<div dir="ltr"><div>Perfect example. It does exactly what I wanted. But... The seek returns false (the other part works perfectly) <div style="margin-left:40px"> CLI='filesrc location=%s ! decodebin ! appsink name=sink' % filename pipeline=Gst.parse_launch(CLI) # get sink appsink=pipeline.get_by_name("sink") # set to PAUSED to make the first frame arrive in the sink pipeline.set_state(Gst.State.PAUSED) pipeline.seek_simple(Gst.Format.BUFFERS, Gst.SeekFlags.FLUSH, frame_number) smp = appsink.emit('pull-preroll') buf = smp.get_buffer() data=buf.extract_dup(0, buf.get_size())[:307200] # Only 1/2 of expected RGB size frame = np.fromstring(data,dtype='uint8').reshape((480,640,1)) </div>Thanks a lot, </div>Hjalmar </div><div class="gmail_extra"> <div class="gmail_quote">On Mon, Dec 7, 2015 at 1:47 PM, Tim Müller <<a href="mailto:tim@centricular.com" target="_blank">tim@centricular.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On Mon, 2015-12-07 at 13:30 -0300, Hjalmar Turesson wrote: Hi Hjalmar, This (C) example shows how to retrieve frames from appsink, perhaps you find it useful: <a href="http://cgit.freedesktop.org/gstreamer/gst-plugins-base/tree/tests/examp les/snapshot/snapshot.c" rel="noreferrer" target="_blank">http://cgit.freedesktop.org/gstreamer/gst-plugins-base/tree/tests/examp les/snapshot/snapshot.c</a> It uses the pull-preroll signal/API, that only works once, if you want to retrieve one frame, and then another one, then just use the pull- sample API N times. There are two ways to use appsink: one is to have it emit a signal (new-sample) whenever a buffer arrives, and then you pull it in the callback). The other is to simply set the pipeline to PLAYING and then do pull-sample, which will block and wait for a simple if none is available yet then. Note that from the "new-sample" signal callback you can also return GST_FLOW_EOS if you don't want to be called again. Cheers -Tim <div><div class="h5"> > Hi, > > I would like read individual frames to python/numpy for analysis. > That is, I want call a function that reads and returns 1 frame. I > thought I could do this with appsink, but I have 2 problems. 1) I > cannot return a frame from the callback function 2) It doesn't just > read 1 frame. > > Simple example that does not do what I want: > > import gi > gi.require_version('Gst', '1.0') > from gi.repository import GObject, Gst, Gtk > GObject.threads_init() > Gst.init(None) > ########## > > CLI='filesrc location=testVideo.mp4 ! decodebin ! appsink > name=sink' > pipeline=Gst.parse_launch(CLI) > appsink=pipeline.get_by_name("sink") > appsink.set_property("max-buffers",1) > appsink.set_property('emit-signals',True) > appsink.set_property('sync',False) > > def on_new_buffer(appsink): > sample = appsink.emit('pull-sample') > #get the buffer > buf=sample.get_buffer() > data=buf.extract_dup(0,buf.get_size()) > return False # Here I would like to return the frame > > appsink.connect('new-sample', on_new_buffer) > pipeline.set_state(Gst.State.PLAYING) > pipeline.set_state(Gst.State.NULL) > > Is it possible to do what I want to do using appsink? > > Another strategy I tried is to use fdsink and read the data from that > location: > > import os > > readfd, writefd = os.pipe() > frame_size_bytes = 460800 > > CLI='filesrc location=testVideo.mp4 ! decodebin ! fdsink > name=sink' > pipeline=Gst.parse_launch(CLI) > fdsink=pipeline.get_by_name("sink") > fdsink.set_property("fd", readfd) > > pipeline.set_state(Gst.State.PLAYING) > data = os.read(readfd, frame_size_bytes) > pipeline.set_state(Gst.State.PAUSED) > > This does not work either. The code hang at the data = os.read... > line, maybe trying to play the entire file before moving on. > > How can I read only one frame? > > Thanks, > Hjalmar </div></div>> _______________________________________________ > gstreamer-devel mailing list > <a href="mailto:gstreamer-devel@lists.freedesktop.org">gstreamer-devel@lists.freedesktop.org</a> > <a href="http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel" rel="noreferrer" target="_blank">http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel</a> -- Tim Müller, Centricular Ltd - <a href="http://www.centricular.com" rel="noreferrer" target="_blank">http://www.centricular.com</a> _______________________________________________ gstreamer-devel mailing list <a href="mailto:gstreamer-devel@lists.freedesktop.org">gstreamer-devel@lists.freedesktop.org</a> <a href="http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel" rel="noreferrer" target="_blank">http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel</a> </blockquote></div> </div>