Server-Side Ad Insertion (SSAI)

What is Server-Side Ad Insertion?

Server-Side Ad Insertion (SSAI), also known as Dynamic Ad Insertion (DAI), stitches advertisements directly into the video stream at the server level before delivery to the viewer. This approach eliminates ad blocker effectiveness, ensures seamless playback, and provides broadcast-quality ad experiences across all devices.

Architecture Overview

┌─────────────────────────────────────────────────────────────────────┐
│                        Video Player (SDK)                            │
│  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐                  │
│  │ HLS.js      │  │ Shaka       │  │ ExoPlayer   │                  │
│  │ AVPlayer    │  │ dash.js     │  │ Native      │                  │
│  └─────┬───────┘  └──────┬──────┘  └──────┬──────┘                  │
└────────┼─────────────────┼────────────────┼─────────────────────────┘
         │                 │                │
         └─────────────────┼────────────────┘
                           │
                    ┌──────▼──────┐
                    │  CDN Edge   │  ← Segments cached at edge
                    └──────┬──────┘
                           │
              ┌────────────▼────────────┐
              │   SSAI Manifest Service │
              │  ┌───────────────────┐  │
              │  │ Session Manager   │  │
              │  │ Pod Decisioning   │  │
              │  │ Manifest Stitcher │  │
              │  │ Tracking Engine   │  │
              │  └───────────────────┘  │
              └────────────┬────────────┘
                           │
         ┌─────────────────┼─────────────────┐
         │                 │                 │
   ┌─────▼─────┐    ┌──────▼──────┐   ┌──────▼──────┐
   │  Origin   │    │  Ad Server  │   │ Demand      │
   │  (CMS)    │    │  (VAST/VMAP)│   │ Partners    │
   └───────────┘    └─────────────┘   └─────────────┘

Request Flow

1. Session Init: Player SDK requests a session manifest URL, providing device capabilities, consent signals, and targeting context.
2. Manifest Fetch: Player fetches the personalized HLS/DASH manifest from the SSAI service (CDN may cache segments but not the manifest).
3. Ad Break Detection: SSAI service detects ad break opportunities from SCTE-35, EXT-X-DATERANGE, or DASH EventStream signals.
4. Pod Decisioning: Real-time auction selects ads matching format requirements, competitive separation rules, and frequency caps.
5. Manifest Stitching: Ad segments are stitched into the manifest with proper discontinuity markers and timing information.
6. Segment Delivery: Player fetches stitched segments from CDN edge (content and ads appear as unified stream).
7. Tracking: Impressions, quartiles, and completion events fire server-side with deduplication for exactly-once delivery.

Integration

{
  "tenant_id": "your-tenant-id",
  "asset": {
    "id": "content-12345",
    "type": "vod",           // "live" | "vod"
    "duration": 3600         // seconds (VOD only)
  },
  "device": {
    "type": "ctv",           // "web" | "mobile" | "ctv" 
    "os": "tvos",
    "model": "Apple TV 4K",
    "player": "avplayer"
  },
  "format": {
    "protocol": "hls",       // "hls" | "dash"
    "container": "cmaf",     // "ts" | "cmaf"
    "drm": null              // "widevine" | "fairplay" | null
  },
  "consent": {
    "gdpr": true,
    "ccpa": false,
    "us_privacy": "1YNN"
  }
}

{
  "session_id": "sess_abc123xyz",
  "manifest_url": "https://ssai.apexmediation.ee/v1/session/sess_abc123xyz/master.m3u8",
  "expires_at": "2025-01-15T12:00:00Z",
  "tracking_url": "https://track.apexmediation.ee/v1/session/sess_abc123xyz"
}

Ad Decisioning & Timing

Pod Structure

Each ad break is organized as a "pod" containing one or more slots. The decisioning engine fills each slot based on format compatibility, competitive separation, and frequency caps.

SLA Guarantees

• Decision Deadline: Pod decisions complete before break start (p99 < 200ms)
• Fallback Behavior: If deadline approaches, slate (fallback content) is served rather than black screen
• Safe Mode: During incidents, system reduces fanout and enforces strict deadlines

Content Correctness

The SSAI system enforces strict content correctness rules to ensure seamless playback:

Observability & Forensics

Every ad decision is fully explainable for debugging and support:

{
  "pod_id": "pod_123",
  "break_type": "midroll",
  "slots_requested": 3,
  "slots_filled": 2,
  "decision_trace": [
    {"step": "partner_request", "partner": "partner_a", "duration_ms": 45},
    {"step": "format_filter", "rejected": 2, "reason": "codec_mismatch"},
    {"step": "competitive_separation", "rejected": 1, "reason": "same_category"},
    {"step": "frequency_cap", "rejected": 0},
    {"step": "final_selection", "selected": 2}
  ],
  "unfilled_reason": "no_compatible_inventory"
}

Metrics Exposed

• Session counts by tenant/channel
• Pod decision latency (p50/p95/p99)
• Fill rate by break type
• Format rejection reasons
• Partner response times
• Tracking event success rate

Security & Privacy

Platform Coverage Matrix