High-Throughput Video Streaming & Ingestion (Netflix & YouTube)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33

-- PostgreSQL / CockroachDB Video Metadata Catalog
CREATE TABLE video_titles (
    video_id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    title VARCHAR(255) NOT NULL,
    duration_seconds INT NOT NULL,
    release_year INT NOT NULL,
    content_rating VARCHAR(10),
    master_manifest_url VARCHAR(512) NOT NULL, -- S3/CDN master .m3u8 URI
    drm_key_id UUID NOT NULL,                  -- Key identifier for Widevine/FairPlay
    created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP
);

-- User Viewing Progress (Cassandra / DynamoDB)
CREATE TABLE user_playback_progress (
    user_id UUID,
    video_id UUID,
    last_position_seconds INT NOT NULL,        -- Playback resume timestamp
    duration_seconds INT NOT NULL,
    completed BOOLEAN NOT NULL DEFAULT FALSE,
    device_type VARCHAR(50),
    updated_at TIMESTAMP,
    PRIMARY KEY (user_id, video_id)
);

-- HLS Master Manifest Example (.m3u8):
-- #EXTM3U
-- #EXT-X-VERSION:6
-- #EXT-X-STREAM-INF:BANDWIDTH=800000,RESOLUTION=640x360,CODECS="avc1.4d401e,mp4a.40.2"
-- 360p/manifest.m3u8
-- #EXT-X-STREAM-INF:BANDWIDTH=2500000,RESOLUTION=1280x720,CODECS="avc1.4d401f,mp4a.40.2"
-- 720p/manifest.m3u8
-- #EXT-X-STREAM-INF:BANDWIDTH=5000000,RESOLUTION=1920x1080,CODECS="av01.0.08M.08,mp4a.40.2"
-- 1080p_av1/manifest.m3u8

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48

// Production Buffer-Based Adaptive Bitrate (BBA) Controller
export interface VideoQualityTier {
  bitrateBps: number;
  resolution: string;
  chunkUriPattern: string;
}

export class BufferBasedABRController {
  private readonly RESERVOIR_SECONDS = 8;    // Panic zone: stay at lowest bitrate
  private readonly CUSHION_SECONDS = 24;      // Operating zone: scale linearly with buffer
  private readonly UPPER_LIMIT_SECONDS = 40;  // Safe zone: lock to maximum quality tier

  constructor(private qualityTiers: VideoQualityTier[]) {
    // Ensure tiers are sorted ascending by bitrate
    this.qualityTiers.sort((a, b) => a.bitrateBps - b.bitrateBps);
  }

  selectNextChunkQuality(currentBufferSeconds: number, measuredBandwidthBps: number): VideoQualityTier {
    const lowestTier = this.qualityTiers[0];
    const highestTier = this.qualityTiers[this.qualityTiers.length - 1];

    // 1. Critical Buffer Starvation: Fall back to minimum bitrate to prevent rebuffering
    if (currentBufferSeconds <= this.RESERVOIR_SECONDS) {
      return lowestTier;
    }

    // 2. Buffer Abundance: Select highest bitrate tier safely
    if (currentBufferSeconds >= this.UPPER_LIMIT_SECONDS) {
      // Guard: Ensure user network can sustain at least 80% of top bitrate
      if (measuredBandwidthBps >= highestTier.bitrateBps * 0.8) {
        return highestTier;
      }
    }

    // 3. Cushion Phase: Map buffer occupancy linearly between lowest and highest tiers
    const bufferRatio = (currentBufferSeconds - this.RESERVOIR_SECONDS) / (this.UPPER_LIMIT_SECONDS - this.RESERVOIR_SECONDS);
    const targetBitrate = lowestTier.bitrateBps + bufferRatio * (highestTier.bitrateBps - lowestTier.bitrateBps);

    // Pick highest tier that stays below targetBitrate AND measured throughput
    let selectedTier = lowestTier;
    for (const tier of this.qualityTiers) {
      if (tier.bitrateBps <= targetBitrate && tier.bitrateBps <= measuredBandwidthBps * 0.85) {
        selectedTier = tier;
      }
    }
    return selectedTier;
  }
}