CM V4L2 SOURCE

The cmV4l2Source is used to get data from the sensor by the V4L2 Interface. It supports the input data format setting and multiple connections for output. The V4L2 device only supports one connection at a time, but cmV4l2Source can output data to multi-pipelines.

API Instructions

create/destroy

/*
 * @device V4l2 device, default "/dev/video0"
 * @return Handle
 */
gpointer cm_video_v4l2_source_create(gchar* device);

void cm_video_v4l2_source_destroy(gpointer hd);

start/stop

void cm_video_v4l2_source_start(gpointer hd);
void cm_video_v4l2_source_stop(gpointer hd);

parameters

If the sensor supports different choices such as YUV, Bayer, 4K, FHD, and so on, set the caps string to get the right video format.

/* @caps_str0 Input data format, "video/...,colorimetry=(string)1:4:7:1,..." */
void cm_video_v4l2_source_set_caps_str0(gpointer hd, const gchar* caps_str0);

/* @return Actual data format from device, "video/...,width=..." */
const char* cm_video_v4l2_source_get_caps_str(gpointer had);

/* The media info(out caps string) is ready, the source whether ready to be linked*/
gboolean cm_video_v4l2_source_is_ready(gpointer hd);

data

/* @ cb data callback to get data */
void cm_video_v4l2_source_set_data_callback(gpointer hd, cm_data_cb_ptr cb, gpointer user_data);
void cm_video_v4l2_source_remove_data_callback(gpointer hd, cm_data_cb_ptr cb, gpointer user_data);

others

/* @max Video buffer cache max */
void cm_video_v4l2_source_set_max_buffers(gpointer hd, gint max);

/* @return return the pipeline*/
GstElement* cm_video_v4l2_source_get_bin(gpointer hd);

Demo and Test

YUV demo

Structure

Get data from the sensor and output them to the data callback.

Main codes

//The yuv data will be output to here
static GstFlowReturn _out_data_cb (GstBuffer *buffer, gpointer user_data) {
    
    ......

	return GST_FLOW_OK;
}

static gboolean _main_loop(gpointer arg) {
	if(!vhd) {
		// Create source with device
		vhd = cm_video_v4l2_source_create("/dev/video0");
        // Set caps string to choose data format
		cm_video_v4l2_source_set_caps_str0(vhd, 
  			"video/x-raw,format=UYVY,width=1280,height=720,colorimetry=(string)1:4:7:1");
		// Set callback to get data
        cm_video_v4l2_source_set_data_callback(vhd, _out_data_cb, vhd);
        // Start the source
		cm_video_v4l2_source_start(vhd);
	}
    
    ......

	return TRUE;
}

For more details please refer to the demo file.

Test result

The YUV data can be saved to the file and played on the PC by YUV tools.

C3V Documentation

CM V4L2 SOURCE

API Instructions

Demo and Test

YUV demo

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