title: ffmpeg & png watermark issue
body: <p>I tried to create a watermark (using a <code>png</code> image) on a video like this:</p>
  
  <pre><code>ffmpeg -i test.wmv -b:a 300k -ar 22050 -t 10 -f flv -s 352x288 -vf "movie = watermark_logo352.png [watermark]; [in][watermark] overlay =0:0 [out]" out.flv
  </code></pre>
  
  <p>but I get the error:</p>
  
  <pre><code>ffmpeg version 0.10.4 Copyright (c) 2000-2012 the FFmpeg developers
  built on Jun 14 2012 13:14:31 with gcc 4.4.5   configuration:
  --prefix=/home/username --enable-cross-compile --enable-shared --arch=amd64 --target-os=linux --disable-yasm --enable-decoder=png --enable-encoder=png   
          libavutil      51. 35.100 / 51. 35.100   
          libavcodec     53. 61.100 / 53. 61.100   
          libavformat    53. 32.100 / 53. 32.100   
          libavdevice    53.  4.100 / 53.  4.100   
          libavfilter     2. 61.100 /  2. 61.100   
          libswscale      2.  1.100 /  2.  1.100   
          libswresample   0.  6.100 /  0.  6.100 
          Input #0, asf, from 'test.wmv':   
          Metadata:
              &gt;     WMFSDKVersion   : 9.00.00.2980
              &gt;     WMFSDKNeeded    : 0.0.0.0000
              &gt;     IsVBR           : 1
              &gt;     VBR Peak        : 351
              &gt;     Buffer Average  : 728   Duration: 00:00:05.59, start: 0.000000, bitrate: 574 kb/s
              &gt;     Stream #0:0(jpn): Audio: wmav2 (a[1][0][0] / 0x0161), 22050 Hz, 2 channels, s16, 32 kb/s
              &gt;     Stream #0:1(jpn): Video: wmv1 (WMV1 / 0x31564D57), yuv420p, 352x288, 520 kb/s, SAR 8:9 DAR 88:81, 29.97 tbr, 1k tbn, 1k tbc File
              &gt; 'out2.flv' already exists. Overwrite ? [y/N] y w:352 h:288
              &gt; pixfmt:yuv420p tb:1/1000000 sar:8/9 sws_param: 
      [image2 @ 0x551f880] decoding for stream 0 failed 
      [image2 @ 0x551f880] Could not find codec parameters (Video: png) 
      [movie @ 0x551f440] Failed to find stream info
      [movie @ 0x551f440] Failed to find any codec 
      Error initializing filter 'movie' with args 'watermark_logo352.png' 
      Error opening filters!
  </code></pre>
  
  <p>When I use a <code>jpg</code>, it works like a charm.</p>
  
  <p>I'm use ffmpeg v 0.10.4 on Debian 6 Squeeze.
  Any help would be much appreciated.</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>The problem is simpler than i thought. If i use ffmpeg -i with any png image i get a similar error:</p>
  
  <pre><code>  libavutil      51. 35.100 / 51. 35.100
    libavcodec     53. 61.100 / 53. 61.100
    libavformat    53. 32.100 / 53. 32.100
    libavdevice    53.  4.100 / 53.  4.100
    libavfilter     2. 61.100 /  2. 61.100
    libswscale      2.  1.100 /  2.  1.100
    libswresample   0.  6.100 /  0.  6.100
    libpostproc    52.  0.100 / 52.  0.100
  [image2 @ 0xc8b73a0] decoding for stream 0 failed
  [image2 @ 0xc8b73a0] Could not find codec parameters (Video: png)
  watermark.png: could not find codec parameters
  </code></pre>