In GstBaseRtpDepayload, the new segment is sent with the RTP timestamp of the
first buffer. The first buffer's timestamp (and the
following ones) is then updated to add the queue
length.

I think the queue length should also be added on the
new segment's timestamp. Then, the new segment and the
first buffer will have the same timestamp.

Or, as someone mentioned on the mailing-list, we could not add the queue delay
to the buffer's timestamp.