feat: WIP; add windows ffmpeg / video backend implementation

Author: Totto16

src/graphics/video_renderer_windows.cpp

@@ -0,0 +1,133 @@
+
+#include "video_renderer.hpp"
+
+#define WIN32_LEAN_AND_MEAN
+#define NOMINMAX
+
+#include <windows.h>
+
+
+struct Decoder {
+    HANDLE hProcess;
+    HANDLE hPipeWrite;
+};
+
+// inspired by: https://github.com/tsoding/musializer/blob/762a729ff69ba1f984b0f2604e0eac08af46327c/src/ffmpeg_windows.c
+VideoRendererBackend::VideoRendererBackend(const std::filesystem::path& destination_path)
+    : m_destination_path{ destination_path },
+      m_decoder{ nullptr } { }
+
+VideoRendererBackend::~VideoRendererBackend() = default;
+
+
+std::optional<std::string> VideoRendererBackend::setup(u32 fps, shapes::UPoint size) {
+
+    HANDLE pipe_read;
+    HANDLE pipe_write;
+
+    SECURITY_ATTRIBUTES saAttr = { 0 };
+    saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
+    saAttr.bInheritHandle = TRUE;
+
+    if (!CreatePipe(&pipe_read, &pipe_write, &saAttr, 0)) {
+        return fmt::format("FFMPEG: Could not create pipe. System Error Code: {}", GetLastError());
+    }
+
+    if (!SetHandleInformation(pipe_write, HANDLE_FLAG_INHERIT, 0)) {
+        return fmt::format(
+                "FFMPEG: Could not mark write pipe as non-inheritable. System Error Code: {}", GetLastError()
+        );
+    }
+
+    // https://docs.microsoft.com/en-us/windows/win32/procthread/creating-a-child-process-with-redirected-input-and-output
+
+    STARTUPINFO siStartInfo;
+    ZeroMemory(&siStartInfo, sizeof(siStartInfo));
+    siStartInfo.cb = sizeof(STARTUPINFO);
+    // NOTE: theoretically setting NULL to std handles should not be a problem
+    // https://docs.microsoft.com/en-us/windows/console/getstdhandle?redirectedfrom=MSDN#attachdetach-behavior
+    siStartInfo.hStdError = GetStdHandle(STD_ERROR_HANDLE);
+    if (siStartInfo.hStdError == INVALID_HANDLE_VALUE) {
+        return fmt::format(
+                "FFMPEG: Could get standard error handle for the child. System Error Code: {}", GetLastError()
+        );
+    }
+    siStartInfo.hStdOutput = GetStdHandle(STD_OUTPUT_HANDLE);
+    if (siStartInfo.hStdOutput == INVALID_HANDLE_VALUE) {
+        return fmt::format(
+                "FFMPEG: Could get standard output handle for the child. System Error Code: {}", GetLastError()
+        );
+    }
+    siStartInfo.hStdInput = pipe_read;
+    siStartInfo.dwFlags |= STARTF_USESTDHANDLES;
+
+    PROCESS_INFORMATION piProcInfo;
+    ZeroMemory(&piProcInfo, sizeof(PROCESS_INFORMATION));
+
+    //TODO: do this in better c++ fashion and deduplicate this
+    char cmd_buffer[1024 * 2];
+    snprintf(
+            cmd_buffer, sizeof(cmd_buffer),
+            "ffmpeg.exe -loglevel verbose -y -f rawvideo -pix_fmt rgba -s %dx%d -r %d -i - -i \"%s\" -c:v libx264 -vb "
+            "2500k -c:a aac -ab 200k -pix_fmt yuv420p output.mp4",
+            (int) width, (int) height, (int) fps, sound_file_path
+    );
+
+    if (!CreateProcess(NULL, cmd_buffer, NULL, NULL, TRUE, 0, NULL, NULL, &siStartInfo, &piProcInfo)) {
+        CloseHandle(pipe_write);
+        CloseHandle(pipe_read);
+
+        return fmt::format("FFMPEG: Could not create child process. System Error Code: {}", GetLastError());
+    }
+
+    CloseHandle(pipe_read);
+    CloseHandle(piProcInfo.hThread);
+
+    m_decoder = std::make_unique<Decoder>(piProcInfo.hProcess, pipe_write);
+    return std::nullopt;
+}
+
+bool VideoRendererBackend::add_frame(SDL_Surface* surface) {
+    DWORD written{};
+
+    if (not WriteFile(
+                m_decoder->hPipeWrite, surface->pixels, static_cast<size_t>(surface->h) * surface->pitch, &written, NULL
+        )) {
+        spdlog::error("FFMPEG: failed to write into ffmpeg pipe. System Error Code: {}", GetLastError());
+        return false;
+    }
+    return true;
+}
+
+bool VideoRendererBackend::finish(bool cancel) {
+
+    FlushFileBuffers(m_decoder->hPipeWrite);
+    CloseHandle(m_decoder->hPipeWrite);
+
+    if (cancel) {
+        TerminateProcess(m_decoder->hProcess, 1);
+    }
+
+    if (WaitForSingleObject(m_decoder->hProcess, INFINITE) == WAIT_FAILED) {
+        spdlog::error("FFMPEG: could not wait on child process. System Error Code: {}", GetLastError());
+        CloseHandle(m_decoder->hProcess);
+        return false;
+    }
+
+    DWORD exit_status{};
+    if (GetExitCodeProcess(m_decoder->hProcess, &exit_status) == 0) {
+        spdlog::error("FFMPEG: could not get process exit code. System Error Code: {}", GetLastError());
+        CloseHandle(m_decoder->hProcess);
+        return false;
+    }
+
+    if (exit_status != 0) {
+        spdlog::error("FFMPEG: command exited with exit code {}", exit_status);
+        CloseHandle(m_decoder->hProcess);
+        return false;
+    }
+
+    CloseHandle(m_decoder->hProcess);
+
+    return true;
+}