Convert a directory of mp4 videos into smaller webm videos, preserving audio tracks where present

convert-directory-mp4-webm.sh

#!/bin/bash

# Set the target height for the output videos
TARGET_HEIGHT=720

# Loop through all files in the current directory
for file in *; do
  # Check if the file is an MP4 video (you can extend this to other formats if needed)
  if [[ "$file" =~ \.mp4$ ]]; then
    # Get the filename without the extension
    filename_no_ext="${file%.*}"
    # Construct the output filename
    output_file="${filename_no_ext}_reduced.webm"

    # Use ffprobe to check for audio streams
    audio_streams=$(ffprobe -v error -show_entries stream=codec_type -of default=noprint_wrappers=1:nokey=1 "$file" | grep audio | wc -l)

    # Print a message to the user
    echo "Processing: $file"
    echo "Outputting: $output_file"

    # Construct the ffmpeg command.  Include "-an" only if no audio streams are found.
    if [ "$audio_streams" -eq 0 ]; then
      ffmpeg_cmd="ffmpeg -i \"$file\" -an -c:v libvpx-vp9 -crf 30 -b:v 0 -vf scale=-1:$TARGET_HEIGHT -preset medium \"$output_file\""
      echo "No audio stream found. Removing audio."
    else
      ffmpeg_cmd="ffmpeg -i \"$file\" -c:v libvpx-vp9 -crf 30 -b:v 0 -vf scale=-1:$TARGET_HEIGHT -preset medium \"$output_file\""
      echo "Audio stream(s) found.  Keeping audio."
    fi

    # Execute the ffmpeg command
    eval "$ffmpeg_cmd"

    # Check if the conversion was successful
    if [ $? -eq 0 ]; then
      echo "Conversion successful."
    else
      echo "Conversion failed."
    fi
  else
    echo "Skipping: $file (not an MP4 file)"
  fi
done

echo "Done!"