GuideConverter

How to Build a Mkv To Mp4 Converter

An MKV to MP4 converter transforms Matroska video files to the more widely compatible MP4 format. Essential for playing videos on devices that don't support MKV.

What is a Mkv To Mp4 Converter?

MKV is an open container format supporting unlimited tracks and chapters. MP4 is more widely supported by devices and browsers. Conversion can often be done by remuxing without quality loss if codecs are compatible.

Code Example

JavaScript

// Fast remux if codecs are compatible (H.264/AAC)
function remuxMKVtoMP4(inputPath, outputPath) {
  // -c copy means no re-encoding, just change container
  const command = `ffmpeg -i "${inputPath}" -c:v copy -c:a copy "${outputPath}"`;
  return execPromise(command);
}

// Transcode if codecs need conversion
function transcodeMKVtoMP4(inputPath, outputPath, options = {}) {
  const {
    videoCodec = 'libx264',
    audioCodec = 'aac',
    crf = 23,
    preset = 'medium' // ultrafast, fast, medium, slow
  } = options;

  const command = `ffmpeg -i "${inputPath}" \
    -c:v ${videoCodec} -crf ${crf} -preset ${preset} \
    -c:a ${audioCodec} -b:a 128k \
    "${outputPath}"`;

  return execPromise(command);
}

// Detect if remux is possible
async function canRemux(inputPath) {
  const probe = await getVideoInfo(inputPath);
  const videoCodec = probe.streams.find(s => s.codec_type === 'video')?.codec_name;
  const audioCodec = probe.streams.find(s => s.codec_type === 'audio')?.codec_name;

  const mp4VideoCodecs = ['h264', 'hevc', 'av1'];
  const mp4AudioCodecs = ['aac', 'mp3', 'ac3'];

  return mp4VideoCodecs.includes(videoCodec) && mp4AudioCodecs.includes(audioCodec);
}