Add ROS2 MCAP file support (.mcap/.mcap.zstd) by Tiryoh · Pull Request #10 · Tiryoh/rosbag-analyzer-web

Tiryoh · 2026-03-25T13:26:01Z

Summary

Add support for ROS2 MCAP files (.mcap / .mcap.zstd) alongside existing ROS1 .bag files
Abstract severity from numeric values to string-based SeverityLevel type ('DEBUG'|'INFO'|'WARN'|'ERROR'|'FATAL') so both ROS1 (1/2/4/8/16) and ROS2 (10/20/30/40/50) are unified
MCAP module is dynamically imported for code splitting — bag-only users don't load MCAP code
Uses @mcap/core for MCAP reading, @foxglove/rosmsg2-serialization for CDR deserialization, fzstd (pure JS) for zstd decompression

Changed files

src/mcapUtils.ts — New MCAP parsing module
src/types.ts — SeverityLevel string type, ROS1_SEVERITY/ROS2_SEVERITY mappings
src/rosbagUtils.ts — loadMessages dispatcher, severity string conversion
src/App.tsx — Accept .mcap, use loadMessages, severity UI updates
src/i18n.ts — Updated file type description
e2e/mcap.spec.ts — 20 E2E test cases for MCAP
e2e/fixtures/ — MCAP fixture + Dockerfile (ROS2 Jazzy)

Test plan

Unit tests: 42 passed (severity type migration verified)
E2E (bag): 44 passed (no regression)
E2E (MCAP): 20 passed (upload, filters, export, diagnostics)
E2E (SQLite): 2 passed (schema update verified)
Lint: clean
Build: successful, MCAP in separate chunk (127KB gzipped 35KB)

🤖 Generated with Claude Code

- Add MCAP parsing with @mcap/core, @foxglove/rosmsg2-serialization, fzstd - Abstract severity to string-based SeverityLevel type (ROS1/ROS2 unified) - Dynamic import for MCAP module to keep bundle split for bag-only users - Add E2E tests (20 cases) with MCAP fixture generated via ROS2 Jazzy Docker - Update file accept to .bag,.mcap, i18n text, and CLAUDE.md Co-Authored-By: Claude Opus 4.6 <[email protected]>

github-actions · 2026-03-25T13:27:21Z

Test Results

42 tests ±0 42 ✅ ±0 0s ⏱️ ±0s
1 suites ±0 0 💤 ±0
1 files ±0 0 ❌ ±0

Results for commit 800dfff. ± Comparison against base commit fbdd49b.

♻️ This comment has been updated with latest results.

github-actions · 2026-03-25T13:27:37Z

🚀 Preview deployed: https://ae12bda6.rosbag-analyzer.pages.dev
🔗 Alias URL: https://feat-mcap-support.rosbag-analyzer.pages.dev

- Add try/catch with detailed error logging (matching loadRosbagMessages style) - Show available topics when no rosout/diagnostics topics are found - Add console logging for load progress and success Co-Authored-By: Claude Opus 4.6 <[email protected]>

MCAP files recorded by some tools lack the summary/footer section, causing McapIndexedReader to fail. Detect the footer magic and fall back to McapStreamReader for incomplete files. Also decompress whole-file zstd-wrapped .mcap files by detecting the zstd magic at the start of the buffer. Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

- Replace unreliable hasMcapFooter() check with try/catch fallback to streaming reader, since all valid MCAP files share the same trailing magic bytes regardless of index presence - Add state-change deduplication for diagnostics to match ROS1 loader behavior, preventing duplicate rows from repeated status samples Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

The filter only compared level and message, causing entries with different values (e.g. packets_received changing) to be incorrectly skipped. This fixes the e2e M-5-3 name filter test failure. Co-Authored-By: Claude Opus 4.6 <[email protected]>

Copilot

Pull request overview

This PR adds ROS2 log/diagnostics ingestion via MCAP (.mcap / .mcap.zstd) alongside existing ROS1 .bag support, and standardizes rosout severity handling across ROS1/ROS2 by moving to a string-based SeverityLevel.

Changes:

Introduces MCAP parsing (src/mcapUtils.ts) and a loadMessages() dispatcher to choose ROS1 bag vs ROS2 MCAP at runtime.
Migrates rosout severity from numeric codes to SeverityLevel strings and updates exports/UI accordingly.
Adds Playwright E2E coverage and fixtures for MCAP, plus updates SQLite export schema and docs.

Reviewed changes

Copilot reviewed 13 out of 15 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/types.ts	Adds `SeverityLevel` and ROS1/ROS2 severity mappings; updates color/bg mappings to string keys.
src/rosbagUtils.ts	Maps ROS1 numeric severity to `SeverityLevel`; updates export formats and SQLite schema; adds `loadMessages()` dispatcher.
src/rosbagUtils.test.ts	Updates unit tests for string-based severities and updated SQLite schema.
src/mcapUtils.ts	New MCAP reader using `@mcap/core`, CDR deserialization, and zstd decompression; collects rosout + diagnostics.
src/i18n.ts	Updates upload file-type hint to include MCAP extensions.
src/App.tsx	Accepts MCAP uploads, uses `loadMessages()`, and updates severity filtering/UI to `SeverityLevel`.
package.json	Adds dependencies required for MCAP + ROS2 deserialization.
package-lock.json	Locks new MCAP/ROS2-related dependencies and transitive updates.
e2e/sqlite-export.spec.ts	Updates assertions for new SQLite severity column.
e2e/mcap.spec.ts	Adds Playwright E2E coverage for MCAP upload/filter/export/diagnostics.
e2e/fixtures/test_sample.mcap	Adds MCAP fixture used by E2E tests.
e2e/fixtures/generate_test_mcap.py	Adds generator script for the MCAP test fixture (ROS2).
e2e/fixtures/Dockerfile.mcap	Adds Docker image to generate the MCAP fixture using ROS2 Jazzy.
README.md	Updates supported formats/versions and dependency list to include MCAP.
CLAUDE.md	Updates repo guidance to reflect MCAP support and severity mapping changes.

Comments suppressed due to low confidence (1)

src/i18n.ts:18

The English i18n strings still say “Loading bag file…” / “Error loading bag file”, but the app now supports MCAP uploads too. Update these strings (and any similar bag-specific wording) to be format-agnostic (e.g., “Loading file…” / “Error loading file”).

    'loading.message': 'Loading bag file...',
    'error.title': 'Error loading bag file',

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Copilot · 2026-03-25T17:40:33Z

    "@foxglove/rosbag": "^0.4.1",
+    "@foxglove/rosmsg": "^5.0.5",
+    "@foxglove/rosmsg2-serialization": "^3.0.3",
+    "@mcap/core": "^2.2.0",
+    "fzstd": "^0.1.1",


@foxglove/rosmsg2-serialization declares engines.node >= 20 (see package-lock), but this repo’s package.json doesn’t declare an engines requirement. Adding an explicit engines field (or documenting the Node >=20 requirement) will prevent confusing install failures for developers on older Node versions.

This is a browser-only app — Node is only used for dev tooling. The runtime doesn't depend on Node engine compatibility, so adding an engines field isn't necessary here.

Copilot · 2026-03-25T17:40:33Z

+    const decompressHandlers: DecompressHandlers = {
+      zstd: (data) => zstdDecompress(new Uint8Array(data)),
+    };


decompressHandlers only registers a zstd handler. MCAP chunks can also be lz4-compressed; without an lz4 handler those files will fail to load. Consider adding an lz4 handler (you already depend on lz4js) or documenting that only zstd-compressed MCAPs are supported.

Added lz4 handler in 6f09f3f. lz4js was already in dependencies (used by the ROS1 bag loader).

Add tests for .mcap.zstd (outer zstd compression) and truncated .mcap files to verify error handling and data recovery. Also update fixture generator to produce these variants automatically. Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

fzstd.decompress() can return a Uint8Array with non-zero byteOffset, so using .buffer directly caused the MCAP reader to read from wrong offsets. Use .slice().buffer to get a properly aligned ArrayBuffer. Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Copilot

Pull request overview

Copilot reviewed 15 out of 19 changed files in this pull request and generated 3 comments.

Comments suppressed due to low confidence (1)

src/i18n.ts:18

UI strings still refer to a "bag file" in loading/error text, but the uploader now supports .mcap/.mcap.zstd too. Please update loading.message and the English error.title to be format-neutral (e.g. "Loading file..." / "Error loading file") to avoid misleading users.

    'upload.fileType': 'ROSbag / MCAP file (.bag, .mcap, .mcap.zstd)',

    // Loading / Error
    'loading.message': 'Loading bag file...',
    'error.title': 'Error loading bag file',

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Copilot · 2026-03-26T16:26:56Z

+    const magic = new Uint8Array(buffer, 0, 4);
+    if (magic[0] === 0x28 && magic[1] === 0xb5 && magic[2] === 0x2f && magic[3] === 0xfd) {
+      const decompressed = zstdDecompress(new Uint8Array(buffer));
+      buffer = decompressed.slice().buffer as ArrayBuffer;


buffer = decompressed.slice().buffer makes an additional full copy of the decompressed data. For large .mcap.zstd files this can double peak memory usage. Consider reusing the Uint8Array’s underlying buffer when possible (or only copying when byteOffset/byteLength require it).

Suggested change

buffer = decompressed.slice().buffer as ArrayBuffer;

if (decompressed.byteOffset === 0 && decompressed.byteLength === decompressed.buffer.byteLength) {

buffer = decompressed.buffer as ArrayBuffer;

} else {

buffer = decompressed.slice().buffer as ArrayBuffer;

}

Fixed in 6f09f3f — now checks byteOffset === 0 && byteLength === buffer.byteLength before reusing the backing buffer directly, only copying when needed.

…n magic check - Remove unused channelsById map from McapMessageCollector - Add lz4 decompression handler for MCAP chunks - Add buffer.byteLength >= 4 guard before reading magic bytes - Avoid unnecessary buffer copy when byteOffset is already 0 - Tighten file picker accept to .mcap.zstd instead of .zstd Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

…nknown severity - Fall back to streaming reader when indexed reader returns 0 messages (handles unchunked MCAPs where messages are not inside Chunk records) - Track pending channels and rebuild readers when their schema arrives later (handles streaming MCAPs with Channel before Schema order) - Map unmapped/unknown severity levels to 'UNKNOWN' instead of 'DEBUG' to preserve original data fidelity Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Tiryoh and others added 5 commits March 25, 2026 22:35

Merge branch 'main' into feat/mcap-support

0d5acc3

Tiryoh requested a review from Copilot March 25, 2026 17:35

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Tiryoh and others added 2 commits March 26, 2026 21:48

Tiryoh requested a review from Copilot March 26, 2026 16:22

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Tiryoh and others added 2 commits March 27, 2026 02:20

Repository owner deleted a comment from s-daisuke Mar 26, 2026

Tiryoh merged commit 57fc11c into main Mar 27, 2026
8 checks passed

Tiryoh deleted the feat/mcap-support branch March 27, 2026 04:24

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Add ROS2 MCAP file support (.mcap/.mcap.zstd)#10

Add ROS2 MCAP file support (.mcap/.mcap.zstd)#10
Tiryoh merged 10 commits intomainfrom
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-      buffer = decompressed.slice().buffer as ArrayBuffer;
+      if (decompressed.byteOffset === 0 && decompressed.byteLength === decompressed.buffer.byteLength) {
+        buffer = decompressed.buffer as ArrayBuffer;
+      } else {
+        buffer = decompressed.slice().buffer as ArrayBuffer;
+      }

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Tiryoh commented Mar 25, 2026

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