gstreamer appsink 输出到标准输出, 给出列子

好的，这个问题属于技术问题，我可以回答。下面是一个简单的示例代码，用于将 Gstreamer 管道中的视频帧输出到标准输出：

#include <gst/gst.h>

static GstFlowReturn new_sample_handler(GstElement *appsink, gpointer user_data) {
    GstSample *sample = NULL;
    g_signal_emit_by_name(appsink, "pull-sample", &sample);
    if (sample != NULL) {
        GstBuffer *buffer = gst_sample_get_buffer(sample);
        GstMapInfo info;
        gst_buffer_map(buffer, &info, GST_MAP_READ);
        fwrite(info.data, 1, info.size, stdout);
        gst_buffer_unmap(buffer, &info);
        gst_sample_unref(sample);
    }
    return GST_FLOW_OK;
}

int main(int argc, char *argv[]) {
    GstElement *pipeline, *appsrc, *appsink;
    GstCaps *caps;
    GstBus *bus;
    GstMessage *msg;
    GMainLoop *loop;
    
    gst_init(&argc, &argv);
    loop = g_main_loop_new(NULL, FALSE);
    
    pipeline = gst_pipeline_new("pipeline");
    appsrc = gst_element_factory_make("appsrc", "appsrc");
    appsink = gst_element_factory_make("appsink", "appsink");
    
    caps = gst_caps_new_simple("video/x-raw",
        "format", G_TYPE_STRING, "RGB",
        "width", G_TYPE_INT, 640,
        "height", G_TYPE_INT, 480,
        "framerate", GST_TYPE_FRACTION, 30, 1,
        NULL);
    gst_app_src_set_caps(GST_APP_SRC(appsrc), caps);
    gst_caps_unref(caps);
    
    g_object_set(G_OBJECT(appsink),
        "emit-signals", TRUE,
        "sync", FALSE,
        "max-buffers", 2,
        "drop", TRUE,
        NULL);
    g_signal_connect(appsink, "new-sample", G_CALLBACK(new_sample_handler), NULL);

    gst_bin_add_many(GST_BIN(pipeline), appsrc, appsink, NULL);
    gst_element_link(appsrc, appsink);

    gst_element_set_state(pipeline, GST_STATE_PLAYING);

    g_main_loop_run(loop);

    gst_element_set_state(pipeline, GST_STATE_NULL);
    gst_object_unref(pipeline);
    g_main_loop_unref(loop);
    return 0;
}

这个程序使用 Gstreamer 创建一个简单的管道，通过 appsrc 向其中输出视频流，再通过 appsink 捕获视频流中的帧数据，并通过标准输出输出。注意这里的输出是二进制数据，需要用其他工具解析才能正确显示。