FFMPEG:webm到mp4的质量损失 [英] FFMPEG: webm to mp4 quality loss

问题描述

当尝试使用ffmpeg(在Mac上为3.4.2)将.webm视频(两种颜色的动画)转换为.mp4视频时，结果有些模糊.我确实研究了这个主题，并尝试了不同的方法来解决这个问题.这是最有前途的命令:

When trying to convert a .webm video (two colored animation) to a .mp4 video using ffmpeg (3.4.2 on mac) the result is somewhat blurry. I did research this topic and tried different approaches to solve this. Here is the most promising command:

ffmpeg -i vidoe.webm -qscale 1 video.mp4

但是，质量变化仍然很大，请参见下面的区别.

However, the quality change is still tremendous, see the difference below.

webm

mp4

两个视频的分辨率相同，但是转换后大小从24,3MB(.webm)降至1,5MB(.mp4).

The resolution of the two videos is the same, however the size dropped from 24,3MB (.webm) to 1,5MB (.mp4) after conversion.

更新

这是转换日志.

ffmpeg version 3.4.2 Copyright (c) 2000-2018 the FFmpeg developers
  built with Apple LLVM version 9.0.0 (clang-900.0.39.2)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/3.4.2 --enable-shared --enable-pthreads --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --disable-jack --enable-gpl --enable-libmp3lame --enable-libx264 --enable-libxvid --enable-opencl --enable-videotoolbox --disable-lzma
  libavutil      55. 78.100 / 55. 78.100
  libavcodec     57.107.100 / 57.107.100
  libavformat    57. 83.100 / 57. 83.100
  libavdevice    57. 10.100 / 57. 10.100
  libavfilter     6.107.100 /  6.107.100
  libavresample   3.  7.  0 /  3.  7.  0
  libswscale      4.  8.100 /  4.  8.100
  libswresample   2.  9.100 /  2.  9.100
  libpostproc    54.  7.100 / 54.  7.100
Input #0, matroska,webm, from 'video.webm':
  Metadata:
    encoder         : whammy
  Duration: 00:00:05.02, start: 0.000000, bitrate: 38755 kb/s
    Stream #0:0: Video: vp8, yuv420p(progressive), 1920x1080, SAR 1:1 DAR 16:9, 60 fps, 60 tbr, 1k tbn, 1k tbc (default)
Please use -q:a or -q:v, -qscale is ambiguous
Stream mapping:
  Stream #0:0 -> #0:0 (vp8 (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 0x7f8625800c00] -qscale is ignored, -crf is recommended.
[libx264 @ 0x7f8625800c00] using SAR=1/1
[libx264 @ 0x7f8625800c00] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x7f8625800c00] profile High, level 4.2
[libx264 @ 0x7f8625800c00] 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=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 'video.mp4':
  Metadata:
    encoder         : Lavf57.83.100
    Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], q=-1--1, 60 fps, 15360 tbn, 60 tbc (default)
    Metadata:
      encoder         : Lavc57.107.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
frame=  301 fps= 45 q=-1.0 Lsize=    1417kB time=00:00:04.96 bitrate=2336.4kbits/s speed=0.735x    
video:1412kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.309675%
[libx264 @ 0x7f8625800c00] frame I:2     Avg QP:13.08  size:  8842
[libx264 @ 0x7f8625800c00] frame P:75    Avg QP:24.29  size:  6785
[libx264 @ 0x7f8625800c00] frame B:224   Avg QP:26.38  size:  4102
[libx264 @ 0x7f8625800c00] consecutive B-frames:  0.7%  0.0%  1.0% 98.3%
[libx264 @ 0x7f8625800c00] mb I  I16..4: 68.1% 28.7%  3.2%
[libx264 @ 0x7f8625800c00] mb P  I16..4:  0.1%  2.2%  0.4%  P16..4:  6.5%  4.0%  1.4%  0.0%  0.0%    skip:85.4%
[libx264 @ 0x7f8625800c00] mb B  I16..4:  0.0%  0.2%  0.0%  B16..8:  8.8%  3.0%  0.3%  direct: 0.3%  skip:87.3%  L0:52.1% L1:47.5% BI: 0.4%
[libx264 @ 0x7f8625800c00] 8x8 transform intra:57.7% inter:67.8%
[libx264 @ 0x7f8625800c00] coded y,uvDC,uvAC intra: 25.7% 8.7% 0.9% inter: 3.9% 0.4% 0.0%
[libx264 @ 0x7f8625800c00] i16 v,h,dc,p: 95%  2%  3%  0%
[libx264 @ 0x7f8625800c00] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 17%  5% 48%  5%  7%  6%  5%  4%  3%
[libx264 @ 0x7f8625800c00] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 20% 14% 31%  6%  7%  7%  6%  5%  4%
[libx264 @ 0x7f8625800c00] i8c dc,h,v,p: 88%  6%  6%  0%
[libx264 @ 0x7f8625800c00] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x7f8625800c00] ref P L0: 55.3%  5.5% 24.8% 14.5%
[libx264 @ 0x7f8625800c00] ref B L0: 75.6% 16.7%  7.7%
[libx264 @ 0x7f8625800c00] ref B L1: 93.9%  6.1%
[libx264 @ 0x7f8625800c00] kb/s:2304.86

关于如何克服这种质量损失的任何想法?

Any idea on how to overcome this quality loss?

推荐答案

将 -qscale 1 更改为 -crf 1 可解决质量问题.工作命令是:

Changing -qscale 1 to -crf 1 resolves the quality issue. The working command is:

ffmpeg -i video.webm -crf 1 -c:v libx264 video.mp4

如 H.264视频编码指南所述-crf需要值从0(无损)到51(最差的质量).

As outlined in the H.264 Video Encoding Guide -crf takes in values from 0 (lossless) to 51 (worst quality).

这篇关于FFMPEG:webm到mp4的质量损失的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！