[FFmpeg-user] Why the fps of concatenate video file change with old video file?

[Lou]

On Fri, Jun 24, 2016, at 05:18 PM, cuizhe wrote:
> ffmpeg version N-73266-g4aa0de6 Copyright (c) 2000-2015 the FFmpeg
> developers

This is old. Consider updating.

> Output #0, asf, to 'output.wmv':
> Metadata:
> WM/EncodingSettings: Lavf56.40.100
> Stream #0:0: Video: wmv3 (WMV3 / 0x33564D57), yuv420p, 720x576 [SAR 16:15
> DAR 4:3], q=2-31, 4194 kb/s, 25 fps, 25 tbr, 1k tbn, 25 tbc

The output is 25 fps. What says it is 30 fps?