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• ffmpeg video and audio duration differ

  30 décembre 2014, par biorad

  I am converting a jpg picture and an mp3 audio into a video, like so :

  ffmpeg -y -loop 1 -i pics\jam_03.jpg -i mp3\jam_03.mp3 -shortest -c:v mpeg4 -b:v 4000k -c:a libmp3lame jam_03.mp4

  When concatenating several of such videos to one (a narrated presentation) like this :

  ffmpeg -i "concat:jam_00.avi|jam_01.avi|jam_02.avi|jam_03.avi|jam_04.avi|jam_05.avi|jam_06.avi|jam_07.avi|jam_08.avi" -c:v copy -c:a copy out.mp4 -y

  video and audio successively get out of sync. Indeed using ffprobe

  ffprobe -show_streams jam_03.avi

  different length are shown for video and audio e.g. 5.12 and 5.19 sec.
  I have tried a lot : x264 and aac codecs instead of the above ones, avi or mp4 container format, cutting the video using -t 5.12, also several variants of audio and video synchronisation (-async 1, -async 25, -async 100, -vsync 1, -vsync 2, ...) all yield more or less the same. My idea is that each video frame is 1/25 sec long and audio must be multiple of this. However, 5.12sec (=multiple of 1/25sec) shows no success.

  Any ideas ?

  thanks

• Real time stereo video stream. How to start

  29 juin 2015, par victor jung

  Here is my problem :

  I have at one side two webcams plugged in a linux computer, and on the other side, an android smartphone. My goal is to program a real time stream of the 2 webcams, and display that stream on the smartphone (to be used in a google cardboard mask). I read quite a lot on the subject, and I found several way to achieve this.

  First there is ffmpeg, which could encode and stream.

  But I need to modify the pictures at some point, to re-size them / or to ad some kind of distortion. So I thought it would be great if I can get the 2 images, with openCv maybe, playwith them, build a new one, and stream them, but how could ffmpeg deal with the newly created image ?

  The other option would be to get the 2 pics and play with them with openCv too, but then, hardcode a stream over, UDP in RTP style, but wouldnt be hard to display the stream nicely on the phone ?, and how to cut the image to fit in small packets ?

  Thanks for your help, I am still digging in the subject, so if you have any other way to do it I am taking !

  ps : My introducing Hello, won’t stay at the beginning of my message...
  Have a nice day every body.
  d-4 before frieday.

• ffserver : local OOB write with custom program name

  6 janvier 2017, par Tobias Stoeckmann

  ffserver : local OOB write with custom program name
  When the command line for children is created, it is assumed that
  
  my_program_name always ends with "ffserver", which doesn’t have to
  
  be true if ffserver is called through a symbolic link.
  In such a case, it could be that not enough space for "ffmpeg" is
  
  available at the end, leading to a buffer overflow.
  One example would be :
  $ ln -s /usr/bin/ffserver /f ; /f
  As this is only a local buffer overflow, i.e. is based on a weird
  
  program call, this has NO security impact.
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] ffserver.c