Thank you or the response. I’m afraid I have tried the specifiers as well and as you said, map pertains to the stream assignment as opposed to a readable PID that my application can recognize. FFMPEG seems to assign constant values though, (0x100 = 256) for video, and (0x101 = 257) for audio. What I would like to do is assign those IDs myself. I am also aware of mpegts metadata fields, but those apply to a whole MPEG-TS. Not the elementary streams.