Service Architecture¶

This page is the conceptual map of the internal object model that a service author works against. It ties together the moving parts: the Service base class, the Title hierarchy a service returns, the Track model those titles carry, the manifest parsers that produce tracks, the DRM hooks that license and decrypt them, and the request/session objects wired up for you at construction time.

Who this page is for

This is a developer reference. If you only want to run downloads, you never touch these classes directly; see Downloading and the CLI reference instead. If you are writing or reading a service plugin, this page explains what each object is and how the pieces connect. For a guided, step-by-step build, see Creating a Service; for exact signatures, see the auto-generated Service API, Titles API, and Tracks API.

The shape of a download¶

A service is a translator between one streaming platform and unshackle's generic pipeline. It never downloads or decrypts anything itself; it just answers questions. The dl command drives the whole flow and only ever calls three required methods on your service, in order:

Service.get_titles        →  which movies / episodes / songs exist
      │
Service.get_tracks        →  fetch a manifest for one title ...
      │
manifest.to_tracks        →  ... parsed into Video / Audio / Subtitle tracks
      │
Track.download            →  fetch + merge segments (core-driven)
      │
DRM license + decrypt     →  service license hooks → CDM → decrypt tool
      │
Tracks.mux                →  mkvmerge → tagged .mkv

get_titles() returns a Titles collection: the movies, episodes, or songs the platform exposes for the requested ID.
get_tracks(title) returns a Tracks object for a single chosen title. In practice this means fetching a manifest and handing it to a parser, which builds the Video/Audio/Subtitle objects.
get_chapters(title) returns any chapter markers.

Everything after that (track selection, licensing, decryption, repacking, subtitle conversion, and muxing) is handled by the core using the objects your service returned. Your job is to produce accurate Title and Track objects; the framework does the rest.

The `Service` base class¶

Every service subclasses unshackle.core.service.Service, an abstract base class. Two kinds of members matter: class variables that describe the service, and methods that the pipeline calls.

Class variables¶

Declared at the top of your service class, these are static descriptors:

Class variable	Type	Purpose
`ALIASES`	`tuple[str, ...]`	Alternate tags the service answers to (resolved by `Services.get_tag`).
`GEOFENCE`	`tuple[str, ...]`	ISO region codes the service requires; empty means no geofence. The first entry is treated as the "main region" for automatic proxy selection.
`VAULT_TAG`	`Optional[str]`	Overrides the key-vault namespace; defaults to the service's own tag.
`AUTH_METHODS`	`Optional[tuple[str, ...]]`	Accepted auth methods (`"cookies"` / `"credentials"`). When `None`, the REST `/services` endpoint infers them from `authenticate()`.

Required methods¶

These are abstract; a service will not load unless it implements all three:

get_titles() -> Titles_T: resolve the requested ID into a title collection.
get_tracks(title) -> Tracks: build the track set for one title.
get_chapters(title) -> Chapters: return chapter markers (may be empty).

Optional methods and hooks¶

authenticate(cookies=None, credential=None): the base implementation loads a CookieJar into self.session.cookies and stores self.credential. Override it to perform a real login handshake.
search(): raises NotImplementedError by default; implement it to support the search command.
DRM license hooks: get_widevine_service_certificate, get_widevine_license, get_playready_license (delegates to Widevine by default), and get_clearkey_license (returns None by default). See DRM hooks below.
request_input(prompt): prompts the user; routed through the serve-mode input bridge or the rich console.
Event callbacks: on_segment_downloaded, on_track_downloaded, on_track_decrypted, on_track_repacked, on_track_multiplex let a service react to pipeline events (for example, MonaLisa decrypts each segment in on_segment_downloaded).
resolve_server_keys(title): an escape hatch for services whose decryption keys are resolved server-side ahead of the normal per-track license flow. Unlike everything else here it is not declared on the Service base class at all: dl.py probes for it with hasattr and calls it (once, after track selection) only if your service defines it. Use it when keys must be fetched or injected in bulk before download, separate from the per-track license callbacks below.

What `init` wires up for you¶

You rarely override __init__; the base constructor takes the Click context and sets up the objects your methods rely on:

Attribute	What it is
`self.config`	The per-service config slice (see Request and session objects).
`self.log`	A `logging.Logger` named after your class.
`self.session`	A ready-to-use HTTP session (headers, retries, and proxy applied).
`self.cache`	A generic key/value `Cacher` namespaced to the service.
`self.title_cache`	A region- and account-aware `TitleCacher`.
`self.cache_dir`	`config.directories.cache / <ServiceName>`.
`self.credential`	The active `Credential`, or `None` until authenticated.
`self.track_request`	A `TrackRequest` describing the requested codecs, ranges, and best-available flag (see below).

The constructor also resolves proxies: it reads --proxy / --proxy-query / --proxy-provider, consults the per-service proxy_map, and, if GEOFENCE is set and no explicit proxy was given, does a live IP check and auto-fetches a proxy to GEOFENCE[0] when it detects a geoblock. See Proxies and VPN.

TrackRequest

self.track_request is a small dataclass built from the CLI: codecs (from --vcodec, empty means "accept any"), ranges (from --range, default [Video.Range.SDR]), and best_available. Use it in get_tracks to decide which variants to fetch.

Titles and the `Title` hierarchy¶

get_titles() returns a title collection, one of the Titles_T types. Each collection holds one or more Title objects (Title_T). There are three parallel families, one per media kind:

Media kind	Item (`Title_T`)	Collection (`Titles_T`)
Movies	`Movie`	`Movies`
TV	`Episode`	`Series`
Music	`Song`	`Album`, and `Music` (the base collection)

All items subclass Title, which carries the shared identity: a unique id, the originating service class, an optional original language, arbitrary data, and a freshly-constructed self.tracks = Tracks() that get_tracks will fill. Collections are sorted lists, so titles stay in a stable order.

The unique ID is validated

Title.__init__ rejects a falsy id_, and rejects any ID shorter than 4 characters ("The unique ID is not large enough, clash likely."). Pick a stable, sufficiently unique identifier from the platform.

Constructors at a glance¶

Each subclass adds its own required fields on top of id_ and service:

MovieEpisodeSong

Movie(id_, service, name, year=None, language=None, data=None, description=None)

name is required; year is optional but must be a positive integer if given.

Episode(id_, service, title, season, number,
        name=None, year=None, language=None, data=None,
        description=None, air_date=None)

title is the show name; season and number are required (0 is allowed). An air_date is normalized to a date so the {date} naming token stays clean, and a placeholder episode name like "Episode 4" is discarded automatically.

Song(id_, service, name, artist, album, track, disc, year,
     language=None, data=None)

name, artist, album, track, disc, and year are all required and validated.

Title remapping¶

After titles are fetched (and after any cache), the framework applies remap_titles(titles, title_map) using the per-service title_map config. This does an exact-string rename (Episodes are matched on their show title, Movies and Songs on their name), so a platform's odd naming can be normalized to what your library expects. Titles are also cache-wrapped via get_titles_cached(), which is region- and account-aware; see the TitleCacher notes.

The ordering here is deliberate on both sides. title_map is applied after the title cache so that editing the map takes effect immediately, without forcing a cache reset, and before metadata enrichment (--enrich) so that an explicit enrich override still wins over a mapped name.

Tracks and the `Track` model¶

A Tracks object is the container get_tracks returns. It has typed buckets (videos, audio, subtitles, chapters, and attachments) plus a manifest_url. Iterating a Tracks yields only video, audio, and subtitle tracks (not chapters or attachments), and the canonical display/mux order is Video → Audio → Subtitle → Chapter → Attachment.

Track IDs must be deterministic

Tracks.add refuses duplicate IDs. Track IDs are CRC32-derived from the track's identity (URL, codec, language, bitrate) and must be stable across requests, never random. The manifest parsers already do this correctly; if you build tracks by hand, keep IDs deterministic or add will raise.

The base `Track`¶

Track is the base for Video, Audio, and Subtitle. (Chapter, Chapters, and Attachment are standalone classes, not Track subclasses.) Every track knows how it is delivered, via Track.Descriptor:

Descriptor	Delivery
`URL`	A single direct URL.
`HLS`	HTTP Live Streaming.
`DASH`	Dynamic Adaptive Streaming over HTTP.
`ISM`	Smooth Streaming.

Key attributes include url (a string or list of strings), language (a langcodes.Language), drm (an optional iterable of DRM objects), needs_repack, and descriptor-specific state stashed in track.data["hls"] / track.data["dash"]. When name is omitted, a human-readable name is derived from the language automatically.

`Video`¶

Video adds codec, range, bitrate, width, height, fps, scan_type, and closed-caption descriptors. The relevant enums:

Video.Codec: AVC (H.264), HEVC (H.265), VC1, VP8, VP9, AV1.
Video.Range: SDR, HLG, HDR10, HDR10P (HDR10+), DV (Dolby Vision), and HYBRID. HYBRID is special: it tells the pipeline to select both an HDR10(+) base and a DV track and merge the DV RPU onto the HDR10 stream with dovi_tool (see Dolby Vision hybrid).

Bitrate units

Both Video and Audio store bitrate in bytes per second (rounded up), even though the string form displays kb/s.

`Audio`¶

Audio adds bitrate, channels, joc (Joint Object Coding, the Atmos indicator), and descriptive. Audio.Codec covers AAC, AC3 (DD), EC3 (DD+), AC4, OPUS, OGG (Vorbis), DTS, ALAC, and FLAC. The atmos property is True when joc is set (or when extra flags it).

`Subtitle`¶

Subtitle adds three mutually-constrained flags: cc (closed captions), sdh (subtitles for the deaf and hard-of-hearing), and forced. A track cannot be both cc and sdh, and forced cannot combine with either. Subtitle.Codec includes SubRip (SRT), WebVTT (VTT), SubStationAlpha/SubStationAlphav4 (SSA/ASS), TimedTextMarkupLang (TTML), SAMI, and the box-encapsulated DASH formats fTTML (STPP) and fVTT (WVTT). Subtitles receive post-download normalization (segment merging, WebVTT sanitization, format conversion, and optional SDH stripping), all documented for users in Subtitles.

Chapters and attachments¶

Chapter(timestamp, name=None): a single marker; the timestamp accepts HH:MM:SS[.mmm], integer milliseconds, or float seconds.
Chapters: a sorted collection that auto-inserts a 00:00:00.000 chapter and reads/writes OGM Simple format.
Attachment: a font or image attached to the mux (e.g. fonts an ASS subtitle references), built from a local path or a url.

Selection, sorting, and muxing¶

Tracks is also the selection engine the dl command uses. It offers sort_videos / sort_audio / sort_subtitles (P2P-standard ordering), predicate-based select_* filters, by_resolutions, and by_language. When downloads finish, the same object multiplexes everything: Tracks.mux(title, ...) builds and runs an mkvmerge command, applying language, default-track, forced, and hearing-impaired flags, attaching chapters and fonts, and writing a .muxed.mkv (or .mka / .mks for audio- or subtitle-only sets). As a service author you never call mux yourself; you just return correct tracks.

Manifest parsers¶

Most services do not build tracks by hand; they hand a manifest to one of three parsers in unshackle.core.manifests. Each parser has the same three-part contract:

Format	Class	Notes
MPEG-DASH (`.mpd`)	`DASH`	Parses `<MPD>`; enumerates tracks from the first content period.
HLS (`.m3u8`)	`HLS`	Requires a variant (master) playlist, not a media playlist.
Smooth Streaming (`.ism`)	`ISM`	Synthesizes init segments from `CodecPrivateData`.

The parser contract¶

Construct: DASH.from_url(url, session=...) or DASH.from_text(text, url) (and likewise for HLS / ISM). A url is always required, even for from_text, because relative segment paths are resolved against it.
to_tracks(...): parses the manifest into a Tracks container of Video, Audio, and Subtitle objects, each carrying descriptor-specific state.
download_track(...): a staticmethod the core calls to fetch, decrypt, and merge segments. You do not call it; you just return the tracks it will operate on.

A typical get_tracks therefore looks like fetching the manifest text with self.session and returning DASH.from_text(mpd, url).to_tracks(language=title.language).

Pass the original language

DASH and HLS to_tracks raise ValueError if a track's language cannot be derived and no valid fallback was supplied. Always pass the title's original recorded language. For HLS this fallback is used directly for the primary track, since HLS variants carry no language.

Segment-filtering hooks¶

HLS: set track.OnSegmentFilter(segment) to drop unwanted segments (ads/bumpers).
DASH: pass a period_filter callable to to_tracks to drop whole periods. Caching-breadth periods some services emit and non-content segment types are dropped automatically.

Format gotchas worth knowing¶

DASH enumerates tracks from only the first content period, but downloads segments from all content periods matching the representation. SegmentTemplate, SegmentList, and SegmentBase addressing and $Number%0Nd$ padding are handled.
HLS re-fetches the media playlist at download time, recovers SUPPLEMENTAL-CODECS from raw text (python-m3u8 drops it) to detect Dolby Vision composite streams, and uses the media-sequence-number IV for AES-128 keys that omit an explicit IV.
ISM has no segment list and no init segments: segment URLs are synthesized from the <c> fragment timeline, and a moov/ftyp init box is rebuilt from CodecPrivateData (supported for AVC, HEVC, DV-over-HEVC, AAC, EC-3, and TTML).

DRM hooks¶

If a track carries DRM, the framework licenses and decrypts it, but it needs your service to talk to the platform's license server. unshackle recognizes five DRM systems:

DRM class	System	License flow
`Widevine`	Widevine	CDM challenge → license server → content keys (`.wvd` device)
`PlayReady`	PlayReady	CDM challenge (WRM header) → license server → content keys (`.prd` device)
`ClearKeyCENC`	W3C `org.w3.clearkey` over CENC	JSON KID request → JWK set; no CDM
`ClearKey`	HLS AES-128	key fetched directly from a URI; no CDM, no challenge
`MonaLisa`	Proprietary WASM DRM	keys extracted locally; no license server

ClearKey vs ClearKeyCENC

Despite the shared prefix these are entirely different systems. ClearKey is HLS AES-128, decrypted in-process. ClearKeyCENC is the W3C EME JWK flow over MPEG-CENC, decrypted with shaka-packager or mp4decrypt like Widevine.

The service-side hooks¶

The framework supplies the CDM and the decryption tool; your service provides the network calls that the CDM's challenge must be sent through. Override the hooks that your platform needs:

Hook	Return	Purpose
`get_widevine_service_certificate(title, track, challenge)`	cert bytes	Optional privacy-mode service certificate.
`get_widevine_license(title, track, challenge)`	license bytes	POST the Widevine challenge to the license server, return the response.
`get_playready_license(title, track, challenge)`	license	Same for PlayReady; defaults to delegating to Widevine.
`get_clearkey_license(title, track, challenge)`	dict / str / bytes / `None`	For `ClearKeyCENC`; return `None` to let the framework POST to the manifest `Laurl`.

You do not open CDM sessions or run shaka-packager yourself. The Widevine/PlayReady classes drive the CDM handshake and invoke the decryption tool. Your hook is just the "send this challenge, give me back the license" step.

How a CDM is chosen and keys are found¶

CDM selection is config-driven: the cdm map resolves a service tag (and optionally the track quality or DRM type) to a device name, which load_cdm instantiates as a local .wvd/.prd or a remote CDM. Before ever requesting a license, the framework tries an in-process key cache and the configured key vaults; only unresolved KIDs trigger an actual license request, and newly licensed keys are written back to every vault. This is why the same key is rarely re-licensed twice. Users configure all of this in DRM and CDM and Key vaults; the API surface is documented in the DRM API reference.

Dolby Vision and hybrid¶

Two DV mechanisms sit on top of the track model. DV fixup re-exposes DV signaling on HLS streams that carry a valid DV RPU but advertise plain HEVC (dv_compatible_bitstream). Hybrid processing (Video.Range.HYBRID) selects an HDR10(+) base and a DV donor, extracts the RPU with dovi_tool, and injects it onto the base layer, producing a single stream with both HDR10 and DV metadata. Both are automatic once the right tracks are selected; a service only needs to expose accurate ranges.

Request and session objects¶

Everything a service does over the network flows through objects the base constructor prepared, all derived from the Click context (ctx) that dl passes in.

self.config: your service's slice of unshackle.yaml, i.e. config.services[<ServiceName>]. This is a plain dict; use it for per-service settings like base URLs, an API key, or a title_map. See Configuration.
self.session: a requests.Session with config.headers applied, a retry policy (total=5, backoff, retry on 429/5xx), and any resolved proxy already mounted. Pass this session into the manifest parsers and DRM calls so headers, cookies, and proxies flow everywhere. (unshackle also ships an rnet-based TLS-fingerprinting session used by the newer session() factory and configured via the network config key.)
self.credential: the active Credential (username:password[:extra]), populated by authenticate. Its sha1 is used as the account hash for cache keys.
self.cache: a generic Cacher: JSON key/value storage under the service's cache dir, with CRC32 integrity checks, versioning, and optional expiry (auto-derived from a JWT exp claim when present). Good for auth tokens and API responses.
self.title_cache: a TitleCacher that wraps get_titles results, keyed by title ID, region, and account hash. It serves fresh data within title_cache_time, falls back to stale data within title_cache_max_retention when an API call fails, and is bypassed by --no-cache.
self.track_request: the TrackRequest describing what the user asked for (codecs, ranges, best-available), for use inside get_tracks.

A minimal service skeleton

services/EXMP/__init__.py

from unshackle.core.service import Service
from unshackle.core.manifests import DASH
from unshackle.core.titles import Movie, Movies


class EXMP(Service):
    ALIASES = ("example",)
    GEOFENCE = ("us",)

    def get_titles(self) -> Movies:
        data = self.session.get(f"https://api.example.com/title/{self.title}").json()
        return Movies([
            Movie(
                id_=data["id"],
                service=self.__class__,
                name=data["name"],
                year=data.get("year"),
                language=data.get("language"),
            )
        ])

    def get_tracks(self, title) -> "Tracks":
        mpd_url = self.session.get(...).json()["manifest"]
        mpd = self.session.get(mpd_url).text
        return DASH.from_text(mpd, mpd_url).to_tracks(language=title.language)

    def get_chapters(self, title):
        return []

    def get_widevine_license(self, *, challenge, title, track):
        return self.session.post("https://lic.example.com/wv", data=challenge).content

The directory name (EXMP) must exactly match the class name; that stem is the service tag. Put your service in one of the directories.services paths.

Where to go next¶

Creating a Service: a guided walkthrough that builds on this model.
Service API: exact signatures for the Service base class.
Titles API and Tracks API: the full object reference.
DRM API: the DRM and CDM classes in detail.
Downloading: how the flags a user passes map onto track selection.