Video QoS Mastery: How to Kill Latency and Stop Packet Loss

Stop using default settings. They are optimized for file storage, not streaming.

4.1 FFmpeg: Tuning for Zero Latency

We need to disable internal buffers and force a strict Group of Pictures (GOP).

The “Low Latency” Command:

ffmpeg -f dshow -i video="Camera" \
  -c:v libx264 \
  -preset fast \
  -tune zerolatency \
  -b:v 2500k -maxrate 2500k -bufsize 5000k \
  -g 60 -keyint_min 60 -sc_threshold 0 \
  -f mpegts udp://127.0.0.1:1234

• -tune zerolatency: Critical. Disables frame reordering (no B-frames).

• -g 60: Locks keyframes to every 2 seconds (assuming 30fps).

• -maxrate: Forces Constant Bitrate (CBR) behavior to predict bandwidth usage.

4.2 NGINX: Preventing the “Thundering Herd”

If you serve HLS/DASH, unoptimized NGINX configs will kill your origin server during traffic spikes.

Optimized NGINX Block:

location /hls {
    # 1. Lock the Cache: Only allow ONE request to go to origin.
    #    Everyone else waits 5ms for the cache to fill.
    proxy_cache_lock on;
    proxy_cache_lock_timeout 5s;
    
    # 2. Serve Stale: Never show a 500 error if the origin blips.
    #    Serve the old segment instead.
    proxy_cache_use_stale error timeout updating http_500;
    
    # 3. Slice Module: Stream the start of the file while the end downloads.
    slice 1m;
    proxy_cache_key $uri$is_args$args$slice_range;
    proxy_set_header Range $slice_range;
}

4.3 The Client: Why You Need BOLA

Throughput-based adaptation is outdated. Use BOLA (Buffer-Based Adaptation).

• How it works: It looks at the buffer health, not just download speed.

• Why it wins: It prevents “quality flapping” (switching from 1080p to 480p and back) which annoys users more than constant 720p.