Question

我正在将一些文件从我的机顶盒（.ASF）格式转换为更便携的，更容易使用plex和roku。这样做我使用ffmpeg，但结果不尽如人意。虽然原件没有任何值得注意的隔行扫描缺陷，但转换后的文件确实存在。我认为它与libx264转换器有关，因为以下实验：

运行此命令：

ffmpeg -i file.asf -vcodec copy -acodec copy -bsf：aac_adtstoasc -ss 150 -t 15 short.mp4

ffmpeg version 3.0.2 Copyright (c) 2000-2016 the FFmpeg developers
  built with Apple LLVM version 7.3.0 (clang-703.0.29)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/3.0.2 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-opencl --enable-libx264 --enable-libmp3lame --enable-libxvid --enable-vda
  libavutil      55. 17.103 / 55. 17.103
  libavcodec     57. 24.102 / 57. 24.102
  libavformat    57. 25.100 / 57. 25.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 31.100 /  6. 31.100
  libavresample   3.  0.  0 /  3.  0.  0
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
[asf @ 0x7f9f84000000] Could not find codec parameters for stream 2 (Unknown: none): unknown codec
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #0, asf, from 'file.asf':
  Metadata:
    title           : Slingbox
    artist          : Sling Media
    comment         : test
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: h264 (High) (h264 / 0x34363268), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 30.30 fps, 30 tbr, 1k tbn, 59.94 tbc
    Stream #0:1: Audio: aac (LC) ([255][0][0][0] / 0x00FF), 32000 Hz, stereo, fltp, 96 kb/s
    Stream #0:2: Unknown: none
File 'short.mp4' already exists. Overwrite ? [y/N] y
Output #0, mp4, to 'short.mp4':
  Metadata:
    title           : Slingbox
    artist          : Sling Media
    comment         : test
    encoder         : Lavf57.25.100
    Stream #0:0: Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 30.30 fps, 30 tbr, 16k tbn, 1k tbc
    Stream #0:1: Audio: aac (LC) ([64][0][0][0] / 0x0040), 32000 Hz, stereo, 96 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
[mp4 @ 0x7f9f8388c200] Timestamps are unset in a packet for stream 0. This is deprecated and will stop working in the future. Fix your code to set the timestamps properly
[mp4 @ 0x7f9f8388c200] pts has no value
    Last message repeated 449 times
frame=  450 fps=0.0 q=-1.0 Lsize=    9002kB time=00:00:15.02 bitrate=4907.9kbits/s speed=92.1x    
video:8817kB audio:173kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.125406%

生成的文件没有隔行扫描伪像，并且看起来与原始文件大小完全相同（如果没有-ss和-t命令运行）。

但是运行此命令（没有任何选项）：

ffmpeg -i test.asf -ss 150 -t 15 short2.mp4

ffmpeg version 3.0.2 Copyright (c) 2000-2016 the FFmpeg developers
  built with Apple LLVM version 7.3.0 (clang-703.0.29)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/3.0.2 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-opencl --enable-libx264 --enable-libmp3lame --enable-libxvid --enable-vda
  libavutil      55. 17.103 / 55. 17.103
  libavcodec     57. 24.102 / 57. 24.102
  libavformat    57. 25.100 / 57. 25.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 31.100 /  6. 31.100
  libavresample   3.  0.  0 /  3.  0.  0
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
[asf @ 0x7fec32801400] Could not find codec parameters for stream 2 (Unknown: none): unknown codec
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #0, asf, from 'test.asf':
  Metadata:
    title           : Slingbox
    artist          : Sling Media
    comment         : test
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: h264 (High) (h264 / 0x34363268), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 30.30 fps, 30 tbr, 1k tbn, 59.94 tbc
    Stream #0:1: Audio: aac (LC) ([255][0][0][0] / 0x00FF), 32000 Hz, stereo, fltp, 96 kb/s
    Stream #0:2: Unknown: none
[libx264 @ 0x7fec32102800] using SAR=1/1
[libx264 @ 0x7fec32102800] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
[libx264 @ 0x7fec32102800] profile High, level 4.0
[libx264 @ 0x7fec32102800] 264 - core 148 r2668 fd2c324 - H.264/MPEG-4 AVC codec - Copyleft 2003-2016 - - 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=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=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'short2.mp4':
  Metadata:
    title           : Slingbox
    artist          : Sling Media
    comment         : test
    encoder         : Lavf57.25.100
    Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], q=-1--1, 30 fps, 15360 tbn, 30 tbc
    Metadata:
      encoder         : Lavc57.24.102 libx264
    Side data:
      unknown side data type 10 (24 bytes)
    Stream #0:1: Audio: aac (LC) ([64][0][0][0] / 0x0040), 32000 Hz, stereo, fltp, 128 kb/s
    Metadata:
      encoder         : Lavc57.24.102 aac
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
  Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
frame=  450 fps= 20 q=-1.0 Lsize=    6732kB time=00:00:15.00 bitrate=3674.9kbits/s speed=0.657x    
video:6481kB audio:240kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.168370%
[libx264 @ 0x7fec32102800] frame I:12    Avg QP:18.85  size: 39804
[libx264 @ 0x7fec32102800] frame P:291   Avg QP:21.40  size: 17543
[libx264 @ 0x7fec32102800] frame B:147   Avg QP:22.61  size:  7167
[libx264 @ 0x7fec32102800] consecutive B-frames: 42.9% 36.9% 11.3%  8.9%
[libx264 @ 0x7fec32102800] mb I  I16..4: 43.2% 52.0%  4.8%
[libx264 @ 0x7fec32102800] mb P  I16..4: 11.9% 16.0%  1.0%  P16..4: 30.2%  3.0%  1.7%  0.0%  0.0%    skip:36.2%
[libx264 @ 0x7fec32102800] mb B  I16..4:  0.6%  0.9%  0.1%  B16..8: 25.7%  1.4%  0.2%  direct: 4.6%  skip:66.6%  L0:49.0% L1:49.4% BI: 1.6%
[libx264 @ 0x7fec32102800] 8x8 transform intra:55.1% inter:92.0%
[libx264 @ 0x7fec32102800] coded y,uvDC,uvAC intra: 22.5% 38.6% 6.6% inter: 6.5% 17.3% 0.5%
[libx264 @ 0x7fec32102800] i16 v,h,dc,p: 28% 47%  8% 17%
[libx264 @ 0x7fec32102800] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 34% 15% 42%  1%  1%  2%  1%  2%  1%
[libx264 @ 0x7fec32102800] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 10% 78%  6%  1%  1%  1%  1%  1%  1%
[libx264 @ 0x7fec32102800] i8c dc,h,v,p: 59% 19% 19%  3%
[libx264 @ 0x7fec32102800] Weighted P-Frames: Y:14.4% UV:3.8%
[libx264 @ 0x7fec32102800] ref P L0: 65.5%  6.6% 19.0%  8.4%  0.4%
[libx264 @ 0x7fec32102800] ref B L0: 89.6%  8.9%  1.5%
[libx264 @ 0x7fec32102800] ref B L1: 98.6%  1.4%
[libx264 @ 0x7fec32102800] kb/s:3539.34
[aac @ 0x7fec32103a00] Qavg: 573.580

通过Plex（通过直接播放启用，显然没有转码）在我的高清投影机上播放时，会生成一个有很多隔行扫描缺陷的文件。

still frame from second transcode showing visual defect

为免我过于挑剔，我让我的妻子参加了这个测试，向她展示了这两个文件，并且她同意使用libx264的那个文件显然更糟糕且无法观看。无法弄清楚如何缩小此文件而不会导致这些隔行扫描缺陷 - 即使我不尝试缩小它也会发生这种情况！有什么想法吗？

视频文件：

https://dl.dropboxusercontent.com/u/23091/m1/short.mp4 https://dl.dropboxusercontent.com/u/23091/m1/short2.mp4

更新：此外，我尝试了一些设置来生成MPEG4（.AVI）文件，但也有类似的缺乏成功。类似的隔行扫描缺陷。

Answer 1

源视频是隔行扫描的，因此需要进行逐行扫描。

在FFmpeg中使用的标准过滤器是YADIF。

所以，基本语法是

ffmpeg -i file.asf -vf yadif -c:a copy -bsf:a aac_adtstoasc file.mp4

使用libx264进行ffmpeg转换看起来很糟糕 - 隔行扫描

1 个答案: