视频在压缩转码的时候一定要选择“二次编码”，二次编码后视频会变成"可变帧速率模式"，与此同时序列图就会和（帧频*时间）对的上（基本对的上，还得考虑压缩的问题）
比如说下面这个视频第4秒的画面和原始序列图的第100张就是可以对上的

General
Complete name                  : testVideo.avi
Format                         : AVI
Format/Info                    : Audio Video Interleave
Format profile                 : OpenDML
File size                      : 1.05 GiB
Duration                       : 56 s 680 ms
Overall bit rate               : 160 Mb/s
Recorded date                  : 2018-06-21T05:16:59.225168
Writing application            : Lavf57.41.100

Video
ID                             : 0
Format                         : AVC
Format/Info                    : Advanced Video Codec
Format profile                 : High@L5.2
Format settings                : CABAC / 4 Ref Frames
Format settings, CABAC         : Yes
Format settings, ReFrames      : 4 frames
Codec ID                       : H264
Duration                       : 56 s 680 ms
Bit rate                       : 160 Mb/s
Width                          : 4 096 pixels
Height                         : 2 048 pixels
Display aspect ratio           : 2.000
Frame rate mode                : Variable
Frame rate                     : 25.000 FPS
Color space                    : YUV
Chroma subsampling             : 4:2:0
Bit depth                      : 8 bits
Scan type                      : Progressive
Bits/(Pixel*Frame)             : 0.763
Stream size                    : 1.05 GiB (100%)
Writing library                : x264 core 148
Encoding settings              : 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=12 / lookahead_threads=2 / 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=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=2pass / mbtree=1 / bitrate=160000 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / aq=1:1.00