2

I am trying to write a bash script to download all the videos from a given public YouTube playlist. Here's what I have so far:

#!/bin/bash

# Default values
decode_video=true
output_format="avi"
audio_codec="libmp3lame"
audio_bitrate="192k"
audio_sample_rate="44100"
audio_channels="2"
video_codec="libxvid"
video_quality="3"

# Function to download and convert each video
download_and_convert() {
    local video_url="$1"
    local output_name="$2"
    
    # Show download start message
    echo "Downloading: $output_name.mp4..."

    # Download the video
    yt-dlp --progress -f "bv*+ba/b" --merge-output-format mp4 "$video_url" -o "$output_name.mp4"

    # Show download end message
    echo "Downloaded: $output_name.mp4"

    # Check if video should be re-encoded
    if $decode_video; then

        # Debug: Output the values of the variables
        echo "output_name: \"$output_name\""
        echo "video_codec: $video_codec"
        echo "video_quality: $video_quality"
        echo "audio_codec: $audio_codec"
        echo "audio_sample_rate: $audio_sample_rate"
        echo "audio_bitrate: $audio_bitrate"
        echo "audio_channels: $audio_channels"

        # Re-encode video to MPEG-4 (Xvid) and convert audio to MP3
        echo "Converting video to MPEG-4 (Xvid) and audio to MP3..."
        
        # Ensure that the script runs the command directly without any prompt
        ffmpeg -hide_banner -i "$output_name.mp4" -c:v libxvid -qscale:v 3 -c:a libmp3lame -ar 44100 -b:a 192k -ac 2 "$output_name.avi"

    else
        # Copy the video and only convert audio
        echo "Copying video and converting audio to MP3..."
        ffmpeg -i "$output_name.mp4" -c:v copy -c:a $audio_codec -ar $audio_sample_rate -b:a $audio_bitrate -ac $audio_channels "$output_name.$output_format"
    fi

    # Clean up the original MP4 file
    #rm "$output_name.mp4"
    echo "Converted: $output_name.$output_format"
}

# Parse command-line options
while [[ $# -gt 0 ]]; do
    case $1 in
        --no-decode-video)
            decode_video=false
            shift
            ;;
        --decode-video)
            decode_video=true
            shift
            ;;
        *)
            playlist_url="$1"
            shift
            ;;
    esac
done

# Ensure playlist URL is provided
if [ -z "$playlist_url" ]; then
    echo "Usage: $0 <playlist_url> [--no-decode-video]"
    exit 1
fi

# Get total number of videos in the playlist
total_videos=$(yt-dlp -j --flat-playlist "$playlist_url" | jq -r '.id' | wc -l)
echo "Total videos in playlist: $total_videos"

# Download the playlist and process each video
current_video=1
yt-dlp -j --flat-playlist "$playlist_url" | jq -r '.id' | while read -r video_id; do
    # Define output filename
    output_name="video_$video_id"
    
    # Show progress
    echo "Processing video $current_video of $total_videos..."
    
    # Download and convert the video
    download_and_convert "https://www.youtube.com/watch?v=$video_id" "$output_name"
    
    # Increment video counter
    current_video=$((current_video + 1))
done

echo "All videos processed successfully!"

Now, downloading videos works, but the conversion with ffmpeg fails. It starts showing the regular ffmpeg output, just as if it was converting it properly, and then shows: Parse error, at least 3 arguments were expected, only 1 given in string 'GC1Y0'. What could that be? I read on a different thread that there's a problem when quoting file names.

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4
  • Why don't you try to use yt-dlp --postprocessor args to execute ffmpeg ? Commented Mar 31 at 7:46
  • 1
    The first step in any debugging is to print your variables and see if you have what you think you have. So add an echo in from of the various commands there and see what you are really running. Or just add set -x to the top of the script so you can get debugging output. Is everything as you expect? Commented Mar 31 at 10:53
  • @nbamba how so? yt-dlp doesn't accept downloading in .avi format. Commented Apr 1 at 3:33
  • @terdon I did that. All the variables are ok. Even if I hardcode everything but video names, it still breaks. Commented Apr 1 at 3:33

2 Answers 2

Reset to default
4

That error is reported by the check_keyboard_interaction() function in the code, so it looks like it's trying to read from its stdin and trying to interpret things there as further instructions.

Here ffmpeg's stdin is going to be the pipe from jq which ffmpeg should not read from. You'll want to disable stdin interaction with the -nostdin option.

Or instead of doing yt-dlp -j --flat-playlist "$playlist_url" | jq -r '.id' twice and feeding the output the second time to the while loop, you could do something like:

readarray -t list < <(
  yt-dlp -j --flat-playlist "$playlist_url" | jq -r .id
)

(with the caveat that the exit status of yt-dlp and jq are lost)

And then get the count with "${#list[@]}" and loop over them with for video_id in "${list[@]" instead of a while read loop in which case the stdin of ffmpeg will be left unmodified allowing the users to interact with it if they invoke that script from a terminal.

Some other notes about your code:

  • progress messages and other user-intended messages are better sent to stderr, while stdout should be left for the output that your script generates. Not critical here as your script doesn't generate output (it writes its output directly to files by itself). You could use a helper function such as info() { printf>&2 '%s\n' "$@"; } which would also help with:
  • echo can't be used for arbitrary data, use printf instead.
  • You're saying echo Downloaded... or echo Converted... but you're not checking the exit status of the previous commands to check if it was actually downloaded or converted. You should add some || return to the yt-dl / ffmpeg commands.
  • there are missing quotes around some of the parameter expansions.
  • read -r line is not the command to read a line. See Understanding "IFS= read -r line". Likely not an issue here though as you're not modifying $IFS and the things that are read are unlikely to contain characters from the default value of $IFS.
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1

I am not familiar with ffmpeg but from a shell perspective the only obviously possible problem is this:

ffmpeg -i "$output_name.mp4" -c:v copy -c:a $audio_codec -ar $audio_sample_rate \
-b:a $audio_bitrate -ac $audio_channels "$output_name.$output_format"

Change that (adding quotes) to

ffmpeg -i "$output_name.mp4" -c:v copy -c:a $audio_codec -ar $audio_sample_rate \
-b:a "$audio_bitrate" -ac "$audio_channels" "$output_name.$output_format"
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