如何在C代码中使用gstreamer读取rtsp流

Question

有人可以，请告诉我，我在哪里可以找到一个例子，如何在C中读取一个带有gstreamer的rtsp ?实际上有很多，但我需要一个"rtspsrc";组件被显式使用时，我只能找到"gst-launch"示例或C代码，但使用"uridecodebin">

我尝试过这个，但是"pad_added_handler()"never被调用，我也没有得到任何错误

#include <gst/gst.h>
static void pad_added_handler (GstElement *src, GstPad *new_pad, GstElement *rtphepay);
int main(int argc, char *argv[]) {
GstBus *bus;
GstMessage *msg;
GstStateChangeReturn ret;
gboolean terminate = FALSE;
/* Initialize GStreamer */
gst_init (&argc, &argv);
GstElement *pipeline = gst_pipeline_new ("rtsp-pipeline");
if (!pipeline) {
g_printerr ("Pipeline could not be created. Exiting.n");
return -1;
}
// input
GstElement *rtspsrc = gst_element_factory_make("rtspsrc", "rtspsrc");
g_object_set (G_OBJECT (rtspsrc), "location", "rtsp://192.168.1.88:554/11", "latency", 10, NULL);
// decoding
GstElement *rtph265depay = gst_element_factory_make("rtph265depay", "rtph265depay");
GstElement *h265parse = gst_element_factory_make("h265parse", "h265parse");
GstElement *avdec_h265 = gst_element_factory_make("avdec_h265", "avdec_h265");
// display
GstElement *videoconvert = gst_element_factory_make("videoconvert", "videoconvert_screen");
GstElement *sink = gst_element_factory_make("autovideosink", "nvvideo_renderer");
gst_bin_add_many(GST_BIN(pipeline), rtph265depay, h265parse, avdec_h265, videoconvert, sink, NULL);
if (!gst_element_link_many(rtph265depay, h265parse, avdec_h265, videoconvert, sink, NULL)) {
g_printerr("Elements could not be linked. Exiting.n");
return -1;
}
// register callback
g_signal_connect (rtspsrc, "pad-added", G_CALLBACK (pad_added_handler), rtph265depay);

/* Start playing */
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;
}
/* Listen to the bus */
bus = gst_element_get_bus (pipeline);
do {
msg = gst_bus_timed_pop_filtered (bus, GST_CLOCK_TIME_NONE,
GST_MESSAGE_STATE_CHANGED | 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: %sn", GST_OBJECT_NAME (msg->src), err->message);
g_printerr ("Debugging information: %sn", debug_info ? debug_info : "none");
g_clear_error (&err);
g_free (debug_info);
terminate = TRUE;
break;
case GST_MESSAGE_EOS:
g_print ("End-Of-Stream reached.n");
terminate = TRUE;
break;
case GST_MESSAGE_STATE_CHANGED:
/* We are only interested in state-changed messages from the pipeline */
if (GST_MESSAGE_SRC (msg) == GST_OBJECT (pipeline)) {
GstState old_state, new_state, pending_state;
gst_message_parse_state_changed (msg, &old_state, &new_state, &pending_state);
g_print ("Pipeline state changed from %s to %s:n",
gst_element_state_get_name (old_state), gst_element_state_get_name (new_state));
}
break;
default:
/* We should not reach here */
g_printerr ("Unexpected message received.n");
break;
}
gst_message_unref (msg);
}
} while (!terminate);
/* Free resources */
gst_object_unref (bus);
gst_element_set_state (pipeline, GST_STATE_NULL);
gst_object_unref (pipeline);
return 0;
}
static void pad_added_handler (GstElement *src, GstPad *new_pad, GstElement *rtphepay) {
GstPad *sink_pad = gst_element_get_static_pad (rtphepay, "sink");
GstPadLinkReturn ret;
GstCaps *new_pad_caps = NULL;
GstStructure *new_pad_struct = NULL;
const gchar *new_pad_type = NULL;
g_print ("Received new pad '%s' from '%s':n", GST_PAD_NAME (new_pad), GST_ELEMENT_NAME (src));
/* If our converter is already linked, we have nothing to do here */
if (gst_pad_is_linked (sink_pad)) {
g_print ("We are already linked. Ignoring.n");
goto exit;
}
/* Check the new pad's type */
new_pad_caps = gst_pad_get_current_caps (new_pad);
new_pad_struct = gst_caps_get_structure (new_pad_caps, 0);
new_pad_type = gst_structure_get_name (new_pad_struct);
if (g_str_has_prefix (new_pad_type, "audio/x-raw")) {
g_print ("It has type '%s' which is raw audio. Ignoring.n", new_pad_type);
goto exit;
}
/* Attempt the link */
ret = gst_pad_link (new_pad, sink_pad);
if (GST_PAD_LINK_FAILED (ret)) {
g_print ("Type is '%s' but link failed.n", new_pad_type);
} else {
g_print ("Link succeeded (type '%s').n", new_pad_type);
}
exit:
/* Unreference the new pad's caps, if we got them */
if (new_pad_caps != NULL)
gst_caps_unref (new_pad_caps);
/* Unreference the sink pad */
gst_object_unref (sink_pad);
}

Answer 1

看起来您遵循了"Hello World"来自GStreamer的例子。你实际上做的不仅仅是"你好，世界"。您希望触发回调事件。这些来自GLib主循环。

我建议你看看"你的第一个申请"。示例来自GStreamer:

https://gstreamer.freedesktop.org/documentation/application-development/basics/helloworld.html?gi-language=c

基本上你想要的是添加GLib主循环，并添加一个总线监视，而不是迭代总线消息。