feat(cmcd): CTA-5004 v1 spec completion - #1
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Add a dependency-free CMCDSerializer that converts structured CMCDEntry records into conformant CTA-5004 §3 header values: nearest-100 rounding for integer keys (br/tb/bl/dl/mtp/rtp), quoted-string encoding (sid/cid/nor/nrr), bare boolean tokens (bs/su), alphabetical key ordering within each group, and omission of unavailable keys. Same-group serialize calls merge and re-sort rather than overwrite. Extend CMCDHeaders with the remaining v1 session/object/request keys (sf, st, cid, pr, d, mtp, su). Header assembly is a template method on the base class: subclasses customise only the object type token (ot) and whether segment metrics are reported, so the per-media-type classes are header-only and the segment-metric entry building is shared rather than duplicated. bs is latched rather than level-triggered: a starvation seen since the prior request is sticky and is reported once on the resumption request, then cleared (CTA-5004 §3: bs marks the buffer being starved at some point since the prior request).
Add collector setters for the session and per-request keys (sf/cid/st/pr, d/mtp/su) and source them from the engine: session format and content id at tune (query/fragment stripped from cid to avoid leaking auth tokens), live/VOD status after manifest parse, playback rate per request (level-triggered so pr is correct on the initial tune), measured throughput from the ABR estimator, object duration per media segment, and the startup-urgent flag during tune/rebuffer.
Add GoogleTest L1 coverage for the serializer primitives (rounding, quoting, group key names, alphabetical ordering, same-group merge) and for the end-to-end CTA-5004 serialization rules across every CMCDHeaders subclass, including omit-when-unavailable, the nor/pr regression guards, and the bs latch behaviour (latched across a non-starving sample, then consumed on report). Repoint the per-media-type test targets at the real CMCDHeaders base and serializer (the subclasses are header-only now), drop the no-op subclass fakes, consolidate the remaining base fake, and raise the metrics test harness to C++17 to match the production library and GoogleTest >= 1.13.
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Summary
CMCD CTA-5004 (v1) spec completion — brings AAMP's Common Media Client Data output into full compliance with CTA-5004 §3, completing the standard key set and correcting serialization so the CMCD attached to segment/manifest requests is a complete, correctly-serialized v1 payload that any spec-compliant CDN or analytics collector can parse.
Changes
New serializer (
CMCDSerializer) — a dependency-free component that converts structuredCMCDEntryrecords into conformant CTA-5004 §3 header values:br/tb/bl/dl/mtp/rtp)sid/cid/nor/nrrbs/suFull v1 key set —
CMCDHeadersextended with the remaining v1 session/object/request keys (sf,st,cid,pr,d,mtp,su), with every per-media-type builder (Video/Audio/Manifest/Subtitle) routed through the shared serializer so output is spec-conformant across all groups.Engine wiring — new keys sourced from the playback path:
sf(session format) andcid(content id, with query/fragment stripped to avoid leaking auth tokens) at tunest(live/VOD) after manifest parsepr(playback rate) per request, level-triggered so it's correct on initial tunemtp(measured throughput) from the ABR estimatord(object duration) per media segmentsu(startup-urgent) during tune/rebufferbslatch semantics —bsis latched rather than level-triggered: a starvation seen since the prior request is sticky and is reported once on the resumption request, then cleared (CTA-5004 §3:bsmarks the buffer being starved at some point since the prior request).Tests
L1 GoogleTest coverage added under
support/aampmetrics/test/tests/:CMCDHeaderssubclass, including omit-when-unavailable,nor/prregression guards, and thebslatch behaviour (latched across a non-starving sample, then consumed on report)Compatibility
The existing CMCD enable/disable config path and per-media-type collector wiring are preserved. Deployed-device behavior changes only where spec compliance requires it (rounding/quoting/sorting/header-name fixes). Transport remains custom HTTP request headers only.