Low Latency DASH Nginx RTMP

Question

I use arut nginx-rtmp-module (https://github.com/arut/nginx-rtmp-module) on the media server, then I tried to stream using FFmpeg to the dash application, then

Answer 1

You may need to change the GOP size in ffmpeg command. The default GOP size for ffmpeg is 250 which means there will be a key frame every 250 frames. If your output is 25fps, then you will have a key frame every 10s in worst case (if scene cut detection is enabled, you may have shorter key frame interval).

For both HLS and DASH, the segments must start with a key frame. So you will have a lot of segments with 10s duration. You need to reduce the segment duration (the GOP size) in order to reduce latency.

Try to modify your ffmpeg command as follow to see if it helps

exec ffmpeg -re -i rtmp://localhost:1935/live/$name
          -c:a libfdk_aac -b:a 32k  -c:v libx264 -g 50 -b:v 128K -f flv rtmp://localhost:1935/hls/$name_low
          -c:a libfdk_aac -b:a 64k  -c:v libx264 -g 50 -b:v 256k -f flv rtmp://localhost:1935/hls/$name_mid
          -c:a libfdk_aac -b:a 128k -c:v libx264 -g 50 -b:v 512K -f flv rtmp://localhost:1935/hls/$name_hi
          -c:a libfdk_aac -b:a 128k -c:v libx264 -g 50 -b:v 512K -f flv rtmp://localhost:1935/dash/$name_dash;