21 files changed, 772 insertions, 208 deletions

diff --git a/src/audio/CMakeLists.txt b/src/audio/CMakeLists.txt
index d98484c6..89a2e54d 100644
--- a/src/audio/CMakeLists.txt
+++ b/src/audio/CMakeLists.txt
@@ -1,6 +1,7 @@
 idf_component_register(
-  SRCS "audio_decoder.cpp" "fatfs_audio_input.cpp" "audio_task.cpp"
+  SRCS "audio_decoder.cpp" "audio_task.cpp" "fatfs_audio_input.cpp" "chunk.cpp"
+  "i2s_audio_output.cpp" "stream_info.cpp"
   INCLUDE_DIRS "include"
-  REQUIRES "codecs" "drivers")
+  REQUIRES "codecs" "drivers" "cbor")
 
 target_compile_options(${COMPONENT_LIB} PRIVATE ${EXTRA_WARNINGS})
diff --git a/src/audio/audio_decoder.cpp b/src/audio/audio_decoder.cpp
index ff9f0d62..7ed67339 100644
--- a/src/audio/audio_decoder.cpp
+++ b/src/audio/audio_decoder.cpp
@@ -1,12 +1,13 @@
 #include "audio_decoder.hpp"
 #include <cstddef>
+#include <cstdint>
+#include <string.h>
 #include "esp_heap_caps.h"
 #include "include/audio_element.hpp"
 #include "include/fatfs_audio_input.hpp"
 
 namespace audio {
 
-static const TickType_t kMaxWaitTicks = portMAX_DELAY;
   // TODO: could this be larger? depends on the codecs i guess
   static const std::size_t kWorkingBufferSize = kMaxFrameSize;
 
@@ -18,22 +19,14 @@ static const TickType_t kMaxWaitTicks = portMAX_DELAY;
     free(working_buffer_);
   }
 
-  auto AudioDecoder::InputCommandQueue() -> QueueHandle_t {
-    return input_queue_;
-  }
-
-  auto AudioDecoder::SetInputCommandQueue(QueueHandle_t queue) -> void {
-    input_queue_ = queue;
-  }
-
-  auto AudioDecoder::SetOutputCommandQueue(QueueHandle_t queue) -> void {
-    output_queue_ = queue;
-  }
-
   auto AudioDecoder::InputBuffer() -> StreamBufferHandle_t {
     return input_buffer_;
   }
 
+  auto AudioDecoder::OutputBuffer() -> StreamBufferHandle_t {
+    return output_buffer_;
+  }
+
   auto AudioDecoder::SetInputBuffer(StreamBufferHandle_t buffer) -> void {
     input_buffer_ = buffer;
   }
@@ -72,12 +65,23 @@ static const TickType_t kMaxWaitTicks = portMAX_DELAY;
       return OK;
     }
 
-    auto result = current_codec_->Process(data, length, working_buffer_, kWorkingBufferSize);
-    if (result.has_value()) {
-      xStreamBufferSend(&output_buffer_, working_buffer_, result.value(), kMaxWaitTicks);
-    } else {
-      // TODO: handle i guess
-      return ERROR;
+    while (true) {
+      auto result = current_codec_->Process(data, length, working_buffer_, kWorkingBufferSize);
+
+      if (result.has_error()) {
+        // TODO: handle i guess
+        return ERROR;
+      }
+      ICodec::Result process_res = result.value();
+
+      if (process_res.flush_output) {
+        xStreamBufferSend(&output_buffer_, working_buffer_, process_res.output_written, kMaxWaitTicks);
+      }
+
+      if (process_res.need_more_input) {
+        // TODO: wtf do we do about the leftover bytes?
+        return OK;
+      }
     }
 
     return OK;
diff --git a/src/drivers/audio_playback.cpp b/src/audio/audio_playback.cpp
index 300bf176..300bf176 100644
--- a/src/drivers/audio_playback.cpp
+++ b/src/audio/audio_playback.cpp
diff --git a/src/audio/audio_task.cpp b/src/audio/audio_task.cpp
index 86eb4f4a..ad0834e2 100644
--- a/src/audio/audio_task.cpp
+++ b/src/audio/audio_task.cpp
@@ -4,6 +4,7 @@
 
 #include <cstdint>
 
+#include "esp-idf/components/cbor/tinycbor/src/cbor.h"
 #include "esp_heap_caps.h"
 #include "freertos/portmacro.h"
 #include "freertos/queue.h"
@@ -11,6 +12,7 @@
 
 #include "audio_element.hpp"
 #include "include/audio_element.hpp"
+#include "stream_message.hpp"
 
 namespace audio {
 
@@ -22,71 +24,114 @@ void audio_task(void* args) {
   std::shared_ptr<IAudioElement> element = real_args->element;
   delete real_args;
 
-  QueueHandle_t commands = element->InputCommandQueue();
-  StreamBufferHandle_t stream = element->InputBuffer();
+  MessageBufferHandle_t *stream = element->InputBuffer();
 
-  // TODO: think about overflow.
-  uint8_t current_sequence_number;
-  uint8_t* frame_buffer =
+  uint8_t* message_buffer =
       (uint8_t*)heap_caps_malloc(kFrameSize, MALLOC_CAP_SPIRAM);
 
   while (1) {
-    IAudioElement::Command command;
-    ProcessResult result;
+    BaseType_t rtos_res;
+    IAudioElement::ProcessResult result;
 
-    if (!xQueueReceive(commands, &command, kCommandWaitTicks)) {
-      result = element->ProcessIdle();
-      if (result == IAudioElement::ERROR) {
-	break;
-      }
-      if (result == IAudioElement::OUTPUT_FULL) {
-	vTaskDelay(kIdleTaskDelay);
-      }
-      continue;
-    };
 
-    if (command.type == IAudioElement::SEQUENCE_NUMBER) {
-      if (command.sequence_number > current_sequence_number) {
-        current_sequence_number = command.sequence_number;
-      }
-      continue;
+    size_t message_size = 0;
+    if (message_buffer != nullptr) {
+      // TODO: tune delay.
+      message_size = xMessageBufferReceive(stream, &message_buffer, kFrameSize, portMAX_DELAY);
     }
 
-    if (command.type == IAudioElement::READ) {
-      assert(command.read_size <= kFrameSize);
-      assert(stream != NULL);
-      xStreamBufferReceive(stream, &frame_buffer, command.read_size, 0);
-
-      if (command.sequence_number == current_sequence_number) {
-        result = element->ProcessData(frame_buffer, command.read_size);
-	if (result == IAudioElement::ERROR) {
-	  break;
-	}
-	if (result == IAudioElement::OUTPUT_FULL) {
-	  // TODO: Do we care about this? could just park indefinitely.
-	}
-      }
-
+    if (message_size == 0) {
+      element->ProcessIdle();
       continue;
     }
 
-    if (command.type == IAudioElement::ELEMENT) {
-      assert(command.data != NULL);
-      if (command.sequence_number == current_sequence_number) {
-        result = element->ProcessElementCommand(command.data);
-	if (result == IAudioElement::ERROR) {
-	  break;
-	}
-	if (result == IAudioElement::OUTPUT_FULL) {
-	  // TODO: what does this mean lol
-	}
-      } else {
-        element->SkipElementCommand(command.data);
+    // We got a valid message. Check what kind it is so that we know how to
+    // process it.
+    CborParser parser;
+    CborValue value;
+    cbor_parser_init(message_buffer, message_size, &parser, &value);
+
+    MessageType message_type;
+    if (!cbor_value_is_integer(&value) || !cbor_value_get_integer(&value, &message_type)) {
+      // We weren't able to parse the message type. This is really bad, so just
+      // abort.
+      break; // TODO.
+    }
+
+    if (message_type == STREAM_INFO) {
+      errs = StreamInfo::Create(message_buffer, message_size).map(element->ProcessStreamInfo);
+      if (errs.has_error) {
+        // TODO;
       }
+    } else if (message_type == CHUNK_HEADER) {
+    } else {
+      // TODO.
     }
 
-    if (command.type == IAudioElement::QUIT) {
-      break;
+    cbor_value_
+    if (!xQueueReceive(commands, &command, wait_time)) {
+      if (bytes_in_stream > 0) {
+        size_t read_length = std::min(kMaxFrameSize - leftover_data, bytes_in_stream);
+        xStreamBufferReceive(stream, &frame_buffer + leftover_data, read_length, 0);
+
+        uint8_t *data_in = frame_buffer;
+        result = element->ProcessData(&data_in, read_length);
+        if (result == IAudioElement::ERROR) {
+          break;
+        }
+
+        if (result == IAudioElement::LEFTOVER_DATA) {
+          leftover_data = frame_buffer + read_length - data_in;
+          memmove(frame_buffer, data_in, leftover_data);
+        } else {
+          leftover_data = 0;
+        }
+      } else {
+        result = element->ProcessIdle();
+        if (result == IAudioElement::ERROR) {
+          break;
+        }
+        if (result == IAudioElement::OUTPUT_FULL) {
+          vTaskDelay(kIdleTaskDelay);
+        }
+      }
+    } else {
+      if (command.type == IAudioElement::SEQUENCE_NUMBER) {
+        if (command.sequence_number > current_sequence_number) {
+          current_sequence_number = command.sequence_number;
+          bytes_in_stream = 0;
+        }
+      } else if (command.type == IAudioElement::READ) {
+        assert(command.read_size <= kFrameSize);
+        assert(stream != NULL);
+
+        if (command.sequence_number == current_sequence_number) {
+          bytes_in_stream += command.read_size;
+        } else {
+          // This data is for a different stream, so just discard it.
+          xStreamBufferReceive(stream, &frame_buffer, command.read_size, 0);
+        }
+      } else if (command.type == IAudioElement::ELEMENT) {
+        assert(command.data != NULL);
+        if (command.sequence_number == current_sequence_number) {
+          if (bytes_in_stream > 0) {
+            // We're not ready to handle this yet, so put it back.
+            xQueueSendToFront(commands, &command, kMaxWaitTicks);
+          } else {
+            result = element->ProcessElementCommand(command.data);
+            if (result == IAudioElement::ERROR) {
+              break;
+            }
+            if (result == IAudioElement::OUTPUT_FULL) {
+              // TODO: what does this mean lol
+            }
+          }
+        } else {
+          element->SkipElementCommand(command.data);
+        }
+      } else if (command.type == IAudioElement::QUIT) {
+        break;
+      }
     }
   }
 
diff --git a/src/audio/chunk.cpp b/src/audio/chunk.cpp
new file mode 100644
index 00000000..a8864930
--- /dev/null
+++ b/src/audio/chunk.cpp
@@ -0,0 +1,115 @@
+#include "chunk.hpp"
+
+#include "cbor_encoder.hpp"
+#include "cbor_decoder.hpp"
+#include <string.h>
+#include <cstdint>
+#include "esp-idf/components/cbor/tinycbor/src/cbor.h"
+#include "stream_message.hpp"
+
+namespace audio {
+
+/*
+ * The maximum size that we expect a header to take up.
+ */
+// TODO: tune this.
+static const size_t kMaxHeaderSize = 64;
+
+auto WriteChunksToStream(MessageBufferHandle_t *stream, uint8_t *working_buffer, size_t working_buffer_length, std::function<size_t(uint8_t*,size_t)> callback, TickType_t max_wait) -> EncodeWriteResult {
+  while (1) {
+    // First, ask the callback for some data to write.
+    size_t chunk_size =
+      callback(
+          working_buffer + kMaxHeaderSize,
+          working_buffer_length - kMaxHeaderSize);
+
+    if (chunk_size == 0) {
+      // They had nothing for us, so bail out.
+      return CHUNK_OUT_OF_DATA;
+    }
+
+    // Put together a header.
+    cbor::Encoder encoder(cbor::CONTAINER_ARRAY, 3, working_buffer, working_buffer_length);
+    encoder.WriteUnsigned(TYPE_CHUNK_HEADER);
+    // Note here that we need to write the offset of the chunk into the header.
+    // We could be smarter here and write the actual header size, allowing us to
+    // pack slightly more data into each message, but this is hard so I haven't
+    // done it. Please make my code better for me.
+    encoder.WriteUnsigned(kMaxHeaderSize);
+    encoder.WriteUnsigned(chunk_size);
+    if (encoder.Finish().has_error()) {
+      return CHUNK_ENCODING_ERROR;
+    };
+
+    // Try to write to the buffer. Note the return type here will be either 0 or
+    // kMaxHeaderSize + chunk_size, as MessageBuffer doesn't allow partial
+    // writes.
+    size_t actual_write_size =
+      xMessageBufferSend(
+          *stream, working_buffer, kMaxHeaderSize + chunk_size, max_wait);
+
+    if (actual_write_size == 0) {
+      // We failed to write in time, so bail out. This is techinically data loss
+      // unless the caller wants to go and parse our working buffer, but we
+      // assume the caller has a good reason to time us out.
+      return CHUNK_WRITE_TIMEOUT;
+    }
+  }
+}
+
+auto ReadChunksFromStream(MessageBufferHandle_t *stream, uint8_t *working_buffer, size_t working_buffer_length, std::function<size_t(uint8_t*,size_t)> callback, TickType_t max_wait) -> EncodeReadResult {
+  // Spillover if the previous iteration did not consume all of the input.
+  size_t leftover_bytes = 0;
+  while (1) {
+    // First, wait for a message to arrive over the buffer.
+    size_t read_size =
+      xMessageBufferReceive(
+          *stream, working_buffer + leftover_bytes, working_buffer_length - leftover_bytes, max_wait);
+
+    if (read_size == 0) {
+      return CHUNK_READ_TIMEOUT;
+    }
+
+    auto decoder = cbor::MapDecoder::Create(working_buffer + leftover_bytes, read_size);
+    if (decoder.has_error()) {
+      // Weird; this implies someone is shoving invalid data into the buffer.
+      return CHUNK_DECODING_ERROR;
+    }
+
+    MessageType type = decoder.value().ParseUnsigned().value_or(TYPE_UNKNOWN);
+    if (type != TYPE_CHUNK_HEADER) {
+      // This message wasn't for us, so put it in a consistent place and let the
+      // caller handle it.
+      memmove(working_buffer, working_buffer + leftover_bytes, read_size);
+      return CHUNK_STREAM_ENDED;
+    }
+
+    // Work the size and position of the chunk (don't assume it's at
+    // kMaxHeaderSize offset for future-proofing).
+    header_length = decoder.ParseUnsigned().value_or(0);
+    chunk_length = decoder.ParseUnsigned().value_or(0);
+    if (decoder.Failed()) {
+      return CHUNK_DECODING_ERROR;
+    }
+
+    // Now we need to stick the end of the last chunk (if it exists) onto the
+    // front of the new chunk. Do it this way around bc we assume the old chunk
+    // is shorter, and therefore faster to move.
+    uint8_t *combined_buffer = working_buffer + header_length - leftover_bytes;
+    size_t combined_buffer_size = leftover_bytes + chunk_length;
+    if (leftover_bytes > 0) {
+      memmove(combined_buffer, working_buffer, leftover_bytes);
+    }
+
+    // Tell the callback about the new data.
+    size_t amount_processed = callback(combined_buffer, combined_buffer_size);
+
+    // Prepare for the next iteration.
+    leftover_bytes = combined_buffer_size - amount_processed;
+    if (leftover_bytes > 0) {
+      memmove(working_buffer, combined_buffer + amount_processed, leftover_bytes);
+    }
+  }
+}
+
+} // namespace audio
diff --git a/src/audio/fatfs_audio_input.cpp b/src/audio/fatfs_audio_input.cpp
index df38f1d6..0cf1abe5 100644
--- a/src/audio/fatfs_audio_input.cpp
+++ b/src/audio/fatfs_audio_input.cpp
@@ -16,59 +16,30 @@ static const TickType_t kMaxWaitTicks = portMAX_DELAY;
 // into memory as soon as possible.
 static constexpr std::size_t kOutputBufferSize = 1024 * 128;
 static constexpr std::size_t kQueueItemSize = sizeof(IAudioElement::Command);
-// Use a large enough command queue size that we can fit reads for the full
-// buffer into the queue.
-static constexpr std::size_t kOutputQueueItemNumber = kOutputBufferSize / kMaxFrameSize;
-static constexpr std::size_t kOutputQueueSize = kOutputQueueItemNumber * kQueueItemSize;
-
-// This should be a relatively responsive element, so no need for a particularly
-// large queue.
-static constexpr std::size_t kInputQueueItemNumber = 4;
-static constexpr std::size_t kInputQueueSize = kInputQueueItemNumber * kQueueItemSize;
 
 FatfsAudioInput::FatfsAudioInput(std::shared_ptr<drivers::SdStorage> storage)
     : IAudioElement(), storage_(storage) {
   working_buffer_ = heap_caps_malloc(kMaxFrameSize, MALLOC_CAP_SPIRAM);
 
-  input_queue_memory_ = heap_caps_malloc(kInputQueueSize, MALLOC_CAP_SPIRAM);
-  input_queue_ = xQueueCreateStatic(
-      kInputQueueItemNumber, kQueueItemSize, input_queue_memory_, &input_queue_metadata_);
-
-  output_queue_memory_ = heap_caps_malloc(kOutputQueueSize, MALLOC_CAP_SPIRAM);
-  output_queue_ =
-      xQueueCreateStatic(kOutputQueueItems, kQueueItemSize, output_queue_memory_,
-                         &output_queue_metadata_);
-
   output_buffer_memory_ =
-      heap_caps_malloc(kOutputBufferSize, MALLOC_CAP_SPIRAM);
+      heap_caps_malloc(kOutputBufferSize + 1, MALLOC_CAP_SPIRAM);
   output_buffer_ =
-      xStreamBufferCreateStatic(kOutputBufferSize - 1, 1, output_buffer_memory_,
+      xMessageBufferCreateStatic(kOutputBufferSize, output_buffer_memory_,
                                 &output_buffer_metadata_);
 }
 
 FatfsAudioInput::~FatfsAudioInput() {
   free(working_buffer_);
-  vStreamBufferDelete(output_buffer_);
+  vMessageBufferDelete(output_buffer_);
   free(output_buffer_memory_);
-  vQueueDelete(output_queue_);
-  free(output_queue_memory_);
-  vQueueDelete(input_queue_);
-  free(input_queue_memory_);
 }
 
-auto FatfsAudioInput::InputCommandQueue() -> QueueHandle_t {
-  return input_queue_;
-}
 
-auto FatfsAudioInput::OutputCommandQueue() -> QueueHandle_t {
-  return output_queue_;
+auto FatfsAudioInput::InputBuffer() -> MessageBufferHandle_t {
+  return input_buffer_;
 }
 
-auto FatfsAudioInput::InputBuffer() -> StreamBufferHandle_t {
-  return nullptr;
-}
-
-auto FatfsAudioInput::OutputBuffer() -> StreamBufferHandle_t {
+auto FatfsAudioInput::OutputBuffer() -> MessageBufferHandle_t {
   return output_buffer_;
 }
 
@@ -94,20 +65,16 @@ auto FatfsAudioInput::ProcessElementCommand(void* command) -> ProcessResult {
   }
 
   is_file_open_ = true;
-  current_sequence_++;
-
-  Command sequence_update;
-  sequence_update.type = SEQUENCE_NUMBER;
-  sequence_update.sequence_number = current_sequence_;
 
   if (real->interrupt) {
+    Command sequence_update;
+    sequence_update.type = SEQUENCE_NUMBER;
+    sequence_update.sequence_number = current_sequence_++;
     xQueueSendToFront(output_queue_, &sequence_update, kMaxWaitTicks);
-  } else {
-    xQueueSendToBack(output_queue_, &sequence_update, kMaxWaitTicks);
   }
 
   OutputCommand *data = new OutputCommand;
-  data->extension = "txt";
+  data->extension = "mp3";
   Command file_info;
   file_info.type = ELEMENT;
   file_info.sequence_number = current_sequence_;
diff --git a/src/audio/include/audio_decoder.hpp b/src/audio/include/audio_decoder.hpp
index 083bd564..2ee43fb7 100644
--- a/src/audio/include/audio_decoder.hpp
+++ b/src/audio/include/audio_decoder.hpp
@@ -12,13 +12,6 @@ class AudioDecoder : public IAudioElement {
   AudioDecoder();
   ~AudioDecoder();
 
-  auto Pause() -> void;
-  auto IsPaused() -> bool;
-
-  auto Resume() -> void;
-
-  auto SetInputCommandQueue(QueueHandle_t) -> void;
-  auto SetOutputCommandQueue(QueueHandle_t) -> void;
   auto SetInputBuffer(StreamBufferHandle_t) -> void;
   auto SetOutputBuffer(StreamBufferHandle_t) -> void;
 
@@ -27,8 +20,6 @@ class AudioDecoder : public IAudioElement {
 
   uint8_t *working_buffer_;
 
-  QueueHandle_t input_queue_;
-  QueueHandle_t output_queue_;
   StreamBufferHandle_t input_buffer_;
   StreamBufferHandle_t output_buffer_;
 };
diff --git a/src/audio/include/audio_element.hpp b/src/audio/include/audio_element.hpp
index 03fefd70..0be58f48 100644
--- a/src/audio/include/audio_element.hpp
+++ b/src/audio/include/audio_element.hpp
@@ -1,6 +1,10 @@
 #pragma once
 
+#include <stdint.h>
 #include <cstdint>
+#include "freertos/portmacro.h"
+#include "types.hpp"
+#include "result.hpp"
 
 namespace audio {
 
@@ -10,71 +14,19 @@ class IAudioElement {
  public:
   virtual ~IAudioElement();
 
-  enum CommandType {
-    /*
-     * Sets the sequence number of the most recent byte stream. Any commands
-     * received that have a lower sequence number than this will be discarded.
-     */
-    SEQUENCE_NUMBER,
-    /*
-     * Instructs this element to read a specific number of bytes from its
-     * input buffer.
-     */
-    READ_FRAME,
-    /*
-     * Represents an element-specific command. This handling of this is
-     * delegated to element implementations.
-     */
-    ELEMENT,
-    /* Instructs this element to shut down. */
-    QUIT,
-  };
-
-  struct Command {
-    CommandType type;
-    uint8_t sequence_number;
-    // TODO: tag data's type
-    union {
-      void* data;
-      std::size_t frame_size;
-    };
-  };
+  virtual auto IdleTimeout() -> TickType_t { return portMAX_DELAY; }
 
-  /*
-   * Returns a queue that should be used for all communication with this
-   * element.
-   */
-  virtual auto InputCommandQueue() -> QueueHandle_t = 0;
+  virtual auto InputBuffer() -> MessageBufferHandle_t* = 0;
 
-  /*
-   * Returns a buffer that will be used to stream input bytes to this element.
-   * This may be NULL, if this element represents a source, e.g. a FATFS
-   * reader.
-   */
-  virtual auto InputBuffer() -> StreamBufferHandle_t = 0;
+  virtual auto OutputBuffer() -> MessageBufferHandle_t* = 0;
 
-  enum ProcessResult {
-    OK,
-    OUTPUT_FULL,
-    ERROR,
+  enum StreamError {
+    BAD_FORMAT
   };
 
-  /*
-   * Called when an element-specific command has been received.
-   */
-  virtual auto ProcessElementCommand(void* command) -> ProcessResult = 0;
-
-  virtual auto SkipElementCommand(void* command) -> void = 0;
-
-  /*
-   * Called with the result of a read bytes command.
-   */
-  virtual auto ProcessData(uint8_t* data, uint16_t length) -> ProcessResult = 0;
-
-  /*
-   * Called periodically when there are no pending commands.
-   */
-  virtual auto ProcessIdle() -> ProcessResult = 0;
+  virtual auto ProcessStreamInfo(StreamInfo &info) -> cpp::result<void, StreamError> = 0;
+  virtual auto ProcessChunk(uint8_t* data, std::size_t length) -> cpp::result<void, StreamError> = 0;
+  virtual auto ProcessIdle() -> cpp::result<void, StreamError> = 0;
 };
 
 }  // namespace audio
diff --git a/src/audio/include/chunk.hpp b/src/audio/include/chunk.hpp
new file mode 100644
index 00000000..1351ecfb
--- /dev/null
+++ b/src/audio/include/chunk.hpp
@@ -0,0 +1,57 @@
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+#include <optional>
+#include <string>
+#include "esp-idf/components/cbor/tinycbor/src/cbor.h"
+#include "freertos/portmacro.h"
+#include "result.hpp"
+
+namespace audio {
+
+enum ChunkWriteResult {
+  // Returned when the callback does not write any data.
+  CHUNK_OUT_OF_DATA,
+  // Returned when there is an error encoding a chunk header using cbor.
+  CHUNK_ENCODING_ERROR,
+  // Returned when max_wait expires without room in the stream buffer becoming
+  // available.
+  CHUNK_WRITE_TIMEOUT,
+};
+
+/*
+ * Invokes the given callback to receive data, breaks the received data up into
+ * chunks with headers, and writes those chunks to the given output stream.
+ *
+ * The callback will be invoked with a byte buffer and its size. The callback
+ * should write as much data as it can to this buffer, and then return the
+ * number of bytes it wrote. Return a value of 0 to indicate that there is no
+ * more input to read.
+ */
+auto WriteChunksToStream(MessageBufferHandle_t *stream, uint8_t *working_buffer, size_t working_buffer_length, std::function<size_t(uint8_t*,size_t)> callback, TickType_t max_wait) -> EncodeWriteResult;
+
+  enum ChunkReadResult {
+    // Returned an error in parsing the cbor-encoded header.
+    CHUNK_DECODING_ERROR,
+    // Returned when max_wait expired before any data was read.
+    CHUNK_READ_TIMEOUT,
+    // Returned when a non-chunk message is received.
+    CHUNK_STREAM_ENDED,
+  };
+
+/*
+ * 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 ReadChunksFromStream(MessageBufferHandle_t *stream, uint8_t *working_buffer, size_t working_buffer_length, std::function<size_t(uint8_t*,size_t)> callback, TickType_t max_wait) -> EncodeReadResult;
+
+} // namespace audio
diff --git a/src/audio/include/fatfs_audio_input.hpp b/src/audio/include/fatfs_audio_input.hpp
index bf5f150d..5651419d 100644
--- a/src/audio/include/fatfs_audio_input.hpp
+++ b/src/audio/include/fatfs_audio_input.hpp
@@ -15,42 +15,24 @@ namespace audio {
 
 class FatfsAudioInput : public IAudioElement {
  public:
-  struct InputCommand {
-    std::string filename;
-    size_t seek_to;
-    bool interrupt;
-  };
-
-  struct OutputCommand {
-    std::string extension;
-  };
-
   FatfsAudioInput(std::shared_ptr<drivers::SdStorage> storage);
   ~FatfsAudioInput();
 
-  auto OutputCommandQueue() -> QueueHandle_t;
-  auto OutputBuffer() -> StreamBufferHandle_t;
+  auto OutputBuffer() -> MessageBufferHandle_t;
 
  private:
   std::shared_ptr<drivers::SdStorage> storage_;
 
   uint8_t *working_buffer_;
 
-  uint8_t current_sequence_ = 0;
   FIL current_file_;
   bool is_file_open_ = false;
 
-  uint8_t* input_queue_memory_;
-  StaticQueue_t input_queue_metadata_;
-  QueueHandle_t input_queue_;
-
-  uint8_t* output_queue_memory_;
-  StaticQueue_t output_queue_metadata_;
-  QueueHandle_t output_queue_;
+  MessageBufferHandle_t input_buffer_;
 
   uint8_t* output_buffer_memory_;
-  StaticStreamBuffer_t output_buffer_metadata_;
-  StreamBufferHandle_t output_buffer_;
+  StaticMessageBuffer_t output_buffer_metadata_;
+  MessageBufferHandle_t output_buffer_;
 };
 
 }  // namespace audio
diff --git a/src/audio/include/stream_info.hpp b/src/audio/include/stream_info.hpp
new file mode 100644
index 00000000..2b1429ea
--- /dev/null
+++ b/src/audio/include/stream_info.hpp
@@ -0,0 +1,44 @@
+#pragma once
+
+#include <cstdint>
+#include <optional>
+#include <string>
+#include "esp-idf/components/cbor/tinycbor/src/cbor.h"
+#include "result.hpp"
+
+namespace audio {
+
+class StreamInfo {
+  public:
+    enum ParseError {
+      WRONG_TYPE,
+      MISSING_MAP,
+    };
+
+    static auto Create(const uint8_t *buffer, size_t length) -> cpp::result<StreamInfo, ParseError>;
+    StreamInfo(CborValue& map);
+
+    StreamInfo() = default;
+    StreamInfo(const StreamInfo&) = default;
+
+    ~StreamInfo() = default;
+
+    auto Path() const -> const std::optional<std::string>& { return path_; }
+    auto Channels() const -> const std::optional<uint8_t>& { return channels_; }
+    auto BitsPerSample() const -> const std::optional<uint8_t>& { return bits_per_sample_; }
+    auto SampleRate() const -> const std::optional<uint16_t>& { return sample_rate_; }
+
+    enum EncodeError {
+      OUT_OF_MEMORY,
+    };
+
+    auto WriteToStream(CborEncoder encoder) -> cpp::result<void, EncodeError>;
+  private:
+
+    std::optional<std::string> path_;
+    std::optional<uint8_t> channels_;
+    std::optional<uint8_t> bits_per_sample_;
+    std::optional<uint16_t> sample_rate_;
+};
+
+} // namespace audio
diff --git a/src/audio/include/stream_message.hpp b/src/audio/include/stream_message.hpp
new file mode 100644
index 00000000..f59aba8d
--- /dev/null
+++ b/src/audio/include/stream_message.hpp
@@ -0,0 +1,11 @@
+#pragma once
+
+namespace audio {
+  
+  enum MessageType {
+    TYPE_UNKNOWN,
+    TYPE_CHUNK_HEADER,
+    TYPE_STREAM_INFO,
+  };
+
+} // namespace audio
diff --git a/src/audio/stream_info.cpp b/src/audio/stream_info.cpp
new file mode 100644
index 00000000..bb9b1fa2
--- /dev/null
+++ b/src/audio/stream_info.cpp
@@ -0,0 +1,90 @@
+#include "stream_info.hpp"
+#include "stream_message.hpp"
+#include <cstdint>
+#include "esp-idf/components/cbor/tinycbor/src/cbor.h"
+
+namespace audio {
+
+  static const char* kKeyPath = "p";
+  static const char* kKeyChannels = "c";
+  static const char* kKeyBitsPerSample = "b";
+  static const char* kKeySampleRate = "r";
+
+  static auto find_uint64(CborValue &map, char *key) -> cpp::optional<uint64_t> {
+    CborValue val;
+    cbor_value_map_find_value(&map, key, &val);
+    if (cbor_value_is_unsigned_integer(&val)) {
+      uint64_t raw_val;
+      cbor_value_get_uint64(&val, &raw_val);
+      return raw_val;
+    }
+    return {};
+  }
+
+
+  static auto write_uint64(CborEncoder &map, const char *key, const optional<uint64_t> &val) -> cpp::result<void, StreamInfo::EncodeError> {
+    if (val) {
+      cbor_encode_byte_string(&map, key, 1);
+      cbor_encode_uint(&map, *val);
+    }
+    return {};
+  }
+
+static auto StreamInfo::Create(const uint8_t *buffer, size_t length) -> cpp::result<StreamInfo, ParseError> {
+  CborParser parser;
+  CborValue value;
+
+  cbor_parser_init(buffer, len, 0, &parser, &value);
+
+  uint8_t type = 0;
+  if (!cbor_value_is_integer(&value)
+      || !cbor_value_get_integer(&value, &type)
+      || type != STREAM_INFO) {
+    return cpp::fail(WRONG_TYPE);
+  }
+
+  cbor_value_advance_fixed(&value);
+
+  if (!cbor_value_is_map(&value)) {
+    return cpp::fail(MISSING_MAP);
+  }
+
+  return StreamInfo(value);
+}
+
+StreamInfo::StreamInfo(CborValue& map) {
+  // TODO: this method is n^2, which seems less than ideal. But you don't do it
+  // that frequently, so maybe it's okay? Needs investigation.
+  channels_ = find_uint64(map, kKeyChannels);
+  bits_per_sample_ = find_uint64(map, kKeyBitsPerSample);
+  sample_rate_ = find_uint64(map, kKeySampleRate);
+
+  CborValue val;
+  cbor_value_map_find_value(&map, kKeyPath, &val);
+  if (cbor_value_is_text_string(&val)) {
+    size_t len;
+    char *str;
+    cbor_value_dup_text_string(&val, &str, &len, &val);
+    path_ = std::string(str, len);
+    free(str);
+  }
+}
+
+auto StreamInfo::WriteToStream(CborEncoder encoder) -> cpp::result<void, EncodeError> {
+  cbor_encode_int(&encoder, STREAM_INFO);
+
+  CborEncoder map;
+  cbor_encoder_create_map(&encoder, &map, length);
+
+  write_uint64(&map, kKeyChannels, channels_);
+  write_uint64(&map, kKeyBitsPerSample, bits_per_sample_);
+  write_uint64(&map, kKeySampleRate, sample_rate_);
+
+  if (path_) {
+    cbor_encode_text_string(&map, path_->c_str(), path_->size());
+  }
+
+  cbor_encoder_close_container(&encoder, &map);
+}
+
+} // namespace audio
diff --git a/src/cbor/CMakeLists.txt b/src/cbor/CMakeLists.txt
new file mode 100644
index 00000000..cd5186e0
--- /dev/null
+++ b/src/cbor/CMakeLists.txt
@@ -0,0 +1,6 @@
+idf_component_register(
+  SRCS "cbor_decoder.cpp" "cbor_encoder.cpp"
+  INCLUDE_DIRS "include"
+  REQUIRES "cbor" "result")
+
+target_compile_options(${COMPONENT_LIB} PRIVATE ${EXTRA_WARNINGS})
diff --git a/src/cbor/cbor_decoder.cpp b/src/cbor/cbor_decoder.cpp
new file mode 100644
index 00000000..eb43e163
--- /dev/null
+++ b/src/cbor/cbor_decoder.cpp
@@ -0,0 +1,158 @@
+#include "cbor_decoder.hpp"
+#include <cstdint>
+#include "esp-idf/components/cbor/tinycbor/src/cbor.h"
+#include "include/cbor_decoder.hpp"
+
+namespace cbor {
+
+static auto ArrayDecoder::Create(uint8_t *buffer, size_t buffer_len) -> cpp::result<std::unique_ptr<ArrayDecoder>, CborError> {
+  auto decoder = std::make_unique<ArrayDecoder>();
+  cbor_parser_init(buffer, buffer_len, &decoder->parser_, &decoder->root_);
+  if (!cbor_value_is_array(&decoder->root_)) {
+    return cpp::fail(CborErrorIllegalType);
+  }
+  CborError err = cbor_value_enter_container(&decoder->root_, &decoder->it_);
+  if (err != CborNoError) {
+    return cpp::fail(err);
+  }
+  return std::move(decoder);
+}
+
+
+auto ArrayDecoder::ParseString() -> cpp::result<std::string, CborError> {
+  if (error_ != CborNoError) {
+    return cpp::fail(error_);
+  }
+
+  if (!cbor_value_is_byte_string(&it_)) {
+    error_ = CborErrorIllegalType;
+    return cpp::fail(error_);
+  }
+  uint8_t *buf; size_t len; CborValue new_val;
+  error_ = cbor_value_dup_byte_string(&it_, &buf, &len, &new_val);
+  if (error_ != CborNoError) {
+    return cpp::fail(error_);
+  }
+  std::string ret(buf, len);
+  free(buf);
+  val_ = new_val;
+  return ret;
+}
+
+auto ArrayDecoder::ParseUnsigned() -> cpp::result<uint32_t, CborError> {
+  if (error_ != CborNoError) {
+    return cpp::fail(error_);
+  }
+
+  if (!cbor_value_is_unsigned_integer(&it_)) {
+    error_ = CborErrorIllegalType;
+    return cpp::fail(error_);
+  }
+  uint64_t ret;
+  error_ = cbor_value_get_uint64(&it_, &ret);
+  if (error_ != CborNoError) {
+    return cpp::fail(error_);
+  }
+  error_ = cbor_value_advance(&it_);
+  if (error_ != CborNoError) {
+    return cpp::fail(error_);
+  }
+  return ret;
+}
+
+auto ArrayDecoder::ParseSigned() -> cpp::result<int32_t, CborError> {
+  if (error_ != CborNoError) {
+    return cpp::fail(error_);
+  }
+  if (!cbor_value_is_unsigned_integer(&it_)) {
+    error_ = CborErrorIllegalType;
+    return cpp::fail(error_);
+  }
+  uint64_t ret;
+  error_ = cbor_value_get_uint64(&it_, &ret);
+  if (error_ != CborNoError) {
+    return cpp::fail(error_);
+  }
+  error_ = cbor_value_advance(&it_);
+  if (error_ != CborNoError) {
+    return cpp::fail(error_);
+  }
+  return ret;
+}
+
+static auto MapDecoder::Create(uint8_t *buffer, size_t buffer_len) -> cpp::result<std::unique_ptr<MapDecoder>, CborError> {
+  auto decoder = std::make_unique<MapDecoder>();
+  cbor_parser_init(buffer, buffer_len, &decoder->parser_, &decoder->root_);
+  if (!cbor_value_is_map(&decoder->root_)) {
+    return cpp::fail(CborErrorIllegalType);
+  }
+  CborError err = cbor_value_enter_container(&decoder->root_, &decoder->it_);
+  if (err != CborNoError) {
+    return cpp::fail(err);
+  }
+  return std::move(decoder);
+}
+
+auto MapDecoder::FindString(const std::string &key) -> std::optional<std::string> {
+  CborValue val;
+  if (error_ != CborNoError) {
+    return {};
+  }
+  if (cbor_value_map_find_value(&it_, key.c_str(), &val) != CborNoError) {
+    return {};
+  }
+  if (!cbor_value_is_byte_string(&val)) {
+    error_ = CborErrorIllegalType;
+    return {};
+  }
+  uint8_t *buf; size_t len;
+  error_ = cbor_value_dup_byte_string(&val, &buf, &len, NULL);
+  if (error_ != CborNoError) {
+    return cpp::fail(error_);
+  }
+  std::string ret(buf, len);
+  free(buf);
+  return ret;
+}
+
+auto MapDecoder::FindUnsigned(const std::string &key) -> std::optional<uint32_t> {
+  CborValue val;
+  if (error_ != CborNoError) {
+    return {};
+  }
+  if (cbor_value_map_find_value(&it_, key.c_str(), &val) != CborNoError) {
+    return {};
+  }
+  if (!cbor_value_is_unsigned_integer(&val)) {
+    error_ = CborErrorIllegalType;
+    return {};
+  }
+  uint64_t ret;
+  error_ = cbor_value_get_uint64(&val, &ret);
+  if (error_ != CborNoError) {
+    return cpp::fail(error_);
+  }
+  return ret;
+}
+
+auto MapDecoder::FindSigned(const std::string &key) -> std::optional<int32_t> {
+  CborValue val;
+  if (error_ != CborNoError) {
+    return {};
+  }
+  if (cbor_value_map_find_value(&it_, key.c_str(), &val) != CborNoError) {
+    return {};
+  }
+  if (!cbor_value_is_integer(&val)) {
+    error_ = CborErrorIllegalType;
+    return {};
+  }
+  int32_t ret;
+  error_ = cbor_value_get_int(&val, &ret);
+  if (error_ != CborNoError) {
+    return cpp::fail(error_);
+  }
+  return ret;
+}
+
+} // namespace cbor
diff --git a/src/cbor/cbor_encoder.cpp b/src/cbor/cbor_encoder.cpp
new file mode 100644
index 00000000..863597b4
--- /dev/null
+++ b/src/cbor/cbor_encoder.cpp
@@ -0,0 +1,53 @@
+#include "cbor_encoder.hpp"
+#include <cstdint>
+#include "esp-idf/components/cbor/tinycbor/src/cbor.h"
+
+namespace cbor {
+
+  static const int kEncoderFlags = 0;
+
+Encoder::Encoder(ContainerType type, uint32_t container_len, uint8_t *buffer, size_t buffer_len) {
+  cbor_encoder_init(&root_encoder, buffer, buffer_len, kEncoderFlags);
+  switch (type) {
+    case CONTAINER_ARRAY:
+      error_ = cbor_encoder_create_array(&encoder, &container_encoder_, container_len);
+      break;
+    case CONTAINER_MAP:
+      error_ = cbor_encoder_create_map(&encoder, &container_encoder_, container_len);
+      break;
+  }
+}
+
+auto Encoder::WriteString(const std::string &val) -> void {
+  if (error_ != CborNoError) {
+    return;
+  }
+  error_ = cbor_encode_byte_string(&container_encoder_, val.c_str(), val.size());
+}
+
+auto Encoder::WriteUnsigned(uint32_t val) -> void {
+  if (error_ != CborNoError) {
+    return;
+  }
+  error_ = cbor_encode_uint(&container_encoder_, val);
+}
+
+auto Encoder::WriteSigned(int32_t val) -> void {
+  if (error_ != CborNoError) {
+    return;
+  }
+  error_ = cbor_encode_int(&container_encoder_, val);
+}
+
+auto Encoder::Finish() -> cpp::result<size_t, CborError> {
+  if (error_ != CborNoError) {
+    return cpp::fail(error_);
+  }
+  if (CborError final_error = cbor_encoder_close_container(&root_encoder, &container_encoder_) != CborNoError) {
+    return cpp::fail(final_error);
+  }
+  return cbor_encoder_get_buffer_size(&root_encoder);
+}
+
+} // namespace cbor
+
diff --git a/src/cbor/include/cbor_decoder.hpp b/src/cbor/include/cbor_decoder.hpp
new file mode 100644
index 00000000..249db9cc
--- /dev/null
+++ b/src/cbor/include/cbor_decoder.hpp
@@ -0,0 +1,47 @@
+#pragma once
+
+#include <cstdint>
+namespace cbor {
+
+  class ArrayDecoder {
+    public:
+      static auto Create(uint8_t *buffer, size_t buffer_len) -> cpp::result<std::unique_ptr<ArrayDecoder>, CborError>;
+
+      auto ParseString() -> cpp::result<std::string, CborError>;
+      auto ParseUnsigned() -> cpp::result<uint32_t, CborError>;
+      auto ParseSigned() -> cpp::result<int32_t, CborError>;
+
+      auto Failed() -> CborError { return error_; }
+
+      ArrayDecoder(const ArrayDecoder&) = delete;
+      ArrayDecoder& operator=(const ArrayDecoder&) = delete;
+    private:
+      CborParser parser_;
+      CborValue root_;
+
+      CborValue it_;
+      CborError error_ = CborNoError;
+  };
+
+  class MapDecoder {
+    public:
+      static auto Create(uint8_t *buffer, size_t buffer_len) -> cpp::result<std::unique_ptr<MapDecoder>, CborError>;
+
+      auto FindString(const std::string &key) -> std::optional<std::string>;
+      auto FindUnsigned(const std::string &key) -> std::optional<uint32_t>;
+      auto FindSigned(const std::string &key) -> std::optional<int32_t>;
+
+      auto Failed() -> CborError { return error_; }
+
+      MapDecoder(const MapDecoder&) = delete;
+      MapDecoder& operator=(const MapDecoder&) = delete;
+    private:
+      CborParser parser_;
+      CborValue root_;
+
+      CborValue it_;
+      CborError error_ = CborNoError;
+  };
+
+
+} // namespace cbor
diff --git a/src/cbor/include/cbor_encoder.hpp b/src/cbor/include/cbor_encoder.hpp
new file mode 100644
index 00000000..0edbbdff
--- /dev/null
+++ b/src/cbor/include/cbor_encoder.hpp
@@ -0,0 +1,30 @@
+#pragma once
+
+#include <cstdint>
+#include "esp-idf/components/cbor/tinycbor/src/cbor.h"
+namespace cbor {
+
+  class Encoder {
+    public:
+      enum ContainerType {
+        CONTAINER_ARRAY,
+        CONTAINER_MAP
+      };
+      Encoder(ContainerType type, uint32_t container_len, uint8_t *buffer, size_t buffer_len);
+
+      auto WriteString(const std::string &val) -> void;
+      auto WriteUnsigned(uint32_t val) -> void;
+      auto WriteSigned(int32_t val) -> void;
+
+      auto Finish() -> cpp::result<size_t, CborError>;
+
+      Encoder(const Encoder&) = delete;
+      Encoder& operator=(const Encoder&) = delete;
+    private:
+      CborEncoder root_encoder_;
+      CborEncoder container_encoder_;
+
+      CborError error_ = CborNoError;
+  };
+
+} // namespace cbor
diff --git a/src/codecs/include/types.hpp b/src/codecs/include/types.hpp
new file mode 100644
index 00000000..8525a136
--- /dev/null
+++ b/src/codecs/include/types.hpp
@@ -0,0 +1,12 @@
+#pragma once
+
+#include <string>
+
+namespace codecs  {
+
+  enum StreamType {
+    STREAM_MP3,
+  };
+
+  auto GetStreamTypeFromFilename(std::string filename);
+}
diff --git a/src/drivers/CMakeLists.txt b/src/drivers/CMakeLists.txt
index 90c1742a..fbecf1c8 100644
--- a/src/drivers/CMakeLists.txt
+++ b/src/drivers/CMakeLists.txt
@@ -1,6 +1,6 @@
 idf_component_register(
   SRCS "dac.cpp" "gpio_expander.cpp" "battery.cpp" "storage.cpp" "i2c.cpp"
-  "audio_playback.cpp" "i2s_audio_output.cpp" "display.cpp" "display_init.cpp" "spi.cpp" 
+  "spi.cpp" "display.cpp" "display_init.cpp"
   INCLUDE_DIRS "include"
   REQUIRES "esp_adc_cal" "fatfs" "result" "lvgl")
 target_compile_options(${COMPONENT_LIB} PRIVATE ${EXTRA_WARNINGS})
diff --git a/src/main/main.cpp b/src/main/main.cpp
index 24d47e9a..62cb430e 100644
--- a/src/main/main.cpp
+++ b/src/main/main.cpp
@@ -30,7 +30,6 @@
 #include "display_init.hpp"
 #include "gpio_expander.hpp"
 #include "i2c.hpp"
-#include "i2s_audio_output.hpp"
 #include "spi.hpp"
 #include "storage.hpp"