FFmpeg重新编码视频后SAR/DAR与设定值不符的问题求助

大家好！我最近在处理视频重新编码的需求，想把temp.mp4转成指定参数的视频，这样才能和另一个MP4文件拼接，但遇到了SAR（样本宽高比）和DAR（显示宽高比）不符合预期的问题，来向各位大佬求助！

我期望得到的视频流参数： #

Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 1067 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)

但实际编码后得到的参数却是： #

Stream #0:00x1: Video: h264 (High) (avc1 / 0x31637661), yuv420p(progressive), 1280x720 [SAR 81:16 DAR 9:1], 674 kb/s, 25 fps, 25 tbr, 12800 tbn (default)

我当前使用的FFmpeg命令： #

ffmpeg.exe -i temp.mp4 -c:a libmp3lame -c:v libx264 -vf "scale=1280:720:force_original_aspect_ratio=decrease,setsar=r=1:max=1,setdar=r=16:max=9" -r 25 -y ef.mp4

命令运行时FFmpeg的完整输出信息： #

ffmpeg version N-83280-gcba4f0e Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 5.4.0 (GCC)
  configuration: --enable-gpl --enable-version3 --enable-cuda --enable-cuvid --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-nvenc --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib
  libavutil      55. 45.100 / 55. 45.100
  libavcodec     57. 76.100 / 57. 76.100
  libavformat    57. 67.100 / 57. 67.100
  libavdevice    57.  2.100 / 57.  2.100
  libavfilter     6. 72.100 /  6. 72.100
  libswscale      4.  3.101 /  4.  3.101
  libswresample   2.  4.100 /  2.  4.100
  libpostproc    54.  2.100 / 54.  2.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'temp.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf57.67.100
  Duration: 00:00:05.04, start: 0.000000, bitrate: 128 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 125 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : VideoHandler
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 00000000025a5800] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
[libx264 @ 00000000025a5800] profile High, level 3.1
[libx264 @ 00000000025a5800] 264 - core 148 r2795 aaa9aa8 - 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=6 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=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'ef.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf57.67.100
    Stream #0:0(und): Video: h264 (avc1 / 0x31637661), yuv420p(progressive), 1280x720 [SAR 81:16 DAR 9:1], q=-1--1, 25 fps, 12800 tbn, 25 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      encoder         : Lavc57.76.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
frame=  126 fps=0.0 q=-1.0 Lsize=     425kB time=00:00:05.00 bitrate= 692.4kbits/s speed= 103x
video:412kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 3.156524%
[libx264 @ 00000000025a5800] frame I:1     Avg QP:19.00  size: 32768
[libx264 @ 00000000025a5800] frame P:32    Avg QP:20.92  size:  8704
[libx264 @ 00000000025a5800] frame B:93    Avg QP:24.71  size:  1568
[libx264 @ 00000000025a5800] consecutive B-frames:  0.8%  0.0%  0.0% 99.2%
[libx264 @ 00000000025a5800] mb I  I16..4: 100.0%  0.0%  0.0%
[libx264 @ 00000000025a5800] mb P  I16..4:  0.0%  0.0%  0.0%  P16..4:  6.0%  0.0%  0.0%  0.0%  0.0%    skip:94.0%
[libx264 @ 00000000025a5800] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8:  1.1%  0.0%  0.0%  direct: 0.0%  skip:98.9%  L0:49.0% L1:51.0% BI: 0.0%
[libx264 @ 00000000025a5800] 8x8 transform intra:0.0% inter:100.0%
[libx264 @ 00000000025a5800] coded y,uvDC,uvAC intra: 0.0% 0.0% 0.0% inter: 0.2% 0.0% 0.0%
[libx264 @ 00000000025a5800] i16 v,h,dc,p: 100%  0%  0%  0%
[libx264 @ 00000000025a5800] i8c dc,h,v,p: 100%  0%  0%  0%
[libx264 @ 00000000025a5800] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 00000000025a5800] ref P L0: 99.7%  0.3%  0.0%
[libx264 @ 00000000025a5800] ref B L0: 50.1% 49.9%
[libx264 @ 00000000025a5800] ref B L1: 100.0%
[libx264 @ 00000000025a5800] kb/s:674.22

我本来想通过scale、setsar和setdar滤镜来强制设置参数，但结果SAR变成了81:16，DAR更是变成了9:1，完全偏离了目标。有没有朋友能帮我看看命令哪里写错了？应该怎么调整才能得到正确的SAR=1:1、DAR=16:9的参数呢？谢谢大家！

备注：内容来源于stack exchange，提问作者Smith Kumar