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• Crontab task scheduled every hour stops running from 11am to 12am

  11 août 2019, par technik

  I have a rather weird issue. My aim is to use ffmpeg to grab a screenshot from a home CCTV cameras rtsp stream every hour. I want to do this in order to make a timelapse. However everyday from 11am to 12am (the next day) there are no snapshots saved.

  On an always on Debian machine, this is the shell script I have that crontab calls :

  dt=$(date +"%d%m%2y%I%M%S")
  
  ffmpeg -rtsp_transport tcp -i "rtsp://IP:554/..." -frames 1 /user/snapshots/ch1/$dt.jpg

  Running it by itself works fine and saves a jpg snapshot successfully to the right folders.

  In crontab -e I have the following line :
  0 * * * * /bin/sh //user/snap.sh

  Thanks.

• FFmpeg : crossfading audio with multiple files, but works with video only

  12 février 2024, par JayCravens

  I've found this script that cross-fade's all mp4's in the directory. If I try to add the audio with AUDIO="[0:a]afade=d=1[a0];", using the same iteration, it doesn't work.

  


  This works fine...

  


  #!/bin/bash

CMD="ffmpeg"
FILES=(*.mp4)
SIZE=${#FILES[@]}
VIDEO=""
OUT=""

i="0"
total_duration="0"
for file in "${FILES[@]}"; do
  echo "$file"
  CMD="$CMD -i '$file'"

  duration=$(ffprobe -v error -select_streams v:0 -show_entries stream=duration -of csv=p=0 "$file" | cut -d'.' -f1)

  if [[ "$i" == "0" ]]
  then
    VIDEO="[0:v]setpts=PTS-STARTPTS[v0];"
  else
    fade_start=$((total_duration))
    VIDEO="${VIDEO}[${i}:v]format=yuva420p,fade=in:st=0:d=1:alpha=1,setpts=PTS-STARTPTS+(${fade_start}/TB)[v${i}];"
    if (( i < SIZE-1 ))
    then
      if (( i == 1 ))
      then
        OUT="${OUT}[v0][v1]overlay[outv1];"
      else
        OUT="${OUT}[outv$((i-1))][v${i}]overlay[outv${i}];"
      fi
    else
      if (( SIZE == 2 ))
      then
        OUT="${OUT}[v0][v1]overlay,format=yuv420p[outv]"
      else
        OUT="${OUT}[outv$((i-1))][v${i}]overlay,format=yuv420p[outv]"
      fi
    fi
  fi

  total_duration=$((total_duration+duration))

  i=$((i+1))
done

CMD="$CMD -filter_complex \"${VIDEO}${OUT}\" -c:v libx264 -preset ultrafast -map [outv] crossfade.mp4"

echo "$CMD"

bash -c "$CMD"


  


  I read acrossfade requires 32bit little endian, so I went to afade.
  It didn't change anything.

  


  I've got this working via fade in/out, for any number of files, with working audio. I still have to preprocess the audio sections which require fading.

  


  #!/bin/bash

if [ -e *.mkv ]; then
  file_type=".mkv"
else
  file_type=".mp4"
fi

mkdir ./temp
for file in *$file_type; do mv "$file" "in_$file"; done

# Function to fade in video
function fade_in() {
file_list1=(in_*)
  echo "Executing fade_in"
  for file in "${file_list1[@]}"; do
    ffmpeg -i "$file" -y -vf fade=in:0:30 -hide_banner -preset ultrafast "out_$file"
  done
mv in_* ./temp
}
export -f fade_in

# Function to fade out video
function fade_out() {
  file_list2=(out_*)
  echo "Executing fade_out"
  for file in "${file_list2[@]}"; do
    frame_count=$(ffmpeg -i $file -map 0:v:0 -c copy -f null -y /dev/null 2>&1 | grep -Eo 'frame= *[0-9]+ *' | grep -Eo '[0-9]+' | tail -1)
      frame_start=$((frame_count - 30))
      ffmpeg -i "$file" -y -vf fade=out:"$frame_start":30 -hide_banner -preset ultrafast "to_mux_$file"
  done
  mv out_* ./temp
}

export -f fade_out

bash -c "fade_in"
bash -c "fade_out"

ls --quoting-style=shell-always -1v *$file_type > tmp.txt
sed 's/^/file /' tmp.txt > list.txt && rm tmp.txt

ffmpeg -f concat -safe 0 -i list.txt -c copy -shortest -movflags +faststart fade_muxed$file_type

mv to_mux_* ./temp
rm list.txt
#rm -rf ./temp

exit 0


  


  Number the file name's sequentially (i.e. 01_file.mkv 02_file.mkv etc.), to ensure order, or it will be up to the directory sort. Using ls --quoting-style=shell-always -v1 has proved very reliable. It should handle 99% of naming conventions.

  It's not a cross fade, but the two second transition is very close. With working and synchronized audio.
If you have a good multi-file concatenation method that includes audio cross-fading, I'm still looking.

  


  Ed Morton, I completely agree, sir. One-hundred percent. I didn't write the first script. I would NEVER use capitals. They're horrible. I "like_full_words" with _'s. Never for any reason other than visual though, so that was a great read, I recommend it.

  


• ffmpeg incorrectly adds a fixed delay to the end of each video chunk

  13 janvier 2023, par Skyler

  I am trying to combine audio a video data to output as an mp4 file using the command below, the videos are segmented to match the exact length of the audio file they are going to be merged with :

  


      command = 'ffmpeg -y -i {} -i {} -strict -2 -q:v 1 {} -loglevel {} -c:v h264_nvenc'.format(
        audio_file, temp_result_avi, outfile, self.ffmpeg_loglevel
    )
    subprocess.call(command, shell=True)


  


  however each video made by this is exactly 24 ms longer so this causes large delays as they get stitched back together. This doesnt work since the combined video needs to be combined back with another video and the desync gets worse as you get further in the combined videos.

  


  How can I remedy this ?