Video Graphics Subsystem (VGS) Application

This chapter describes the GK7206 video graphics subsystem (VGS) application example — sample_vgs. The application demonstrates the various graphics processing functions of VGS, including cover (masking), OSD (text overlay), luma (brightness adjustment), scale (resizing), rotate (rotation), and more.

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

1 Application Overview

1.1 Features

Cover (masking): adds masking regions on top of the video picture
OSD (text overlay): overlays text and time information on the video picture
Luma (brightness adjustment): adjusts the brightness of the video picture
Scale (resizing): resizes the video picture
Rotate (rotation): rotates the video picture (90°/180°/270°)

1.2 Technical Specifications

Parameter	Value
`Function index`	0=cover+osd+luma+scale, 1=rotate
`Dependencies`	sensor + VPSS
`Output`	RTSP stream or VO display

1.3 Test Case List

index	Name	Command	Expected behavior
0	cover+osd+luma+scale	`./sample_vgs 0`	Cover/OSD overlaid, brightness adjusted, picture scaled; visible over RTSP
1	rotate	`./sample_vgs 1`	Picture rotated

1.4 Directory Structure

sample/vgs/
├── Makefile              # Build script
└── sample_vgs.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 vgs sample
make -C vgs clean && make -C vgs

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/vgs/sample_vgs root@<board IP>:/sd_card/

2.4 Run the Application

# Add execute permission
chmod +x /sd_card/sample_vgs

# Enter the SD card directory
cd /sd_card

# Run (index 0: cover+osd+luma+scale)
./sample_vgs 0

# Or (index 1: rotate)
./sample_vgs 1

2.5 Expected Output

After a successful run, the terminal prints information similar to the following:

sample_vgs running
vgs test index: 0
...
rtsp://192.168.1.100:554/livestream/0

After pulling the stream you can see:

A masking region on the picture (cover)
Overlaid text on the picture (OSD)
The picture brightness has been adjusted (luma)
The picture size has changed (scale)

3 Internal Execution Logic in Detail

3.1 Application Architecture

The application uses the following architecture:

Sensor → VI → VPSS → VGS → VENC → RTSP streaming

3.2 VGS 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: Initialize VGS
xmedia_vgs_init();

// Step 6: Configure the VGS tasks
xmedia_vgs_handle_t vgs_handle = xmedia_vgs_begin_job(...);

// Add a cover task
xmedia_vgs_add_cover_task(vgs_handle, &cover_attr);

// Add an OSD task
xmedia_vgs_add_osd_task(vgs_handle, &osd_attr);

// Add a luma task
xmedia_vgs_add_luma_task(vgs_handle, &luma_attr);

// Submit the tasks
xmedia_vgs_end_job(vgs_handle);

// Step 7: Start VENC
sample_comm_venc_start(...);

// Step 8: Bind the modules
xmedia_bind_vpss_to_vgs(...);
xmedia_bind_vgs_to_venc(...);

4 Key Programming Points

4.1 Cover Configuration

xmedia_vgs_cover_attr_t cover_attr;

cover_attr.enable = XMEDIA_TRUE;
cover_attr.rect.x = 100;
cover_attr.rect.y = 100;
cover_attr.rect.width = 200;
cover_attr.rect.height = 200;
cover_attr.color = 0xFF0000;  // Red

4.2 OSD Configuration

xmedia_vgs_osd_attr_t osd_attr;

osd_attr.enable = XMEDIA_TRUE;
osd_attr.rect.x = 10;
osd_attr.rect.y = 10;
osd_attr.rect.width = 200;
osd_attr.rect.height = 30;
osd_attr.font_color = 0xFFFFFF;  // White
osd_attr.bg_color = 0x000000;    // Black
strcpy(osd_attr.text, "Hello VGS");

4.3 Luma Configuration

xmedia_vgs_luma_attr_t luma_attr;

luma_attr.enable = XMEDIA_TRUE;
luma_attr.luma_factor = 120;  // 100=normal, >100=brighter, <100=darker

4.4 Scale Configuration

xmedia_vgs_scale_attr_t scale_attr;

scale_attr.enable = XMEDIA_TRUE;
scale_attr.dst_width = 640;
scale_attr.dst_height = 480;

4.5 Rotate Configuration

xmedia_vgs_rotate_attr_t rotate_attr;

rotate_attr.enable = XMEDIA_TRUE;
rotate_attr.rotate = VGS_ROTATE_90;  // 90/180/270 degrees

5 Troubleshooting

Problem	Possible cause	Solution
OSD not displayed	OSD misconfigured	Check the OSD position and color settings
Wrong cover region	Cover coordinates outside the picture	Check that the cover coordinates are in a valid range
Picture too bright/dark	Inappropriate luma value	Adjust the luma value to around 100
Distorted scaling	Mismatched aspect ratio	Keep the target aspect ratio the same as the source