Question

我正在尝试使用ffmpeg裁剪视频，但遇到了三个问题。首先，我使用以下代码裁剪1080p视频。

ffmpeg -i 1080vid.avi -vf "crop=1920:1080:0:0" -c:v libx264 -crf 1 -c:a copy output.mp4

但是，在压缩率参数中，仅当我将-crf设置为正值时它才起作用。如果将其设置为0，则Windows 10视频播放器无法播放输出视频。但是，由于我要进行无损转换，因此存在问题。输出mp4小于原始大小的5％。

最初的目标是将1080 * 15360视频分割为8个1080p视频。但是，使用以下代码，在使用所有设置后，我将获得无法播放的输出。

ffmpeg -i sample.avi -vf "crop=1920:1080:0:0" -c:v libx264 -crf 1 -c:a copy output.mp4

输入sample.avi是比特率大于1GB / s的无损avi，输出是70kb无法播放的文件。打开后，将显示一个弹出窗口：

Choose something else to play. This item is in a format we don't support.
0xc00d36b4

以下是命令行输出。

ffmpeg version N-94396-g47b6ca0b02 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 9.1.1 (GCC) 20190716
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt
  libavutil      56. 32.100 / 56. 32.100
  libavcodec     58. 55.100 / 58. 55.100
  libavformat    58. 30.100 / 58. 30.100
  libavdevice    58.  9.100 / 58.  9.100
  libavfilter     7. 58.100 /  7. 58.100
  libswscale      5.  6.100 /  5.  6.100
  libswresample   3.  6.100 /  3.  6.100
  libpostproc    55.  6.100 / 55.  6.100
Input #0, avi, from 'sample.avi':
  Metadata:
    date            : 2019-07-26T07:09:04.185811
  Duration: 00:00:03.00, start: 0.000000, bitrate: 11932176 kb/s
    Stream #0:0: Video: rawvideo, bgr24, 15360x1080, 12066071 kb/s, 29.97 fps, 29.97 tbr, 29.97 tbn, 29.97 tbc
File 'output.mp4' already exists. Overwrite ? [y/N] y
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 000002a4a910b900] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 000002a4a910b900] profile High 4:4:4 Predictive, level 6.0, 4:4:4, 8-bit
[libx264 @ 000002a4a910b900] 264 - core 157 r2970 5493be8 - H.264/MPEG-4 AVC codec - Copyleft 2003-2019 - 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=4 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=crf mbtree=1 crf=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'output.mp4':
  Metadata:
    date            : 2019-07-26T07:09:04.185811
    encoder         : Lavf58.30.100
    Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuv444p, 15360x1080, q=-1--1, 29.97 fps, 30k tbn, 29.97 tbc
    Metadata:
      encoder         : Lavc58.55.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
frame=   90 fps=8.0 q=-1.0 Lsize=      65kB time=00:00:02.90 bitrate= 183.7kbits/s speed=0.258x
video:63kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 3.042484%
[libx264 @ 000002a4a910b900] frame I:1     Avg QP: 0.35  size: 22252
[libx264 @ 000002a4a910b900] frame P:23    Avg QP: 0.09  size:   476
[libx264 @ 000002a4a910b900] frame B:66    Avg QP: 0.00  size:   467
[libx264 @ 000002a4a910b900] consecutive B-frames:  2.2%  0.0%  0.0% 97.8%
[libx264 @ 000002a4a910b900] mb I  I16..4: 92.1%  6.5%  1.5%
[libx264 @ 000002a4a910b900] mb P  I16..4:  0.0%  0.0%  0.0%  P16..4:  0.0%  0.0%  0.0%  0.0%  0.0%    skip:100.0%
[libx264 @ 000002a4a910b900] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8:  0.0%  0.0%  0.0%  direct: 0.0%  skip:100.0%
[libx264 @ 000002a4a910b900] 8x8 transform intra:6.5% inter:0.0%
[libx264 @ 000002a4a910b900] coded y,u,v intra: 0.4% 0.0% 0.0% inter: 0.0% 0.0% 0.0%
[libx264 @ 000002a4a910b900] i16 v,h,dc,p: 96%  2%  2%  0%
[libx264 @ 000002a4a910b900] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 93%  1%  7%  0%  0%  0%  0%  0%  0%
[libx264 @ 000002a4a910b900] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 42% 25% 31%  0%  0%  0%  0%  0%  0%
[libx264 @ 000002a4a910b900] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 000002a4a910b900] kb/s:170.49

Answer 1

这里有两个问题。

当编码为无损（crf 0）时，H.264编码器会将配置文件High Predictive 4:4:4设置为只能由几个播放器播放。

此外，您的输入是RGB。 ffmpeg会将其转换为编码器支持的最佳格式。在这种情况下，就是yuv444p。这种像素格式也没有广泛的支持。

所以，使用

ffmpeg -i sample.avi -vf "crop=1920:1080:0:0" -pix_fmt yuv420p -c:v libx264 -crf 1 -c:a copy out.mp4

Windows Video Player无法播放ffmpeg裁剪的视频

1 个答案: