08 Region Overlay Application

This chapter describes the GK7206 region overlay application example — sample_region. The application demonstrates overlaying OSD (overlay), cover, mosaic, and corner-rect (corner mark) elements on VPSS/VO/VENC.

The application source code is located in the SDK directory sample/region/, and serves as a reference template for developing video-overlay-related applications.

1 Application Overview

1.1 Features

Multiple overlay targets: VPSS, VO, VENC
Multiple overlay types: OVERLAYEX (character overlay), COVEREX (cover), MOSAICEX (mosaic), CORNER RECTEX (corner mark)
Flexible configuration: supports various resolution and position configurations

1.2 Technical Parameters

Parameter	Value
`index`	0~10 (see table below)
`Dependencies`	index 0~3 requires VPSS (sensor), 4~6 requires VO (panel), 7~10 requires VENC

1.3 Test Case List

index	Target	index	Target
0	VPSS OVERLAYEX	6	VO CORNER RECTEX
1	VPSS COVEREX	7	VENC OVERLAY
2	VPSS MOSAICEX	8	VENC COVER
3	VPSS CORNER RECTEX	9	VENC MOSAIC
4	VO OVERLAYEX	10	VENC CORNER RECT
5	VO COVEREX

1.4 Directory Structure

sample/region/
├── Makefile              # Build script
└── sample_region.c       # Main program

2 Build and Deployment

2.1 Build the Application

# Enter the sample directory
cd <SDK_PATH>/sample

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

2.2 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/region/sample_region root@<board IP>:/sd_card/

2.3 Run the Application

# Add execute permission
chmod +x /sd_card/sample_region

# Enter the SD card directory
cd /sd_card

# Run (index 7: VENC OSD; you can pull the RTSP stream to view it)
./sample_region 7

# Exit
Press e + Enter

2.4 Expected Output

After a successful run (index 7), the terminal prints output similar to the following:

sample_region running
region test index: 7
target: VENC
type: OVERLAY
...
rtsp://192.168.1.100:554/livestream/0

After pulling the stream, you can see the overlaid OSD text on the picture.

3 Internal Execution Logic

3.1 Application Architecture

The application adopts the following architecture:

Sensor → VI → VPSS → REGION → VENC → RTSP streaming

3.2 REGION Initialization Flow

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

// Step 2: ISP initialization
sample_comm_isp_init();

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

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

// Step 5: VENC start
sample_comm_venc_start(...);

// Step 6: REGION initialization
xmedia_region_init();

// Step 7: configure REGION tasks
switch(index) {
    case 7:  // VENC OVERLAY
        xmedia_region_attach_venc_chn(venc_chn, &region_attr);
        break;
    // ... other cases
}

// Step 8: bind modules
xmedia_bind_vpss_to_venc(...);

4 Key Programming Points

4.1 OVERLAYEX Configuration

xmedia_region_attr_t region_attr;

region_attr.type = XMEDIA_REGION_TYPE_OVERLAYEX;
region_attr.rect.x = 10;
region_attr.rect.y = 10;
region_attr.rect.width = 200;
region_attr.rect.height = 30;
region_attr.color = 0xFFFFFF;  // white
strcpy(region_attr.text, "Hello Region");

4.2 COVEREX Configuration

region_attr.type = XMEDIA_REGION_TYPE_COVEREX;
region_attr.rect.x = 100;
region_attr.rect.y = 100;
region_attr.rect.width = 200;
region_attr.rect.height = 200;
region_attr.color = 0xFF0000;  // red

4.3 MOSAICEX Configuration

region_attr.type = XMEDIA_REGION_TYPE_MOSAICEX;
region_attr.rect.x = 150;
region_attr.rect.y = 150;
region_attr.rect.width = 100;
region_attr.rect.height = 100;
region_attr.mosaic_blk_size = 16;  // mosaic block size

5 Troubleshooting

Problem	Possible Cause	Solution
Overlay not displayed	REGION misconfiguration	Check the REGION position and color settings
VENC overlay fails	VENC channel not set up	Check whether the VENC channel is initialized
VO overlay fails	No display device	Use VENC overlay or connect a display device