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video-vod

adaptive-bitrate video on demand

Netflix, YouTube

SystemTechniques · 17Primitives · 62 video-vod CDN and edgecloud · medium: CDNs cache content in hundreds of PoPs near users, cutting latency and egress bills; edge compute runs small code there. Bandwidth price spreads 10x between providers.›Deterministic simulation testingdistributed · medium: Run the whole system in one thread under a seeded scheduler with simulated network, disk and clock, so every failure replays from its seed.›Durable job queuedistributed · medium: Persisted tasks that workers lease for a visibility timeout, ack on success and retry with backoff; at-least-once execution that survives worker and queue crashes.›Primary-backup replicationdistributed · medium: One node orders all writes and ships them to standbys; the acknowledgement rule (none, one, all) sets what a crash loses, and an external arbiter decides who takes over.›Adaptive bitrate streamingmedia · medium: The client fetches short HTTP segments and picks each segment's rendition from throughput estimates, buffer level, or both, trading stalls against quality and switches.›Chunked parallel encodingmedia · medium: Split video at keyframes, encode chunks in parallel, stitch with rate consistencyVideo transcoding laddermedia · medium: Turn one source into resolution x bitrate x codec renditions chosen from measured rate-quality points, cut on aligned keyframes so players can switch mid-stream.›HTTP caching semanticsnetworking · low: The rules (RFC 9111) that decide whether a stored response is still fresh, and how a cheap conditional request revalidates it when it is not.›Adaptive streaming manifestsmedia · low: HLS playlists and DASH MPDs: renditions, segment timelines, codecs stringsMedia containersmedia · low: MP4/ISO BMFF, fragmented MP4/CMAF, Matroska and MPEG-TS mux/demuxHTTP range requestsnetworking · low: Ask for byte offsets with Range and get a 206 slice back; the standard way to resume, seek and read big remote files piecewise.›Perceptual quality metrics (PSNR, S…media · low: Full-reference scores that say how bad a compressed picture looks: PSNR (pixel error), SSIM (structure), VMAF (learned fusion), and when each one lies.›BBR congestion controlnetworking · low: Model-based congestion control that paces at the measured bottleneck bandwidth and caps inflight near one BDP, instead of reacting to loss.›Object storagecloud · low: S3-compatible blob storage at cents per GB-month with 11 nines durability; pick by egress price, request price and latency, not by storage price alone.›S3-FIFOsystems · low: Three FIFO queues (small, main, ghost) that evict one-hit wonders quickly and keep reused objects; low miss ratios with no list moves on hits.›Hdr histogramdata-structures · low: Log-linear bucketed histograms with bounded relative error for latency percentilesConsistent hashingdistributed · low: Hash nodes and keys onto a ring; each key belongs to the next node clockwise, so membership changes move only about 1/n of keys.›Process supervisionhardware-os · low: A parent process starts services, reaps their exits and restarts them under a delay and burst-limit policy, then stops them with SIGTERM before SIGKILL.›Common Encryption (CENC)media · low: ISO/IEC 23001-7 fixes how MP4 samples are encrypted and where key ID, IVs and clear/protected byte ranges are stored, so one file serves many DRM systems.›Mutual TLSsecurity · low: TLS where the client also proves a certificate key, so every connection carries a verified, rotatable machine identity.›Signed URLssecurity · low: A URL carrying its expiry and a MAC or signature over method, path and query, so a verifier holding the key needs no lookup.›Graceful drainingsystems · low: On a termination signal, stop taking new work, finish in-flight work until a deadline, tell clients to reconnect elsewhere, then exit; clients resume from a token.›Request coalescingsystems · low: Collapse concurrent identical requests into one backend fetch (singleflight)+ 10 more techniques+ 46 more primitives

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