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• Understanding a script which uses ffmpeg to send rtmp input to node.js script

  4 juin 2022, par Arpit Shukla

  I was trying to understand this shell script which uses ffmpeg to take an rtmp input stream and send it to a node.js script. But I am having trouble understanding the syntax. What is going on here ?

  


  The script :

  


  while :
do
  echo "Loop start"

  feed_time=$(ffprobe -v error -show_entries format=start_time -of default=noprint_wrappers=1:nokey=1 $RTMP_INPUT)
  printf "feed_time value: ${feed_time}"

  if [ ! -z "${feed_time}" ]
  then
  ffmpeg -i $RTMP_INPUT -tune zerolatency -muxdelay 0 -af "afftdn=nf=-20, highpass=f=200, lowpass=f=3000" -vn -sn -dn -f wav -ar 16000 -ac 1 - 2>/dev/null | node src/transcribe.js $feed_time

  else
  echo "FFprobe returned null as a feed time."
  
  fi

  echo "Loop finish"
  sleep 3
done


  


  

  • What is feed_time here ? What does it represent ?

  


  • What is this portion doing - 2>/dev/null | node src/transcribe.js $feed_time ?

  


  • What is the use of sleep 3 ? Does this mean that we are sending audio stream to node.js in chuncks of 3 seconds ?

  


  


• FFmpeg can 'encode' to mp3, but will not accept an 'input' mp3

  21 novembre 2011, par Jonathan Coe

  FYI : Fedora 8 running on Amazon EC2...

  Having a difficult time with FFmpeg doing a (what should be pretty simple) conversion. I can get FFmpeg to encode an mp3 file from an m4a file using the following :

  ffmpeg -i file1.m4a -acodec libmp3lame -ab 160k file2.mp3

  However, I cannot get it to to convert an mp3 -> mp3, it responds with "Unknown Format" using the following :

  ffmpeg -i file1.mp3 -acodec libmp3lame -ab 160k file2.mp3

  I get the following command string :

  FFmpeg version UNKNOWN, Copyright (c) 2000-2008 Fabrice Bellard, et al.
  
  
  
  
  
  configuration: --prefix=/usr --libdir=/usr/lib --shlibdir=/usr/lib --mandir=/usr/share/man --incdir=/usr/include/ffmpeg --enable-libmp3lame --enable-libvorbis --enable-libtheora --enable-libfaad --enable-libfaac --enable-libgsm --enable-libxvid --enable-libx264 --enable-liba52 --enable-liba52bin --enable-pp --enable-shared --enable-pthreads --enable-gpl --disable-strip
  
    libavutil version: 49.6.0
  
    libavcodec version: 51.50.1
  
    libavformat version: 52.7.0
  
    libavdevice version: 52.0.0
  
    built on Feb 14 2008 17:47:08, gcc: 4.1.2 20070925 (Red Hat 4.1.2-33)
  
  file1.mp3: Unknown format

  Any help would be hugely appreciated !

  Edit for clarity :
  The input file is in /ebs/queue/input.mp3 and the output is /ebs/converted/output.mp3

• What's the best FFMPEG method for frequent, automated compilation of timelapse videos ?

  5 août 2020, par GoOutside

  I have a web application running on a not-particularly beefy Ubuntu Amazon Lightsail instance that uses FFMPEG to build a timelapse video generated from downloaded .jpg webcam photos taken every 2 minutes throughout the day (720 total images each day, which grows throughout the day as new images are downloaded).

  


  The code I'm running every 20 minutes is this :

  


  ffmpeg -y -r 24 -pattern_type glob -I 'picturefolder/*.jpg' -s 1024x576 -vcodec libx264 picturefolder/timelapse.mp4

  


  This mostly works, but it is often quite slow, taking 30-60 seconds to run and getting slower as the day goes on, of course.

  


  Recently, I tried to use concat instead of globbing the entire folder over and over. I did not see a noticeable performance improvement, ass it appears the concat processes the entire video in order to add even just a few frames to the end of it.

  


  My question for any FFMPEG experts out there : what is the most efficient way to handle this kind of automated timelapse creation, given my setup ? Is there a flag I'm missing ? Perhaps a different, more efficient method ? Or maybe a way to have the FFMPEG process just crawl through this at a more 'slow and steady' pace instead of big bursts of CPU usage.

  


  Or am I stuck with this and should just deal with it ? My ultimate goal would be to continue using my current tier (2 GB RAM, 1 vCPU) without the expense of upgrading. Thank you very kindly for your help !