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• How to output a sequence of images in a loop with ffmpeg from rtsp stream

  6 juillet 2017, par The Doctor

  I am reading an RTSP stream from a surveillance camera and want to use ffmpeg to create a snapshot of the camera as jpeg. Principally it works to create a snapshot.jpg using the -update 1 option, but if it happens (what it does very often) that the client application reads the file while ffmpeg writes to it, the image is displayed only partially.

  Hence I want to use ffmpeg to capture more than 1 images in a kind of ring buffer, so I can access the image captured just before the current one and have also the last n images as short history.

  Though ffmpeg allows to create a series of jpgs, this seems infinite. Is it possible to tell ffmpeg to create images in a file pattern like this :

  pic1.jpg, pic2.jpg, pic3.jpg, pic4.jpg, pic5.jpg and after pic5.jpg to start over again using pic1.jpg etc. This way it could consume a stream continuously without filling up my drive. Unfortunately something like -update 5 seems not to work (ffmpeg simply exits).

  Principally I can also let it run infinitely and clean up all files older than n seconds, but that would introduce additional overhead and is IMHO not really clean programming compared to ffmpeg using this kind of ring buffer approach.

  Any help would be appreciated.

• Split a movie so that each GIF is under a certain file size

  9 novembre 2014, par Terence Eden

  Problem

  I want to convert a long movie into a series on animated GIFs.

  Each GIF needs to be <5MB.

  Is there any way to determine how large a GIF will be while it is being encoded ?

  Progress So Far

  I can split the movie into individual frames :

  ffmpeg -i movie.ogv -r 25 frameTemp.%05d.gif

  I can then use convert from ImageMagick to create GIFs. However, I can’t find a way to determine the likely file size before running the command.

  Alternatively, I can split the movie into chunks :

  ffmpeg -i movie.ogv -vcodec copy -ss 00:00:00 -t 00:20:00 output1.ogv

  But I’ve no way of knowing if, when I convert the file to a GIF it will be under 5MB.

  A 10 second scene with a lot of action may be over 5MB (bad !) and a static scene could be under 5MB (not a problem, but not very efficient).

  Ideas

  I think that what I want to do is convert the entire movie into a GIF, then find a way to split it by file size.

  Looking at ImageMagick, I can split a GIF into frames, but I don’t see a way to split it into animated GIFs of a certain size / length.

  So, is this possible ?

• Wildcard for sequential images

  16 septembre 2013, par abalter

  I'm trying to animate a series of jpg files using avconv. Based on numerous examples, I'm trying using %d.jpg to specify the files. Or %05d.jpg. However, I'm getting :

  avconv -i %d.jpg a.avi
  
  avconv version 0.8.3-4:0.8.3-0ubuntu0.12.04.1, Copyright (c) 2000-2012 the Libav developers built on Jun 12 2012 16:37:58 with gcc 4.6.3
  
  %d.jpg: No such file or directory

  Here is a snip of my directory listing :

  10380.jpg
  
  10390.jpg
  
  10400.jpg
  
  1040.jpg
  
  10410.jpg
  
  10420.jpg
  
  10430.jpg
  
  10440.jpg

  There are jpegs from 00000.jpg to 14400.jpg

  I don't really understand that wildcard system, but that is what is in examples.

  (note : I tagged it ffmpeg because a tag for avconv does not exist, and avconv supersedes ffmpeg)

  Update
  I'm updating the question based on the answer below by @av501.

  To begin with, I have a list of png files with sequential ordering by 10. They have text preceding a 5 digit integer. For example :

  SkinMattekNutrient_py_00000.png
  
  SkinMattekNutrient_py_00010.png
  
  SkinMattekNutrient_py_00020.png
  
  ...
  
  SkinMattekNutrient_py_10440.png

  What would be the way to batch convert these to jpg ? I tried

  convert ...
  
  SkinMattekNutrient_py_%05d.png %05d.jpg

  and

  convert ...
  
  SkinMattekNutrient_py_%5d.png %5d.jpg

  But I get :

  convert SkinMattekNutrient_py_%05d.png %05d.jpg
  
  convert: missing an image filename `%05d.jpg' @ error/convert.c/ConvertImageCommand/3011.