Youtube

• Func requirements

• NonFunc requirements

  • High performance

  • Scalability

• Real world practices

  • Facebook

    • Appendix

      • Video formats

      • Container

      • Codecs

      • Streaming protocls

  • TODO: Adaptive streaming

Func requirements

• Upload videos online

• Watch videos online

• Search videos online

NonFunc requirements

High performance

Scalability

Real world practices

Facebook

• Proactive CDN caching at Facebook: https://www.youtube.com/watch?v=CbbeSg1t224&ab_channel=JustinMiller

• Building and scaling a performant CDN: https://www.youtube.com/watch?v=TLbzvbfWmfY&ab_channel=Fastly

• How does Facebook encoding videos: https://engineering.fb.com/2021/04/05/video-engineering/how-facebook-encodes-your-videos/

• Distributed processing at FB scale

Facebook live

• Facebook livestream architecture: https://www.youtube.com/watch?v=IO4teCbHvZw&ab_channel=InfoQ

Youtube

• Summary of Youtube technology

Appendix

Video formats

• One video episode could contain up to 1200 files.

• References:

  • Intro to video format

Container

• Container: Represented by video file extension. It includes video stream, audio stream and metadata (bitrate, device, resolution, time of creation, subtitles, etc.)

  • FLV: Flash video format created by Adobe.

  • MP4: Standard MPEG-4 format.

  • WMV: Windows media video.

  • MOV: Apple quicktime

Codecs

• Video codecs:

  • H.264 - the most commonly used video format

  • H.265(HEVC) - double compression rate of H.264, however need triple resources to encode, proprietary protocol.

  • VP9

  • Av1

• Audio codecs:

  • MP3 - Popular with wide support. Save space without noticeable quality loss. Limited functionality.

  • AAC - Widely supported. More efficient than MP3. Limit on audio channel.

  • AC3

Streaming protocls

• Defs: A standardized set of rules for storing containers, codecs, metadata, and folder structure.

• TCP/IP based

  • RTP: RTSP and RTCP

  • RTMP: Real time messaging protocol

• HTTP based

  • MPEG4 (MPEG-4 Part10/12/14 )

  • HLS (Http Live stream)

    • .m3u8

  • MPEG-DASH (Dynamic adaptive streaming over HTTP)

  • RTMP

    • https://www.wowza.com/blog/rtmp-streaming-real-time-messaging-protocol

    • Quick dive: https://www.youtube.com/watch?v=AoRepm5ks80&ab_channel=Heavybit

TODO: Adaptive streaming

• https://underhood.blog/adaptive-http-streaming

• Facebook livestream: https://www.youtube.com/watch?v=IO4teCbHvZw&t=223s&ab_channel=InfoQ