Video Input Application

This chapter describes the GK7206 video input (VI) application example — sample_vio. The application demonstrates the various working modes of VI/VPSS, including online/offline modes, single/dual sensor, WDR, LDC, AHD, and other advanced features.

The application source code is located in the SDK directory sample/vio/. It serves as a reference template for developing video capture applications.

1 Application Overview

1.1 Features

Multiple working modes: online/offline, single/dual sensor, WDR, LDC, AHD, and more
Dual output paths: VO output (display) or VENC output (encoding)
Flexible configuration: supports various combinations of resolutions and features
Memory-efficient: supports lightweight modes suited to the 26 MB memory environment

1.2 Technical Specifications

Parameter	Value
`Working modes`	0~11 (see the table below)
`Output mode`	0=VO output, 1=VENC output
`Resolution`	Per the sensor configuration
`Frame rate`	Determined by the sensor
`Memory footprint`	Relatively high (heavy modes easily OOM)

1.3 Working Mode List

work_mode	Description	Command example
0	vi online vpss online	`./sample_vio 0`
1	vi offline vpss online (for 4K)	`./sample_vio 1`
2	vi offline vpss offline	`./sample_vio 2`
3	online/offline + WDR	`./sample_vio 3`
4	offline switching linear/WDR	`./sample_vio 4`
5	offline switching resolution	`./sample_vio 5`
6	Dual sensor	`./sample_vio 6`
7	Dual sensor stitching	`./sample_vio 7`
10	offline online LDC	`./sample_vio 10`
11	ahd mipi	`./sample_vio 11`

1.4 Directory Structure

sample/vio/
├── Makefile              # Build script
└── sample_vio.c          # Main program

2 Build and Deployment

2.1 Prerequisites

Before building this application, make sure the following preparations have been completed:

SDK environment is set up: follow SDK Compilation to set up the cross-compilation toolchain and SDK configuration
Sensor is connected: an SC465SL or compatible image sensor must be connected

2.2 Build the Application

# Enter the sample directory
cd <SDK_PATH>/sample

# Build the vio sample
make -C vio clean && make -C vio

2.3 Deploy to the Board

# Mount the SD card (recommended)
mkdir -p /sd_card
mount -t vfat /dev/mmcblk1p1 /sd_card

# Transfer to the development board via SCP
scp sample/vio/sample_vio root@<board IP>:/sd_card/

Warning

Heavy modes (e.g. dual sensor, 4K) easily run out of memory; it is recommended to mount the SD card before running.

2.4 Run the Application

# Add execute permission
chmod +x /sd_card/sample_vio

# Enter the SD card directory
cd /sd_card

# Run (work_mode 0, stream_mode 1)
./sample_vio 0 1

# Or with VENC output (RTSP stream can be pulled)
./sample_vio 0 1

# Or with VO output (requires a display device)
./sample_vio 0 0

2.5 Expected Output

After a successful run (stream_mode=1), the terminal prints information similar to the following:

sample_vio running
work_mode: 0
stream_mode: 1
...
rtsp://192.168.1.100:554/livestream/0
...

3 Internal Execution Logic in Detail

3.1 Application Architecture

The application uses the following architecture:

Sensor → VI → VPSS → VO/VENC

3.2 Online Mode vs Offline Mode

Mode	Description	Suitable scenarios
Online mode	VI outputs directly to VPSS without a memory copy	High real-time requirements
Offline mode	VI writes to memory; VPSS reads from memory	Buffering or post-processing needed

3.3 VI/VPSS Initialization Flow

// Step 1: System initialization
sample_comm_sys_init(&sys_config);

// Step 2: ISP initialization
sample_comm_isp_init();

// Step 3: Start VI
sample_comm_vi_start(...);

// Step 4: Start VPSS
sample_comm_vpss_start(...);

// Step 5: Select the output based on stream_mode
if (stream_mode == 0) {
    // VO output
    sample_comm_vo_start(...);
    xmedia_bind_vpss_to_vo(...);
} else {
    // VENC output
    sample_comm_venc_start(...);
    xmedia_bind_vpss_to_venc(...);
}

4 Key Programming Points

4.1 Working Mode Configuration

switch(work_mode) {
    case 0:  // vi online vpss online
        sys_config.sys_conf.pipe_mode[0].vicap_viproc_mode = XMEDIA_WORK_MODE_ONLINE;
        sys_config.sys_conf.pipe_mode[0].viproc_vpss_mode = XMEDIA_WORK_MODE_ONLINE;
        break;
    case 1:  // vi offline vpss online
        sys_config.sys_conf.pipe_mode[0].vicap_viproc_mode = XMEDIA_WORK_MODE_OFFLINE;
        sys_config.sys_conf.pipe_mode[0].viproc_vpss_mode = XMEDIA_WORK_MODE_ONLINE;
        break;
    // ... other modes
}

4.2 Dual Sensor Configuration

// Configure two sensors
sys_config.sensor_num = 2;
sys_config.sensor_type[0] = SENSOR0_TYPE;
sys_config.sensor_type[1] = SENSOR1_TYPE;

5 Troubleshooting

Problem	Possible cause	Solution
`Killed` (OOM)	Heavy mode in 26 MB of memory	Mount the SD card and use a lightweight mode
`sample_comm_vi_init failed!`	Sensor initialization failed	Check the sensor connection and configuration
`open vo err`	No display device	Use stream_mode=1 or connect a display device