动态替换正在播放的gstreamer管道中的元素

Question

I'm looking for the correct technique, if one exists, for dynamically replacing an element in a running gstreamer pipeline. I have a gstreamer based c++ app and the pipeline it creates looks like this (using gst-launch syntax) :

souphttpsrc location="http://localhost/local.ts" ! mpegtsdemux name=d ! queue ! mpeg2dec ! xvimagesink d. ! queue ! a52dec ! pulsesink

During the middle of playback (ie GST_STATE_PLAYING is the pipeline state and the user is happily watching video), I need to remove souphttpsrc from the pipeline and create a new souphttpsrc, or even a new neonhttpsource, and then immediately add that back into the pipeline and continue playback of the same uri source stream at the same time position where playback was before we performed this operation. The user might see a small delay and that is fine.

We've barely figured out how to remove and replace the source, and we need more understanding. Here's our best attempt thus far:

gst_element_unlink(source, demuxer);
gst_element_set_state(source, GST_STATE_NULL);
gst_bin_remove(GST_BIN(pipeline), source);
source = gst_element_factory_make("souphttpsrc", "src");
g_object_set(G_OBJECT(source), "location", url, NULL);
gst_bin_add(GST_BIN(pipeline), source);
gst_element_link(source, demuxer);
gst_element_sync_state_with_parent(source);

This doesn't work perfectly because the source is playing back from the beginning and the rest of the pipeline is waiting for the correct timestamped buffers (I assume) because after several seconds, playback picks back up. I tried seeking the source in multiple ways but nothing has worked.

I need to know the correct way to do this. It would be nice to know a general technique, if one exists, as well, in case we wanted to dynamically replace the decoder or some other element.

thanks

Answer 1

I think this may be what you are looking for: http://cgit.freedesktop.org/gstreamer/gstreamer/tree/docs/design/part-block.txt

(starting at line 115)