Gstreamer - appsrc push model - stream

Question

I'm developing a C application (under linux) that receives a raw h.264 stream and should visualize this stream using gstreamer APIs.
I am a newbie with GStreamer so maybe I am doing huge stupid mistakes or ignoring well-known stuff, sorry about that.
I got a raw h264 video (I knew it was the exact same format I need) and developed an application that plays it. It correctly works with appsrc in pull mode (when need data is called, I get new data from the file and perform push-buffer).
Now I'm trying to do the exact same thing but in push mode, this is basically because I don't have a video, but a stream. So I have a method inside my code that will be called every time new data (in the form of an uint8_t buffer) arrives, and this is my video source.
I googled my problem and had a look at the documentation, but I found no simple code snippets for my use case, even if it seems a very simple one. I understood that I have to init the pipeline and appsrc and then only push-buffer when I have new data.
Well, I developed two methods: init_stream() for pipeline/appsrc initialization and populate_app(void *inBuf, size_t len) to send data when they are available.
It compiles and correctly runs, but no video:
struct _App
{
GstAppSrc *appsrc;
GstPipeline *pipeline;
GstElement *h264parse;
GstElement *mfw_vpudecoder;
GstElement *mfw_v4lsin;
GMainLoop *loop;
};
typedef struct _App App;
App s_app;
App *app = &s_app;
static gboolean bus_message (GstBus * bus, GstMessage * message, App * app)
{
GST_DEBUG ("got message %s", gst_message_type_get_name (GST_MESSAGE_TYPE (message)));
switch (GST_MESSAGE_TYPE (message)) {
case GST_MESSAGE_ERROR:
g_error ("received error");
g_main_loop_quit (app->loop);
break;
case GST_MESSAGE_EOS:
g_main_loop_quit (app->loop);
break;
default:
break;
}
return TRUE;
}
int init_stream()
{
GstBus *bus;
gst_init (NULL, NULL);
fprintf(stderr, "gst_init done\n");
/* create a mainloop to get messages */
app->loop = g_main_loop_new (NULL, TRUE);
fprintf(stderr, "app loop initialized\n");
app->pipeline = gst_parse_launch("appsrc name=mysource ! h264parse ! mfw_vpudecoder ! mfw_v4lsin", NULL);
app->appsrc = gst_bin_get_by_name (GST_BIN(app->pipeline), "mysource");
gst_app_src_set_stream_type(app->appsrc, GST_APP_STREAM_TYPE_STREAM);
gst_app_src_set_emit_signals(app->appsrc, TRUE);
fprintf(stderr, "Pipeline and appsrc initialized\n");
/* Create Bus from pipeline */
bus = gst_pipeline_get_bus(app->pipeline);
fprintf(stderr, "bus created\n");
/* add watch for messages */
gst_bus_add_watch (bus, (GstBusFunc) bus_message, app);
gst_object_unref(bus);
fprintf(stderr, "bus_add_watch done\n");
GstCaps* video_caps = gst_caps_new_simple ("video/x-h264",
"width", G_TYPE_INT, 800,
"height", G_TYPE_INT, 480,
"framerate", GST_TYPE_FRACTION, 25,
1, NULL);
gst_app_src_set_caps(GST_APP_SRC(app->appsrc), video_caps);
/* go to playing and wait in a mainloop. */
gst_element_set_state ((GstElement*) app->pipeline, GST_STATE_PLAYING);
fprintf(stderr, "gst_element_set_state play\n");
/* this mainloop is stopped when we receive an error or EOS */
g_main_loop_run (app->loop);
fprintf(stderr, "g_main_loop_run called\n");
gst_element_set_state ((GstElement*) app->pipeline, GST_STATE_NULL);
fprintf(stderr, "gst_element_set_state GST_STATE_NULL\n");
/* free the file */
// g_mapped_file_unref (app->file);
gst_object_unref (bus);
g_main_loop_unref (app->loop);
return 0;
}
void populateApp(void *inBuf , size_t len) {
guint8 *_buffer = (guint8*) inBuf;
GstFlowReturn ret;
GstBuffer *buffer = gst_buffer_new();
GstCaps* video_caps = gst_caps_new_simple ("video/x-h264",
"width", G_TYPE_INT, 800,
"height", G_TYPE_INT, 480,
"framerate", GST_TYPE_FRACTION, 25,
1, NULL);
gst_buffer_set_caps(buffer, video_caps);
GST_BUFFER_DATA (buffer) = _buffer;
GST_BUFFER_SIZE (buffer) = len;
// g_signal_emit_by_name (app->appsrc, "push-buffer", buffer, &ret);
ret = gst_app_src_push_buffer(GST_APP_SRC(app->appsrc), buffer);
gst_buffer_unref (buffer);
}
As said, I am a total newbie at GStreamer so there's a lot of cut-and-paste code from the internet, but IMHO it should work.
Do you see any issues?

Answer 1

It's not clear how you are calling populateApp, but you need to call that repeatedly as you have data to push to your pipeline. This can be done in a separate thread from the one blocked by g_main_loop_run, or you can restructure your program to avoid using GMainLoop.