# Gstreamer Docs > > - **Type:** Skill - **Install:** `agentstack add skill-damionrashford-media-os-gstreamer-docs` - **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior - **Seller:** [damionrashford](https://agentstack.voostack.com/s/damionrashford) - **Installs:** 0 - **Category:** [Content & Media](https://agentstack.voostack.com/c/content-and-media) - **Latest version:** 0.1.0 - **License:** MIT - **Upstream author:** [damionrashford](https://github.com/damionrashford) - **Source:** https://github.com/damionrashford/media-os/tree/main/.claude/skills/gstreamer-docs - **Website:** https://damionrashford.github.io/media-os/ ## Install ```sh agentstack add skill-damionrashford-media-os-gstreamer-docs ``` Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent. ## About # GStreamer Docs **Context:** $ARGUMENTS ## Quick start - **Find an element / property / signal:** -> Step 2 (`search --query `) - **Read the full docs for one element:** -> Step 3 (`element --name `) - **Read one section by anchor:** -> Step 4 (`section --page --id `) - **Grab a whole page:** -> Step 5 (`fetch --page `) - **Prime cache for offline use:** -> Step 6 (`index`) ## When to use - User asks "what does element `X` do?" or "what properties does `webrtcbin` expose?" - Need to verify an element name, property, pad, or signal exists before recommending it. - Need the canonical gstreamer.freedesktop.org URL to cite in a response. - Before writing any non-trivial gst-launch-1.0 pipeline, verify the element and its caps/properties. - Need to know which plugin package an element ships in. --- ## Step 1 — Know the page catalog The script targets a fixed list of plugin-index pages + top-level guides. Get the list: ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py list-pages ``` Common picks: | Question | Page | |---|---| | "What does filesrc / queue / tee / capsfilter do?" | `coreelements` | | "How do I use playbin3 / decodebin3 / uridecodebin3?" | `playback` | | "RTSP client / server elements?" | `rtsp`, `rtspserver` | | "HLS / DASH muxing / sinks?" | `hls`, `dash` | | "WebRTC — webrtcbin (C) vs webrtcsink (Rust)?" | `webrtc`, `rswebrtc` | | "SRT source / sink?" | `srt` | | "x264enc / x265enc / VP9 options?" | `x264`, `x265`, `vpx` | | "NVENC / NVDEC in GStreamer?" | `nvcodec` | | "MP4 / QuickTime mux / demux?" | `isomp4` | | "Matroska / WebM mux?" | `matroska` | | "V4L2 webcam?" | `v4l2` | | "OpenGL elements?" | `opengl` | | "gst-launch-1.0 syntax rules?" | `gst-launch` | | "gst-inspect-1.0 output fields?" | `gst-inspect` | | "Core GObject API / GstElement / GstPad / GstCaps?" | `gstreamer` | | "Base classes for writing elements (GstBaseSrc etc.)?" | `base` | Read [`references/pages.md`](references/pages.md) for the full catalog. --- ## Step 2 — Search first (this is the default) When the user names an element, property, pad, or signal, search across all pages: ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py search --query "webrtcbin" --limit 5 ``` Scope to a page when you know it (faster, less noise): ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py search --query "animation-mode" --page videotestsrc ``` Output per hit: ``` --- : — ``` `--format json` for machine-parseable output; `--regex` for anchored patterns. --- ## Step 3 — Read one element's docs When you know the element name (e.g. `filesrc`, `playbin3`, `webrtcbin`): ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py element --name filesrc uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py element --name webrtcbin --format json ``` The script resolves element pages automatically across the two URL shapes GStreamer uses: - **Multi-element plugin**: `//.html` (e.g. `/coreelements/filesrc.html`, `/playback/playbin3.html`, `/rtsp/rtspsrc.html`, `/hls/hlssink2.html`, `/srt/srtsrc.html`, `/rswebrtc/webrtcsink.html`). - **Singleton plugin**: `//index.html` (e.g. `/videotestsrc/index.html`, `/audiotestsrc/index.html`, `/webrtclib/index.html`, `/x264/index.html`). You can also debug which shape was picked: ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py resolve --element webrtcbin ``` --- ## Step 4 — Read one section When a search hit shows an anchor like `[§videotestsrc:animation-mode]` and you want the whole block: ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py section --page videotestsrc --id "videotestsrc:animation-mode" uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py section --element webrtcbin --id ice-agent ``` `--id` accepts a raw anchor id or a heading keyword (case-insensitive substring match on the first matching heading). --- ## Step 5 — Fetch a whole page Rare — usually overkill. When you need it: ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py fetch --page coreelements uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py fetch --element playbin3 --format json ``` --- ## Step 6 — Prime cache (optional) ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py index ``` Downloads every known landing page into `~/.cache/gstreamer-docs/` with a 0.3s delay. Override the cache directory with `export GSTREAMER_DOCS_CACHE=/path/to/dir`. Clear: `gstdocs.py clear-cache`. --- ## Gotchas - **Bare `/.html` is universally 404.** Elements live under a plugin dir — `/coreelements/filesrc.html`, not `/filesrc.html`. The `element` subcommand handles this for you; never construct the URL yourself. - **Two element-page shapes exist.** Multi-element plugin: `//.html`. Singleton plugin: `//index.html`. `resolve --element` tells you which shape was picked. - **Anchor syntax is Hotdoc-specific.** You'll see three flavours inside page text: `#` (the element landing block), `#:` with a literal colon (e.g. `#videotestsrc:animation-mode`), and `#Gst!` (e.g. `#GstVideoTestSrc!src` for the `src` pad). Pass the form you see in search output verbatim to `section --id`. - **webrtcbin vs webrtcsink are distinct.** `webrtcbin` is the low-level C element in plugin `webrtc` — you handle SDP + ICE yourself. `webrtcsink` / `webrtcsrc` are the high-level Rust elements in plugin `rswebrtc` that speak WHIP/WHEP and negotiate automatically. Don't mix their properties. - **playbin vs playbin3.** `playbin` is the legacy high-level player. `playbin3` is the current one — different signals, different bus messages, different stream-selection API. Check which one you're actually using. - **decodebin3 / urisourcebin stream-selection is different from decodebin/uridecodebin.** Events are `GST_EVENT_SELECT_STREAMS` + `GST_MESSAGE_STREAM_COLLECTION` rather than the old `autoplug-*` signals. Don't port old code verbatim. - **`gst-inspect-1.0 ` is authoritative for local builds.** If the online docs don't match what your installed GStreamer exposes, the CLI is right — some plugins are rolled from different upstreams (gst-plugins-good vs bad vs ugly vs rs) and versions diverge. - **Docs are Hotdoc-generated, NOT Sphinx.** Don't assume Sphinx conventions like `:py:class:` or `_CPPv4N...` — GStreamer anchors are flatter (`element`, `element:property`, `GstType!pad`). - **Plugin packages: good/bad/ugly/base/rs.** "bad" means "not yet up to par", NOT "buggy". Many widely-used elements (`webrtcbin`, `hlssink2`, `srtsink`) live in `gst-plugins-bad` or `gst-plugins-rs`. If `gst-inspect-1.0 foo` comes up empty, you probably haven't installed the plugin-set it ships in. - **Rust plugins (`gst-plugins-rs`) ship separately.** `webrtcsink`, `awstranscriber`, `fallbackswitch`, etc. are Rust — check `rswebrtc` and related index pages, not the C plugin pages. - **Search may miss content in complex tables.** The text extractor flattens multi-column property tables. If a search hit looks incomplete, open the canonical URL printed in the hit header. - **Cache never expires automatically.** After a GStreamer release reshuffles plugins, run `clear-cache` + `index`. - **The script is stdlib-only** — no pip install. Works anywhere Python 3.9+ runs. --- ## Examples ### Example 1 — "What properties does webrtcbin expose?" ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py element --name webrtcbin ``` Or search + jump: ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py search --query "webrtcbin" --page webrtc --limit 5 uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py section --element webrtcbin --id "webrtcbin:stun-server" ``` ### Example 2 — "Does hlssink2 support fMP4 / CMAF?" ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py search --query "hlssink2" --page hls uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py element --name hlssink2 ``` ### Example 3 — "What's the gst-launch-1.0 syntax for named elements and caps filters?" ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py search --query "pipeline description" --page gst-launch ``` ### Example 4 — "What does `videotestsrc animation-mode=frames` actually do?" ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py section --page videotestsrc --id "videotestsrc:animation-mode" ``` ### Example 5 — "Which plugin provides rtspclientsink?" ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/gstdocs.py resolve --element rtspclientsink ``` (Prints URL + shape. URL's first path segment is the plugin.) --- ## Troubleshooting ### Error: `unknown page: foo` **Cause:** The name isn't in the catalog. **Solution:** Run `list-pages`. Common mistakes: using `elements` instead of `coreelements`; `rtspsrc` (an element) instead of `rtsp` (the plugin). ### Error: `could not resolve element ` **Cause:** The element isn't in `ELEMENT_HINTS`, the singleton-plugin guess failed, and no known plugin landing page linked to it. **Solution:** Run `gst-inspect-1.0 ` to confirm the element exists and see its plugin. Then `search --query ""` across the whole catalog to find the right plugin page. If it's a Rust plugin not in our list yet, the element lives at `//.html` under `gst-plugins-rs` — fetch the URL directly with `urllib` until the catalog is updated. ### Error: `urlopen error [SSL: CERTIFICATE_VERIFY_FAILED]` **Cause:** System certificate store is out of date (usually macOS Python). **Solution:** Run `/Applications/Python\ 3.x/Install\ Certificates.command`, or set `SSL_CERT_FILE` to a valid CA bundle. Do NOT disable SSL verification. ### Search returns zero hits **Cause:** The term isn't on the pages you queried. **Solution:** Drop `--page` to search everything; try a broader query. Some APIs are in the base-class pages (`base`, `gstreamer`) rather than the element page. ### Anchor not found with `section --id` **Cause:** Hotdoc anchors include colons and `!` which copy-paste fine but may confuse shells. Quote them. **Solution:** `--id "videotestsrc:animation-mode"` with quotes, or fall back to a heading keyword: `--id animation-mode`. ### Cache is stale after GStreamer upstream release **Solution:** `gstdocs.py clear-cache` then `gstdocs.py index`. --- ## Reference docs - Full page catalog with element-to-plugin hints and anchor-syntax details -> [`references/pages.md`](references/pages.md) ## Source & license This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code. - **Author:** [damionrashford](https://github.com/damionrashford) - **Source:** [damionrashford/media-os](https://github.com/damionrashford/media-os) - **License:** MIT - **Homepage:** https://damionrashford.github.io/media-os/ Install and usage instructions live in the source repository linked above. ## Pricing - **Free** — Free ## Security capabilities Automated source analysis of v0.1.0 — what this tool can access: - **Network access:** yes - **Filesystem access:** no - **Shell / process execution:** no - **Environment & secrets:** no - **Dynamic code execution:** no *"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.* ## Versions - **0.1.0** — security scan: passed — Imported from the upstream source. ## Links - Listing page: https://agentstack.voostack.com/l/skill-damionrashford-media-os-gstreamer-docs - Seller: https://agentstack.voostack.com/s/damionrashford - Browse the marketplace: https://agentstack.voostack.com/browse --- Listed on AgentStack — the marketplace for AI agent skills and MCP servers. 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