Qcarcam Api [Android]

For embedded software engineers, systems architects, and ADAS developers, understanding the Qcarcam API is no longer optional—it is a prerequisite for building reliable, low-latency camera pipelines on Snapdragon Ride, SA8155P, SA8295P, and other Qualcomm Automotive Development Platforms (QADP).

// 4. Buffer Queuing (Zero-copy pipeline) int32_t qcarcam_req_buf(session_id, uint32_t num_buffers); int32_t qcarcam_qbuf(session_id, qcarcam_buffer_t *buf); // Enqueue for filling int32_t qcarcam_dqbuf(session_id, qcarcam_buffer_t **buf); // Dequeue filled buffer The API uses callbacks for event notification: qcarcam api

| SoC | Max Cameras | Max Resolution | Special Notes | | :--- | :--- | :--- | :--- | | | 5 | 8MP @ 30fps | Limited to 4 CSI lanes total | | SA8155P | 7 | 20MP aggregate | Supports 4K @ 60fps | | SA8195P | 5 | 8K @ 30fps | Dual ISP, virtual channel support | | SA8295P | 11 | 20MP per camera | Real-time warping, 3D surround view acceleration | Hardware Sync via GPIO or Frame Sync Signal

Always set num_buffers >= 3 to prevent pipeline stalls on automotive ISP pipelines. 5. Multi-Camera Synchronization: The Killer Feature Where the Qcarcam API truly shines is multi-camera synchronization. For surround-view or stereo vision, frame timestamps across cameras must match within microseconds. Hardware Sync via GPIO or Frame Sync Signal The API provides a qcarcam_set_sync_config() function that ties capture start times across sessions: typedef void (*qcarcam_error_cb)(uint32_t session_id

typedef void (*qcarcam_frame_ready_cb)(uint32_t session_id, qcarcam_buffer_t *buf); typedef void (*qcarcam_error_cb)(uint32_t session_id, qcarcam_error_t error); qcarcam_register_callback(session_id, QCARCAM_CB_FRAME_READY, my_frame_handler); Let’s walk through a minimal implementation for capturing YUV frames from a single automotive camera (e.g., a 2MP front camera on SA8155P). Step 1: Initialize the API qcarcam_init_params_t init_param = .debug_mask = QCARCAM_DBG_INFO, .num_sessions = 1 ; qcarcam_init(&init_param); Step 2: Configure the Hardware (Sensor + CSI) qcarcam_hw_cfg_t hw_cfg = .csi_lane_id = 0, .csi_lane_assign = 0x4321, .csi_data_type = QCARCAM_CSI_DT_RAW10, .sensor_id = SONY_IMX390_ID ; qcarcam_set_hw_config(session_id, &hw_cfg); Step 3: Set Stream Parameters qcarcam_stream_cfg_t stream_cfg = .width = 1920, .height = 1080, .pixel_format = QCARCAM_PIX_FMT_NV12, // Popular YUV 4:2:0 .framerate_min = 30, .framerate_max = 30, .num_buffers = 4 // Double buffering for smooth flow ; qcarcam_configure_stream(session_id, QCARCAM_STREAM_MAIN, &stream_cfg); Step 4: Allocate ION Buffers and Start Streaming qcarcam_req_buf(session_id, 4); qcarcam_start_session(session_id); // Main loop: block on frame_ready callback while (running) qcarcam_buffer_t *buf; qcarcam_dqbuf(session_id, &buf); // wait for frame process_frame(buf->vaddr, buf->size, buf->timestamp); qcarcam_qbuf(session_id, buf); // return buffer to driver

// 3. Stream Control int32_t qcarcam_start_session(session_id); int32_t qcarcam_stop_session(session_id);