[FFmpeg-user] ffmpeg udp stream to decklink card low latency

Paul DeBaun pdebaun at ilm.com
Tue May 21 02:30:01 EEST 2019

Hello!  I am trying to configure ffmpeg to be able to take a udp stream and
play it out on a decklink
card.  I am having a bit of a buffering issue and I can't seem to figure
out what part of the code is introducing the delay.  Here are the two
commands I'm using.

send:  ./ffmpeg -f decklink -i 'DeckLink SDI 4K' -v 0 -vcodec mpeg4 -b:v
30M -f mpegts udp://

receive: ./ffmpeg -i "udp://@:23002?overrun_nonfatal=1&fifo_size=100000"
-fflags nobuffer -f decklink -preroll 0.1 -pix_fmt uyvy422 'DeckLink SDI 4K'

They delay here is about 5 seconds.  However, if I have the stream playing
and then I restart the encoder and give the receiver time to drain its
buffers, the delay will get down to about 2 frames.

Also, when I use ffplay with the nobuffer flag, the delay is about 2

./ffplay -i "udp://@:23002?overrun_nonfatal=1&fifo_size=100000" -fflags

Any help would be appreciated.  Thanks!

-Paul DeBaun
ILM San Francisco

More information about the ffmpeg-user mailing list