Explore MCAP robotics log files in VS Code: topics, schemas, statistics, metadata and attachments — instant summary even for multi-GB files, local or over Remote SSH.
Installation
Launch VS Code Quick Open (Ctrl+P), paste the following command, and press enter.
Explore MCAP robotics log files directly in VS Code: open a .mcap file and instantly see its topics, schemas, statistics, metadata records and attachments — even for multi-GB files, local or over Remote SSH.
Status: v0.1 — summary explorer. Message browsing, image/video preview and time-series plots are on the roadmap below.
Features
Instant summary — opens the index (footer + summary section) only, never scanning message data. A 2.7 GB production recording opens in ~20 ms reading ~400 KiB.
Schemas — lazy-loaded schema source (text schemas rendered as-is, binary schemas as a hex dump).
Metadata records — browse key/value metadata by name.
Attachments — list and save to disk (streamed in 4 MB windows, never held in memory).
Unindexed files — graceful fallback with an explicit, cancellable full scan with progress; truncated files (e.g. still being recorded) are handled without crashing.
MCAP: Show Info — right-click a .mcap file in the explorer for a plain-text summary in the output channel.
Large files & Remote SSH
MCAP Explorer runs entirely on the machine where the file lives (extensionKind: workspace). Over Remote SSH only compact, JSON-safe summaries cross the wire — raw file bytes never do. Opening a huge recording on a training server is as fast as opening it locally.
Safety rails:
Summary, schema, metadata and attachment reads are always index-based random access.
Chunks that would inflate beyond mcapExplorer.maxChunkUncompressedSize (default 256 MB) are refused rather than risking OOM.
Full scans of unindexed files above mcapExplorer.unindexedScanConfirmSize require explicit confirmation, report progress, and can be cancelled.
Install
From source: npm ci && npm run build && npx @vscode/vsce package --no-dependencies, then install the generated .vsix via Extensions: Install from VSIX…
Marketplace / Open VSX: coming with the first tagged release.
Roadmap
Phase
Scope
Status
1
Summary explorer (topics/schemas/stats/metadata/attachments)
✅
2
Message browsing with decoders (json, protobuf, ros1/ros2, cdr)
planned
3
Image / video frame preview (WebCodecs)
planned
4
Time-series plots for numeric topics
planned
Contributing
npm ci # install
npm run watch # rebuild on change (launch with F5 in VS Code)
npm test # unit tests (vitest, in-memory MCAP fixtures)
npm run smoke -- /path/to/file.mcap # acceptance metrics against a real file
The core reader (src/extension/readerService.ts) has no dependency on the VS Code API and is fully covered by unit tests against generated fixtures — including unindexed, truncated, zstd-compressed and oversized-chunk files.
