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• avfilter/af_stereowiden : fix read/write past the end of buffer

  12 juillet 2016, par Alexey Tourbin

  avfilter/af_stereowiden : fix read/write past the end of buffer
  The stereowiden filter uses a buffer, s->buffer[], and a pointer
  
  within the buffer, s->write, to implement inter-channel delays.
  
  The loop which applies the delayed samples turns out to be faulty.
     109      for (n = 0 ; n < in->nb_samples ; n++, src += 2, dst += 2) 
  
     110          const float left = src[0], right = src[1] ;
  
     111          float *read = s->write + 2 ;
  
     112
  
     113          if (read > s->buffer + s->length)
  
     114              read = s->buffer ;
  
     115
  
     116          dst[0] = drymix * left - crossfeed * right - feedback * read[1] ;
  
     117          dst[1] = drymix * right - crossfeed * left - feedback * read[0] ;
  
     118
  
     119          s->write[0] = left ;
  
     120          s->write[1] = right ;
  
     121
  
     122          if (s->write == s->buffer + s->length)
  
     123              s->write = s->buffer ;
  
     124          else
  
     125              s->write += 2 ;
  
     126      
  For one, the buffer gets written past its end in lines 119-120, before
  
  the bound check is done in lines 122-123.  This can be easily confirmed
  
  by valgrind.
  ==3544== Invalid read of size 4
  
  ==3544==    at 0x593B41 : filter_frame (af_stereowiden.c:116)
  
  ==3544==  Address 0xb1b03c4 is 4 bytes after a block of size 7,680 alloc’d
  
  ==3544==
  
  ==3544== Invalid read of size 4
  
  ==3544==    at 0x593B66 : filter_frame (af_stereowiden.c:117)
  
  ==3544==  Address 0xb1b03c0 is 0 bytes after a block of size 7,680 alloc’d
  
  ==3544==
  
  ==3544== Invalid write of size 4
  
  ==3544==    at 0x593B79 : filter_frame (af_stereowiden.c:119)
  
  ==3544==  Address 0xb1b03c0 is 0 bytes after a block of size 7,680 alloc’d
  
  ==3544==
  
  ==3544== Invalid write of size 4
  
  ==3544==    at 0x593B7D : filter_frame (af_stereowiden.c:120)
  
  ==3544==  Address 0xb1b03c4 is 4 bytes after a block of size 7,680 alloc’d
  Also, using two separate pointers, s->write and read = s->write + 2,
  
  does not seem to be well thought out.  To apply the delay of s->buffer[],
  
  it is enough to read the delayed samples at the current position within
  
  the buffer, and then to store new samples at the same current position.
  
  Thus the application of delayed samples can probably be best described
  
  with a single pointer s->cur.
  I also introduce a minor change to ensure that the size of s->buffer[]
  
  is always a multiple of 2.  Since the delay parameter is a float, it is
  
  otherwise possible to trick the code into allocating off-by-one buffer.
  

  • [DH] libavfilter/af_stereowiden.c

• avfilter/formats : Remove pointless checks

  11 septembre 2020, par Andreas Rheinhardt

  avfilter/formats : Remove pointless checks
  ff_formats_ref() takes a pointer to an AVFilterFormats and a pointer to
  
  a pointer to an AVFilterFormats as arguments and adds the latter as an
  
  owner to the list pointed to by the former ; the latter is hereby always
  
  the address of a list contained in an AVFilterFormatsConfig and can
  
  therefore not be NULL. So remove the check for whether it is NULL ; also
  
  do the same for ff_channel_layouts_ref().
  Also do the same for the unref functions where argument is never NULL
  
  because it is always the address of an existing lvalue.
  Reviewed-by : Nicolas George <george@nsup.org>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavfilter/formats.c

• "Error opening filters !" when using fluent-ffmpeg with Node

  3 février 2015, par doremi

  I’m trying to get a basic example of html5 video streaming working in an express node app, but I keep running into ffmpeg errors that I’m unsure of how to resolve.

  The input file/stream is the sample.mp4 located here.

  Complete example :

  var ffmpeg = require('fluent-ffmpeg');
  
  var express    = require('express');
  
  var fs         = require('fs');
  
  var sampleApp  = express();
  
  var videoApp   = express();
  
  
  
  var SAMPLE_SERVER_PORT = 3000;
  
  var VIDEO_SERVER_PORT  = 5000;
  
  
  
  sampleApp.get('/:video', function (req, res) {
  
    var videoURL = 'http://localhost:' + VIDEO_SERVER_PORT + '/' + req.params.video;
  
    return res.end('<video controls="controls" src=" + videoURL +"></video>');
  
  });
  
  
  
  videoApp.get('/:video', function(req, res) {
  
  
  
    res.statusCode = 200;
  
    res.setHeader('content-type','video/mp4');
  
  
  
    var stream = fs.createReadStream('./samples/' + req.params.video);
  
  
  
    var proc = ffmpeg(stream)
  
  
  
      .format('mp4')
  
      .size('320x?')
  
      .videoBitrate('512k')
  
      .videoCodec('libx264')
  
      .fps(24)
  
      .audioBitrate('96k')
  
      .audioCodec('aac')
  
      .audioFrequency(22050)
  
      .audioChannels(2)
  
  
  
      .on('error', function(err) {
  
        console.log('an error happened: ' + err.message);
  
      })
  
  
  
      .pipe(res, { end:true });
  
  });
  
  
  
  var server = sampleApp.listen(SAMPLE_SERVER_PORT, function () {
  
    console.log('Example app listening at http://%s:%s', server.address().address, SAMPLE_SERVER_PORT);
  
  });
  
  
  
  
  
  var videoServer = videoApp.listen(VIDEO_SERVER_PORT, function () {
  
    console.log('Video Server listening at http://%s:%s', server.address().address, VIDEO_SERVER_PORT);
  
  });

  The error (via console) :

  an error happened: ffmpeg exited with code 1: Error opening filters!

  ffmpeg configuration :

  ./configure  --prefix=/usr/local --enable-gpl --enable-nonfree --enable-libass \                                                                         
  
  --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus \
  
  --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-libfaac --enable-libfdk-aac

  Any input would be greatly appreciated.