这里写目录标题
前言
因为涉及很多细节的GStreamer官方论坛有详细解链接: GStreamer官网，这里不做说明，以下只是涉及到个人的理解和认知，方便后续的查阅。
个人的总结
1)了解pipeline的使用，简单说就是通道的概念, 因为涉及到数据的复用和拓展， 里面有一个filter(tee插件), 通过tee和后续拓展
的绑定关系复用数据，很像许多Soc编解码芯片中的vpss通道的概念。 数据复用为视频编码通道， 数据jpeg通道以及对数据处理的通道。
2)重点是去了解Pad Templates 中的Availability,这个关系到link的方式，另外关注Element Properties的属性设置。
3)工作使用最多的不是作为播放器，而是将采集数据获取后做后续的图像处理，因此以下是从v4l2src插件中获取到数据的方式：
4)GStreamer复用的拓展性导致其复杂性, 还涉及到glib的学习，因此学习成本还是比较高的， 但现主流的流媒体芯片或边缘化芯片大部分都用到GStreamer，
比如NVIDIA和瑞芯微,特别是瑞芯微直接将GStreamer作为框架，增加自己的硬编解码。
5) GStreamer的许多控件非常适合拓展， 比如推流rtp/rtsp/rtmp/webrtc开发非常快，但走API这套的调试以及对API的理解和学习周期比较长。
这里只花了3天时间学习， 做一个记录。
v4l2src插件的简单使用
/**
*
@brief 实现从v4l2src中拿到数据,方便后续数据的操作，比如用作重新硬编解码用
appsink关键属性： emit-signals默认是关闭
emit-signals : Emit new-preroll and new-sample signals
flags: readable, writable
Boolean. Default: false
Element Signals:
"eos" : void user_function (GstElement* object,
gpointer user_data);
"new-preroll" : GstFlowReturn user_function (GstElement* object,
gpointer user_data);
"new-sample" : GstFlowReturn user_function (GstElement* object,
gpointer user_data);
Element Actions:
"pull-preroll" : GstSample * user_function (GstElement* object);
"pull-sample" : GstSample * user_function (GstElement* object);
"try-pull-preroll" : GstSample * user_function (GstElement* object,
guint64 arg0);
"try-pull-sample" : GstSample * user_function (GstElement* object,
guint64 arg0);
*/
#include <unistd.h>
#include <gst/gst.h>
#include <pthread.h>
#include <time.h>
#include <sys/time.h>
#define TEST_MODULE
//#define VIDEO_X_RAW
typedef struct ExtraCtrl_
{
int s32brightness;
int s32Contrast;
int s32Saturation;
int s32Hue;
int s32Sharpness;
}Extra_Ctrl_S;
/*
* @brief 设置ISP图像质量，主要是图像增强类
@prams[in] source - SRC plugin extraCtrl - 外部的图像喜好
@return null
@test:
1. 通过inspect查看插件支持的图像属性有哪些
*/
void setCameraQuality(GstElement *source, const Extra_Ctrl_S *extraCtrl)
{
g_object_set(source, "do-timestamp", TRUE, NULL);
#if 0
GstStructure* extraCtrls = gst_structure_new("logitech_controls",
"brightness", extraCtrl->s32brightness,
"contrast", G_TYPE_INT, extraCtrl->s32Contrast,
"saturation", G_TYPE_INT, extraCtrl->s32Saturation,
"hue", G_TYPE_INT, extraCtrl->s32Hue,
"sharpness", G_TYPE_INT, extraCtrl->s32Sharpness,
// "focus_auto", G_TYPE_BOOLEAN, FALSE,
// "white_balance_temperature_auto", G_TYPE_BOOLEAN, FALSE,
// "white_balance_temperature", G_TYPE_INT, 3500,
NULL);
#else
/*gst-1.0 无sharpness
默认值 brightness 0， hue 0 contrast 36 saturation:54
*/
int brightness = 1, hue = 1, contrast = 1, saturation = 1;
g_object_get(source , "brightness", &brightness, "hue", &hue, "contrast", &contrast, "saturation", &saturation, NULL);
g_print("get: brightness:%d, hue:%d, contrast:%d, saturation:%d\n", brightness, hue, contrast, saturation);
#if 1
int setBrightness = 0;
GstStructure* extraCtrls = gst_structure_new("logitech_controls",
"brightness", G_TYPE_INT, brightness ,
"hue", G_TYPE_INT, hue,
"contrast", G_TYPE_INT, contrast,
"saturation", G_TYPE_INT, saturation,//160,
NULL);
g_object_set(source, "extra-controls" , extraCtrls, NULL);
#endif
#endif
g_object_get(source , "brightness", &brightness, "hue", &hue, "contrast", &contrast, "saturation", &saturation, NULL);
g_print("get: brightness:%d, hue:%d, contrast:%d, saturation:%d\n", brightness, hue, contrast, saturation);
}
TEST_MODULE void *ispCtlProc(void *arg)
{
while(1)
{
GstElement * element = (GstElement*)arg;
if(element)
{
static int rec = 0;
g_print("rec:%d\n", rec++);
Extra_Ctrl_S s;memset(&s, 0, sizeof(s));
static int count = 0;
s.s32brightness = count++ % 255;
s.s32Contrast = 128;
s.s32Saturation = 128;
s.s32Hue = 128;
s.s32Sharpness = 128;
setCameraQuality(element, &s);
}
usleep(1000*100);
}
return NULL;
}
/*
@brief 原始数据回调
*/
GstFlowReturn cb_appsink_new_sample(GstElement* appsink, gpointer user_data)
{
// LOG_INFO_MSG ("cb_appsink_new_sample called, user data: %p", user_data);
#if 0
SinkPipeline* sp = reinterpret_cast<SinkPipeline*> (user_data);
#endif
GstSample* sample = NULL;
GstBuffer* buffer = NULL;
GstMapInfo map;
const GstStructure* info = NULL;
GstCaps* caps = NULL;
GstFlowReturn ret = GST_FLOW_OK;
int sample_width = 0;
int sample_height = 0;
// equals to gst_app_sink_pull_sample (GST_APP_SINK_CAST (appsink), sample);
g_signal_emit_by_name (appsink, "pull-sample", &sample, &ret);
if (ret != GST_FLOW_OK) {
g_print ("can't pull GstSample.\n");
return ret;
}
if (sample)
{
buffer = gst_sample_get_buffer (sample);
if ( buffer == NULL ) {
g_print ("get buffer is null\n");
goto exit;
}
gboolean mapret= gst_buffer_map (buffer, &map, GST_MAP_READ);
if(mapret == FALSE)
{
goto exit;
}
/**/
caps = gst_sample_get_caps (sample);
if ( caps == NULL ) {
g_print ("get caps is null\n");
goto exit;
}
info = gst_caps_get_structure (caps, 0);
if ( info == NULL ) {
g_print ("get info is null\n");
goto exit;
}
// -------- Read frame and convert to opencv format --------
// convert gstreamer data to OpenCV Mat, you could actually
// resolve height / width from caps...
gst_structure_get_int (info, "width", &sample_width);
gst_structure_get_int (info, "height", &sample_height);
g_print("format:%s, width:%d, height:%d\n", gst_structure_get_string(info, "format"), sample_width, sample_height);
if(NULL == map.data)
{
g_print("appsink buffer data empty\n");
goto exit;
}
static struct timeval s, e;
static int flag = 1;
if(flag)
{
gettimeofday(&s, 0); e = s;
flag = 0;
}
gettimeofday(&e, 0);
static int frameNo = 0;
frameNo++;
unsigned int timespan = (e.tv_sec - s.tv_sec )*1000*1000 + e.tv_usec - s.tv_usec;
if(timespan >= 1000000)
{
g_print("frame siz:%d, max_siz:%d, %02d FPS\n", map.size, map.maxsize, frameNo);
frameNo = 0;
gettimeofday(&s, 0);
}
//FILE *fp =
#if 0
// customized user action
{
// init a cv::Mat with gst buffer address: deep copy
// sometime you may got a empty buffer
if (map.data == NULL) {
LOG_ERROR_MSG("appsink buffer data empty\n");
return GST_FLOW_OK;
}
cv::Mat img (sample_height, sample_width, CV_8UC3,
(unsigned char*)map.data, cv::Mat::AUTO_STEP);
img = img.clone();
// redirection outside operation: for decoupling use
if (sp->m_putDataFunc) {
sp->m_putDataFunc(std::make_shared<cv::Mat> (img),
sp->m_putDataArgs);
} else {
goto exit;
}
}
#endif
exit:
if (buffer) {
gst_buffer_unmap (buffer, &map);
}
if (sample) {
gst_sample_unref (sample);
}
return GST_FLOW_OK;
}
}
/*
@brief 创造线程设置图像数据， TEST 模块
*/
TEST_MODULE int ispInit(GstElement *source)
{
int ret = 0;
pthread_t ispControlThread;
pthread_create(&ispControlThread, 0, ispCtlProc, (void *)source);
}
int main(int argc, char *argv[])
{
GstElement *pipeline, *source;
GstElement *converter,*appsink;
GstBus *bus;
GstMessage *msg;
/* Initialize GStreamer */
gst_init (&argc, &argv);
/* Create the elements */
/*src(always)*/
source = gst_element_factory_make ("v4l2src", "v4l2src");
converter= gst_element_factory_make("videoconvert","converter01");
//sink
appsink = gst_element_factory_make("appsink", "appsink");
/* Create the empty pipeline */
pipeline = gst_pipeline_new ("test-pipeline");
if ( !pipeline || !source || !appsink ) {
g_printerr ("Not all elements could be created.\n");
return -1;
}
// set appsink
g_object_set(appsink, "emit-signals", TRUE, NULL);
g_signal_connect (appsink, "new-sample", G_CALLBACK (cb_appsink_new_sample), NULL);
/* Link all elements that can be automatically linked because they have "Always" pads */
gst_bin_add_many (GST_BIN (pipeline), source, converter, appsink, NULL);
// TEST_MODULE ispInit(source);
/*
@note:
1. 需要在gst_bin_add_many之后调用
先需要知道摄像头支持的Pixel Format,通过命令可查，
v4l2-ctl --list-formats-ext --device /dev/video0可以查看支持的格式只有YUYV和MJPG,另外可以查看到具体的分辨率和帧率
*/
#if defined(VIDEO_X_RAW)
GstCaps *caps = gst_caps_new_simple ("video/x-raw",
// "format", G_TYPE_STRING, "YV12", //<<< IF THIS IS SET TO ARGB (THE FORMAT I WANT IT FAILS ON LINKING)
// "format", G_TYPE_STRING, "NV21",
"framerate", GST_TYPE_FRACTION, 25, 1,
// "pixel-aspect-ratio", GST_TYPE_FRACTION, 1, 1,
"width", G_TYPE_INT, 320,
"height", G_TYPE_INT, 240,
NULL);
#else
GstCaps *caps = gst_caps_new_simple ("video/mpeg",
"mpegversion", G_TYPE_INT, 2,
"systemstream", G_TYPE_BOOLEAN, TRUE,
NULL);
#endif
gst_element_link_filtered(source, converter, caps);
gst_caps_unref(caps);
/*这里做了转换，需要逐一连接*/
gst_element_link(source, converter);
gst_element_link(converter, appsink);
/* Start playing the pipeline */
gst_element_set_state (pipeline, GST_STATE_PLAYING);
/* Wait until error or EOS */
bus = gst_element_get_bus (pipeline);
msg = gst_bus_timed_pop_filtered (bus, GST_CLOCK_TIME_NONE, GST_MESSAGE_ERROR | GST_MESSAGE_EOS);
if(msg != NULL)
{
GError *err;
gchar *debug_info;
switch (GST_MESSAGE_TYPE (msg)) {
case GST_MESSAGE_ERROR:
gst_message_parse_error (msg, &err, &debug_info);
g_printerr ("Error received from element %s: %s\n",
GST_OBJECT_NAME (msg->src), err->message);
g_printerr ("Debugging information: %s\n",
debug_info ? debug_info : "none");
g_clear_error (&err);
g_free (debug_info);
break;
case GST_MESSAGE_EOS:
g_print ("End-Of-Stream reached.\n");
break;
default:
/* We should not reach here because we only asked for ERRORs and EOS */
g_printerr ("Unexpected message received.\n");
break;
}
gst_message_unref (msg);
}else
{
g_printerr("error.");
}
/* Release the request pads from the Tee, and unref them */
/* Free resources */
if (msg != NULL)
gst_message_unref (msg);
gst_object_unref (bus);
gst_element_set_state (pipeline, GST_STATE_NULL);
gst_object_unref (pipeline);
return 0;
}
编译:
cmake_minimum_required(VERSION 3.0)
project(test_project)
find_package(PkgConfig REQUIRED)
pkg_search_module(GST1 REQUIRED gstreamer-1.0)#查找到gstreamer-1.0 并用GST1代表，GST1自己定义
add_executable(a.out v4l2src_appsink.c)
target_include_directories(a.out PRIVATE ${GST1_INCLUDE_DIRS})
target_link_libraries(a.out ${GST1_LIBRARIES} -lpthread)
message("GST1_LIBRARIES
${GST1_LIBRARIES}
")
运行结果：
format:YUY2, width:1920, height:1080
format:YUY2, width:1920, height:1080
format:YUY2, width:1920, height:1080
format:YUY2, width:1920, height:1080
format:YUY2, width:1920, height:1080
format:YUY2, width:1920, height:1080
format:YUY2, width:1920, height:1080
frame siz:4147200, max_siz:4147200, 07 FPS
format:YUY2, width:1920, height:1080
format:YUY2, width:1920, height:1080
format:YUY2, width:1920, height:1080
format:YUY2, width:1920, height:1080