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• Fast seeking ffmpeg multiple times for screenshots

  7 mars 2017, par user3786834

  I have come across http://askubuntu.com/questions/377579/ffmpeg-output-screenshot-gallery/377630#377630, it’s perfect. That has done exactly what I wanted.

  However, I’m using remote URLs to generate the screenshot timeline. I do know it’s possible to fast seek with remote files using https://trac.ffmpeg.org/wiki/Seeking%20with%20FFmpeg (using -ss before the -i) but this only runs the once.

  I’m looking for a way to use the

  ./ffmpeg -i input -vf "select=gt(scene\,0.4),scale=160:-1,tile,scale=600:-1" \
  
  -frames:v 1 -qscale:v 3 preview.jpg

  command but using the fast seek method as it’s currently very slow when used with a remote file. I use PHP but I am aware that a C method exists by using av_seek_frame, I barely know C so I’m unable to implement this into a PHP script I’m writing. So hopefully, it is possible to do this directly with ffmpeg in the PHP system() function.

  Currently, I run seperate ffmpeg commands (with the -ss method) and then combine the screenshots together in PHP. However, with this method it will be refetching the metadata each time and a more optimized method would be to have it all happen in the same command line because I want to reduce the amount of requests made to the remote url so I can run more scripts in sequence with each other.

  Thank you for your help.

• Insert Random silence multiple times between Audios in ffmpeg

  23 septembre 2021, par Gracie williams

  suppose I have MP3 of around 1 minute duration and increase its duration longer.Duration can be any.

  


  I want to randomly add N seconds of silence to that audio.

  


  I can generate the silence like below

  


  ffmpeg -f lavfi -i anullsrc=r=44100:cl=mono -t <seconds> -q:a 9 -acodec libmp3lame out.mp3&#xA;</seconds>

  


  And I can insert silence to audio like below

  


  ffmpeg -i in.wav -filter_complex "anullsrc,atrim=0:4[s];[0]atrim=0:14[a];[0]atrim=14,asetpts=N/SR/TB[b];[a][s][b]concat=3:v=0:a=1" out.wav


  


  Is there anyway to insert silence at multiple areas.With php I can generate random time to insert based on 60 seconds audio like below.

  


  $arr = [];
$arr[3] = 2; //here 3 is original audio insert time and 2 is the duration of silence
$arr[6] = 3;  //here 6 is original audio insert time and 3 is the duration of silence
$arr[10] = 1;
$arr[12] = 3;


  


  Now I want to insert silence between seconds based on above array like

  


  2 seconds silence at 3rd second
3 seconds silence at 6th second
1 second silence at 10th second


  


  and son on..

  


• Can't use ffmpeg 3.2 in Android project

  21 novembre 2016, par world2ashish

  Tried almost everything, spent almost 4-5 days trying and still counting.

  The reason I want to compile recent version of ffmpeg is because https://github.com/WritingMinds/ffmpeg-android-java doesn’t work for video rotation. For this also I tried multiple answers, different versions of answer (transpose=1, transpose=dir=cclock, etc)

  Somewhere it was mentioned that rotate command wont work with previous versions of ffmpeg, so after a lot of trials, I started working on compilation of new ffmpeg. But all the tutorials for ffmpeg belong to earlier versions (of Android NDk, ffmpeg) which wont work with ffmpeg 3.2 and NDK r13b (I also tried with NDK downloaded by studio itself but no luck). In case it worked for you, please help.

  After a lot of frustrating experience I am writing this. Please help with a workflow or a clear direction. Thanks

  Wasnt able to tag ffmpeg3.2 because of reputation.