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Macos: Recording pipeline repeatedly stalls for 5–22 s (whole process), causing ~10% video loss and multi-second audio gaps

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評価

難易度
5/5
見積もり時間
1週間以上
初心者へのやさしさ
32/100
issue の種類
バグ
明瞭さ
説明が足りない
活発さ
活発
技術スタック
macos, rust, tauri
領域
audio-video-rtc, desktop, performance

調査の方向性

Start with the attached cap-desktop.log and correlate the process-wide silent windows with video, microphone, and system-audio events. Trace the recording pipeline and shared runtime for the suspected blocking I/O and investigate the VideoToolbox, warning, and upload-state observations separately. Done means reproducing or isolating the stall cause and defining scoped fixes with tests or log evidence for the affected behaviors.

索引モデルが issue の本文から書いたものです。

説明

bug
Description

38.5-minute recording (14:01:52 → 14:40:24 UTC). During it, the pipeline froze 16 times:

  • Video: 16 Wall-clock-confirmed forward jump events, total_forward_skew_secs="222.033" (~10% of the recording missing)
  • Mic: 6 silence insertions, total_silence_ms=64429
  • System audio: 172 silence insertions, total_silence_ms=69615, plus dropping frames due to full channel

Evidence that the whole process stalls, not just capture
The periodic memory snapshot normally fires at :25 every minute. During the stalls it fires late:

  • 14:06:32 (+6.4 s), 14:19:37 (+12 s), 14:21:42 (+16.5 s), 14:28:32 (+6.5 s)

There are also windows with no log lines at all from any thread:

  • 14:13:57.7 → 14:14:22.2 (24.5 s)
  • 14:15:57.4 → 14:16:20.1 (22.6 s)
  • 14:19:15.3 → 14:19:37.9 (22.6 s)
  • 14:21:17.9 → 14:21:42.4 (24.5 s)
  • 14:28:07.8 → 14:28:32.4 (24.6 s)

Mic and system-audio drops happen exactly in these windows: the sources keep producing data, but consumers are not draining the channels.

Suspicious pattern
The longest video gaps are almost identical: 21.33, 21.35, 21.47, 21.23, 21.44, 21.77 s. This looks like a fixed timeout somewhere rather than random I/O latency.

Hypothesis (unverified)
Blocking file I/O on the shared async runtime. If the output volume (an SD card here) has a write-latency spike, all runtime workers block, including the muxers and timers. A recorder should absorb storage hiccups with buffering instead of dropping audio.

Other observations from the same log

  • VideoToolbox zero-copy input unavailable ... scaling 4112x2658 -> 4096x2648 requires the software input path, but the encoder is then initialized at 4112×2658. These messages contradict each other, and the software path adds load for no apparent reason.
  • System audio dropping frames WARN is re-logged every 5 s even when the dropped counter does not change, producing hundreds of redundant warnings.
  • At recording start: Recording upload state could not be read; files retained error=No such file or directory (state is read before it is created).

Full log attached- cap-desktop.log

Additional Context
  • Cap version: 0.6.0
  • Operating system, version: 26.2 (25C56)
  • Device (optional): MacBook Pro M1 Pro, 16 GB RAM
主要言語
Rust
スター
22.8k
フォーク
2k
平均マージ
10時間 44分
マージ済み PR（30日）
88

環境構築

はじめの一歩

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  3. リポジトリをフォークし、ブランチを切って変更します。
  4. issue 番号を参照したプルリクエストを送ります。

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