title: ffmpeg, dash manifest cannot be created due to unspecified pixel format
body: <p>I am using ffmpeg 2.8 on OSX.</p>
  
  <p>I try to convert a short mp4 video to webm for adaptive streaming like suggested here <a href="http://wiki.webmproject.org/adaptive-streaming/instructions-to-playback-adaptive-webm-using-dash" rel="nofollow">http://wiki.webmproject.org/adaptive-streaming/instructions-to-playback-adaptive-webm-using-dash</a> like this:</p>
  
  <pre><code>VP9_DASH_PARAMS="-tile-columns 6 -frame-parallel 1"
  
  ffmpeg -i t2.mp4 -c:v libvpx-vp9 -s 160x90 -b:v 250k -keyint_min 150 -g 150 ${VP9_DASH_PARAMS} -an -f webm -dash 1 video_160x90_250k.webm
  ffmpeg -i t2.mp4 -c:a libvorbis -b:a 128k -vn -f webm -dash 1 audio_128k.webm
  
  ffmpeg \
   -f webm_dash_manifest -i video_160x90_250k.webm \
   -f webm_dash_manifest -i audio_128k.webm \
   -c copy -map 0 -map 1 \
   -f webm_dash_manifest \
   -adaptation_sets "id=0,streams=0 id=1,streams=1" \
   manifest.mpd
  </code></pre>
  
  <p>However this gives me a warning <strong>unspecified pixel format</strong>:</p>
  
  <pre><code>[webm_dash_manifest @ 0x7f9414812800] Could not find codec parameters for stream 0 (Video: vp9, none, 160x90): unspecified pixel format
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  video_160x90_250k.webm: could not find codec parameters
  Input #0, webm_dash_manifest, from 'video_160x90_250k.webm':
    Metadata:
      encoder         : Lavf56.36.100
    Duration: 00:00:09.97, bitrate: 111 kb/s
      Stream #0:0: Video: vp9, none, 160x90, SAR 1:1 DAR 16:9, 23.98 fps, 23.98 tbr, 1k tbn, 1k tbc (default)
      Metadata:
        webm_dash_manifest_duration: 9969
        webm_dash_manifest_initialization_range: 437
        webm_dash_manifest_file_name: video_160x90_250k.webm
        webm_dash_manifest_track_number: 1
        webm_dash_manifest_cues_start: 139297
        webm_dash_manifest_cues_end: 139399
        webm_dash_manifest_bandwidth: 99164
        webm_dash_manifest_cluster_keyframe: 1
        webm_dash_manifest_cue_timestamps: 0,2085,4171,6256,8342
  Input #1, webm_dash_manifest, from 'audio_128k.webm':
    Metadata:
      encoder         : Lavf56.36.100
    Duration: 00:00:10.01, bitrate: 120 kb/s
      Stream #1:0: Audio: vorbis, 48000 Hz, stereo, fltp (default)
      Metadata:
        webm_dash_manifest_duration: 10009
        webm_dash_manifest_initialization_range: 4697
        webm_dash_manifest_file_name: audio_128k.webm
        webm_dash_manifest_track_number: 1
        webm_dash_manifest_cues_start: 151174
        webm_dash_manifest_cues_end: 151240
        webm_dash_manifest_bandwidth: 105517
        webm_dash_manifest_cluster_keyframe: 1
        webm_dash_manifest_cue_timestamps: 0,4999,9998
  Output #0, webm_dash_manifest, to 'manifest.mpd':
    Metadata:
      encoder         : Lavf56.36.100
      Stream #0:0: Video: vp9, none, 160x90 [SAR 1:1 DAR 16:9], q=2-31, 23.98 fps, 23.98 tbr, 1k tbn, 1k tbc (default)
      Metadata:
        webm_dash_manifest_duration: 9969
        webm_dash_manifest_initialization_range: 437
        webm_dash_manifest_file_name: video_160x90_250k.webm
        webm_dash_manifest_track_number: 1
        webm_dash_manifest_cues_start: 139297
        webm_dash_manifest_cues_end: 139399
        webm_dash_manifest_bandwidth: 99164
        webm_dash_manifest_cluster_keyframe: 1
        webm_dash_manifest_cue_timestamps: 0,2085,4171,6256,8342
      Stream #0:1: Video: vorbis, none, q=2-31, 1k tbn, 1k tbc (default)
      Metadata:
        webm_dash_manifest_duration: 10009
        webm_dash_manifest_initialization_range: 4697
        webm_dash_manifest_file_name: audio_128k.webm
        webm_dash_manifest_track_number: 1
        webm_dash_manifest_cues_start: 151174
        webm_dash_manifest_cues_end: 151240
        webm_dash_manifest_bandwidth: 105517
        webm_dash_manifest_cluster_keyframe: 1
        webm_dash_manifest_cue_timestamps: 0,4999,9998
  Stream mapping:
    Stream #0:0 -&gt; #0:0 (copy)
    Stream #1:0 -&gt; #0:1 (copy)
  Press [q] to stop, [?] for help
  frame=    0 fps=0.0 q=-1.0 Lsize=       1kB time=00:00:00.00 bitrate=N/A    
  video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
  Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)
  </code></pre>
  
  <p>Nevertheless the manifest file is created. I tried to specify the pixel format:</p>
  
  <pre><code>-pix_fmt yuv420p
  </code></pre>
  
  <p>However this did not change anything. The warning remains the same.</p>
  
  <p>Any ideas why the warning appears and how to fix this?</p>