Tutorial 1: Streaming packets to a DumpFrameFilter¶

Downloads: Python · C++

In this first tutorial we build the simplest possible Limef pipeline:

        flowchart TD
    src["MediaFileThread"]
    dump["DumpFrameFilter"]
    src --> dump

Limef::thread::MediaFileThread reads a media file and pushes encoded Limef::frame::PacketFrames downstream. Limef::ff::DumpFrameFilter prints a one-line description of every passing frame to stdout and passes it on.

We stream at the file’s natural playback speed by setting fps = -1.

import time
import sys
import limef

Build the filterchain¶

First create the DumpFrameFilter, then connect the source thread to it. Filters must be wired before start() is called.

dump = limef.DumpFrameFilter("dump")

Configure the source thread¶

Limef::thread::MediaFileContext holds the parameters for the source thread.

Key options:

Parameter	Value	Meaning
`fps`	`0`	feed as fast as possible (default)
`fps`	`-1`	feed at the stream’s natural playback speed
`fps`	`N`	feed at N frames per second
`loop`	`-1`	do not loop (default)
`loop`	`0`	loop immediately at EOF
`loop`	`N`	pause N ms before restarting

Here we use fps = -1 so packets are paced to the stream’s original timing.

media_file = sys.argv[1] if len(sys.argv) > 1 else "video.mp4"

ctx      = limef.MediaFileContext(media_file, slot=1)
ctx.fps  = -1   # natural live speed

Start and stop¶

Connect the thread to the filterchain with cc(), start it, wait, then stop. stop() sends a stop signal through the pipeline and blocks until the thread exits.

thread = limef.MediaFileThread("reader", ctx)
thread.cc(dump)
thread.start()

print("Streaming for 5 seconds — watch the DumpFrameFilter output ...")
try:
    time.sleep(5)
except KeyboardInterrupt:
    pass

thread.stop()
print("Done.")