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• Random Weird HLS generation with ffmpeg

  16 août 2022, par user15006279

  I am doing some live streaming setup for my personal project and I noticed that sometime ffmpeg will not generate any hls auto it was running. I copied the same command and run in shell and it was generating HLS files successfully but somehow it was not generating with nginx.

  


  Enter image description here

  


  

  


  The more weird thing is that if i restart nginx for like a couple of times, it will regenerate. I am only playing youtube video from browser somehow ffmpeg process is not generating hls. Even after a couple of restarts, it will generate sometimes but its random. Mostly not generating at all. Can you guys help me with it ?

  


  image

  


  

  


• 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 ?

  


• 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.