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• ffmpeg segment command flac output broken 'length' metadata

  7 février 2023, par Martin

  I am trying to use this ffmpeg command :

  


  ffmpeg -i "full_lowq.flac" -c copy -map 0 -f segment -segment_times "302.825,552.017" "%03d_output.flac"


  


  to take my flac file input "full_lowq.flac" and split it at specific points 302.825,552.017 into output audio files like so :

  


  %01d_output.flac
%02d_output.flac
%03d_output.flac


  


  And this command does work at the moment, except that my three outputted flac files display the wrong 'length' metadata number when viewed in the win10 file browser. like in this example every outputted file has the same length as 11:16


  


  But if i view the audio files in audacity i can see the correct file length such as file 0 have a length of 05:02

  


  Is it possible my input file (https://file.io/oof3eykKwXiI) is corrupted ? or my command is making a mistake here ? wrong codec ?

  


• ffmpeg command exports flac with wrong 'length' metadata, works fine for mp3

  21 juillet 2023, par Martin

  I have some audio recorded in Audacity 3.2.3 that I have exported as an mp3 and a flac. Then I have this file split_by_silence.sh

  


  Which has hardcoded input path values that take an input file, split it by detecting silence, and then finally run an ffmpeg command to split the files. If you save the below code into a file split.sh, you can call it with the command $ ./split_by_silence.sh "value1" "value2"

  


  # ./split_by_silence.sh "full_lowq.flac" %03d_output.flac
#IN=$1
#OUT=$2

OUT="%03d_output.flac"
IN="/mnt/e/martinradio/rips/vinyl/WIP/Dogs On Fire (1983, Vinyl)/dog on fire.flac"
OUTPUT_LOCATION="/mnt/e/martinradio/rips/vinyl/WIP/Dogs On Fire (1983, Vinyl)/"

true ${SD_PARAMS:="-18dB"};
true ${MIN_FRAGMENT_DURATION:="20"};
export MIN_FRAGMENT_DURATION
if [ -z "$OUT" ]; then
    echo "Usage: split_by_silence.sh full.mp3 output_template_%03d.mp3"
    echo "Depends on FFmpeg, Bash, Awk, Perl 5. Not tested on Mac or Windows."
    echo ""
    echo "Environment variables (with their current values):"
    echo "    SD_PARAMS=$SD_PARAMS       Parameters for FFmpeg's silencedetect filter: noise tolerance and minimal silence duration"
    echo "    MIN_FRAGMENT_DURATION=$MIN_FRAGMENT_DURATION    Minimal fragment duration"
    exit 1
fi
#
# get comma separated list of split points (use ffmpeg to determine points where audio is at SD_PARAMS [-18db] )
#

echo "_______________________"
echo "Determining split points..." >& 2
SPLITS=$(
    ffmpeg -v warning -i "$IN" -af silencedetect="$SD_PARAMS",ametadata=mode=print:file=-:key=lavfi.silence_start -vn -sn  -f s16le  -y /dev/null \
    | grep lavfi.silence_start= \
    | cut -f 2-2 -d= \
    | perl -ne '
        our $prev;
        INIT { $prev = 0.0; }
        chomp;
        if (($_ - $prev) >= $ENV{MIN_FRAGMENT_DURATION}) {
            print "$_,";
            $prev = $_;
        }
    ' \
    | sed 's!,$!!'
)
echo "SPLITS= $SPLITS"

#
# Add 5 seconds to each of the comma separated numbers
#
# Convert the comma-separated string into an array
arr=($(echo $SPLITS | tr ',' '\n'))
# Initialize a new array to store the results
new_arr=()
# Iterate through each element and add 5 seconds of padding
for i in "${arr[@]}"; do
  result=$(echo "$i + 5" | bc -l)
  new_arr+=("$result")
done
# Convert the array back into a comma-separated string
NEW_SPLITS=$(IFS=,; echo "${new_arr[*]}")
# Print the result
echo "NEW_SPLITS= $NEW_SPLITS"
SPLITS=$NEW_SPLITS

#
# Print how many tracks should be exported
#
res="${SPLITS//[^,]}"
CHARCOUNT="${#res}"
num=$((CHARCOUNT + 2))
echo "Exporting $num tracks"
echo "_______________________"

#
# Split audio into individual tracks
#
current_directory=$(pwd)

cd "$OUTPUT_LOCATION"

echo "Running ffmpeg command: "

ffmpeg -i "$IN" -c copy -map 0 -f segment -segment_times "$SPLITS" "$OUT"
#ffmpeg -i "full_lowq.flac" -c copy -map 0 -f segment -segment_times "302.825,552.017" "%03d_output.flac"


echo "Done."

cd $current_directory

echo "running flac command"
# check flac file intrgrity


  


  If I call this code for my flac file :

  


  OUT="%03d_output.flac"
IN="/mnt/e/martinradio/rips/vinyl/WIP/Dogs On Fire (1983, Vinyl)/dog on fire.flac"


  


  The outputted files have an incorrect metadata for the length. They all report as having the same length, but if i import any of them into audacity, the file has a correct length.

  


  

  


  but if i run this for my mp3 file, we can see the correct length metadata :

  


  OUT="%03d_output.mp3"
IN="/mnt/e/martinradio/rips/vinyl/WIP/Dogs On Fire (1983, Vinyl)/dogs on fire.mp3"


  


  

  


  So there is something with my ffmpeg command that causes it to export flac files with wrong 'length' metadata

  


  ffmpeg -i "$IN" -c copy -map 0 -f segment -segment_times "$SPLITS" "$OUT"



  


  I've tried with the flac example to change -c copy to -c:a flac, but that just gives every output flac file a length of 00:00:00

  


  is it a problem with my ffmpeg command ? Or my files ? https://file.io/tIFsa1l70076
it works for mp3 files just fine, why does it have this issue with flac ?

  


• ffmpeg : Make output file duration that of the file with the longest length [closed]

  27 février 2024, par losercantcode

  I'm going crazy trying to figure this out.

  


  Essentially I'm trying to apply sidechain compression using ffmpeg (for the sake of speed and automation). a2.mp3 in this example is the full length track and a1.wav is a short 5 second, spoken-word clip. The code currently applies the sidechain compression well, but the output file is only that of the spoken-word clips length, so 5 seconds. Is it at all possible to make the output match that of a2.mp3's length instead ? Switching around the input order is not something that's possible as it'll apply the compression to the incorrect track.

  


  Essentially, i'm trying to make it so i'm just layering the spoken-word file on top of the audio track without having to pre-pad the file. I'd rather, if it's possible, this just happen with one block of code within the in one program. I'm interested to see if this is at all possible within ffmpeg.

  


  ffmpeg -i a2.mp3 -i a1.wav -filter_complex "[1:a]asplit=2[sc][mix];[0:a][sc]sidechaincompress=threshold=0.000976563:ratio=10:level_sc=0.015625:release=100:attack=10[compr];[compr][mix]amix=duration=longest[aout]" -map "[aout]" output.wav


  


  a1.wav is mon, a2.mp3 is stereo.

  


  Attempted to implement amix=duration=longest to no avail. Research similar problems on the Stack Exchange that gave unrelated answers.