fix: restructure video writer to fix Windows build and address review comments

Major changes:
- Replace ccap_writer.mm with ccap_writer.cpp (pure C++ dispatch layer)
  using factory function pattern instead of #include of .mm/.cpp files
- Compile platform implementations as separate source files (Apple-only
  .mm, Windows-only .cpp) matching the existing file reader pattern
- Rewrite Windows implementation to use MFCreateSinkWriterFromURL
  (correct API) instead of non-existent MFCreateMediaSinkForURL
- Guard #pragma comment(lib) behind _MSC_VER for MinGW compatibility

Review comment fixes:
- Respect WriterConfig::codec preference (try requested codec first)
- Replace usleep() with std::this_thread::sleep_for (portability)
- Use high-precision timescale (600000) for CMTime instead of truncating
  to integer fps
- Add reportError() calls throughout (not just CCAP_LOG_E)
- Validate frame dimensions match configured output in writeFrame()
- Require even dimensions in open() for NV12 encoding
- Check m_mfInitialized in Windows open() before calling MF APIs
- Fix C API timestamp: pass resolved timestamp to writeFrame()
- Share NV12 conversion code via inline helpers in ccap_writer_imp.h
- Support I420/BGRA32 conversion on Windows (was BGR24/NV12 only)
- Guard playback validation in tests behind CCAP_ENABLE_FILE_PLAYBACK
- Zero-initialize VideoFrame structs in tests
- Use std::error_code overloads in test TearDown() for robustness
- Update frameRate docs to reflect actual behavior (default 30fps)
- Set sample duration on Windows for better seek/playback behavior
- Run format_all.sh

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: wysaid

CMakeLists.txt

@@ -135,15 +135,20 @@ endif ()
 # Video writer sources (Windows and macOS only)
 option(CCAP_ENABLE_VIDEO_WRITER "Enable video file writing support (Windows/macOS)" ON)
 if (CCAP_ENABLE_VIDEO_WRITER AND (APPLE OR WIN32))
-    # Exclude writer sources from main glob to avoid double-compilation (platform impl included via #include)
+    # Exclude writer sources from main glob to avoid double-compilation
     list(FILTER LIB_SOURCE EXCLUDE REGEX ".*ccap_writer_apple.*")
     list(FILTER LIB_SOURCE EXCLUDE REGEX ".*ccap_writer_windows.*")
     list(FILTER LIB_SOURCE EXCLUDE REGEX ".*ccap_writer_c\..*$")
     list(FILTER LIB_SOURCE EXCLUDE REGEX ".*ccap_writer\..*$")
     list(APPEND LIB_SOURCE
-        ${CMAKE_CURRENT_SOURCE_DIR}/src/ccap_writer.mm
+        ${CMAKE_CURRENT_SOURCE_DIR}/src/ccap_writer.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/src/ccap_writer_c.cpp
     )
+    if (APPLE)
+        list(APPEND LIB_SOURCE ${CMAKE_CURRENT_SOURCE_DIR}/src/ccap_writer_apple.mm)
+    elseif (WIN32)
+        list(APPEND LIB_SOURCE ${CMAKE_CURRENT_SOURCE_DIR}/src/ccap_writer_windows.cpp)
+    endif ()
     message(STATUS "ccap: Video file writing support enabled")
 else ()
     message(STATUS "ccap: Video file writing support disabled (unsupported platform or disabled)")
@@ -152,7 +157,6 @@ endif ()
 if (APPLE)
     file(GLOB LIB_SOURCE_MAC ${CMAKE_CURRENT_SOURCE_DIR}/src/*.mm)
     list(FILTER LIB_SOURCE_MAC EXCLUDE REGEX ".*ccap_writer_apple.*")
-    list(FILTER LIB_SOURCE_MAC EXCLUDE REGEX ".*ccap_writer\.mm$")
     message(STATUS "ccap: Using Objective-C++ for macOS: ${LIB_SOURCE_MAC}")
     list(APPEND LIB_SOURCE ${LIB_SOURCE_MAC})
 endif ()

include/ccap_writer.h

@@ -47,7 +47,7 @@ struct WriterConfig {
     VideoFormat container = VideoFormat::MP4;
     uint32_t width = 0;          ///< Frame width in pixels
     uint32_t height = 0;         ///< Frame height in pixels
-    double frameRate = 30.0;     ///< Target frame rate; 0 = variable rate
+    double frameRate = 30.0;     ///< Target frame rate (default 30fps; used for timestamp generation when timestampNs is 0)
     uint64_t bitRate = 5'000'000; ///< Target bit rate in bits/s; 0 = auto
 };
 

include/ccap_writer_c.h

@@ -45,7 +45,7 @@ typedef struct {
     CcapVideoFormat container;     ///< Container format
     uint32_t width;                ///< Frame width
     uint32_t height;               ///< Frame height
-    double frameRate;              ///< Target frame rate (0 = variable)
+    double frameRate;              ///< Target frame rate (default 30fps)
     uint64_t bitRate;              ///< Target bit rate in bits/s (0 = auto)
 } CcapWriterConfig;
 

src/ccap_imp_linux.h

@@ -101,12 +101,12 @@ class ProviderV4L2 : public ProviderImp {
     bool m_isStreaming = false;
 
     // V4L2 device capabilities
-    struct v4l2_capability m_caps {};
+    struct v4l2_capability m_caps{};
     std::vector<V4L2Format> m_supportedFormats;
     std::vector<DeviceInfo::Resolution> m_supportedResolutions;
 
     // Current format
-    struct v4l2_format m_currentFormat {};
+    struct v4l2_format m_currentFormat{};
 
     // Buffer management
     std::vector<V4L2Buffer> m_buffers;

src/ccap_imp_windows.cpp

@@ -1003,7 +1003,7 @@ HRESULT STDMETHODCALLTYPE ProviderDirectShow::BufferCB(double SampleTime, BYTE*
     return S_OK;
 }
 
-HRESULT STDMETHODCALLTYPE ProviderDirectShow::QueryInterface(REFIID riid, _COM_Outptr_ void __RPC_FAR* __RPC_FAR* ppvObject) {
+HRESULT STDMETHODCALLTYPE ProviderDirectShow::QueryInterface(REFIID riid, _COM_Outptr_ void __RPC_FAR * __RPC_FAR * ppvObject) {
     static constexpr const IID IID_ISampleGrabberCB = { 0x0579154A, 0x2B53, 0x4994, { 0xB0, 0xD0, 0xE7, 0x73, 0x14, 0x8E, 0xFF, 0x85 } };
 
     if (riid == IID_IUnknown) {
@@ -1168,7 +1168,7 @@ void ProviderDirectShow::close() {
 bool ProviderDirectShow::start() {
     if (!m_isOpened) return false;
 
-        // File mode
+    // File mode
 #ifdef CCAP_ENABLE_FILE_PLAYBACK
     if (m_isFileMode && m_fileReader) {
         return m_fileReader->start();

src/ccap_imp_windows.h

@@ -93,7 +93,7 @@ class ProviderDirectShow : public ProviderImp, public ISampleGrabberCB {
     inline FrameOrientation frameOrientation() const { return m_frameOrientation; }
 
 private:
-    HRESULT STDMETHODCALLTYPE QueryInterface(REFIID riid, _COM_Outptr_ void __RPC_FAR* __RPC_FAR* ppvObject) override;
+    HRESULT STDMETHODCALLTYPE QueryInterface(REFIID riid, _COM_Outptr_ void __RPC_FAR * __RPC_FAR * ppvObject) override;
     ULONG STDMETHODCALLTYPE AddRef(void) override;
     ULONG STDMETHODCALLTYPE Release(void) override;
 

src/ccap_writer.mm src/ccap_writer.cppsrc/ccap_writer.mm renamed to src/ccap_writer.cpp

@@ -1,43 +1,22 @@
 /**
- * @file ccap_writer.mm
+ * @file ccap_writer.cpp
  * @author wysaid (this@wysaid.org)
- * @brief Video writer platform dispatch layer.
+ * @brief Video writer platform dispatch layer (pure C++).
  * @date 2025-05
  */
 
 #include "ccap_writer.h"
-#include "ccap_writer_imp.h"
-#include "ccap_imp.h"
-
-#include "ccap_convert.h"
-#include "ccap_utils.h"
 
-#include <cstring>
-#include <memory>
-#include <vector>
+#include "ccap_writer_imp.h"
 
 #ifdef CCAP_ENABLE_VIDEO_WRITER
 
-#if __APPLE__
-#include "ccap_writer_apple.mm"
-#elif defined(_WIN32) || defined(_MSC_VER)
-#include "ccap_writer_windows.cpp"
-#endif
-
 namespace ccap {
 
-// ---- Platform dispatch ----
-
 static VideoWriter::Impl* impl(void* p) { return reinterpret_cast<VideoWriter::Impl*>(p); }
 static const VideoWriter::Impl* impl(const void* p) { return reinterpret_cast<const VideoWriter::Impl*>(p); }
 
-VideoWriter::VideoWriter() : m_impl(nullptr) {
-#if __APPLE__
-    m_impl = new WriterApple();
-#elif defined(_WIN32) || defined(_MSC_VER)
-    m_impl = new WriterWindows();
-#endif
-}
+VideoWriter::VideoWriter() : m_impl(createVideoWriterImpl()) {}
 
 VideoWriter::~VideoWriter() {
     delete impl(m_impl);