<html> <head> <style></style> </head> <body class='hmmessage'> Hi All, I have a non generic audio video capture device with multiple inputs and i am trying to integrate it as my first gstreamer plugin. To start simple i am only aiming at creating an element with one video source. So I am extending GstBaseSrc. The device provide mmap yuv buffers in either PAL or NTSC resolution through ioctl calls. I have tried to take as an example the v4l2src source code. i test it with the command gst-launch-0.10 myfilter device="/dev/xecap0" video-mode=0 chan-bitmap=0xffff chan-select=0 ! fakesink And get the following /********************BEGIN**********************/ Setting pipeline to PAUSED ... Pipeline is live and does not need PREROLL ... Setting pipeline to PLAYING ... New clock: GstSystemClock (gst-launch-0.10:854): GStreamer-CRITICAL **: gst_pad_push: assertion `GST_IS_BUFFER (buffer)' failed ERROR: from element /pipeline0/myfilter0: Internal data flow error. Additional debug info: gstbasesrc.c(2165): gst_base_src_loop (): /pipeline0/myfilter0: streaming task paused, reason error (-5) Execution ended after 426026 ns. Setting pipeline to PAUSED ... Setting pipeline to READY ... (gst-launch-0.10:854): GStreamer-CRITICAL **: gst_mini_object_unref: assertion `mini_object->refcount > 0' failed gst_myfilter_stopped Setting pipeline to NULL ... FREEING pipeline ... /********************END***********************/ With gst-debug=*:3, everything seems fine until i get the following warning and the pipeline stops ... /********************BEGIN**********************/ (gst-launch-0.10:796): GStreamer-CRITICAL **: gst_pad_push: assertion `GST_IS_BUFFER (buffer)' failed 0:00:00.211305419   796 0x929a770 INFO               basesrc gstbasesrc.c:2114:gst_base_src_loop:<myfilter0> pausing after gst_pad_push() = error 0:00:00.211320520   796 0x929a770 WARN               basesrc gstbasesrc.c:2165:gst_base_src_loop:<myfilter0> error: Internal data flow error. 0:00:00.211328857   796 0x929a770 WARN               basesrc gstbasesrc.c:2165:gst_base_src_loop:<myfilter0> error: streaming task paused, reason error (-5) /********************END***********************/ I have implemented the following methods gstbasesrc_class->set_caps = GST_DEBUG_FUNCPTR (gst_myfilter_set_caps); gstbasesrc_class->start = GST_DEBUG_FUNCPTR (gst_myfilter_start); gstbasesrc_class->stop = GST_DEBUG_FUNCPTR (gst_myfilter_stop); gstbasesrc_class->create = GST_DEBUG_FUNCPTR (gst_myfilter_create); I initialise the buffer in the set_caps method like this: static gboolean gst_myfilter_set_caps (GstBaseSrc * src, GstCaps * caps) {      .      .      .      if (!gst_pad_set_caps (src->srcpad, caps))     {         GST_WARNING ("gst_myfilter_set_caps caps negotiation failed %" GST_PTR_FORMAT "from elem",                 caps, GST_ELEMENT_NAME(src));         return FALSE;     }     .     .     .     GST_BUFFER_DATA (filter->my_buffer) = (guchar*)dev_buf;     GST_BUFFER_SIZE (filter->my_buffer) = (filter->video_mode == 0)?704*576*2:704*480*2;     GST_BUFFER_FLAG_SET (filter->my_buffer, GST_BUFFER_FLAG_READONLY);     gst_buffer_set_caps (GST_BUFFER (filter->my_buffer), caps);    return TRUE; } Here is the create method, it always seems to get called 3 times ok untils the error shows which puzzle me the most. static GstFlowReturn gst_myfilter_create (GstBaseSrc * basesrc, guint64 offset, guint length,     GstBuffer ** buffer) {     Gstmyfilter *src;     GstState state = GST_STATE (basesrc);     if(state != GST_STATE_PLAYING)     {         return GST_FLOW_WRONG_STATE;     }     src = GST_MYFILTER (basesrc);     gchar * dev_buf = NULL;     dev_error dev_ret = dev_get_framebuffer(src->chan_select, src->dev_handle, &dev_buf);     if(dev_ret == DEV_ERROR || dev_buf == NULL)     {         return GST_FLOW_ERROR;     }     GST_BUFFER_OFFSET (src->my_buffer) = src->offset++;     GST_BUFFER_OFFSET_END (src->my_buffer) = src->offset;     GST_BUFFER_TIMESTAMP (src->my_buffer) = GST_CLOCK_TIME_NONE;     GST_BUFFER_DATA (src->my_buffer) = (guint8*)dev_buf;     *buffer = src->my_buffer;     return GST_FLOW_OK; } Any ideas why the (gst-launch-0.10:796): GStreamer-CRITICAL **: gst_pad_push: assertion `GST_IS_BUFFER (buffer)' failed error shows up ? Regards, Pierre </body> </html>