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• What are my FFMPEG command wrong parameters that causes ugly quality on streaming ?

  6 juillet 2022, par Lucas FAURE

  Good day, I'm scaling videos with FFMPEG, and when the scaled file comes out, quality is pretty good (enough good for me).

  


  My problem is that I'm as well streaming the file while it's scaling, but it comes in an ugly quality. And I guess it's because of missing or not needed parameters.

  


  Here is my command that starts scaling the file and send it via RTMP for streaming :

  


  "ffmpeg -i " + file + " -vf scale=-2:" + resolution + " -preset slow -crf 18 -movflags +frag_keyframe+separate_moof+omit_tfhd_offset+empty_moov " + output + " -listen 1 -f flv rtmp://127.0.0.1:10000/" + stream + ""


  


  This is called in Python, where file is the source file, resolution the new height, output the file to be saved, and stream a streaming key.

  


  Once the scaling has started, I provide to the user a streaming link with the new resolution :

  


  'ffmpeg -v verbose -i rtmp://127.0.0.1:10000/'.$stream.' -c:v libx264 -c:a aac -ac 1 -strict -2 -crf 18 -profile:v baseline -maxrate 400k -bufsize 1835k -pix_fmt yuv420p -flags -global_header -hls_time 10 -hls_list_size 6 -start_number 1 '.$streamURL.$stream;


  


  Here, it's called with PHP, and there are as well variables : stream the streaming key to retreive the right content, and streamURL the domain to visit.

  


  It actually works but the difference of quality between what is scaling and what is streaming is huge, and I think so that, in the command that creates the streaming link, there is parameters that cause this. (Because I took it from a live example and I didn't want to make an error by removing parameters I don't know well)

  


  Do you have any idea about where it can be coming from ?

  


  Thank you in advance for your help and time.

  


• Video modifications using ffmpeg and bash command

  26 février 2019, par macenike

  I have a series of 8 videos which have different number of frames, some of them lose a couple of them at the beginning. I was trying to concatenate at the beginning of the videos with less frame a copy of their first frame. Unfortunately my code either crash while comparing the length of the videos or fail to accomplish the task required. Here I add the code that I’m using.

  @ECHO off
  
  SETLOCAL EnableDelayedExpansion
  
  MKDIR COMPRESSED\
  
  MKDIR RAW\
  
  SET  j=0
  
  SET  jj=1
  
  SET max=1
  
  FOR %%a IN (*.avi) DO (
  
      SET /A j=j+1
  
      FOR /F "delims=" %%V IN ('ffprobe.exe -v error -count_frames -select_streams v:0 -show_entries stream^=nb_read_frames -of       default^=noprint_wrappers^=1:nokey^=1 ".\%%~nxa" 2^>^&1') DO SET elem[!j!]=%%V
  
  SET elem[!j!]
  
  )
  
  
  
  FOR %%a IN (*.avi) DO (
  
      IF !elem[%jj%]! GTR !elem[%max%]!(
  
          SET max=!jj!
  
      )
  
  SET /A jj=jj+1  
  
  ) 
  
  SET max
  
  
  
  SET /A x=1
  
  FOR %%a IN (*.avi) DO ( 
  
  
  
      IF "!elem[!x!]!" LSS "!elem[!max!]!" (
  
              ffmpeg -i ".\%%~nxa" -vf "select=eq(n\,0)" -q:v 3 output_image.jpg
  
              ffmpeg -y -i ".\%%~nxa" -loop 1 -i output_image.jpg -t 0.01 -s 1936x1216 ".\%%~nxa"
  
              SET elem[!x!]=elem[!x!]+1
  
              SET elem[!x!]                   
  
      )
  
  SET /A x=x+1    
  
  ) 
  
  
  
  
  
  FOR %%a IN (*.avi) DO (
  
      ffprobe -v error -count_frames -select_streams v:0 -show_entries stream=nb_read_frames ".\%%~nxa"
  
      ffmpeg -i ".\%%~nxa" -c:v libxvid -vtag xvid -qscale:v 2 -force_key_frames 1 -s 968x400 -r 100 ".\COMPRESSED\%%a"
  
      SET mystr=%%~na
  
      SET mystr=!mystr:~-1!
  
      IF !mystr! == 3 (
  
          ffmpeg -i ".\%%~nxa" -c:v mpeg4 -b:v 4M -c:a libfdk_aac -b:a 192k ".\COMPRESSED\%%~na.mp4"
  
      )
  
      IF !mystr! == 5 (
  
          ffmpeg -i ".\%%~nxa" -c:v mpeg4 -b:v 4M -c:a libfdk_aac -b:a 192k ".\COMPRESSED\%%~na.mp4"
  
      )
  
  )

• ffmpeg build thumbnail sequence while transcoding

  9 novembre 2018, par Redtopia

  With the goal of improving performance while processing a video file and outputting it into 3 parallel output files, would it be possible to also build a thumbnail sequence as another parallel output or in another process ?

  To create the 3 parallel outputs, I’m following the example on this page : https://trac.ffmpeg.org/wiki/Creating%20multiple%20outputs

  ...and using this example :

  ffmpeg -i input \
  
      -s 1280x720 -acodec … -vcodec … output1 \
  
      -s 640x480  -acodec … -vcodec … output2 \
  
      -s 320x240  -acodec … -vcodec … output3

  My command to generate thumbnails looks like this :

  ffmpeg -f image2 -ss 2 -r "1/3" -s 100x50 ./thumbs/th-%04d.png

  I’m using the ffmpeg 4.1

  What I’m finding is that building a series of thumbnails, say 1 every 10 seconds, can be quite time consuming for large video files, so I’m guessing I could save some processing time if I could build the thumbs at the same time.