ffmpeg not working complains of frame rate

I am using PHP-ffmpeg to convert .avi files to .flv files.But there seems to be some problem with it as I always get the error comaplining about the frame rate.My knwodge about frames and videos in general is limited .

Could you please help mwe here ...This happens on Red Hat Linux


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FFmpeg version SVN-r15575, Copyright (c) 2000-2008 Fabrice Bellard, et al.
  configuration: --enable-shared
  libavutil     49.11. 0 / 49.11. 0
  libavcodec    52. 0. 0 / 52. 0. 0
  libavformat   52.22. 1 / 52.22. 1
  libavdevice   52. 1. 0 / 52. 1. 0
  built on Nov 18 2008 21:37:53, gcc: 4.1.2 20071124 (Red Hat 4.1.2-42)
[NULL @ 0x9984460]Invalid and inefficient vfw-avi packed B frames detected

Seems stream 0 codec frame rate differs from container frame rate: 30000.00 (30000/1) -> 25.00 (25/1)
Input #0, avi, from '/something.avi':
  Duration: 00:00:55.00, start: 0.000000, bitrate: 791 kb/s
    Stream #0.0: Video: mpeg4, yuv420p, 480x270 [PAR 1:1 DAR 16:9], 25.00 tb(r)
Output #0, flv, to 'output.flv':
    Stream #0.0: Video: flv, yuv420p, 480x360 [PAR 4:3 DAR 16:9], q=2-31, 500 kb/s, 25.00 tb(c)
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop encoding

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