Initial commit

native/include/video_decoder.h

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+#ifndef VIDEO_DECODER_H
+#define VIDEO_DECODER_H
+
+#include <cstdint>
+#include <cstddef>
+#include <string>
+
+// Video decoder using NDK MediaCodec API
+// Decodes video files to YUV420 frames and writes to shared memory ring buffer
+// for consumption by the HAL hook in the camera provider process.
+
+namespace video_decoder {
+
+// Shared memory ring buffer header
+// This structure is placed at the beginning of the memfd shared memory region.
+struct RingBufferHeader {
+    uint32_t magic;           // 0xCAM2MAGC
+    uint32_t version;         // Header version (1)
+    uint32_t frame_count;     // Number of frame slots in ring buffer
+    uint32_t frame_width;     // Decoded frame width
+    uint32_t frame_height;    // Decoded frame height
+    uint32_t frame_size;      // Size of one YUV420 frame (w * h * 3/2)
+    uint32_t write_index;     // Atomic: next slot to write
+    uint32_t read_index;      // Atomic: last slot read by consumer
+    uint32_t sequence;        // Monotonically increasing frame counter
+    uint32_t flags;           // Bit flags (bit 0: decoder running)
+    uint64_t last_timestamp;  // Timestamp of last written frame (us)
+    uint8_t  reserved[216];   // Padding to 256 bytes
+};
+
+static constexpr uint32_t RING_MAGIC = 0xCA22A61C;
+static constexpr uint32_t RING_VERSION = 1;
+static constexpr uint32_t RING_FRAME_COUNT = 4;
+static constexpr uint32_t RING_HEADER_SIZE = 256;
+static constexpr uint32_t FLAG_DECODER_RUNNING = 0x1;
+
+// Calculate total shared memory size needed
+inline size_t calc_shmem_size(uint32_t width, uint32_t height, uint32_t frame_count = RING_FRAME_COUNT) {
+    size_t frame_size = (size_t)width * height * 3 / 2; // YUV420
+    return RING_HEADER_SIZE + (frame_size * frame_count);
+}
+
+// Get pointer to frame slot in shared memory
+inline uint8_t* get_frame_ptr(uint8_t* base, uint32_t index, uint32_t frame_size, uint32_t frame_count) {
+    return base + RING_HEADER_SIZE + ((index % frame_count) * frame_size);
+}
+
+// Decoder state
+struct DecoderState {
+    std::string video_path;
+    int32_t width;
+    int32_t height;
+    int32_t rotation;  // 0, 90, 180, 270
+    bool loop;
+    bool running;
+    
+    // Shared memory
+    int shmem_fd;
+    uint8_t* shmem_base;
+    size_t shmem_size;
+    RingBufferHeader* header;
+    
+    // Decoder thread
+    pthread_t decoder_thread;
+};
+
+// Initialize the video decoder
+// Returns 0 on success, negative on error
+int init_decoder(const char* video_path, bool loop = true);
+
+// Start the decoder thread
+// Returns 0 on success
+int start_decoder();
+
+// Stop the decoder thread
+void stop_decoder();
+
+// Release decoder resources
+void release_decoder();
+
+// Get the shared memory fd (for passing to other processes)
+// Returns -1 if not initialized
+int get_shmem_fd();
+
+// Get decoder state info
+int get_decoder_width();
+int get_decoder_height();
+bool is_decoder_running();
+
+// Write a YUV420 frame to the shared memory ring buffer
+// Called internally by the decoder thread
+// y_data, u_data, v_data: pointers to Y, U, V planes
+// y_stride, uv_stride: stride of Y and UV planes
+// width, height: frame dimensions
+bool write_frame_to_ring(const uint8_t* y_data, const uint8_t* u_data, const uint8_t* v_data,
+                         int y_stride, int uv_stride, int width, int height);
+
+} // namespace video_decoder
+
+#endif // VIDEO_DECODER_H