gst中, srcpad buffer探针附加字符串, 下一个插件srcpad buffer探针获取, c实现, 使用gst_buffer_add_custom_meta

可以使用 gst_buffer_add_meta() 函数来添加自定义的 meta 数据。具体实现可以参考以下代码：

#include <gst/gst.h>

typedef struct {
  GstMeta meta;
  gchar *data;
} CustomMeta;

static GstMetaInfo *custom_meta_info = NULL;

static void custom_meta_init(GstBuffer *buffer, gpointer data)
{
  CustomMeta *meta = (CustomMeta *)data;
  meta->data = NULL;
}

static void custom_meta_free(GstBuffer *buffer, gpointer data)
{
  CustomMeta *meta = (CustomMeta *)data;
  g_free(meta->data);
  meta->data = NULL;
}

static gboolean custom_meta_transform(GstBuffer *buffer, GstMeta *meta, GstBuffer *dest)
{
  CustomMeta *src_meta = (CustomMeta *)meta;
  CustomMeta *dest_meta = NULL;

  dest_meta = (CustomMeta *)gst_buffer_add_meta(dest, custom_meta_info, NULL);
  dest_meta->data = g_strdup(src_meta->data);

  return TRUE;
}

static CustomMeta *custom_meta_new(const gchar *data)
{
  CustomMeta *meta = NULL;

  meta = (CustomMeta *)gst_meta_new(custom_meta_info, NULL);
  meta->data = g_strdup(data);

  return meta;
}

static gboolean custom_meta_add(GstBuffer *buffer, const gchar *data)
{
  CustomMeta *meta = NULL;

  meta = custom_meta_new(data);
  gst_buffer_add_meta(buffer, (GstMeta *)meta, NULL);

  return TRUE;
}

static CustomMeta *custom_meta_get(GstBuffer *buffer)
{
  CustomMeta *meta = NULL;

  meta = (CustomMeta *)gst_buffer_get_meta(buffer, custom_meta_info);

  return meta;
}

static void custom_meta_register(void)
{
  custom_meta_info = gst_meta_register(
    "CustomMeta",
    sizeof(CustomMeta),
    custom_meta_init,
    custom_meta_free,
    custom_meta_transform
  );
}

static gboolean srcpad_buffer_probe(GstPad *pad, GstPadProbeInfo *info, gpointer user_data)
{
  GstBuffer *buffer = GST_PAD_PROBE_INFO_BUFFER(info);
  CustomMeta *meta = NULL;

  meta = custom_meta_get(buffer);
  if (meta != NULL) {
    g_print("CustomMeta data: %s\n", meta->data);
  }

  return TRUE;
}

static gboolean next_plugin_srcpad_buffer_probe(GstPad *pad, GstPadProbeInfo *info, gpointer user_data)
{
  GstBuffer *buffer = GST_PAD_PROBE_INFO_BUFFER(info);
  CustomMeta *meta = NULL;

  meta = custom_meta_get(buffer);
  if (meta != NULL) {
    g_print("CustomMeta data: %s\n", meta->data);
  }

  return TRUE;
}

int main(int argc, char *argv[])
{
  GstElement *pipeline, *src, *next_plugin;
  GstPad *srcpad, *next_plugin_srcpad;
  GstBus *bus;
  GstMessage *msg;
  GstStateChangeReturn ret;

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

  /* Register custom meta */
  custom_meta_register();

  /* Create the elements */
  pipeline = gst_pipeline_new("pipeline");
  src = gst_element_factory_make("videotestsrc", "src");
  next_plugin = gst_element_factory_make("next_plugin", "next_plugin");

  /* Add elements to the pipeline */
  gst_bin_add_many(GST_BIN(pipeline), src, next_plugin, NULL);

  /* Link the elements */
  gst_element_link(src, next_plugin);

  /* Get pads */
  srcpad = gst_element_get_static_pad(src, "src");
  next_plugin_srcpad = gst_element_get_static_pad(next_plugin, "src");

  /* Add buffer probes */
  gst_pad_add_probe(srcpad, GST_PAD_PROBE_TYPE_BUFFER, srcpad_buffer_probe, NULL, NULL);
  gst_pad_add_probe(next_plugin_srcpad, GST_PAD_PROBE_TYPE_BUFFER, next_plugin_srcpad_buffer_probe, NULL, NULL);

  /* Start playing */
  ret = gst_element_set_state(pipeline, GST_STATE_PLAYING);
  if (ret == GST_STATE_CHANGE_FAILURE) {
    g_printerr("Failed to start pipeline\n");
    return -1;
  }

  /* 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);

  /* 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;
}

在 srcpad_buffer_probe() 函数中，我们可以使用 custom_meta_get() 函数获取 buffer 中的自定义 meta 数据。在 next_plugin_srcpad_buffer_probe() 函数中同样可以获取自定义 meta 数据。在这个例子中，我们只是简单地打印出自定义 meta 数据，你可以根据实际需求进行处理。