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• How to shrink/expand a video file length in UNIX

  26 mars 2015, par Maria Feena

  I need to shrink/expand a video file (mp4, avi) length using command line tools,

  say the original file have 1 min length and output file should have length of 1:10 min or 0:50 min. I would like to keep other aspects of the video as it is.

  I would like to do same thing on mp3 file too. there are many files so I need to do it all in command line only.

  help me please.

• mov : Fix handling of zero-length metadata values

  15 décembre 2014, par Martin Storsjö

  mov : Fix handling of zero-length metadata values
  Since 3cec81f4d4, a zero-length metadata value would try to
  
  allocate 2*0 bytes, where av_malloc() returns NULL.
  Always add one to the allocated length, to allow space for
  
  a null terminator in the zero-length case.
  Incidentally, this fixes fate-alac on RVCT 4.0, where a compiler
  
  bug seems to mess up the mov muxer to the point that it writes
  
  the wrong sort of metadata. Previously this bug was undetected,
  
  but since 3cec81f4d4 such mov files started returning
  
  AVERROR(ENOMEM) in the mov demuxer.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavformat/mov.c

• Script doesnt recognize bars / length right for cutting audio , ffmpeg terminal

  14 avril 2024, par totzillarbeats

  This terminal script doesn't recognize bars / length right for cutting audio, maybe somebody knows what's wrong with the calculation ...

  


  Would be happy about any help the cutting already works !

  


  #!/bin/bash

# Function to extract BPM from filename

get_bpm() {
    local filename="$1"
    local bpm=$(echo "$filename" | grep -oE '[0-9]{1,3}' | head -n1)
    echo "$bpm"
}

# Function to cut audio based on BPM
cut_audio() {
    local input_file="$1"
    local bpm="$2"
    local output_file="${input_file%.*}_cut.${input_file##*.}" # Appends "_cut" to original filename

    # Define the number of beats per bar (assuming 4 beats per bar)
    beats_per_bar=4

    # Calculate the duration of each bar in seconds
    bar_duration=$((60 * beats_per_bar / bpm))

    # Define start and end times for each bar range
    start_times=(0 21 33 45 57 69 81 93 105 117 129 141)
    end_times=(20 29 41 53 65 77 89 101 113 125 137 149)

    # Iterate through each bar range
    for ((i = 0; i < ${#start_times[@]}; i++)); do
        start_time=${start_times[$i]}
        end_time=${end_times[$i]}
        echo "Cutting audio file $input_file at $bpm BPM for bar $((i + 1)) ($start_time-$end_time) for $bar_duration seconds..."

        # Cut audio for current bar range using ffmpeg
        ffmpeg -i "$input_file" -ss "$start_time" -to "$end_time" -c copy "$output_file"_"$((i + 1)).${input_file##*.}" -y
    done

    # Check if the output files are empty and delete them if so
    for output_file in "${output_file}"_*; do
        if [ ! -s "$output_file" ]; then
            echo "Output file $output_file is empty. Deleting..."
            rm "$output_file"
        fi
    done

    echo "Audio cut and saved as $output_file"
}


# Main script
if [ "$#" -eq 0 ]; then
    echo "Usage: $0 [audio_file1] [audio_file2] ..."
    exit 1
fi

for file in "$@"; do
    bpm=$(get_bpm "$file")
    if [ -z "$bpm" ]; then
        echo "Error: No BPM found in filename $file"
    else
        cut_audio "$file" "$bpm"
    fi
done


  


  Maybe its only the math calc in the beginning but idk :)

  


  If you need more details just lmk