Steinar H. Gunderson

Sun, 10 Oct 2010 - VLC latency, part 6: Notes and corrections

My five-part series on our low-latency VLC setup ended yesterday, with a discussion about muxing and various one-frame-latency-inducing effects in different parts of VLC. Before that, I'd been talking about motivations, the overall plan, codec latency and timing.

This time there is no new material, only a few comments from readers of the series of the last few days. Thanks; you know who you are.

Finally, I realized I hadn't actually posted our current command-line anywhere, so here goes:

vlc \
  --decklink-caching 20 --sout-mux-caching 1 --sout-ts-dts-delay 60 --sout-ts-shaping 1 --sout-udp-caching 1 --no-sout-transcode-hurry-up \
  --decklink-aspect-ratio 16:9 --decklink-mode pal \
  --sout-x264-preset medium --sout-x264-tune zerolatency,film \
  --sout-x264-intra-refresh --no-sout-x264-interlaced --sout-x264-weightp 0 --sout-x264-bpyramid strict --sout-x264-ref 1 \
  --sout-x264-keyint 25 --sout-x264-lookahead 0 \
  --sout-x264-vbv-bufsize 60 --sout-x264-vbv-maxrate 1500 \
  -I dummy -v decklink:// vlc://quit \
  --sout '#transcode{vcodec=h264,vb=1500,acodec=lpcm}:std{access=udp,mux=ts,dst=}'

You'll probably want to up the bitrate for a real stream. A lot. And of course, coding PAL as non-interlaced doesn't make much sense either, unless it happens to be a progressive signal sent as interlaced.

I'll keep you posted if there's any new movement (new latency tests, more patches going into VLC, or similar), but for now, that's it. Enjoy :-)

[22:21] | | VLC latency, part 6: Notes and corrections

Steinar H. Gunderson <>