[Libav-user] Framerate of video is not exact

[Exclusive Goods Warehouse]

 Hello,

I'm trying to use "muxing.c" file from the examples. I need to export
videos in multiple formats with exact fps, let's say 25. I'm using VLC
player to check the real fps. When i pick .avi format as output, it is
exactly 25. Hovewer, when i pick .mp4 file, the output video has always
slightly different framerate, for example 25.166666. This somehow depends
on duration of the video. Short videos can have even more than 26 fps. This
does not happen in console tool ffmpeg, just in the file muxing.c. I don't
want to use the console version though.
I have no idea how to fix this. Would somebody be so kind and help me?

Here is the output:

[libx264 @ 0x56419e134b00]
using cpu capabilities: MMX2 SSE2Fast LZCNT SSSE3 SSE4.2 AVX
[libx264 @ 0x56419e134b00]
profile High, level 1.3
[libx264 @ 0x56419e134b00] 264 - core 152 r2854 e9a5903 - H.264/MPEG-4 AVC
codec - Copyleft 2003-2017 - http://www.videolan.org/x264.html - options:
cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1
psy_rd=1,00:0,00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1
cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=1
lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0
bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1
b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=12 keyint_min=1
scenecut=40 intra_refresh=0 rc_lookahead=12 rc=abr mbtree=1 bitrate=400
ratetol=1,0 qcomp=0,60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1,40 aq=1:1,00
Output #0, mp4, to '/home/****/Videos/test.mp4':
    Stream #0:0: Video: h264, yuv420p, 352x288, q=2-31, 400 kb/s, 25 tbn
    Stream #0:1: Audio: aac (LC), 44100 Hz, stereo, fltp, 64 kb/s
[libx264 @ 0x56419e134b00]
frame I:13    Avg QP: 9,53  size:  3837
[libx264 @ 0x56419e134b00] frame P:38    Avg QP: 9,60  size:   974
[libx264 @ 0x56419e134b00] frame B:100   Avg QP:13,21  size:   970
[libx264 @ 0x56419e134b00] consecutive B-frames:  8,6%  1,3% 23,8% 66,2%
[libx264 @ 0x56419e134b00] mb I  I16..4: 77,9% 12,5%  9,7%
[libx264 @ 0x56419e134b00] mb P  I16..4: 76,4%  4,9%  0,2%  P16..4: 18,1%
 0,2%  0,3%  0,0%  0,0%    skip: 0,0%
[libx264 @ 0x56419e134b00] mb B  I16..4:  0,0%  0,0%  0,0%  B16..8: 11,9%
 0,5%  0,0%  direct:60,1%  skip:27,5%  L0:39,3% L1:56,6% BI: 4,1%
[libx264 @ 0x56419e134b00] final ratefactor: 6,01
[libx264 @ 0x56419e134b00] 8x8 transform intra:7,9% inter:39,2%
[libx264 @ 0x56419e134b00] coded y,uvDC,uvAC intra: 7,0% 15,9% 10,0% inter:
0,2% 74,0% 7,7%
[libx264 @ 0x56419e134b00] i16 v,h,dc,p:  0%  0%  0% 100%
[libx264 @ 0x56419e134b00] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 19% 17%  6% 57%
 0%  0%  0%  0%  0%
[libx264 @ 0x56419e134b00] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 11%  4%  5% 74%
 4%  0%  0%  2%  1%
[libx264 @ 0x56419e134b00] i8c dc,h,v,p:  0%  5%  7% 89%
[libx264 @ 0x56419e134b00] Weighted P-Frames: Y:0,0% UV:0,0%
[libx264 @ 0x56419e134b00] ref P L0: 98,4%  0,2%  0,6%  0,8%
[libx264 @ 0x56419e134b00] ref B L0: 90,0%  8,9%  1,1%
[libx264 @ 0x56419e134b00] ref B L1: 95,9%  4,1%
[libx264 @ 0x56419e134b00] kb/s:243,60
[aac @ 0x56419e11d6a0] Qavg: 321,284
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