Tradeoff between Latency and Buffer in the context of Live video - devrath/MediaAlchemySuite GitHub Wiki

Why It’s a Tradeoff between Latency and Buffer in the context of Live video

• More Buffer = Smooth Playback but Higher Latency
• Less Buffer = Low Latency but Higher Risk of Rebuffering

🎯 Example in Live Streaming

        Live Camera Capture Time: 10:00:00
                   │
                   ▼
            Streamer encodes video
                   │
                   ▼
       ┌──────────────────────────────┐
       │   Player Buffers 10 seconds  │  ← High buffer
       └──────────────────────────────┘
                   │
                   ▼
         Viewer sees video at 10:00:10  ← 10s latency

Now reduce buffer:

       ┌──────────────────────────────┐
       │   Player Buffers 2 seconds   │  ← Low buffer
       └──────────────────────────────┘
                   │
                   ▼
         Viewer sees video at 10:00:02  ← 2s latency

Latency vs Buffer

    ┌──────────────┐         ┌──────────────┐
    │    Buffer    │         │   Latency    │
    └────┬─────────┘         └────┬─────────┘
         │                            │
         ▼                            ▼

 More Buffering                 Less Latency
 (Safe but Late)               (Fast but Risky)

         ▲                            ▲
         │                            │
    ┌────┴─────────┐         ┌────────┴─────┐
    │ Rebuffer Rare│         │ Rebuffer Risk│
    └──────────────┘         └──────────────┘

🧪 In ExoPlayer (Media3)

• Buffer size affects startup time and resilience
• You can tune this using LoadControl or MediaItem.LiveConfiguration

    val mediaItem = MediaItem.Builder()
    .setUri("https://live.example.com/stream.m3u8")
    .setLiveConfiguration(
        MediaItem.LiveConfiguration.Builder()
            .setTargetOffsetMs(3000) // ~3 seconds behind live edge
            .build()
    )
    .build()

Summary

Feature	More Buffer	Less Buffer
Latency	High (5–30s)	Low (1–3s)
Smoothness	Very smooth	May stutter
Use Case	VOD, casual live	Live events, sports
Tradeoff	Delayed viewing	Risk of rebuffering

Why can't you have ultra-low latency + high buffer.

📉 The Tradeoff:

• If you try to increase the buffer, you naturally delay the playback, increasing latency.
• If you try to decrease latency, you must reduce the buffer, making playback more fragile.

⚖️ Latency vs Buffer

         High Buffer                        Low Buffer
     ┌────────────────┐                ┌────────────────┐
     │ 10 seconds pre │                │ 1 second pre    │
     │ download       │                │ download        │
     └──────┬─────────┘                └──────┬──────────┘
            ▼                                 ▼
     Viewer sees video                 Viewer sees video
     10 sec behind live               1 sec behind live
     (High latency)                  (Ultra-low latency)

               ❗ You can’t have both at the same time ❗

Action	Effect
Add buffer	Player holds more data before playing → increases delay
Cut latency	Player stays closer to live → can't afford a large buffer (risk of stall)

• You must choose between being close to live vs. safeguarding against interruptions
• Streaming over real-world networks requires tradeoffs between speed and stability