MKV to MP4 via CLI

Re-encode Matroska to H.264 + AAC with ffmpeg.

Packages to install

Only ffmpeg with libx264 and AAC is required.

ffmpeg

sudo apt-get update
sudo apt-get install -y ffmpeg

How to run the command

ffmpeg -i input.mkv -c:v libx264 -preset ultrafast -crf 23 -pix_fmt yuv420p -c:a aac -b:a 128k -movflags +faststart output.mp4.

ffmpeg -y -i input.mkv -c:v libx264 -preset ultrafast -crf 23 -pix_fmt yuv420p -c:a aac -b:a 128k -movflags +faststart output.mp4

Dockerfile example

Build a minimal Ubuntu image with the required packages and run the conversion inside the container.

FROM ubuntu:24.04

RUN apt-get update && \
    apt-get install -y --no-install-recommends \
        ffmpeg && \
    rm -rf /var/lib/apt/lists/*

WORKDIR /work

docker build -t mkv-to-mp4 .
docker run --rm -v "$PWD:/work" -w /work mkv-to-mp4 \
  ffmpeg -y -i input.mkv -c:v libx264 -preset ultrafast -crf 23 -pix_fmt yuv420p -c:a aac -b:a 128k -movflags +faststart output.mp4

Example commands

Run these locally after installing the packages, or inside the container from the Dockerfile.

ffmpeg -y -i input.mkv -c:v libx264 -preset ultrafast -crf 23 -pix_fmt yuv420p -c:a aac -b:a 128k -movflags +faststart output.mp4

ffmpeg -y -i video.mkv -c:v libx264 -preset fast -crf 20 -pix_fmt yuv420p -c:a aac -b:a 160k -movflags +faststart video.mp4