Bash script for converting mkv to mp4 without transcoding video

convert.mkv.sh

#!/bin/bash

# Configure inputs
INPUT_FOLDER='/media'
DELETE_ORIGINALS=false #set to true to delete original files

# Set $IFS variable to handle files whitespace in name
SAVEIFS=$IFS
IFS=$(echo -en "\n\b")

# Generate list of files to be processed
FILES=`find "$INPUT_FOLDER" -name "*.mkv" | sort`

# Iterate over files in list
for FILE in $FILES
do  
  # Generate output file name
  OUTPUT_FILE=`echo $FILE | rev | cut -d. -f2- | rev`".mp4"

  # Analyse file params with ffprobe
  AUDIO_CH=`ffprobe "${FILE}" -show_streams -select_streams a:0 -loglevel quiet | sed -n '/channels=/s/channels=//p'`
  AUDIO_CODEC=`ffprobe "${FILE}" -show_streams -select_streams a:0 -loglevel quiet | sed -n '/codec_name=/s/codec_name=//p'`

  # Process with ffmpeg
  if [[ $AUDIO_CH == "6" ]]; then
    # Downmix 6ch audio to 2ch aac
    ffmpeg -i "${FILE}" -c:v copy -af aresample=matrix_encoding=dplii -ac 2 -c:a aac -strict -2 -b:a 128k "${OUTPUT_FILE}"
  elif [[ $AUDIO_CODEC == "ac3" ]]; then
    # Convert ac3 audio to aac for better compatibility
    ffmpeg -i "${FILE}" -c:v copy -c:a aac -strict -2 -b:a 128k "${OUTPUT_FILE}"
  elif [[ $AUDIO_CODEC == "dca" ]]; then
    # Convert dts audio to aac for better compatibility
    ffmpeg -i "${FILE}" -c:v copy -c:a aac -strict -2 -b:a 128k "${OUTPUT_FILE}"
  else
    # Simple container change for files that do not hit conditions above
    ffmpeg -i "${FILE}" -codec copy "${OUTPUT_FILE}"
  fi

  # Delete original file if configured to do so
  if $DELETE_ORIGINALS; then
    rm "${FILE}"
  fi

done

Updated to handle files with white space in filename

Further work:

• option to transcode or skip for video codecs such as h265
• publish as Docker container using Alpine Linux
• Docker run command to set environmental variable that determines whether original files are deleted

Updated to fix problem where only first file was being processed when multiple files in input folder