {
diff --git a/src/audio/include/audio_output.hpp b/src/audio/include/audio_output.hpp
deleted file mode 100644
index 074f21d4..00000000
--- a/src/audio/include/audio_output.hpp
+++ /dev/null
@@ -1,35 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <cstdint>
-#include <memory>
-
-#include "audio_common.h"
-#include "audio_element.h"
-#include "audio_element.hpp"
-
-namespace audio {
-
-class AudioOutput : IAudioElement {
- public:
-  AudioOutput();
-  ~AudioOutput();
-
-  auto GetAudioElement() -> audio_element_handle_t { return element_; }
-
-  auto SetInputBuffer(StreamBufferHandle_t buffer) -> void;
-
-  virtual auto Configure(audio_element_info_t& info) -> void = 0;
-  virtual auto SetSoftMute(bool enabled) -> void = 0;
-
- private:
-  audio_element_handle_t element_;
-  uint8_t volume_;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/audio_sink.hpp b/src/audio/include/audio_sink.hpp
index b5d6ef57..cce14242 100644
--- a/src/audio/include/audio_sink.hpp
+++ b/src/audio/include/audio_sink.hpp
@@ -8,11 +8,10 @@
 
 #include <stdint.h>
 #include <cstdint>
-#include "audio_element.hpp"
+
 #include "esp_heap_caps.h"
 #include "freertos/FreeRTOS.h"
 #include "idf_additions.h"
-#include "stream_info.hpp"
 
 namespace audio {
 
diff --git a/src/audio/include/audio_source.hpp b/src/audio/include/audio_source.hpp
index 6c54a882..a0d690a6 100644
--- a/src/audio/include/audio_source.hpp
+++ b/src/audio/include/audio_source.hpp
@@ -6,19 +6,7 @@
 
 #pragma once
 
-#include <stdint.h>
-
-#include <bitset>
-#include <memory>
-
-#include "freertos/FreeRTOS.h"
-#include "freertos/portmacro.h"
-#include "freertos/semphr.h"
-
 #include "codec.hpp"
-#include "stream_info.hpp"
-#include "track.hpp"
-#include "types.hpp"
 
 namespace audio {
 
diff --git a/src/audio/include/audio_task.hpp b/src/audio/include/audio_task.hpp
index cd79b708..d2c25add 100644
--- a/src/audio/include/audio_task.hpp
+++ b/src/audio/include/audio_task.hpp
@@ -6,12 +6,9 @@
 
 #pragma once
 
-#include <sys/_stdint.h>
-
 #include <cstdint>
 #include <memory>
 
-#include "audio_decoder.hpp"
 #include "audio_sink.hpp"
 #include "audio_source.hpp"
 #include "codec.hpp"
diff --git a/src/audio/include/bt_audio_output.hpp b/src/audio/include/bt_audio_output.hpp
index e11a5d44..d762bab6 100644
--- a/src/audio/include/bt_audio_output.hpp
+++ b/src/audio/include/bt_audio_output.hpp
@@ -6,20 +6,16 @@
 
 #pragma once
 
-#include <sys/_stdint.h>
 #include <cstdint>
 #include <memory>
 #include <vector>
 
-#include "audio_element.hpp"
-#include "audio_sink.hpp"
-#include "bluetooth.hpp"
-#include "chunk.hpp"
 #include "result.hpp"
 
+#include "audio_sink.hpp"
+#include "bluetooth.hpp"
 #include "gpios.hpp"
 #include "i2s_dac.hpp"
-#include "stream_info.hpp"
 
 namespace audio {
 
diff --git a/src/audio/include/chunk.hpp b/src/audio/include/chunk.hpp
deleted file mode 100644
index f5ba6654..00000000
--- a/src/audio/include/chunk.hpp
+++ /dev/null
@@ -1,65 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <cstddef>
-#include <cstdint>
-#include <memory>
-#include <optional>
-#include <string>
-
-#include "freertos/FreeRTOS.h"
-
-#include "cbor.h"
-#include "freertos/message_buffer.h"
-#include "freertos/portmacro.h"
-#include "freertos/queue.h"
-#include "result.hpp"
-#include "span.hpp"
-#include "stream_buffer.hpp"
-
-namespace audio {
-
-/**
- * Utility for handling an input stream of chunk data, which simplifies needing
- * access to blocks of data spanning two chunks.
- */
-class ChunkReader {
- public:
-  explicit ChunkReader(std::size_t chunk_size);
-  ~ChunkReader();
-
-  auto HandleBytesLeftOver(std::size_t bytes_left) -> void;
-  auto HandleBytesUsed(std::size_t bytes_used) -> void;
-
-  /*
-   * Reads chunks of data from the given input stream, and invokes the given
-   * callback to process each of them in turn.
-   *
-   * The callback will be invoked with a byte buffer and its size. The callback
-   * should process as much data as it can from this buffer, and then return the
-   * number of bytes it was able to read. Any leftover bytes will be added as a
-   * prefix to the next chunk.
-   *
-   * If this function encounters a message in the stream that is not a chunk, it
-   * will place the message at the start of the working_buffer and then return.
-   */
-  auto HandleNewData(cpp::span<std::byte> data) -> cpp::span<std::byte>;
-
-  auto GetLeftovers() -> cpp::span<std::byte>;
-
-  ChunkReader(const ChunkReader&) = delete;
-  ChunkReader& operator=(const ChunkReader&) = delete;
-
- private:
-  std::byte* raw_working_buffer_;
-  cpp::span<std::byte> working_buffer_;
-  cpp::span<std::byte> last_data_in_working_buffer_;
-  std::size_t leftover_bytes_ = 0;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/fatfs_audio_input.hpp b/src/audio/include/fatfs_audio_input.hpp
index df40696a..da44d2ec 100644
--- a/src/audio/include/fatfs_audio_input.hpp
+++ b/src/audio/include/fatfs_audio_input.hpp
@@ -12,13 +12,12 @@
 #include <memory>
 #include <string>
 
-#include "codec.hpp"
 #include "ff.h"
+#include "freertos/portmacro.h"
 
 #include "audio_source.hpp"
-#include "freertos/portmacro.h"
+#include "codec.hpp"
 #include "future_fetcher.hpp"
-#include "stream_info.hpp"
 #include "tag_parser.hpp"
 #include "types.hpp"
 
diff --git a/src/audio/include/fatfs_source.hpp b/src/audio/include/fatfs_source.hpp
new file mode 100644
index 00000000..e4187d60
--- /dev/null
+++ b/src/audio/include/fatfs_source.hpp
@@ -0,0 +1,44 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+
+#include "codec.hpp"
+#include "ff.h"
+
+#include "audio_source.hpp"
+
+namespace audio {
+
+/*
+ * Handles coordination with a persistent background task to asynchronously
+ * read files from disk into a StreamBuffer.
+ */
+class FatfsSource : public codecs::IStream {
+ public:
+  FatfsSource(codecs::StreamType, std::unique_ptr<FIL> file);
+  ~FatfsSource();
+
+  auto Read(cpp::span<std::byte> dest) -> ssize_t override;
+
+  auto CanSeek() -> bool override;
+
+  auto SeekTo(int64_t destination, SeekFrom from) -> void override;
+
+  auto CurrentPosition() -> int64_t override;
+
+  FatfsSource(const FatfsSource&) = delete;
+  FatfsSource& operator=(const FatfsSource&) = delete;
+
+ private:
+  std::unique_ptr<FIL> file_;
+};
+
+}  // namespace audio
\ No newline at end of file
diff --git a/src/audio/include/fir.h b/src/audio/include/fir.h
deleted file mode 100644
index e50c3eff..00000000
--- a/src/audio/include/fir.h
+++ /dev/null
@@ -1,131 +0,0 @@
-/*
- * FIR filter coefficients from resample-1.x smallfilter.h 
- * see Digital Audio Resampling Home Page located at
- * http://ccrma.stanford.edu/~jos/resample/
- */
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--1519, -1603, -1685, -1767, -1848, -1928, -2006, -2084, -2161, -2237,
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--3610, -3665, -3719, -3772, -3824, -3875, -3925, -3974, -4022, -4069,
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--5080, -5098, -5116, -5133, -5149, -5164, -5178, -5192, -5205, -5217,
--5228, -5238, -5248, -5257, -5265, -5272, -5278, -5284, -5289, -5293,
--5297, -5299, -5301, -5303, -5303, -5303, -5302, -5300, -5298, -5295,
--5291, -5287, -5282, -5276, -5270, -5263, -5255, -5246, -5237, -5228,
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--4363, -4332, -4301, -4270, -4238, -4206, -4174, -4142, -4109, -4076,
--4042, -4009, -3975, -3940, -3906, -3871, -3836, -3801, -3765, -3729,
--3693, -3657, -3620, -3584, -3547, -3510, -3472, -3435, -3397, -3360,
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--1345, -1306, -1268, -1230, -1191, -1153, -1115, -1077, -1040, -1002,
--965, -927, -890, -854, -817, -780, -744, -708, -672, -636, -600,
--565, -530, -494, -460, -425, -391, -356, -322, -289, -255, -222,
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-110, 100, 90, 80, 70, 60, 51, 41, 31, 22, 12, 3, -5, -14, -23, -32,
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--148, -156, -163, -170, -178, -185, -192, -199, -206, -212, -219,
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--418, -420, -422, -424, -426, -428, -430, -432, -433, -435, -436,
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--449, -449, -448, -448, -447, -447, -446, -445, -444, -443, -443,
--442, -441, -440, -438, -437, -436, -435, -433, -432, -430, -429,
--427, -426, -424, -422, -420, -419, -417, -415, -413, -411, -409,
--407, -405, -403, -400, -398, -396, -393, -391, -389, -386, -384,
--381, -379, -376, -374, -371, -368, -366, -363, -360, -357, -355,
--352, -349, -346, -343, -340, -337, -334, -331, -328, -325, -322,
--319, -316, -313, -310, -307, -304, -301, -298, -294, -291, -288,
--285, -282, -278, -275, -272, -269, -265, -262, -259, -256, -252,
--249, -246, -243, -239, -236, -233, -230, -226, -223, -220, -217,
--213, -210, -207, -204, -200, -197, -194, -191, -187, -184, -181,
--178, -175, -172, -168, -165, -162, -159, -156, -153, -150, -147,
--143, -140, -137, -134, -131, -128, -125, -122, -120, -117, -114,
--111, -108, -105, -102, -99, -97, -94, -91, -88, -86, -83, -80, -78,
--75, -72, -70, -67, -65, -62, -59, -57, -55, -52, -50, -47, -45, -43,
--40, -38, -36, -33, -31, -29, -27, -25, -22, -20, -18, -16, -14, -12,
--10, -8, -6, -4, -2, 0, 0, 2, 4, 6, 8, 9, 11, 13, 14, 16, 17, 19, 21,
-22, 24, 25, 27, 28, 29, 31, 32, 33, 35, 36, 37, 38, 40, 41, 42, 43,
-44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 56, 57, 58, 59,
-59, 60, 61, 62, 62, 63, 63, 64, 64, 65, 66, 66, 66, 67, 67, 68, 68,
-69, 69, 69, 70, 70, 70, 70, 71, 71, 71, 71, 71, 72, 72, 72, 72, 72,
-72, 72, 72, 72, 72, 72, 72, 72, 72, 72, 72, 72, 72, 72, 72, 72, 72,
-72, 71, 71, 71, 71, 71, 70, 70, 70, 70, 69, 69, 69, 69, 68, 68, 68,
-67, 67, 67, 66, 66, 66, 65, 65, 64, 64, 64, 63, 63, 62, 62, 62, 61,
-61, 60, 60, 59, 59, 58, 58, 58, 57, 57, 56, 56, 55, 55, 54, 54, 53,
-53, 52, 52, 51, 51, 50, 50, 49, 48, 48, 47, 47, 46, 46, 45, 45, 44,
-44, 43, 43, 42, 42, 41, 41, 40, 39, 39, 38, 38, 37, 37, 36, 36, 35,
-35, 34, 34, 33, 33, 32, 32, 31, 31, 30, 30, 29, 29, 28, 28, 27, 27,
-26, 26, 25, 25, 24, 24, 23, 23, 23, 22, 22, 21, 21, 20, 20, 20, 19,
-19, 18, 18, 17, 17, 17, 16, 16, 15, 15, 15, 14, 14, 14, 13, 13, 12,
-12, 12, 11, 11, 11, 10, 10, 10, 9, 9, 9, 9, 8, 8, 8, 7, 7, 7, 7, 6, 6,
-6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 3, 3, 3, 3, 3, 2, 2, 2, 2, 2, 1, 1, 1,
-1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, -1, -1,
--1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -2, -2, -2, -2, -2,
--2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
--2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
--2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
--2, -2, -2, -2, -2, -2, -2, -2, -1, -1, -1, -1, -1, -1, -1, -1, -1,
--1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
diff --git a/src/audio/include/i2s_audio_output.hpp b/src/audio/include/i2s_audio_output.hpp
index 717e6519..13cb183f 100644
--- a/src/audio/include/i2s_audio_output.hpp
+++ b/src/audio/include/i2s_audio_output.hpp
@@ -6,19 +6,14 @@
 
 #pragma once
 
-#include <sys/_stdint.h>
 #include <cstdint>
 #include <memory>
 #include <vector>
 
-#include "audio_element.hpp"
 #include "audio_sink.hpp"
-#include "chunk.hpp"
-#include "result.hpp"
-
 #include "gpios.hpp"
 #include "i2s_dac.hpp"
-#include "stream_info.hpp"
+#include "result.hpp"
 
 namespace audio {
 
diff --git a/src/audio/include/pipeline.hpp b/src/audio/include/pipeline.hpp
deleted file mode 100644
index bb773006..00000000
--- a/src/audio/include/pipeline.hpp
+++ /dev/null
@@ -1,51 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <memory>
-#include <optional>
-#include <string>
-#include <vector>
-
-#include "freertos/portmacro.h"
-
-#include "audio_element.hpp"
-#include "stream_info.hpp"
-
-namespace audio {
-
-static const std::size_t kPipelineBufferSize = 64 * 1024;
-
-class Pipeline {
- public:
-  explicit Pipeline(IAudioElement* output);
-  ~Pipeline();
-  auto AddInput(IAudioElement* input) -> Pipeline*;
-
-  auto OutputElement() const -> IAudioElement*;
-
-  auto NumInputs() const -> std::size_t;
-
-  auto InStreams(std::vector<RawStream>*) -> void;
-
-  auto OutStream() -> RawStream;
-
-  auto GetIterationOrder() -> std::vector<Pipeline*>;
-
-  // Not copyable or movable.
-  Pipeline(const Pipeline&) = delete;
-  Pipeline& operator=(const Pipeline&) = delete;
-
- private:
-  IAudioElement* root_;
-  std::vector<std::unique_ptr<Pipeline>> subtrees_;
-
-  std::array<std::byte, kPipelineBufferSize> output_buffer_;
-  StreamInfo output_info_;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/resample.hpp b/src/audio/include/resample.hpp
index 7b114f59..a9464cb1 100644
--- a/src/audio/include/resample.hpp
+++ b/src/audio/include/resample.hpp
@@ -1,6 +1,12 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
 #pragma once
 
-#include <sys/_stdint.h>
+#include <cstdint>
 #include <vector>
 
 #include "span.hpp"
diff --git a/src/audio/include/sink_mixer.hpp b/src/audio/include/sink_mixer.hpp
index 4a7627e8..37143439 100644
--- a/src/audio/include/sink_mixer.hpp
+++ b/src/audio/include/sink_mixer.hpp
@@ -6,19 +6,15 @@
 
 #pragma once
 
-#include <sys/_stdint.h>
 #include <cstdint>
 #include <memory>
 
 #include "resample.hpp"
 #include "sample.hpp"
 
-#include "audio_decoder.hpp"
 #include "audio_sink.hpp"
 #include "audio_source.hpp"
 #include "codec.hpp"
-#include "pipeline.hpp"
-#include "stream_info.hpp"
 
 namespace audio {
 
@@ -38,7 +34,7 @@ class SinkMixer {
  private:
   auto Main() -> void;
 
-  auto SetTargetFormat(const StreamInfo::Pcm& format) -> void;
+  auto SetTargetFormat(const IAudioSink::Format& format) -> void;
   auto HandleSamples(cpp::span<sample::Sample>, bool) -> size_t;
 
   struct Args {
diff --git a/src/audio/include/stream_buffer.hpp b/src/audio/include/stream_buffer.hpp
deleted file mode 100644
index 06fe8af5..00000000
--- a/src/audio/include/stream_buffer.hpp
+++ /dev/null
@@ -1,65 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <cstddef>
-#include <cstdint>
-
-#include "freertos/FreeRTOS.h"
-
-#include "freertos/message_buffer.h"
-#include "span.hpp"
-
-namespace audio {
-
-/*
- * A collection of the buffers required for two IAudioElement implementations to
- * stream data between each other.
- *
- * Currently, we use a FreeRTOS MessageBuffer to hold the byte stream, and also
- * maintain two chunk-sized buffers for the elements to stage their read and
- * write operations (as MessageBuffer copies the given data into its memory
- * space). A future optimisation here could be to instead post himem memory
- * addresses to the message buffer, and then maintain address spaces into which
- * we map these messages, rather than 'real' allocated buffers as we do now.
- */
-class StreamBuffer {
- public:
-  explicit StreamBuffer(std::size_t chunk_size, std::size_t buffer_size);
-  ~StreamBuffer();
-
-  /* Returns the handle for the underlying message buffer. */
-  auto Handle() -> MessageBufferHandle_t* { return &handle_; }
-
-  /*
-   * Returns a chunk-sized staging buffer that should be used *only* by the
-   * reader (sink) element.
-   */
-  auto ReadBuffer() -> cpp::span<std::byte> { return input_chunk_; }
-
-  /*
-   * Returns a chunk-sized staging buffer that should be used *only* by the
-   * writer (source) element.
-   */
-  auto WriteBuffer() -> cpp::span<std::byte> { return output_chunk_; }
-
-  StreamBuffer(const StreamBuffer&) = delete;
-  StreamBuffer& operator=(const StreamBuffer&) = delete;
-
- private:
-  std::byte* raw_memory_;
-  StaticMessageBuffer_t metadata_;
-  MessageBufferHandle_t handle_;
-
-  std::byte* raw_input_chunk_;
-  cpp::span<std::byte> input_chunk_;
-
-  std::byte* raw_output_chunk_;
-  cpp::span<std::byte> output_chunk_;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/stream_event.hpp b/src/audio/include/stream_event.hpp
deleted file mode 100644
index d98d9baa..00000000
--- a/src/audio/include/stream_event.hpp
+++ /dev/null
@@ -1,57 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <memory>
-
-#include "arena.hpp"
-#include "freertos/FreeRTOS.h"
-#include "freertos/queue.h"
-
-#include "span.hpp"
-#include "stream_info.hpp"
-
-namespace audio {
-
-struct StreamEvent {
-  static auto CreateStreamInfo(QueueHandle_t source, const StreamInfo& payload)
-      -> StreamEvent*;
-  static auto CreateArenaChunk(QueueHandle_t source, memory::ArenaPtr ptr)
-      -> StreamEvent*;
-  static auto CreateChunkNotification(QueueHandle_t source) -> StreamEvent*;
-  static auto CreateEndOfStream(QueueHandle_t source) -> StreamEvent*;
-  static auto CreateLogStatus() -> StreamEvent*;
-
-  StreamEvent();
-  ~StreamEvent();
-  StreamEvent(StreamEvent&&);
-
-  QueueHandle_t source;
-
-  enum {
-    UNINITIALISED,
-    STREAM_INFO,
-    ARENA_CHUNK,
-    CHUNK_NOTIFICATION,
-    END_OF_STREAM,
-    LOG_STATUS,
-  } tag;
-
-  union {
-    StreamInfo* stream_info;
-
-    memory::ArenaPtr arena_chunk;
-
-    // FIXME: It would be nice to also support a pointer to himem data here, to
-    // save a little ordinary heap space.
-  };
-
-  StreamEvent(const StreamEvent&) = delete;
-  StreamEvent& operator=(const StreamEvent&) = delete;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/stream_info.hpp b/src/audio/include/stream_info.hpp
deleted file mode 100644
index 01dd282a..00000000
--- a/src/audio/include/stream_info.hpp
+++ /dev/null
@@ -1,174 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <stdint.h>
-#include <sys/_stdint.h>
-#include <cstdint>
-#include <optional>
-#include <string>
-#include <string_view>
-#include <type_traits>
-#include <utility>
-#include <variant>
-
-#include "esp_heap_caps.h"
-#include "freertos/FreeRTOS.h"
-#include "freertos/ringbuf.h"
-#include "freertos/stream_buffer.h"
-
-#include "result.hpp"
-#include "span.hpp"
-#include "types.hpp"
-
-namespace audio {
-
-class StreamInfo {
- public:
-  StreamInfo() : bytes_in_stream_(0), total_length_bytes_(), format_() {}
-
-  // The number of bytes that are available for consumption within this
-  // stream's buffer.
-  auto bytes_in_stream() -> std::size_t& { return bytes_in_stream_; }
-  auto bytes_in_stream() const -> std::size_t { return bytes_in_stream_; }
-
-  auto total_length_bytes() -> std::optional<std::uint32_t>& {
-    return total_length_bytes_;
-  }
-  auto total_length_bytes() const -> std::optional<std::uint32_t> {
-    return total_length_bytes_;
-  }
-
-  auto total_length_seconds() -> std::optional<std::uint32_t>& {
-    return total_length_seconds_;
-  }
-  auto total_length_seconds() const -> std::optional<std::uint32_t> {
-    return total_length_seconds_;
-  }
-
-  struct Encoded {
-    // The codec that this stream is associated with.
-    codecs::StreamType type;
-
-    bool operator==(const Encoded&) const = default;
-  };
-
-  /*
-   * Two-channel, interleaved, 32-bit floating point pcm samples.
-   */
-  struct FloatingPointPcm {
-    // Number of channels in this stream.
-    uint8_t channels;
-    // The sample rate.
-    uint32_t sample_rate;
-
-    bool operator==(const FloatingPointPcm&) const = default;
-  };
-
-  struct Pcm {
-    // Number of channels in this stream.
-    uint8_t channels;
-    // Number of bits per sample.
-    uint8_t bits_per_sample;
-    // The sample rate.
-    uint32_t sample_rate;
-
-    auto bytes_per_sample() const -> uint8_t {
-      return bits_per_sample == 16 ? 2 : 4;
-    }
-
-    bool operator==(const Pcm&) const = default;
-  };
-
-  typedef std::variant<std::monostate, Encoded, FloatingPointPcm, Pcm> Format;
-  auto format() const -> const Format& { return format_; }
-  auto set_format(Format f) -> void { format_ = f; }
-
-  template <typename T>
-  auto format_as() const -> std::optional<T> {
-    if (std::holds_alternative<T>(format_)) {
-      return std::get<T>(format_);
-    }
-    return {};
-  }
-
-  bool operator==(const StreamInfo&) const = default;
-
- private:
-  std::size_t bytes_in_stream_;
-  std::optional<std::uint32_t> total_length_bytes_;
-  std::optional<std::uint32_t> total_length_seconds_;
-  Format format_{};
-};
-
-class InputStream;
-class OutputStream;
-
-class RawStream {
- public:
-  explicit RawStream(std::size_t size);
-  RawStream(std::size_t size, uint32_t);
-  ~RawStream();
-
-  auto info() -> StreamInfo& { return info_; }
-  auto data() -> cpp::span<std::byte>;
-  template <typename T>
-  auto data_as() -> cpp::span<T> {
-    auto orig = data();
-    return {reinterpret_cast<T*>(orig.data()), orig.size_bytes() / sizeof(T)};
-  }
-  auto empty() const -> bool { return info_.bytes_in_stream() == 0; }
-
- private:
-  StreamInfo info_;
-  std::size_t buffer_size_;
-  std::byte* buffer_;
-};
-
-class InputStream {
- public:
-  explicit InputStream(RawStream* s) : raw_(s) {}
-
-  void consume(std::size_t bytes) const;
-
-  const StreamInfo& info() const;
-
-  cpp::span<const std::byte> data() const;
-  template <typename T>
-  auto data_as() const -> cpp::span<const T> {
-    auto orig = data();
-    return {reinterpret_cast<const T*>(orig.data()),
-            orig.size_bytes() / sizeof(T)};
-  }
-
- private:
-  RawStream* raw_;
-};
-
-class OutputStream {
- public:
-  explicit OutputStream(RawStream* s) : raw_(s) {}
-
-  void add(std::size_t bytes) const;
-
-  void prepare(const StreamInfo::Format& new_format,
-               std::optional<uint32_t> length);
-
-  const StreamInfo& info() const;
-
-  cpp::span<std::byte> data() const;
-  template <typename T>
-  auto data_as() const -> cpp::span<T> {
-    auto orig = data();
-    return {reinterpret_cast<T*>(orig.data()), orig.size_bytes() / sizeof(T)};
-  }
-
- private:
-  RawStream* raw_;
-};
-
-}  // namespace audio
diff --git a/src/audio/include/stream_message.hpp b/src/audio/include/stream_message.hpp
deleted file mode 100644
index cf9ba39c..00000000
--- a/src/audio/include/stream_message.hpp
+++ /dev/null
@@ -1,69 +0,0 @@
-/*
- * Copyright 2023 jacqueline <me@jacqueline.id.au>
- *
- * SPDX-License-Identifier: GPL-3.0-only
- */
-
-#pragma once
-
-#include <cstdint>
-#include <functional>
-#include <optional>
-
-#include "cbor.h"
-#include "result.hpp"
-#include "span.hpp"
-
-namespace audio {
-
-extern const int kEncoderFlags;
-extern const int kDecoderFlags;
-
-enum MessageType {
-  TYPE_UNKNOWN,
-  TYPE_CHUNK_HEADER,
-  TYPE_STREAM_INFO,
-};
-
-template <typename Writer>
-auto WriteMessage(MessageType type, Writer&& writer, cpp::span<std::byte> data)
-    -> cpp::result<size_t, CborError> {
-  CborEncoder root;
-  CborEncoder container;
-  uint8_t* cast_data = reinterpret_cast<uint8_t*>(data.data());
-
-  cbor_encoder_init(&root, cast_data, data.size(), kEncoderFlags);
-  cbor_encoder_create_array(&root, &container, 2);
-  cbor_encode_uint(&container, type);
-
-  std::optional<CborError> inner_err = std::invoke(writer, container);
-  if (inner_err) {
-    return cpp::fail(inner_err.value());
-  }
-
-  cbor_encoder_close_container(&root, &container);
-  return cbor_encoder_get_buffer_size(&root, cast_data);
-}
-
-template <typename Result, typename Reader>
-auto ReadMessage(Reader&& reader, cpp::span<std::byte> data)
-    -> cpp::result<Result, CborError> {
-  CborParser parser;
-  CborValue root;
-  CborValue container;
-
-  cbor_parser_init(reinterpret_cast<uint8_t*>(data.data()), data.size(),
-                   kDecoderFlags, &parser, &root);
-  cbor_value_enter_container(&root, &container);
-  // Skip the type header
-  cbor_value_advance_fixed(&container);
-
-  return std::invoke(reader, container);
-}
-
-auto WriteTypeOnlyMessage(MessageType type, cpp::span<std::byte> data)
-    -> cpp::result<size_t, CborError>;
-auto ReadMessageType(cpp::span<std::byte> msg) -> MessageType;
-auto GetAdditionalData(cpp::span<std::byte> msg) -> cpp::span<std::byte>;
-
-}  // namespace audio