Video Streaming & Media Delivery Flashcards

In server-side ad insertion (SSAI), what problem does it solve compared to client-side ad insertion?

Answer: Eliminates ad blockers by stitching ads into the video stream at the server

SSAI stitches advertisements directly into the video stream server-side, making the ads indistinguishable from content and immune to client-side ad blockers.

What is the purpose of a CDN 'token authentication' mechanism for video content?

Answer: Ensures only authorized users with valid signed URLs can access protected video segments

Token authentication uses cryptographically signed URLs or cookies to ensure only authenticated users can retrieve protected video content from the CDN.

Which metric best measures viewer-perceived video quality during adaptive bitrate streaming?

Answer: Mean Opinion Score (MOS) or Video Multimethod Assessment Fusion (VMAF)

VMAF and MOS are perceptual quality metrics that correlate with how viewers subjectively experience video quality, unlike purely technical throughput metrics.

A CDN delivers a 2-hour VOD film. Which caching strategy is most appropriate for the video segments?

Answer: Long TTL with immutable cache headers since VOD segments never change

VOD segments are static and never change, so immutable cache headers with long TTLs maximize cache efficiency and minimize origin load.

What is 'chunked transfer encoding' and why is it relevant to live video streaming?

Answer: Sends data in chunks without knowing the total content length, enabling streaming of live segments as they are generated

Chunked transfer encoding allows HTTP to send data in pieces without a predetermined content length, which is essential for delivering live video as it is encoded.

What is the function of a 'media manifest' in adaptive streaming?

Answer: Describes available quality levels and provides URLs or templates for video segments

A media manifest (like HLS .m3u8 or DASH MPD) is a metadata file that lists available bitrate renditions and tells the player where to fetch each segment.

During a major live event, a CDN operator observes a sudden 10x spike in concurrent viewers. Which CDN feature automatically handles this traffic surge?

Answer: Elastic scaling with request coalescing to prevent origin overload

Request coalescing (or request collapsing) on elastic CDN infrastructure combines simultaneous cache-miss requests for the same segment into a single origin fetch, protecting origin during traffic spikes.