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• apply ffmpeg to many files

  30 juillet 2015, par puchu

  I have written simple script :

  #!/bin/bash
  
  find . -name "*.m4a" | while read filename;
  
  do
  
      new_filename=$(echo "$filename" | sed "s/^\(.*\)m4a$/\1flac/g");
  
      if [ ! -f "$new_filename" ]
  
      then
  
              #ffmpeg -i "$filename" -acodec flac "$new_filename" > /dev/null 2>&1;
  
              #wait $!;
  
              echo "$filename";
  
              echo "$new_filename";
  
      fi
  
  done

  it outputs correct result :

  ./Equilibrium, ALAC [GER] viking.folk/2003 - Demo 2003, ALAC/04 - Met.m4a
  
  ./Equilibrium, ALAC [GER] viking.folk/2003 - Demo 2003, ALAC/04 - Met.flac
  
  ./Equilibrium, ALAC [GER] viking.folk/2003 - Demo 2003, ALAC/02 - Nach Dem Winter.m4a
  
  ./Equilibrium, ALAC [GER] viking.folk/2003 - Demo 2003, ALAC/02 - Nach Dem Winter.flac

  if uncomment ffmpeg and wait :

  ./Equilibrium, ALAC [GER] viking.folk/2003 - Demo 2003, ALAC/04 - Met.m4a
  
  ./Equilibrium, ALAC [GER] viking.folk/2003 - Demo 2003, ALAC/04 - Met.flac
  
  uilibrium, ALAC [GER] viking.folk/2003 - Demo 2003, ALAC/02 - Nach Dem Winter.m4a
  
  uilibrium, ALAC [GER] viking.folk/2003 - Demo 2003, ALAC/02 - Nach Dem Winter.flac

  And no flacs has been done !

  PS

  #!/bin/bash
  
  find . -name "*.m4a" | while read filename;
  
  do
  
      new_filename=$(echo "$filename" | sed "s/^\(.*\)m4a$/\1flac/g");
  
      if [ ! -f "$new_filename" ]
  
      then
  
              ffmpeg -i "$filename" -acodec flac "$new_filename";
  
              echo "$filename";
  
              echo "$new_filename";
  
      fi
  
      sleep 5;
  
  done

  1) encode start but suddenly stop with no error messages

  2) encode couldn’t start because of "uilibrium" instead of "./Equilibrium"

  3) = 1)

  4) = 2)

  ...

  last) correctly

• Split mp4 video from URL (stored on AWS s3) with ffmpeg without re-encode, causes an issue with the start point

  25 avril 2023, par DArkO

  I am building an API endpoint as part of which i am signing an AWS s3 url to a video file encoded with mp4, then using ffmpeg to split the provided video by url to a time range (for example from second 4.0 to second 12.0), and pipe it to a stream which is directly returned to the user.

  


  I am running into an issue where the video is split starting on the 10 second mark. In the command below it is splitting from 0-14 sec instead of 6-14. if i specify 12-18 it will split from 10-18 etc..

  


  As part of this process this is the ffmpeg command i am using to split the video (omitting the full signed S3 url and writing to a file instead of a pipe).

  


  ffmpeg -protocol_whitelist file,http,https,tcp,tls,crypto -ss 6.0 -to 14.0 -i https://XXXXXXXX.s3.amazonaws.com/stopwatch.mp4 -movflags +frag_keyframe+separate_moof+omit_tfhd_offset+empty_moov -f mp4 -c copy output.mp4


  


  If i try to re-encode the video instead of using -c copy splitting works perfectly well, but is quite a lot slower.

  


  This is the command i use to initially encode the videos and make them uniform as I upload them to AWS S3. I can control the encoding process and change if needed to be able to do the splits correctly.

  


  ffmpeg -i video.mp4 -vf scale=1280:-2 -c:v libx264 -movflags faststart -preset slow -crf 24 -r 25 -c:a aac -b:a 128k


  


  From the ffmpeg docs :

  


  -ss position (input/output)
When used as an input option (before -i), seeks in this input file to position. Note that in most formats it is not possible to seek exactly, so ffmpeg will seek to the closest seek point before position. When transcoding and -accurate_seek is enabled (the default), this extra segment between the seek point and position will be decoded and discarded. When doing stream copy or when -noaccurate_seek is used, it will be preserved.


  


  So this looks like intended behaviour, I also found out that mp4 will have IFrames set on every 10 seconds (250 frames on 25fps in my case) where the fastseek (-ss) option will seek on remote videos to the nearest Iframe and use that as a starting point.

  


  Is there a way to change this behavior ? Add IFrames to at least 1 second so i can split accurately at least to 1 second ? If so are there any drawbacks to doing that ? Is there another option to avoid re-encoding the segments ?

  


  I was thinking i can do multiple splits and a concat where i split-re-encode 6-10sec then split-copy 10-14 then concat the 2 segments to get 6-14sec video.

  


  What i find strange is that with the same video provided as a local file reference to ffmpeg it splits it correctly if i simply do :

  


  ffmpeg -ss 6.0 -to 14.0 -i stopwatch.mp4 -c copy output.mp4


  


• Using ffmpeg with Flash Media Server and HDS

  20 avril 2012, par Jonathan

  I want to use ffmpeg to encode and publish a live stream to Flash Media Server. In order to support iOS devices, I need to implement HTTP Live Streaming as well. The video needs to be in H.264 format and the audio should be AAC. I don't have much experience working with ffmpeg, and I'm having a hard time getting this to work. This is the command that I've tried (and some variations as well) :

  ffmpeg.exe -threads 15 -f dshow -i video="USB2.0 UVC WebCam":audio="Microphone (Realtek High Defini" \
  
        -map_channel 0.1.1 -r 24 -acodec libvo_aacenc -ar 22050 -ab 128k -vcodec libx264 \
  
        -s vga -vb 100k -f flv "rtmp:///livepkgr/livestream1?adbe-live-event=liveevent" \
  
        -r 24 -acodec libvo_aacenc -ar 22050 -ab 128k -vcodec libx264 -s qvga -vb 200k \
  
        -f flv "rtmp:///livepkgr/livestream2?adbe-live-event=liveevent" \
  
        -r 24 -acodec libvo_aacenc -ar 22050 -ab 128k -vcodec libx264 -s vga -vb 350k 
  
        -f flv "rtmp:///livepkgr/livestream3?adbe-live-event=liveevent"

  When I run this, it appears to connect to FMS, but then I get a lot of error messages about dropped frames - I'm not sure if ANY frames get encoded successfully. My CPU usage is very high as well. I get a 404 error from FMS when I enter the URL of the *.m3u8 file for one of the individual streams (the main livestream.m3u8 file is accessible though). I have also tried outputting to a file instead of FMS, with no success. All I get is some very garbled sound and no video.

  Any suggestions for what options/commands I should use to get this working ? Is anyone using ffmpeg with FMS to do HTTP Dynamic Streaming / HLS with MP4 video ? I've been struggling to get HDS/HLS working for some time now, and any help would be much appreciated ! It shouldn't make a difference, but I'm using FMS on Amazon EC2 with their AMI image.

  Thanks !