Hi, I attach to this mail a minimal test to provide a gstreamer behaviour that I do not understand. Actually, I would like to know why the clock can be not set yet whereas some buffers are dispatched. I mean I put an identity element between a videotestsrc and a fakesink, and I am checking the clock availability in the identity handoff callback. Why am I able to get raw video buffers from handoff callback whereas no clock is set on identity yet ? Moreover in this case the timestamp buffer is valid, but I assume this timestamp was set by the internal clock. I can understand that the internal clock was already there before playing, and I can also understand that the internal clock is affected on elements only when going to playing state (or at least ready). But I think the clock should be always available from a handoff callback, at least if the buffer timestamp is valid. ( to compile the test: gcc -Wall $(pkg-config --cflags --libs gstreamer-0.10) main.c -o main ) (output: identity has clock: 0, timestamp is valid: 1 pipeline is now playing new clock set from: pipeline identity has clock: 1, timestamp is valid: 1 identity has clock: 1, timestamp is valid: 1 identity has clock: 1, timestamp is valid: 1 identity has clock: 1, timestamp is valid: 1 identity has clock: 1, timestamp is valid: 1 identity has clock: 1, timestamp is valid: 1 identity has clock: 1, timestamp is valid: 1 identity has clock: 1, timestamp is valid: 1 identity has clock: 1, timestamp is valid: 1 End of stream ) Sincerely Julien