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• WebM Semantic Video Demo

  18 août 2010, par noreply@blogger.com (John Luther)

  Brett Gaylor at WebMadeMovies has posted an HTML5 demo of popcorn.js, “a javascript library for manipulating open video on the web.” The demo plays a video while using semantic data in the video to trigger machine-translated subtitles, map lookups, Twitter feeds and other elements on the page. If you’re using a WebM-enabled browser the page serves a WebM video, otherwise it serves an Ogg or MP4 video depending on the browser’s capabilities.

  See Brett’s post or the popcorn.js wiki page for more info. You can also download the source from the Mozilla github repo.

  

• ffplay - how to have video and audio waveform [duplicate]

  19 février 2018, par francis

  This question already has an answer here :

  • ffplay / ffmpeg setup table with audio and video filters
    
    1 answer
    

  I’ve been trying out various commands trying to figure out how to have a stack of video and audio waveform according to : https://trac.ffmpeg.org/wiki/FancyFilteringExamples#waveform

  Video only :

  ffplay -i abc.mp4 -vf "split[a][b];[a]waveform=e=1,split=1[c];[c]crop=in_w:16:0:0,lutyuv=y=val:v=180[high]; [b][high]vstack=2"

  Audio only :

  ffplay -f lavfi 'amovie=april.flac,asplit=2[out1][a]; [a]showwaves=s=640x240[waves]; [waves] vstack[out0]'

  But there isn’t any that combines and shows the top half as video and bottom half as the audio waveform. Is it possible ?

• How to stop perl buffering ffmpeg output

  4 février 2017, par Sebastian King

  I am trying to have a Perl program process the output of an ffmpeg encode, however my test program only seems to receive the output of ffmpeg in periodic chunks, thus I am assuming there is some sort of buffering going on. How can I make it process it in real-time ?

  My test program (the tr command is there because I thought maybe ffmpeg’s carriage returns were causing perl to see one big long line or something) :

  #!/usr/bin/perl
  
  
  
  $i = "test.mkv"; # big file, long encode time
  
  $o = "test.mp4";
  
  
  
  open(F, "-|", "ffmpeg -y -i '$i' '$o' 2>&1 | tr '\r' '\n'")
  
          or die "oh no";
  
  
  
  while(<f>) {
  
          print "A12345: $_"; # some random text so i know the output was processed in perl
  
  }
  
  </f>

  Everything works fine when I replace the ffmpeg command with this script :

  #!/bin/bash
  
  
  
  echo "hello";
  
  
  
  for i in `seq 1 10`; do
  
          sleep 1;
  
          echo "hello $i";
  
  done
  
  
  
  echo "bye";

  When using the above script I see the output each second as it happens. With ffmpeg it is some 5-10 seconds or so until it outputs and will output sometimes 100 lines each output.

  I have tried using the program unbuffer ahead of ffmpeg in the command call but it seems to have no effect. Is it perhaps the 2>&1 that might be buffering ?
  Any help is much appreciated.

  If you are unfamiliar with ffmpeg’s output, it outputs a bunch of file information and stuff to STDOUT and then during encoding it outputs lines like

  frame=  332 fps= 93 q=28.0 size=     528kB time=00:00:13.33 bitrate= 324.2kbits/s speed=3.75x

  which begin with carriage returns instead of new lines (hence tr) on STDERR (hence 2>&1).