Excessive RAM usage (~15GB)

[CharitSinghChauhan]

Description

Cap consumes extremely high memory (~15GB RAM)

After recording for an extended period (high resolution session), pausing the recording does not reduce memory usage. The application continues holding a large amount of RAM, which causes significant system slowdown and memory pressure.

Memory is only released after fully quitting the application.

Expected behavior:
When recording is paused, memory usage should stabilize or partially release instead of retaining the entire buffer in memory.

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Reproduction

1. Start a screen recording
2. Record for an 4 min duration
3. Pause the recording
4. Open Activity Monitor
5. Observe Cap memory usage (~15GB)

Memory remains high while paused and is only freed after quitting the app.

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Additional Context

• Cap version: Version 0.4.5 (0.4.5)
• Operating system, version: macOS Tahoe 26.2
• Device (optional): (e.g., MacBook Pro M1 / 8GB RAM)

The issue appears to be related to recording buffer retention or memory not being released when entering the paused state.

[linear]

CAP-634

[tembo]

Thanks for the detailed report. Looking at the codebase and recent work, here's some context that may help:

Related Prior Work

There have been several memory-related fixes merged recently:

• PR #1462 (Dec 2025) - "Fix memory leaks and reduce memory usage in recording pipeline" addressed macOS screen capture and camera buffer handling, and added a fragmented MP4 muxer to reduce memory footprint during encoding
• PR #1381 (Nov 2025) - Fixed a memory leak where memory would increase while recording on Windows

Since you're on v0.4.5, these fixes should already be included. The behavior you're seeing (memory retained during pause) appears to be a separate issue.

Technical Context

Looking at the recording pipeline, the pause implementation in crates/recording/src/output_pipeline/core.rs uses an atomic flag (SharedPauseState) that filters frames at the source level - when paused, pause.adjust() returns None and frames are skipped. However, this doesn't actively drain or clear existing buffers.

The relevant buffer sizes are configurable via environment variables if you want to experiment:

• CAP_VIDEO_SOURCE_BUFFER_SIZE - video source channel capacity (default: 300 frames)
• CAP_SCREEN_BUFFER_SIZE - screen capture buffer (default: 15)
• CAP_MUXER_BUFFER_SIZE - muxer buffer size (default: 240)

For a 4-minute high-resolution recording, 15GB does seem excessive. A few questions that might help narrow this down:

• What recording mode are you using (Studio or Instant)? Studio mode creates separate pipeline segments on pause/resume, while Instant mode keeps the same pipeline alive.
• What resolution is being captured? High-resolution displays with retina scaling can significantly increase frame buffer memory.
• Is camera recording enabled? That adds additional buffer overhead.

Potential Root Cause

Given the symptoms (memory retained on pause, only released on quit), this could be related to encoder buffers or IOSurface retention not being released when the recording pauses. The screen capture source (crates/recording/src/sources/screen_capture/macos.rs) and output pipeline (crates/recording/src/output_pipeline/macos_fragmented_m4s.rs) would be the primary areas to investigate.

[kbegiedza]

I'm facing similar issue...
but for me it's over 87 GB