title: ffmpeg is reading SDP from RTSP stream but unable to save a screenshot. is it network or utility issue?
body: <p>My task is to get a screenshot from IP camera rtsp stream via <code>ffmpeg</code>.
  I got following error when I'm trying to do that on DigitalOcean droplet:</p>
  
  <pre><code>root@docker-512mb-fra1-01:~# ffmpeg -hide_banner -loglevel debug -i rtsp://10.132.193.9//ch0.h264 -f image2 latest.jpg
  Splitting the commandline.
  Reading option '-hide_banner' ... matched as option 'hide_banner' (do not show program banner) with argument '1'.
  Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument 'debug'.
  Reading option '-i' ... matched as input url with argument 'rtsp://10.132.193.9//ch0.h264'.
  Reading option '-f' ... matched as option 'f' (force format) with argument 'image2'.
  Reading option 'latest.jpg' ... matched as output url.
  Finished splitting the commandline.
  Parsing a group of options: global .
  Applying option hide_banner (do not show program banner) with argument 1.
  Applying option loglevel (set logging level) with argument debug.
  Successfully parsed a group of options.
  Parsing a group of options: input url rtsp://10.132.193.9//ch0.h264.
  Successfully parsed a group of options.
  Opening an input file: rtsp://10.132.193.9//ch0.h264.
  [rtsp @ 0x1298440] SDP:
  v=0
  o=- 1499314217993040 1 IN IP4 192.168.1.128
  s=H.264 Program Stream, streamed by the LIVE555 Media Server
  i=ch0.h264
  t=0 0
  a=DevVer:pusher2
  a=GroupName:IPCAM
  a=NickName:CIF
  a=CfgSection:PROG_CHN0
  a=tool:LIVE555 Streaming Media v2011.08.13
  a=type:broadcast
  a=control:*
  a=range:npt=0-
  a=x-qt-text-nam:H.264 Program Stream, streamed by the LIVE555 Media Server
  a=x-qt-text-inf:ch0.h264
  m=video 0 RTP/AVP 96
  c=IN IP4 0.0.0.0
  b=AS:4000
  a=rtpmap:96 H264/90000
  a=control:trackID=1
  a=fmtp:96 packetization-mode=1;profile-level-id=64001F;sprop-parameter-sets=Z2QAH6wrUCgC3IA=,aO48MA==
  a=framesize:96 1280-720
  a=cliprect:0,0,1280,720
  m=audio 0 RTP/AVP 97
  a=rtpmap:97 mpeg4-generic/8000/2
  a=fmtp:97 streamtype=5;profile-level-id=1;cpresent=0;mode=AAC-hbr;sizelength=13;indexlength=3;indexdeltalength=3;config=1590
  a=control:trackID=2
  
  Failed to parse interval end specification ''
  [rtsp @ 0x1298440] video codec set to: h264
  [rtsp @ 0x1298440] RTP Packetization Mode: 1
  [rtsp @ 0x1298440] RTP Profile IDC: 64 Profile IOP: 0 Level: 1f
  [rtsp @ 0x1298440] Extradata set to 0x1298a20 (size: 23)
  [rtsp @ 0x1298440] audio codec set to: aac
  [rtsp @ 0x1298440] audio samplerate set to: 8000
  [rtsp @ 0x1298440] audio channels set to: 2
  [udp @ 0x129e7e0] end receive buffer size reported is 131072
  [udp @ 0x129e680] end receive buffer size reported is 131072
  [udp @ 0x12bf380] end receive buffer size reported is 131072
  [udp @ 0x12bf1c0] end receive buffer size reported is 131072
  [rtsp @ 0x1298440] hello state=0
  [rtsp @ 0x1298440] UDP timeout, retrying with TCP
  [rtsp @ 0x1298440] hello state=0
  [rtsp @ 0x1298440] Could not find codec parameters for stream 0 (Video: h264, 1 reference frame, none(left), 1280x720, 1/180000): unspecified pixel format
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  Input #0, rtsp, from 'rtsp://10.132.193.9//ch0.h264':
    Metadata:
      title           : H.264 Program Stream, streamed by the LIVE555 Media Server
      comment         : ch0.h264
    Duration: N/A, start: 0.000000, bitrate: N/A
      Stream #0:0, 0, 1/90000: Video: h264, 1 reference frame, none(left), 1280x720, 1/180000, 90k tbr, 90k tbn, 180k tbc
      Stream #0:1, 0, 1/8000: Audio: aac, 8000 Hz, stereo, fltp
  Successfully opened the file.
  Parsing a group of options: output url latest.jpg.
  Applying option f (force format) with argument image2.
  Successfully parsed a group of options.
  Opening an output file: latest.jpg.
  Successfully opened the file.
  detected 1 logical cores
  [graph 0 input from stream 0:0 @ 0x1298280] Setting 'video_size' to value '1280x720'
  [graph 0 input from stream 0:0 @ 0x1298280] Setting 'pix_fmt' to value '-1'
  [buffer @ 0x12f9680] Unable to parse option value "-1" as pixel format
  [graph 0 input from stream 0:0 @ 0x1298280] Setting 'time_base' to value '1/90000'
  [graph 0 input from stream 0:0 @ 0x1298280] Setting 'pixel_aspect' to value '0/1'
  [graph 0 input from stream 0:0 @ 0x1298280] Setting 'sws_param' to value 'flags=2'
  [graph 0 input from stream 0:0 @ 0x1298280] Setting 'frame_rate' to value '180000/2'
  [buffer @ 0x12f9680] Unable to parse option value "-1" as pixel format
  [buffer @ 0x12f9680] Error setting option pix_fmt to value -1.
  [graph 0 input from stream 0:0 @ 0x1298280] Error applying options to the filter.
  Error opening filters!
  Exiting normally, received signal 2.
  </code></pre>
  
  <p>As you see, ffmpeg is able to read SDP metadata, but for some reason is unable to save a screenshot</p>
  
  <p>Also same command works fine on my laptop with same VPN configuration!</p>
  
  <p>Just in case, IP camera doesn't have a public IP address and accessible via VPN. </p>
  
  <p>What could be wrong and how to debug?</p>
  
  <p>I tried to increase <code>-analyzeduration</code> and <code>-probesize</code> options from default 5s to 30s, but it doesn't work.</p>