<div dir="ltr">Hello GStreamer-devel, I am trying to write a GStreamer element, embedfoo, which embeds data in received GStreamer video frame buffers using the function gst_buffer_add_meta. The data added to the buffer is retrieved from a database using the frame index of the GstBuffer. I am using the value of GST_BUFFER_PTS and the framerate to obtain the frame index of the received GstBuffers. The issue I am having is that the value of the PTS timestamps in the received GstBuffer objects differs according to the source. For example, if I output the value of GST_BUFFER_PTS for the first buffer received in the following pipelines I get differing results: Pipeline 1: videotestsrc ! video/x-raw,framerate=15/1 ! embedfoo location=database.txt ! x265enc ! mpegtsmux ! filesink location=test.ts Pipeline 1 First PTS value: 0 Pipeline 2: filesrc location=test.ts ! decodebin ! embedfoo location=database.txt ! videoconvert ! ximagesink Pipeline 2 First PTS value: 125000000 The embedfoo element is implemented as a subclass of GstBaseTransform and I am using GStreamer 1.14.5 as provided by Ubuntu 18.04. I have tried using the methods gst_segment_position_from* and gst_segment_to_stream_time using the segment member of GstBaseTransform, but I am unable to correctly calculate the frame index of a buffer from the PTS timestamp. Any pointers would be awesome. Thanks, Mark </div>