Recherche avancée

Sur d’autres sites (10360)

• avfilter/formats : Fix heap-buffer overflow when merging channel layouts

  13 août 2020, par Andreas Rheinhardt

  avfilter/formats : Fix heap-buffer overflow when merging channel layouts
  The channel layouts accepted by ff_merge_channel_layouts() are of two
  
  types : Ordinary channel layouts and generic channel layouts. These are
  
  layouts that match all layouts with a certain number of channels.
  
  Therefore parsing these channel layouts is not done in one go ; instead
  
  first the intersection of the ordinary layouts of the first input
  
  list of channel layouts with the ordinary layouts of the second list is
  
  determined, then the intersection of the ordinary layouts of the first
  
  one and the generic layouts of the second one etc. In order to mark the
  
  ordinary channel layouts that have already been matched as used they are
  
  zeroed. The inner loop that does this is as follows :
  for (j = 0 ; j < b->nb_channel_layouts ; j++) 
  
      if (a->channel_layouts[i] == b->channel_layouts[j]) 
  
          ret->channel_layouts[ret_nb++] = a->channel_layouts[i] ;
  
          a->channel_layouts[i] = b->channel_layouts[j] = 0 ;
  
      
  
  
  (Here ret->channel_layouts is the array containing the intersection of
  
  the two input arrays.)
  Yet the problem with this code is that after a match has been found, the
  
  loop continues the search with the new value a->channel_layouts[i].
  
  The intention of zeroing these elements was to make sure that elements
  
  already paired at this stage are ignored later. And while they are indeed
  
  ignored when pairing ordinary and generic channel layouts later, it has
  
  the exact opposite effect when pairing ordinary channel layouts.
  To see this consider the channel layouts A B C D E and E D C B A. In the
  
  first round, A and A will be paired and added to ret->channel_layouts.
  
  In the second round, the input arrays are 0 B C D E and E D C B 0.
  
  At first B and B will be matched and zeroed, but after doing so matching
  
  continues, but this time it will search for 0, which will match with the
  
  last entry of the second array. ret->channel_layouts now contains A B 0.
  
  In the third round, C 0 0 will be added to ret->channel_layouts etc.
  
  This gives a quadratic amount of elements, yet the amount of elements
  
  allocated for said array is only the sum of the sizes of a and b.
  This issue can e.g. be reproduced by
  
  ffmpeg -f lavfi -i anullsrc=cl=7.1 \
  
   af 'aformat=cl=mono|stereo|2.1|3.0|4.0,aformat=cl=4.0|3.0|2.1|stereo|mono' \
  
   f null -
  The fix is easy : break out of the inner loop after having found a match.
  Reviewed-by : Nicolas George <george@nsup.org>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavfilter/formats.c

• How to read percentage from ffmpeg command in java ?

  23 juillet 2019, par Prasab R

  I am trying to convert video file to specific format by executing ffmpeg command. In that process I want to read percentage by using timepattern format. Somehow I am not able to do it.

  I have tried using the below code. Specially I am getting null in the while loop condition.

  import java.io.*;
  
  import java.util.Scanner;
  
  import java.util.regex.Pattern;
  
  
  
  class Test {
  
    public static void main(String[] args) throws IOException {
  
      ProcessBuilder pb = new ProcessBuilder("ffmpeg","-i","in.webm","out.mp4");
  
      final Process p = pb.start();
  
  
  
      new Thread() {
  
        public void run() {
  
  
  
          Scanner sc = new Scanner(p.getErrorStream());
  
  
  
          // Find duration
  
          Pattern durPattern = Pattern.compile("(?<=Duration: )[^,]*");
  
          String dur = sc.findWithinHorizon(durPattern, 0);
  
          if (dur == null)
  
            throw new RuntimeException("Could not parse duration.");
  
          String[] hms = dur.split(":");
  
          double totalSecs = Integer.parseInt(hms[0]) * 3600
  
                           + Integer.parseInt(hms[1]) *   60
  
                           + Double.parseDouble(hms[2]);
  
          System.out.println("Total duration: " + totalSecs + " seconds.");
  
  
  
          // Find time as long as possible.
  
          Pattern timePattern = Pattern.compile("(?<=time=)[\\d.]*");
  
          String match;
  
          while (null != (match = sc.findWithinHorizon(timePattern, 0))) {
  
            double progress = Double.parseDouble(match) / totalSecs;
  
            System.out.printf("Progress: %.2f%%%n", progress * 100);
  
          }
  
        }
  
      }.start();
  
  
  
    }
  
  }

  I am expecting a value in the while condition, but it coming as null.enter code here

• dashenc : Write segment timelines properly if the timeline has gaps

  28 novembre 2014, par Martin Storsjö

  dashenc : Write segment timelines properly if the timeline has gaps
  Write a new start time if the duration of the previous segment
  
  didn’t match the start of the next one. Check that segments
  
  actually are continuous before writing a repeat count.
  This makes sure timestamps deduced from the timeline actually
  
  match the real start timestamp as written in filenames (if
  
  using a template containing $Time$).
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavformat/dashenc.c