Install ffmpeg for torchcodec runtime support

Dockerfile

@@ -17,6 +17,8 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     libportaudio2 \
     libopenblas-dev \
     libomp-dev \
+    ffmpeg \
+    libavcodec-extra \
     && rm -rf /var/lib/apt/lists/*
 
 COPY requirements.txt .