Cleanup

.gitea/workflows/ci.yml

@@ -29,9 +29,9 @@ jobs:
             ca-certificates \
             cmake \
             g++-12 \
-            g++-aarch64-linux-gnu \
+            g++-12-aarch64-linux-gnu \
             gcc-12 \
-            gcc-aarch64-linux-gnu \
+            gcc-12-aarch64-linux-gnu \
             git \
             ninja-build \
             pkg-config \
@@ -44,13 +44,13 @@ jobs:
         uses: actions/cache@v4
         with:
           path: build/build_common/conan_cache
-          key: conan-${{ runner.os }}-${{ hashFiles('conanfile.py', 'modulus.json') }}
+          key: conan-${{ runner.os }}-${{ hashFiles('conanfile.py', 'modulus.json', '.gitea/workflows/ci.yml') }}
           restore-keys: conan-${{ runner.os }}-
       - name: Configure native release
         run: python3 modulus.py configure --target x86_64_gcc12_release --update
       - name: Check code style
         run: |
-          python3 -m pip install --no-cache-dir -r build/build_tools/docker/format-requirements.txt
+          python3 -m pip install --no-cache-dir -r build/build_tools/docker/format_requirements.txt
           python3 modulus.py format --check
       - name: Build native release
         run: python3 modulus.py build --target x86_64_gcc12_release

CMakeLists.txt

@@ -29,6 +29,7 @@ add_library(sonus
   src/metronome.cpp
   src/detail/errors.cpp
   src/engine.cpp
+  src/transport.cpp
   src/sequence.cpp
 )
 target_include_directories(sonus PUBLIC
@@ -56,7 +57,7 @@ if(BUILD_TESTING)
 endif()
 
 install(TARGETS sonus
-  EXPORT sonus-targets
+  EXPORT sonus_targets
   ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
   LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
   RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
@@ -64,25 +65,25 @@ install(TARGETS sonus
 
 install(DIRECTORY include/ DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
 
-install(EXPORT sonus-targets
+install(EXPORT sonus_targets
   NAMESPACE sonus::
   DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/sonus
 )
 
 configure_package_config_file(
   ${CMAKE_CURRENT_SOURCE_DIR}/cmake/sonus_config.cmake.in
-  ${CMAKE_CURRENT_BINARY_DIR}/sonus-config.cmake
+  ${CMAKE_CURRENT_BINARY_DIR}/sonusConfig.cmake
   INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/sonus
 )
 
 write_basic_package_version_file(
-  ${CMAKE_CURRENT_BINARY_DIR}/sonus-config-version.cmake
+  ${CMAKE_CURRENT_BINARY_DIR}/sonusConfigVersion.cmake
   VERSION ${PROJECT_VERSION}
   COMPATIBILITY SameMajorVersion
 )
 
 install(FILES
-  ${CMAKE_CURRENT_BINARY_DIR}/sonus-config.cmake
+  ${CMAKE_CURRENT_BINARY_DIR}/sonusConfig.cmake
-  ${CMAKE_CURRENT_BINARY_DIR}/sonus-config-version.cmake
+  ${CMAKE_CURRENT_BINARY_DIR}/sonusConfigVersion.cmake
   DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/sonus
 )

README.md

@@ -47,3 +47,7 @@ python3 modulus.py package --all
 ## License
 
 Sonus is released under the MIT License.
+
+Recording transports combine a streamed backing file with preloaded click WAVs on one rendered-frame clock. `prepared_transport::create(config, sample_rate, channels)` performs file preparation away from the audio callback; `engine::play_transport()` publishes it atomically and returns a `transport_session`. The session exposes `frames()`, `status()` and `stop()`. Replacing a transport cancels the previous session, and `engine::stop_all()` cancels it too.
+
+`transport_config` takes an optional `backing` path, `beat1`/`beat2` paths, ordered `click_event` frame positions and a `duration_frames` boundary. With a backing file, its complete decoded length defines completion and must cover that boundary. Click samples are cut off at the boundary, allowing a recording tail without clicks. Without backing, the boundary defines completion. WAV decoding preserves the configured channel count. Stream refill happens on miniaudio workers; the callback mixes into a preallocated buffer, reports underruns as `FAILED`, and publishes only frames actually rendered. Call `collect_finished()` on a control thread to retire finished resources.

cmake/sonus_config.cmake.in

@@ -3,4 +3,4 @@
 include(CMakeFindDependencyMacro)
 find_dependency(modulus CONFIG REQUIRED)
 
-include("${CMAKE_CURRENT_LIST_DIR}/sonus-targets.cmake")
+include("${CMAKE_CURRENT_LIST_DIR}/sonus_targets.cmake")

include/sonus/engine.hpp

@@ -9,6 +9,7 @@
 #include <modulus.hpp>
 #include <sonus/config.hpp>
 #include <sonus/sequence.hpp>
+#include <sonus/transport.hpp>
 
 namespace sonus {
 
@@ -37,6 +38,7 @@ public:
   auto play_sequence(sonus::sample_sequence sequence) -> std::expected<sonus::playback_session, modulus::error>;
   auto play_sequence(sonus::prepared_sequence sequence) -> std::expected<sonus::playback_session, modulus::error>;
   auto stop_sequence() -> void;
+  auto play_transport(sonus::prepared_transport transport) -> std::expected<sonus::transport_session, modulus::error>;
   auto is_playing(std::uint64_t handle) -> std::expected<std::bool_t, modulus::error>;
   auto collect_finished() -> std::uint64_t;
   auto active_sound_count() -> std::uint64_t;

include/sonus/transport.hpp

@@ -0,0 +1,66 @@
+#pragma once
+
+#include <atomic>
+#include <cstdint>
+#include <expected>
+#include <filesystem>
+#include <memory>
+#include <vector>
+#include <sonus/sequence.hpp>
+
+
+namespace sonus {
+
+namespace detail {
+
+struct transport_state;
+
+class transport_player;
+
+}
+
+struct click_event {
+  std::uint64_t frame{};
+  bool downbeat{};
+};
+
+struct transport_config {
+  std::filesystem::path backing{};
+  std::filesystem::path beat1{};
+  std::filesystem::path beat2{};
+  std::vector<sonus::click_event> clicks{};
+  std::uint64_t duration_frames{};
+  std::float32_t click_volume{0.45F};
+};
+
+struct transport_progress {
+  std::atomic<sonus::playback_status> status{sonus::playback_status::PLAYING};
+  std::atomic<std::uint64_t> frames{};
+};
+
+class transport_session {
+public:
+  transport_session() = default;
+  explicit transport_session(std::shared_ptr<sonus::transport_progress> progress);
+  auto status() const -> sonus::playback_status;
+  auto frames() const -> std::uint64_t;
+  auto stop() const -> void;
+private:
+  std::shared_ptr<sonus::transport_progress> progress_{};
+};
+
+class prepared_transport {
+public:
+  static auto create(sonus::transport_config config, std::uint32_t sample_rate, std::uint32_t channels) -> std::expected<sonus::prepared_transport, modulus::error>;
+  prepared_transport(prepared_transport const &) = delete;
+  auto operator=(prepared_transport const &) -> prepared_transport & = delete;
+  prepared_transport(prepared_transport &&) noexcept;
+  auto operator=(prepared_transport &&) noexcept -> prepared_transport &;
+  ~prepared_transport();
+private:
+  friend class sonus::detail::transport_player;
+  explicit prepared_transport(std::unique_ptr<sonus::detail::transport_state> state);
+  std::unique_ptr<sonus::detail::transport_state> state_{};
+};
+
+}

modulus.py

@@ -9,7 +9,7 @@ import sys
 
 PACKAGE_REF = "modulus/latest"
 CONAN_VERSION = "2.26.2"
-FETCH_IMAGE = "modulus-fetch:dev"
+FETCH_IMAGE = "modulus_fetch:dev"
 COMMANDS = (
   "configure",
   "build",
@@ -19,6 +19,8 @@ COMMANDS = (
   "clangd",
   "format",
   "run",
+  "python",
+  "publish",
 )
 COMMON_DIR = pathlib.Path("build") / "build_common"
 TOOLS_DIR = pathlib.Path("build") / "build_tools"
@@ -26,7 +28,7 @@ RUNTIME_DIR = COMMON_DIR / "modulus"
 CONAN_HOME_DIR = COMMON_DIR / "conan_cache"
 DEFAULT_REMOTE_NAME = "khodo"
 DEFAULT_REMOTE_URL = "https://git.thyme-labs.com/api/packages/khodo/conan"
-DEFAULT_DOCKER_MARKER = "/opt/modulus-build-image"
+DEFAULT_DOCKER_MARKER = "/opt/modulus_build_image"
 
 def repo_root():
   root = pathlib.Path(__file__).resolve().parent
@@ -66,6 +68,9 @@ def runtime_ready(root):
     and (root / TOOLS_DIR / "format.py").is_file()
     and (root / RUNTIME_DIR / "modulus" / "formatting.py").is_file()
     and (root / RUNTIME_DIR / "modulus" / "format_layout.py").is_file()
+    and (root / RUNTIME_DIR / "modulus" / "python.py").is_file()
+    and (root / RUNTIME_DIR / "modulus" / "artifacts.py").is_file()
+    and (root / TOOLS_DIR / "python_runner.py").is_file()
   )
 
 def env_flag(name):
@@ -114,9 +119,9 @@ RUN apt-get update \\
     python3-venv \\
   && rm -rf /var/lib/apt/lists/*
 
-RUN python3 -m venv /opt/modulus-python
+RUN python3 -m venv /opt/modulus_python
 
-ENV PATH=/opt/modulus-python/bin:$PATH
+ENV PATH=/opt/modulus_python/bin:$PATH
 
 RUN python -m pip install --no-cache-dir conan=={CONAN_VERSION}
 

src/detail/transport_player.hpp

@@ -0,0 +1,38 @@
+#pragma once
+#include <sonus/transport.hpp>
+#include "render_snapshot.hpp"
+#include <miniaudio.h>
+#include <array>
+
+
+namespace sonus::detail {
+
+struct transport_state {
+  ma_resource_manager resources{};
+  mutable ma_resource_manager_data_source backing{};
+  bool resources_ready{};
+  bool backing_ready{};
+  std::uint32_t sample_rate{};
+  std::uint32_t channels{};
+  std::uint64_t duration{};
+  mutable std::uint64_t cursor{};
+  mutable std::size_t first_live_click{};
+  sonus::transport_config config{};
+  std::array<std::vector<std::float32_t>, 2> samples{};
+  mutable std::vector<std::float32_t> scratch{};
+  std::shared_ptr<sonus::transport_progress> progress{std::make_shared<sonus::transport_progress>()};
+  ~transport_state();
+};
+
+class transport_player {
+public:
+  auto play(sonus::prepared_transport transport, std::uint32_t rate, std::uint32_t channels) -> std::expected<sonus::transport_session, modulus::error>;
+  auto stop() -> void;
+  auto collect() -> void;
+  auto fail() -> void;
+  auto render(std::float32_t *output, std::uint64_t frames, std::uint32_t channels, std::float32_t gain) -> void;
+private:
+  sonus::detail::render_snapshot<sonus::detail::transport_state> snapshots_{};
+};
+
+}

src/engine.cpp

@@ -26,6 +26,7 @@
 #include "detail/metronome_player.hpp"
 #include "detail/playback_devices.hpp"
 #include "detail/sequence_player.hpp"
+#include "detail/transport_player.hpp"
 
 
 namespace {
@@ -137,6 +138,7 @@ struct sonus::engine::impl {
   std::unordered_map<std::uint64_t, std::unique_ptr<active_sound>> sounds{};
   std::uint64_t next_sound_handle{1};
   sonus::detail::sequence_player sequences{};
+  sonus::detail::transport_player transport{};
   std::atomic<std::float32_t> sequence_volume{0.70F};
   sonus::detail::metronome_player metronome{};
   impl() = default;
@@ -232,6 +234,7 @@ struct sonus::engine::impl {
     }
     sounds.clear();
     sequences.stop();
+    transport.stop();
     if (mixer_initialized) {
       ma_engine_uninit(&mixer);
       mixer_initialized = false;
@@ -338,6 +341,7 @@ struct sonus::engine::impl {
   auto stop_all_sounds() -> void {
     auto lock = std::scoped_lock{mutex};
     sequences.stop();
+    transport.stop();
     for (auto &entry : sounds) {
       static_cast<void>(ma_sound_stop(&entry.second->sound));
     }
@@ -361,6 +365,7 @@ struct sonus::engine::impl {
   auto collect_finished_sounds() -> std::uint64_t {
     auto lock = std::scoped_lock{mutex};
     sequences.collect();
+    transport.collect();
     auto const collected = collect_finished_locked();
     metronome.collect();
     return collected;
@@ -430,9 +435,11 @@ struct sonus::engine::impl {
     auto result = ma_engine_read_pcm_frames(&mixer, output, frame_count, nullptr);
     if (result != MA_SUCCESS) {
       sequences.fail();
+      transport.fail();
       std::fill(output, output + sample_count, 0.0F);
       return result;
     }
+    transport.render(output, frame_count, config.channels, sequence_volume.load(std::memory_order_relaxed));
     metronome.render(output, frame_count, config.channels);
     sequences.render(output, frame_count, config.channels, sequence_volume.load(std::memory_order_relaxed));
     return MA_SUCCESS;
@@ -652,3 +659,11 @@ auto sonus::engine::render(std::float32_t *output, std::uint64_t frame_count) ->
   }
   return {};
 }
+
+auto sonus::engine::play_transport(sonus::prepared_transport transport) -> std::expected<sonus::transport_session, modulus::error> {
+  if (!implementation_) {
+    return sonus::detail::fail<sonus::transport_session>(unavailable("engine is not initialized"));
+  }
+  auto lock = std::scoped_lock{implementation_->mutex};
+  return implementation_->transport.play(std::move(transport), sample_rate(), channels());
+}

src/transport.cpp

@@ -0,0 +1,193 @@
+#include <sonus/transport.hpp>
+#include <sonus/detail/errors.hpp>
+#include "detail/transport_player.hpp"
+#include <algorithm>
+#include <cmath>
+
+
+namespace {
+
+auto failure(std::string text) -> std::unexpected<modulus::error> {
+  return std::unexpected(sonus::detail::make_error(sonus::detail::error_invalid_argument, std::move(text)));
+}
+
+}
+
+sonus::detail::transport_state::~transport_state() {
+  if (backing_ready) {
+    ma_resource_manager_data_source_uninit(&backing);
+  }
+  if (resources_ready) {
+    ma_resource_manager_uninit(&resources);
+  }
+}
+
+sonus::prepared_transport::prepared_transport(std::unique_ptr<sonus::detail::transport_state> state)
+    : state_(std::move(state)) {}
+
+sonus::prepared_transport::prepared_transport(prepared_transport &&) noexcept = default;
+
+auto sonus::prepared_transport::operator=(prepared_transport &&) noexcept -> prepared_transport & = default;
+
+sonus::prepared_transport::~prepared_transport() = default;
+
+auto sonus::prepared_transport::create(sonus::transport_config config, std::uint32_t rate, std::uint32_t channels) -> std::expected<sonus::prepared_transport, modulus::error> {
+  if (rate < 8000 || rate > 192000 || channels < 1 || channels > 2 || config.duration_frames == 0 || !std::isfinite(config.click_volume) || config.click_volume < 0 || config.click_volume > 1 || config.clicks.size() > 100000) {
+    return failure("invalid recording transport configuration");
+  }
+  auto state = std::make_unique<sonus::detail::transport_state>();
+  state->sample_rate = rate;
+  state->channels = channels;
+  state->duration = config.duration_frames;
+  state->scratch.resize(1024 * channels);
+  if (!config.backing.empty()) {
+    auto options = ma_resource_manager_config_init();
+    options.decodedFormat = ma_format_f32;
+    options.decodedChannels = channels;
+    options.decodedSampleRate = rate;
+    if (ma_resource_manager_init(&options, &state->resources) != MA_SUCCESS) {
+      return failure("cannot initialize recording stream");
+    }
+    state->resources_ready = true;
+    if (ma_resource_manager_data_source_init(&state->resources, config.backing.string().c_str(), MA_RESOURCE_MANAGER_DATA_SOURCE_FLAG_STREAM, nullptr, &state->backing) != MA_SUCCESS) {
+      return failure("cannot open backing recording");
+    }
+    state->backing_ready = true;
+    ma_uint64 length{};
+    if (ma_resource_manager_data_source_get_length_in_pcm_frames(&state->backing, &length) != MA_SUCCESS || length < config.duration_frames) {
+      return failure("backing recording is shorter than the performance");
+    }
+    state->duration = length;
+  }
+  if (!config.clicks.empty()) {
+    for (std::size_t index = 0; index < 2; ++index) {
+      auto decoder = ma_decoder{};
+      auto options = ma_decoder_config_init(ma_format_f32, channels, rate);
+      auto path = index == 0 ? config.beat1 : config.beat2;
+      if (ma_decoder_init_file(path.string().c_str(), &options, &decoder) != MA_SUCCESS) {
+        return failure("cannot decode metronome sample");
+      }
+      auto guard = std::unique_ptr<ma_decoder, decltype(&ma_decoder_uninit)>{&decoder, &ma_decoder_uninit};
+      ma_uint64 length{}, read{};
+      if (ma_decoder_get_length_in_pcm_frames(&decoder, &length) != MA_SUCCESS || length == 0 || length > rate * 4U) {
+        return failure("invalid metronome sample length");
+      }
+      state->samples[index].resize(length * channels);
+      auto result = ma_decoder_read_pcm_frames(&decoder, state->samples[index].data(), length, &read);
+      if ((result != MA_SUCCESS && result != MA_AT_END) || read != length) {
+        return failure("truncated metronome sample");
+      }
+    }
+    if (!std::is_sorted(config.clicks.begin(), config.clicks.end(), [](auto const &a, auto const &b) { return a.frame < b.frame; }) || config.clicks.back().frame >= config.duration_frames) {
+      return failure("invalid click schedule");
+    }
+  }
+  state->config = std::move(config);
+  return sonus::prepared_transport{std::move(state)};
+}
+
+sonus::transport_session::transport_session(std::shared_ptr<sonus::transport_progress> progress)
+    : progress_(std::move(progress)) {}
+
+auto sonus::transport_session::frames() const -> std::uint64_t {
+  return progress_ ? progress_->frames.load(std::memory_order_acquire) : 0;
+}
+
+auto sonus::transport_session::status() const -> sonus::playback_status {
+  return progress_ ? progress_->status.load(std::memory_order_acquire) : sonus::playback_status::STOPPED;
+}
+
+auto sonus::transport_session::stop() const -> void {
+  if (progress_) {
+    auto expected = sonus::playback_status::PLAYING;
+    progress_->status.compare_exchange_strong(expected, sonus::playback_status::STOPPED);
+  }
+}
+
+auto sonus::detail::transport_player::play(sonus::prepared_transport transport, std::uint32_t rate, std::uint32_t channels) -> std::expected<sonus::transport_session, modulus::error> {
+  if (!transport.state_ || transport.state_->sample_rate != rate || transport.state_->channels != channels) {
+    return failure("transport format does not match engine");
+  }
+  stop();
+  auto session = sonus::transport_session{transport.state_->progress};
+  snapshots_.publish(std::move(transport.state_));
+  return session;
+}
+
+auto sonus::detail::transport_player::stop() -> void {
+  if (auto state = snapshots_.current()) {
+    sonus::transport_session{state->progress}.stop();
+  }
+  snapshots_.publish(nullptr);
+}
+
+auto sonus::detail::transport_player::collect() -> void {
+  if (auto state = snapshots_.current(); state && state->progress->status.load() != sonus::playback_status::PLAYING) {
+    snapshots_.publish(nullptr);
+  }
+  snapshots_.collect();
+}
+
+auto sonus::detail::transport_player::fail() -> void {
+  auto guard = snapshots_.read();
+  if (auto state = guard.get()) {
+    state->progress->status.store(sonus::playback_status::FAILED);
+  }
+}
+
+auto sonus::detail::transport_player::render(std::float32_t *output, std::uint64_t frames, std::uint32_t channels, std::float32_t gain) -> void {
+  auto guard = snapshots_.read();
+  auto state = guard.get();
+  if (!state || channels != state->channels) {
+    return;
+  }
+  for (std::uint64_t offset = 0; offset < frames && state->cursor < state->duration;) {
+    if (state->progress->status.load(std::memory_order_acquire) != sonus::playback_status::PLAYING) {
+      return;
+    }
+    auto count = std::min({frames - offset, state->duration - state->cursor, std::uint64_t{1024}});
+    std::fill(state->scratch.begin(), state->scratch.end(), 0.F);
+    if (state->backing_ready) {
+      ma_uint64 read{};
+      auto result = ma_resource_manager_data_source_read_pcm_frames(&state->backing, state->scratch.data(), count, &read);
+      if ((result != MA_SUCCESS && result != MA_AT_END) || read != count) {
+        state->progress->status.store(sonus::playback_status::FAILED, std::memory_order_release);
+        return;
+      }
+    }
+    // Retain overlapping tails, but never revisit an expired schedule prefix.
+    // The cursor is owned by the render thread and needs no allocation or lock.
+    while (state->first_live_click < state->config.clicks.size()) {
+      auto const &click = state->config.clicks[state->first_live_click];
+      auto length = state->samples[click.downbeat ? 0 : 1].size() / channels;
+      if (click.frame > state->cursor || length > state->cursor - click.frame) {
+        break;
+      }
+      ++state->first_live_click;
+    }
+    for (auto index = state->first_live_click; index < state->config.clicks.size(); ++index) {
+      auto const &click = state->config.clicks[index];
+      if (click.frame >= state->cursor + count) {
+        break;
+      }
+      auto const &sample = state->samples[click.downbeat ? 0 : 1];
+      auto start = std::max(click.frame, state->cursor);
+      auto end = std::min({click.frame + sample.size() / channels, state->cursor + count, state->config.duration_frames});
+      for (auto frame = start; frame < end; ++frame) {
+        for (std::uint32_t channel = 0; channel < channels; ++channel) {
+          state->scratch[(frame - state->cursor) * channels + channel] += sample[(frame - click.frame) * channels + channel] * state->config.click_volume;
+        }
+      }
+    }
+    for (std::uint64_t index = 0; index < count * channels; ++index) {
+      output[offset * channels + index] += state->scratch[index] * gain;
+    }
+    state->cursor += count;
+    offset += count;
+    state->progress->frames.store(state->cursor, std::memory_order_release);
+  }
+  if (state->cursor == state->duration) {
+    auto expected = sonus::playback_status::PLAYING;
+    state->progress->status.compare_exchange_strong(expected, sonus::playback_status::COMPLETED);
+  }
+}

tests/CMakeLists.txt

@@ -3,23 +3,24 @@ if(sonus_interface_libraries AND sonus_interface_libraries MATCHES "miniaudio|Op
   message(FATAL_ERROR "sonus::sonus must not expose private audio or unrelated third-party libraries in its public link interface")
 endif()
 
-add_executable(sonus-test
+add_executable(sonus_test
   test.cpp
   render_snapshot.cpp
   control.cpp
+  transport.cpp
   sequence.cpp
 )
 find_package(Threads REQUIRED)
-target_include_directories(sonus-test PRIVATE
+target_include_directories(sonus_test PRIVATE
   ${CMAKE_CURRENT_SOURCE_DIR}
   ${PROJECT_SOURCE_DIR}/src
 )
-target_link_libraries(sonus-test PRIVATE
+target_link_libraries(sonus_test PRIVATE
   sonus::sonus
   Threads::Threads
 )
-target_compile_features(sonus-test PRIVATE cxx_std_23)
+target_compile_features(sonus_test PRIVATE cxx_std_23)
-add_test(NAME sonus COMMAND sonus-test)
+add_test(NAME sonus COMMAND sonus_test)
 set_tests_properties(sonus PROPERTIES TIMEOUT 20)
 add_custom_target(check
   COMMAND ${CMAKE_CTEST_COMMAND}

tests/transport.cpp

@@ -0,0 +1,148 @@
+#include <boost/test/unit_test.hpp>
+#include <sonus.hpp>
+#include <array>
+#include <filesystem>
+#include <fstream>
+#include <unistd.h>
+
+
+namespace {
+
+struct recordings {
+  std::filesystem::path root;
+  recordings() {
+    auto path = (std::filesystem::temp_directory_path() / "sonus-recordings-XXXXXX").string();
+    BOOST_REQUIRE(::mkdtemp(path.data()));
+    root = path;
+    write("backing.wav", 16, 1024, -1024);
+    write("beat1.wav", 2, 8192, -8192);
+    write("beat2.wav", 2, 4096, -4096);
+  }
+  ~recordings() {
+    std::error_code error;
+    std::filesystem::remove_all(root, error);
+  }
+  auto write(char const *name, unsigned frames, int left, int right) -> void {
+    auto output = std::ofstream{root / name, std::ios::binary};
+    auto word = [&](unsigned value, unsigned bytes) { for (unsigned i = 0; i < bytes; ++i){ output.put(static_cast<char>(value >> (8 * i)));
+} };
+    output.write("RIFF", 4);
+    word(36 + frames * 4, 4);
+    output.write("WAVEfmt ", 8);
+    word(16, 4);
+    word(1, 2);
+    word(2, 2);
+    word(48000, 4);
+    word(192000, 4);
+    word(4, 2);
+    word(16, 2);
+    output.write("data", 4);
+    word(frames * 4, 4);
+    for (unsigned i = 0; i < frames; ++i) {
+      word(static_cast<unsigned>(left), 2);
+      word(static_cast<unsigned>(right), 2);
+    }
+  }
+  auto config() const -> sonus::transport_config {
+    return {.backing = root / "backing.wav", .beat1 = root / "beat1.wav", .beat2 = root / "beat2.wav", .clicks = {{4, true}, {8, false}}, .duration_frames = 10, .click_volume = 1.F};
+  }
+};
+
+}
+
+BOOST_AUTO_TEST_CASE(recording_transport_preserves_stereo_and_has_one_sample_clock) {
+  auto files = recordings{};
+  auto prepared = sonus::prepared_transport::create(files.config(), 48000, 2);
+  BOOST_REQUIRE(prepared);
+  auto engine = sonus::engine::create({.sample_rate = 48000, .channels = 2, .master_volume = 1.F, .no_device = true});
+  BOOST_REQUIRE(engine);
+  auto session = engine->play_transport(std::move(*prepared));
+  BOOST_REQUIRE(session);
+  std::array<float, 40> output{};
+  BOOST_REQUIRE(engine->render(output.data(), 20));
+  BOOST_TEST(session->frames() == 16U);
+  BOOST_CHECK(session->status() == sonus::playback_status::COMPLETED);
+  for (unsigned frame = 0; frame < 20; ++frame) {
+    auto value = frame < 16 ? .03125F : 0.F;
+    if (frame == 4 || frame == 5) {
+      value += .25F;
+    }
+    if (frame == 8 || frame == 9) {
+      value += .125F;
+    }
+    BOOST_TEST(output[frame * 2] == value);
+    BOOST_TEST(output[frame * 2 + 1] == -value);
+  }
+  engine->collect_finished();
+  BOOST_CHECK(session->status() == sonus::playback_status::COMPLETED);
+}
+
+BOOST_AUTO_TEST_CASE(recording_transport_replacement_cancels_old_session_and_validates_inputs) {
+  auto files = recordings{};
+  auto engine = sonus::engine::create({.sample_rate = 48000, .channels = 2, .no_device = true});
+  BOOST_REQUIRE(engine);
+  auto config = files.config();
+  auto first = sonus::prepared_transport::create(config, 48000, 2);
+  BOOST_REQUIRE(first);
+  auto session = engine->play_transport(std::move(*first));
+  BOOST_REQUIRE(session);
+  auto second = sonus::prepared_transport::create(config, 48000, 2);
+  BOOST_REQUIRE(second);
+  auto replacement = engine->play_transport(std::move(*second));
+  BOOST_REQUIRE(replacement);
+  BOOST_CHECK(session->status() == sonus::playback_status::STOPPED);
+  replacement->stop();
+  std::array<float, 16> output{};
+  BOOST_REQUIRE(engine->render(output.data(), 8));
+  BOOST_TEST(replacement->frames() == 0U);
+  BOOST_TEST(output.front() == 0.F);
+  config.duration_frames = 17;
+  BOOST_CHECK(!sonus::prepared_transport::create(config, 48000, 2));
+  config = files.config();
+  config.beat1 = files.root / "missing.wav";
+  BOOST_CHECK(!sonus::prepared_transport::create(config, 48000, 2));
+  config = files.config();
+  config.clicks = {{9, true}, {4, false}};
+  BOOST_CHECK(!sonus::prepared_transport::create(config, 48000, 2));
+  config = files.config();
+  config.backing.clear();
+  config.clicks.push_back({10, true});
+  BOOST_CHECK(!sonus::prepared_transport::create(config, 48000, 2));
+}
+
+BOOST_AUTO_TEST_CASE(recording_transport_long_schedule_preserves_overlaps_across_buffer_sizes) {
+  auto files = recordings{};
+  files.write("beat1.wav", 1537, 1, -1);
+  files.write("beat2.wav", 17, 2, -2);
+  auto config = files.config();
+  config.backing.clear();
+  config.duration_frames = 40000;
+  config.clicks.clear();
+  for (std::uint64_t i = 0; i < 2000; ++i) {
+    config.clicks.push_back({i * 20, i % 7 == 0});
+  }
+  auto expected = std::vector<float>(config.duration_frames * 2);
+  for (auto const &click : config.clicks) {
+    auto length = click.downbeat ? 1537U : 17U;
+    auto value = click.downbeat ? 1.F / 32768 : 2.F / 32768;
+    for (auto frame = click.frame; frame < std::min(click.frame + length, config.duration_frames); ++frame) {
+      expected[frame * 2] += value;
+      expected[frame * 2 + 1] -= value;
+    }
+  }
+  for (auto chunk : {317U, 1024U, 1701U}) {
+    auto prepared = sonus::prepared_transport::create(config, 48000, 2);
+    BOOST_REQUIRE(prepared);
+    auto engine = sonus::engine::create({.sample_rate = 48000, .channels = 2, .master_volume = 1.F, .no_device = true});
+    BOOST_REQUIRE(engine);
+    auto session = engine->play_transport(std::move(*prepared));
+    BOOST_REQUIRE(session);
+    auto actual = std::vector<float>(expected.size());
+    for (std::uint64_t frame = 0; frame < config.duration_frames; frame += chunk) {
+      BOOST_REQUIRE(engine->render(actual.data() + frame * 2, std::min<std::uint64_t>(chunk, config.duration_frames - frame)));
+    }
+    BOOST_CHECK_EQUAL_COLLECTIONS(actual.begin(), actual.end(), expected.begin(), expected.end());
+    BOOST_CHECK(session->status() == sonus::playback_status::COMPLETED);
+    BOOST_TEST(session->frames() == config.duration_frames);
+  }
+}