Check out using ffprobe instead of ffmpeg. It doesn't try to play the video and you can pick an output format that suits you.

$ ffprobe -i http://bennugd-vlc.googlecode.com/files/sintel_trailer-48
+0p.mp4 -show_streams -print_format csv 2>/dev/null
stream,0,h264,H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10,video,1/48,avc
+1,0x31637661,854,480,2,N/A,N/A,yuv420p,30,N/A,1,4,N/A,24/1,24/1,1/24,
+0.000000,52.208333,537875,1253,N/A,N/A,1970-01-01 00:00:00,und,VideoH
+andler
stream,1,aac,Advanced Audio Coding,audio,1/48000,mp4a,0x6134706d,s16,4
+8000,2,0,N/A,0/0,0/0,1/48000,0.000000,51.946667,126694,2435,N/A,N/A,1
+970-01-01 00:00:00,und,SoundHandler
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