Add isolated FFmpeg movie decoder shim

native/age_movie_ffmpeg/age_movie.h

@@ -0,0 +1,63 @@
+#ifndef AGE_MOVIE_H
+#define AGE_MOVIE_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#if defined(_WIN32)
+#define AGE_MOVIE_API __declspec(dllexport)
+#define AGE_MOVIE_CALL __cdecl
+#else
+#define AGE_MOVIE_API __attribute__((visibility("default")))
+#define AGE_MOVIE_CALL
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct age_movie age_movie;
+
+typedef struct age_movie_info {
+    int32_t width;
+    int32_t height;
+    int64_t stop_time_ms;
+    int32_t frame_rate_num;
+    int32_t frame_rate_den;
+    int32_t has_audio;
+} age_movie_info;
+
+enum age_movie_result {
+    AGE_MOVIE_EOF = 0,
+    AGE_MOVIE_FRAME = 1,
+    AGE_MOVIE_ERROR = -1,
+    AGE_MOVIE_INVALID_ARGUMENT = -2,
+    AGE_MOVIE_BUFFER_TOO_SMALL = -3
+};
+
+AGE_MOVIE_API uint32_t AGE_MOVIE_CALL age_movie_abi_version(void);
+
+/* Copies bytes before returning; the caller's buffer is borrowed only during this call. */
+AGE_MOVIE_API int32_t AGE_MOVIE_CALL age_movie_open(
+    const uint8_t *bytes,
+    size_t length,
+    age_movie **out_movie,
+    age_movie_info *out_info,
+    char *error_buffer,
+    size_t error_buffer_size);
+
+/* Writes one tightly packed top-down RGBA8 frame and its zero-based presentation timestamp. */
+AGE_MOVIE_API int32_t AGE_MOVIE_CALL age_movie_decode_video(
+    age_movie *movie,
+    uint8_t *rgba,
+    size_t rgba_size,
+    int64_t *out_pts_ms);
+
+AGE_MOVIE_API const char *AGE_MOVIE_CALL age_movie_last_error(const age_movie *movie);
+AGE_MOVIE_API void AGE_MOVIE_CALL age_movie_close(age_movie *movie);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif