Control parts reference

Part of SABR in the extractor. The server may place control parts between media parts. SabrResponseDecoder recognizes their numeric ids and stores either the fields needed by YoutubeSabrSession or a bounded structural summary. The current source does not define one Java class for every control part.

Pacing and protection

NEXT_REQUEST_POLICY — id 35

The decoder keeps the raw policy and reads its field 4 as the requested backoff in milliseconds. YoutubeSabrSession also reads field 7 as the playback cookie. A backoff above 30,000 ms is rejected; a valid delay defers the next requestOnce call without sending HTTP.

STREAM_PROTECTION_STATUS — id 58

#	Field
1	raw protection status
2	server-provided maximum retries

The status is deliberately kept as a raw integer. Status 2 is exposed as attestation pending; status 3 is exposed as attestation required. The caller may set a content-bound PO token with YoutubeSabrSession.setPoToken(...).

Navigation and player state

SABR_REDIRECT — id 43

Field 1 is the replacement streaming URL. The session accepts only HTTPS URLs on googlevideo.com or its subdomains and caps redirects at three per session.

SABR_SEEK — id 45

The part is retained as a structural summary. The current extractor does not apply a server-initiated seek itself; the application decides how to rebuild a YoutubeSabrRequest.

RELOAD_PLAYER_RESPONSE — id 46

The decoder sets reloadRequested. YoutubeSabrSession surfaces this as a protocol error; fetching a new player response and creating a new YoutubeSabrInfo is an application-level recovery step.

PLAYBACK_START_POLICY — id 47

Retained as a structural summary. It does not change the extractor's requestOnce result directly.

Context and live metadata

SABR_CONTEXT_UPDATE — id 57

The session parses the fields it needs:

#	Field
1	context type
3	opaque value bytes
4	send by default
5	write policy

Values are stored by type. SABR_CONTEXT_SENDING_POLICY (id 59) adds, removes or discards types through fields 1, 2 and 3; active values are echoed in later streamerContext messages.

LIVE_METADATA — id 31

The session currently consumes:

#	Meaning
3	live-head sequence number
4	live-head time in milliseconds
8	post-live DVR flag

Receiving the part marks the session live. The values are available through isLive(), getLiveHeadSequenceNumber(), getLiveHeadTimeMs() and isPostLiveDvr().

Format and media controls

• FORMAT_INITIALIZATION_METADATA (id 42) is decoded into SabrFormatInitializationMetadata and supplies initialization/index ranges;
• MEDIA_HEADER, MEDIA, and MEDIA_END (ids 20–22) are assembled by SabrMediaSegmentCollector, as described in Media, segments, and the index;
• FORMAT_SELECTION_CONFIG (37), SELECTABLE_FORMATS (51), onesie parts (10–12), request controls (52–56), cache/bandwidth hints (48–50, 60–66), and SNACKBAR_MESSAGE (67) are currently summarized for diagnostics.

SABR_ERROR — id 44

Fields 1 (string type) and 2 (numeric code) are rendered in the response summary and cause the session to throw a protocol error.

Unknown or malformed parts are retained as bounded diagnostics. This lets valid media from the same response continue to the integrity checks.

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