diff --git a/infra/docker/ci.Dockerfile b/infra/docker/ci.Dockerfile
index a9422ee40..8849bf135 100644
--- a/infra/docker/ci.Dockerfile
+++ b/infra/docker/ci.Dockerfile
@@ -30,6 +30,14 @@ RUN apt-get update \
     && apt-get install -y --no-install-recommends docker-ce-cli docker-buildx-plugin \
     && rm -rf /var/lib/apt/lists/*
 
+# Pre-bake ffmpeg: unit-tests run in fresh containers each time; installing ffmpeg
+# on every job cost ~24 min (apt update + hundreds of codec deps). Bake it into the
+# image so step_install_ffmpeg.sh detects it and exits instantly.
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends ffmpeg \
+    && ffmpeg -version | head -1 \
+    && rm -rf /var/lib/apt/lists/*
+
 # Pre-install base deps (layer cache)
 COPY requirements-base.txt ./
 RUN python -m venv "$VIRTUAL_ENV" \