Spotlight's Film Festival Nearly Fried My Mac

My Mac had been dragging for a day or so. First suspect was Colima, since it’s usually the thing quietly hogging my CPU. This time it wasn’t.

The Setup

Colima checked out clean, 2 CPUs, 2GiB RAM, VM process sitting under 1% CPU. So I ran ps aux and found the real offender straight away.

USER   PID   %CPU  %MEM  COMMAND
eric   86198 129.7 8.9   mediaanalysisd

mediaanalysisd is the built-in macOS daemon that handles face recognition, scene detection, and search indexing for Photos. It had been sitting at 130% CPU and 3GB of RAM since 5:07pm the day before.

Chasing the Wrong Lead

I assumed Photos, maybe an iCloud sync had kicked off a re-index. lsof backed that up at first, it had Photos.sqlite and MediaAnalysis.sqlite open under ~/Pictures/Photos Library.photoslibrary.

Except that database had zero assets in it.

❯ sqlite3 "Photos Library.photoslibrary/database/Photos.sqlite" \
    "select count(*) from ZASSET;"
0

There was an iCloud sync status file claiming 197 photos, so maybe those just hadn’t downloaded yet. But I don’t use iCloud for photos… Let’s dig deeper.

Sampling the Process

When ps and lsof run out of answers, sample is the next step, it grabs a process’s call stack over a short window so you can see what it’s actually doing on the CPU.

❯ sample 86198 1 -mayDie -f /tmp/sample.txt

-[VCPMovieAnalyzer analyzeAsset:streamed:]
  -[VCPAudioAnalyzer analyzeAsset:cancel:results:]
    -[VCPAudioAnalyzer processSampleBuffer:]
      -[VCPAudioClassifier processAudioSamples:timestamp:]
        SoundAnalysis framework

It was the audio classification, which Apple uses to tag video with sound categories (music, speech, applause) for Siri Suggestions and Spotlight search. And it had been stuck in that exact stack for over 17 hours straight.

lsof again, this time looking at the actual open files, cleared things up.

mediaanal 86198 eric 34r  .../Downloads/movie-1.mp4
mediaanal 86198 eric 37r  .../Movies/movie-2.mp4
mediaanal 86198 eric 38r  .../Movies/movie-3.mp4
mediaanal 86198 eric 39r  .../Movies/movie-4.mp4
mediaanal 86198 eric 42r  .../Movies/movie-5.mp4
mediaanal 86198 eric 43r  .../Movies/movie-6.mp4
mediaanal 86198 eric 44r  .../Downloads/movie-7.mp4
mediaanal 86198 eric 45r  .../Downloads/movie-8.mp4

Eight full 1080p movies, all with 5.1 audio, all open at once. Spotlight had been running sound classification across my entire movie collection and gotten stuck somewhere in the middle of it.

The Fix

❯ kill -9 86198

CPU dropped immediately. To stop it happening again I excluded my movie folders from Spotlight entirely, System Settings > Siri & Spotlight > Spotlight Privacy, added ~/Downloads and ~/Media/Movies.

Takeaway

mediaanalysisd isn’t just a Photos thing. It reaches into Downloads, Desktop, wherever it can find media, and runs audio classification on video files too. If your Mac slows down and Activity Monitor points at it, sample the process and check what files it actually has open, then exclude them from Spotlight.