title: FFmpeg.js Extract images (jpeg/png) from MP4 file
body: <p>I'm trying to extract images/frames from a mp4 on client side with the help of <a href="https://github.com/Kagami/ffmpeg.js" rel="nofollow noreferrer">ffmpeg.js</a>. </p>
  
  <p><strong><em>Equivalent Ffmpeg command:</em></strong> </p>
  
  <blockquote>
    <p>ffmpeg -i Sample.mp4 -r 1 output%d.png</p>
  </blockquote>
  
  <p>However i could try to create webm file from jpeg files but i couldn't do the reverse and ends up with following error message</p>
  
  <blockquote>
    <p>Unable to find a suitable output format for 'output%d.png'</p>
  </blockquote>
  
  <p>Here is the code i'm trying to use.</p>
  
  <pre><code>var ffmpeg = require("ffmpeg.js/ffmpeg-mp4");
  var fs = require("fs");
  var stdout = "";
  var stderr = "";
  
  var testData = new Uint8Array(fs.readFileSync("Sample.mp4"));
  
  var result = ffmpeg({
    MEMFS: [{name: "Sample.mp4", data: testData}],
    stdin: function() {},
    arguments: ["-i", "Sample.mp4","-r","1", "output%d.png"],
  });
  
  console.log(result.MEMFS.length)
  if(result.MEMFS.length&gt;0){
      var out = result.MEMFS[0].data;
      fs.writeFileSync("test.jpg", Buffer(out.data));
      }
  </code></pre>
  
  <p><strong>Console Output</strong></p>
  
  <pre><code>ffmpeg version n3.1.2 Copyright (c) 2000-2016 the FFmpeg developers
    built with emcc (Emscripten gcc/clang-like replacement) 1.36.7 ()
    configuration: --cc=emcc --enable-cross-compile --target-os=none --arch=x86 --disable-runtime-cpudetect --disable-asm --disable-fast-unaligned --disable-pthreads --disable-w32threads --di
  sable-os2threads --disable-debug --disable-stripping --disable-all --enable-ffmpeg --enable-avcodec --enable-avformat --enable-avutil --enable-swresample --enable-swscale --enable-avfilter
  --disable-network --disable-d3d11va --disable-dxva2 --disable-vaapi --disable-vda --disable-vdpau --enable-decoder=vp8 --enable-decoder=vp9 --enable-decoder=theora --enable-decoder=mpeg2vid
  eo --enable-decoder=mpeg4 --enable-decoder=h264 --enable-decoder=hevc --enable-decoder=png --enable-decoder=mjpeg --enable-decoder=vorbis --enable-decoder=opus --enable-decoder=mp3 --enable
  -decoder=ac3 --enable-decoder=aac --enable-decoder=ass --enable-decoder=ssa --enable-decoder=srt --enable-decoder=webvtt --enable-demuxer=matroska --enable-demuxer=ogg --enable-demuxer=avi
  --enable-demuxer=mov --enable-demuxer=flv --enable-demuxer=mpegps --enable-demuxer=image2 --enable-demuxer=mp3 --enable-demuxer=concat --enable-protocol=file --enable-filter=aresample --ena
  ble-filter=scale --enable-filter=crop --enable-filter=overlay --disable-bzlib --disable-iconv --disable-libxcb --disable-lzma --disable-sdl --disable-securetransport --disable-xlib --disabl
  e-zlib --enable-encoder=libx264 --enable-encoder=libmp3lame --enable-encoder=aac --enable-muxer=mp4 --enable-muxer=mp3 --enable-muxer=null --enable-gpl --enable-libmp3lame --enable-libx264
  --extra-cflags=-I../lame/dist/include --extra-ldflags=-L../lame/dist/lib
    libavutil      55. 28.100 / 55. 28.100
    libavcodec     57. 48.101 / 57. 48.101
    libavformat    57. 41.100 / 57. 41.100
    libavfilter     6. 47.100 /  6. 47.100
    libswscale      4.  1.100 /  4.  1.100
    libswresample   2.  1.100 /  2.  1.100
  [h264 @ 0x809d50] Warning: not compiled with thread support, using thread emulation
  [aac @ 0x80e640] Warning: not compiled with thread support, using thread emulation
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'Sample.mp4':
    Metadata:
      major_brand     : isom
      minor_version   : 512
      compatible_brands: isomiso2avc1mp41
      encoder         : Lavf57.56.100
    Duration: 00:01:00.00, start: 0.000000, bitrate: 137 kb/s
      Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 360x214, 113 kb/s, 1 fps, 1 tbr, 16384 tbn, 32768 tbc (default)
      Metadata:
        handler_name    : VideoHandler
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 22050 Hz, mono, fltp, 23 kb/s (default)
      Metadata:
        handler_name    : SoundHandler
  [NULL @ 0x810d00] Unable to find a suitable output format for 'output%d.png'
  output%d.png: Invalid argument
  </code></pre>