Multimedia Databases, Hypermedia and Web Delivery
What this domain tests
Storing and finding media at scale, structuring linked content, and getting streams to users. Items ask how content-based retrieval works, what distinguishes hypermedia from plain documents, or which delivery protocol suits a scenario.
Core rules and concepts
- Multimedia database requirements: very large objects (BLOBs), continuous media with timing constraints, synchronisation across streams, QoS guarantees, spatio-temporal queries, and retrieval by content rather than only by keyword.
- Retrieval. Metadata/keyword search versus content-based retrieval (CBIR): colour histograms, texture descriptors (GLCM, Gabor), shape descriptors (Fourier), and for audio MFCC features. Similarity is measured by Euclidean or cosine distance over feature vectors, ranked and refined with relevance feedback. Feature indexes include k-d trees, R-trees for spatial data, and inverted indexes. MPEG-7 standardises descriptors so they are interoperable.
- Hypermedia: nodes (text, image, audio, video), links with anchors, and link types (structural, associative, reference). Navigation aids - breadcrumbs, site maps, search, back-tracking - counter disorientation and cognitive overload in large link spaces.
- Delivery. Progressive download over plain HTTP plays a file as it arrives but cannot adapt. True streaming uses RTSP for control, RTP for media transport and RTCP for feedback. Adaptive HTTP streaming dominates the web: HLS uses an m3u8 playlist of short TS/fMP4 segments, and MPEG-DASH uses an MPD manifest; both switch rendition by measured throughput and buffer level (ABR). CDNs place segments close to users. HTML5 video with Media Source Extensions enables ABR in the browser, and EME provides DRM.
Worked example
A public live webinar for thousands of viewers across firewalls, with 10–20 s latency acceptable. HLS or MPEG-DASH over HTTPS via a CDN is the right answer: segments traverse port 443, scale by caching, and ABR protects viewers on weak links, at the cost of latency tied to segment length. RTSP/RTP would give lower latency but needs open ports and does not scale as cheaply; it suits surveillance or controlled networks instead.
Traps that cost marks
- Calling progressive download "streaming" when no adaptation or control channel exists.
- Swapping RTSP (control), RTP (transport) and RTCP (feedback).
- Assuming keywords equal content-based retrieval.
- Ignoring that shorter HLS segments lower latency but raise request overhead.
Multimedia Project Management, Standards and Intellectual Property
What this domain tests
Managing scope, schedule and cost on media-rich projects; knowing which body publishes which standard; and applying copyright, patent, trademark and licensing rules to real asset use.
Core rules and concepts
- Project constraints: scope, time, cost and quality are interdependent; changing one forces adjustment elsewhere. Tools include WBS decomposition, milestones, Gantt charts, critical path method (longest dependent path, zero float) and a risk register.
- Process models: waterfall when requirements are stable; prototype or iterative models when requirements emerge, which is common in multimedia because clients react to what they can see.
- Roles and documents: project manager, instructional designer/scriptwriter, art director, developer, QA. Deliverables include the requirements specification, script and storyboard, design document, test cases and acceptance report.
- Standards bodies: ISO/IEC publishes JPEG, MPEG and MPEG-7; ITU-T publishes H.261/H.263/H.264/H.265 and audio recommendations; IETF publishes RTP, RTSP and HTTP; W3C publishes HTML, SVG and WCAG; national GB/T standards apply in China. De facto standards (PDF, MP4) matter commercially even without formal ratification.
- Intellectual property. Copyright arises automatically on creation and needs no registration; in China protection generally lasts the author's life plus 50 years, and 50 years from first publication for works of a legal person. Invention patents last 20 years, utility models 10, trademarks 10 years renewable indefinitely, and trade secrets last while secrecy is maintained. Licensing ranges from exclusive assignments through Creative Commons (BY, NC, ND, SA) and open-source licences (GPL, MIT) to royalty-free stock. DRM and digital watermarking support enforcement.
Worked example
A training vendor wants to score a paid online course with a track released under CC BY-NC. The BY condition requires attribution, which is easy to satisfy; the NC condition forbids commercial use, and a fee-paying course is commercial. So the track cannot be used without a separate commercial licence. Changing to a CC BY or royalty-free track, or paying for a licence, are the compliant options - and the reasoning must cite the NC clause explicitly.
Traps that cost marks
- Believing copyright requires registration before it is enforceable.
- Confusing patent (20 years) with trademark (10 years, renewable) terms.
- Treating "free to download" as "licensed for reuse in a product".
- Using NC or ND licensed assets in commercial or modified works.