无法链接元素，要链接哪些元素？(gstreamer c)

Question

我一直在研究 gstreamer，我不明白我在哪里出错，但我尝试转动代码的每个管道都会给我“无法链接元素”，并且我在具有上游内核的 ubuntu 20.04 上运行此代码版本 5.13.0-35（我认为这不是问题）与 gcc 9 的代码如下：

#include <gst/gst.h>
#include <stdio.h>

/* Structure to contain all our information, so we can pass it to callbacks */
typedef struct _CustomData {
  GstElement *pipeline;
  GstElement *source;
  GstCaps *caps;
  GstElement *depay;
  GstElement *parse;
  GstElement *decode;
  GstElement *convert;
  GstElement *sink;
} CustomData;


int main (int argc, char *argv[])
{
  CustomData data;
  GstBus *bus;
  GstMessage *msg;
  GstStateChangeReturn ret;

  /* Initialize GStreamer */
  gst_init (&argc, &argv);

  /* Create the elements */
  data.source = gst_element_factory_make ("udpsrc", "source");
  data.caps = gst_caps_new_simple("application/x-rtp", 
    "media", G_TYPE_STRING, "video",
    "clock-rate", G_TYPE_INT, 90000,
    "encoding-name", G_TYPE_STRING, "H264",
    "payload", G_TYPE_INT, 96,
    NULL);
  data.depay = gst_element_factory_make ("rtph264depay", "depay");
  data.parse = gst_element_factory_make ("h264parse", "parse");
  data.decode = gst_element_factory_make ("decodebin", "decode");
  data.convert = gst_element_factory_make ("videoconvert", "convert");
  data.sink = gst_element_factory_make ("autovideosink", "sink");

  /* Create the empty pipeline */
  data.pipeline = gst_pipeline_new ("test-pipeline");

  if (!data.pipeline || !data.source || !data.depay || !data.parse || !data.decode  || !data.convert || !data.sink) {
    g_printerr ("Not all elements could be created.\n");
    return -1;
  }

  gst_bin_add_many (GST_BIN (data.pipeline), data.source, data.depay, data.parse, data.decode, data.convert, data.sink, NULL);
  if (gst_element_link_many (data.source, data.depay, data.parse, data.decode, data.convert, data.sink, NULL) != TRUE) {
    g_printerr ("Elements could not be linked.\n");
    gst_object_unref (data.pipeline);
    return -1;
  }  
  /* Set the port and caps to play */
  g_object_set (data.source, "port", 5000, NULL);
  g_object_set (data.source, "caps", data.caps, NULL);
  g_object_set (data.sink, "sync", FALSE, NULL);


  /* Start playing */
  ret = gst_element_set_state (data.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 (data.pipeline);
    return -1;
  }

  /* Wait until error or EOS */
  bus = gst_element_get_bus (data.pipeline);
  msg =
      gst_bus_timed_pop_filtered (bus, GST_CLOCK_TIME_NONE,
      GST_MESSAGE_ERROR | GST_MESSAGE_EOS);

  /* Parse message */
  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);
  }

  /* Free resources */
  gst_object_unref (bus);
  gst_element_set_state (data.pipeline, GST_STATE_NULL);
  gst_object_unref (data.pipeline);
  return 0;
}

接收管道是：

gst-launch-1.0 -v udpsrc port=5000 ! "application/x-rtp, media=(string)video, clock-rate=(int)90000, encoding-name=(string)H264, payload=(int)96" ! rtph264depay ! h264parse ! decodebin ! videoconvert ! autovideosink sync=false

发件人是：

gst-launch-1.0 -v filesrc location=test.mp4 ! qtdemux ! h264parse ! avdec_h264 ! x264enc ! rtph264pay ! udpsink host=$HOST port=5000

提前致谢。

Answer 1

您可以尝试使用 gst_parse_launch() ，它将像 gst-launch 一样协商上限：

const gchar *pipeline_str = "udpsrc port=5000 ! application/x-rtp,encoding-name=H264 ! rtph264depay ! h264parse ! decodebin ! videoconvert ! autovideosink sync=false";
GstElement *pipeline = gst_parse_launch (pipeline_str, NULL);
if (!pipeline) {
   g_error ("Failed to create pipeline\n");
   exit(-1);
}
...

否则，您可能必须添加 capsfilters。