moq-mux: add seek(sequence) on importers for explicit group boundaries

[kixelated]

Summary

Adds seek(sequence: u64) to every moq-mux importer (and to the underlying container::Producer<C>) so callers can open the next group at an explicit sequence instead of always starting at 0. Useful for joining mid-stream and signalling discontinuities.

Default auto-rotate behavior (video → new group on keyframe, AAC/Opus → one frame per group, fMP4 → new group when a traf contains a sync sample) is unchanged when seek is not invoked, so existing callers (moq-cli, moq-gst, libmoq, moq-ffi, moq-boy, hang) are unaffected.

The standalone AAC/Opus "one-frame-per-group" finalize stays as-is for now. A multi-frame-per-group knob for LL-HLS-style import was discussed and deferred; seek alone solves the join/discontinuity case.

How it works

• container::Producer<C> gains a pending_sequence: Option<u64> field. seek(n) flushes + finishes the current group and stores Some(n). The next write opens the new group via TrackProducer::create_group(Group { sequence: n }) instead of append_group(), then clears the pending slot so subsequent groups auto-increment from n.
• Codec importers (h264, h265, av1, aac, opus) forward seek to their inner container::Producer.
• container::fmp4::Import and container::mkv::Import fan seek out across every per-track entry so all renditions advance together. (Broadcast-wide by design; per-track control intentionally not exposed.)
• import::Framed and import::Stream dispatchers forward to the contained importer.

Test plan

• cargo test -p moq-mux (144/144 passing, including 2 new unit tests on container::Producer and 1 new end-to-end test on fmp4::Import).
• cargo check --all-targets --workspace (excluding moq-boy/moq-gst which need system ffmpeg/gstreamer in this sandbox).
• cargo clippy --all-targets --workspace -- -D warnings (same exclusions).
• cargo fmt --all --check.

(Written by Claude)

https://claude.ai/code/session_01E5uGooj9DFQm7Hc1fy9PYL

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Generated by Claude Code

[coderabbitai]

Walkthrough

This PR adds a seek(sequence: u64) method throughout the moq-mux media import pipeline. The core mechanism in Producer<C> introduces a pending_sequence field that schedules the next group at an explicit sequence number instead of auto-incrementing. Container implementations (fMP4, MKV) and codec importers (AAC, AV1, H264, H265, Opus) delegate to their underlying track producers. Top-level importers (Framed, Stream) dispatch seek calls to the active decoder variant. The fMP4 container adds per-track pending sequence state and tests validate that seek sets the initial group sequence and subsequent groups auto-increment correctly.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: adding seek(sequence) methods to moq-mux importers for explicit group boundary control, which is the primary focus across all modified files.
Description check	✅ Passed	The description is comprehensive and directly related to the changeset, explaining the motivation (join mid-stream, signal discontinuities), implementation approach across all layers, and test coverage.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch claude/moq-mux-group-start-cnY8i

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@rs/moq-mux/src/container/fmp4/import_test.rs`:
- Line 10: The test helper is silently swallowing errors by turning Err into
None using .now_or_never().and_then(|r| r.ok().flatten()); update the loop to
explicitly handle the Result from consumer.recv_group(): call
consumer.recv_group().now_or_never(), match on Some(Ok(Some(group))) to
continue, Some(Ok(None)) to break, and treat Some(Err(e)) as a test-failure
(panic or propagate) so recv_group errors fail fast instead of being hidden.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 99340bf4-8eb6-42db-be3b-244c3add73df

📥 Commits

Reviewing files that changed from the base of the PR and between b6e7f4c and 670b7de.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (11)

• rs/moq-mux/Cargo.toml
• rs/moq-mux/src/codec/aac/import.rs
• rs/moq-mux/src/codec/av1/import.rs
• rs/moq-mux/src/codec/h264/import.rs
• rs/moq-mux/src/codec/h265/import.rs
• rs/moq-mux/src/codec/opus/import.rs
• rs/moq-mux/src/container/fmp4/import.rs
• rs/moq-mux/src/container/fmp4/import_test.rs
• rs/moq-mux/src/container/mkv/import.rs
• rs/moq-mux/src/container/producer.rs
• rs/moq-mux/src/import.rs

[coderabbitai]

⚠️ Potential issue | 🟡 Minor | ⚡ Quick win

Don’t silently swallow recv_group errors in the test helper.

Line 10 converts Err into None, which can hide real failures and let tests pass for the wrong reason. Fail fast on Some(Err(_)).

Suggested fix

 fn drain_group_sequences(consumer: &mut moq_net::TrackConsumer) -> Vec<u64> {
 	let mut sequences = Vec::new();
-	while let Some(group) = consumer.recv_group().now_or_never().and_then(|r| r.ok().flatten()) {
-		sequences.push(group.sequence);
-	}
+	loop {
+		match consumer.recv_group().now_or_never() {
+			Some(Ok(Some(group))) => sequences.push(group.sequence),
+			Some(Ok(None)) | None => break,
+			Some(Err(err)) => panic!("recv_group failed: {err:?}"),
+		}
+	}
 	sequences
 }

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@rs/moq-mux/src/container/fmp4/import_test.rs` at line 10, The test helper is
silently swallowing errors by turning Err into None using
.now_or_never().and_then(|r| r.ok().flatten()); update the loop to explicitly
handle the Result from consumer.recv_group(): call
consumer.recv_group().now_or_never(), match on Some(Ok(Some(group))) to
continue, Some(Ok(None)) to break, and treat Some(Err(e)) as a test-failure
(panic or propagate) so recv_group errors fail fast instead of being hidden.