GStreamer学习2.1----获取mp4中的图片

这里通过获取mp4中的图片例子来加深Gstreamer的理解，问问AI实现这样功能的命令，

得到

gst-launch-1.0 filesrc location=test.mp4 ! qtdemux ! queue ! h264parse ! avdec_h264 ! videoconvert ! jpegenc ! multifilesink location=output_image_%03d.jpg

在window环境上试了下，有问题

WARNING: erroneous pipeline: no element "avdec_h264"

修改为下面的命令后，可以保存图片了

gst-launch-1.0 filesrc location=test.mp4 ! decodebin ! jpegenc ! multifilesink location=output_image_%03d.jpg

接下来可以根据这个命令来生成对应的api代码了，目前AI生成的代码一般会有问题，需要修改，

#include <gst/gst.h>

#define FILE_PATH "D:\\2024\\06\\Test\\test.mp4"

static void pad_added_handler(GstElement* src, GstPad* new_pad, gpointer user_data) {
  GstElement* dest = GST_ELEMENT(user_data);
  GstPad* dest_pad = gst_element_get_static_pad(dest, "sink");

  g_print(" pad '%s' ，sink pad '%s'.\n", GST_PAD_NAME(new_pad), GST_PAD_NAME(dest_pad));
  if (gst_pad_is_linked(dest_pad)) {
    g_printerr("Destination pad is already linked.\n");
    goto exit;
  }

  if (gst_pad_link(new_pad, dest_pad) != GST_PAD_LINK_OK) {
    g_printerr("Failed to link pads.\n");
    goto exit;
  }

exit:
  gst_object_unref(dest_pad);
}


int main(int argc, char* argv[]) {
  GstElement* pipeline, * filesrc, * decodebin, * jpegenc, * app_sink;
  GstBus* bus;
  GstMessage* msg;
  GstStateChangeReturn ret;

  
  gst_init(&argc, &argv);

  
  pipeline = gst_pipeline_new("image-pipeline");
  filesrc = gst_element_factory_make("filesrc", "filesrc");
  decodebin = gst_element_factory_make("decodebin", "decodebin");
  jpegenc = gst_element_factory_make("jpegenc", "jpegenc");
  app_sink = gst_element_factory_make("multifilesink", "app_sink");

  if (!pipeline || !filesrc || !decodebin || !jpegenc || !app_sink) {
    g_printerr("Not all elements could be created.\n");
    return -1;
  }

  g_object_set(filesrc, "location", FILE_PATH, NULL);
 
  g_object_set(G_OBJECT(app_sink), "location", "output_image_%03d.jpg", NULL);
 
  gst_bin_add_many(GST_BIN(pipeline), filesrc, decodebin, jpegenc, app_sink, NULL);

  
  g_signal_connect(decodebin, "pad-added", G_CALLBACK(pad_added_handler), jpegenc);

  
  if (!gst_element_link(filesrc, decodebin) || !gst_element_link(jpegenc, app_sink)) {
    g_printerr("Elements could not be linked.\n");
    gst_object_unref(pipeline);
    return -1;
  }

  
  ret = gst_element_set_state(pipeline, GST_STATE_PLAYING);
  if (ret == GST_STATE_CHANGE_FAILURE) {
    g_printerr("Unable to set the pipeline to the playing state.\n");
    gst_object_unref(pipeline);
    return -1;
  }

  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)
    gst_message_unref(msg);
  gst_object_unref(bus);
  gst_element_set_state(pipeline, GST_STATE_NULL);
  gst_object_unref(pipeline);

  return 0;
}

在windows vs中，中文注释可能会导致程序问题，这个比较奇怪。

执行后，可以看到生成了很多图片