.avi 文件到 .webm 文件与 alpha 通道

问题描述

我不知道如何使用 FFmpeg，但我的 .avi 文件对于 2 秒视频来说太大了？知道如何将其转换为 WebM 吗？同时保留其 Alpha 通道？

我试过了：

ffmpeg -i "1.avi" -c:v libvpx -pix_fmt yuva420p "1.webm"

输出显示：

ffmpeg version 4.4-essentials_build-www.gyan.dev copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 10.2.0 (Rev6,Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-lzma --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-sdl2 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-libass --enable-libfreetype --enable-libfribidi --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libgme --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libtheora --enable-libvo-amrwbenc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-librubberband
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
[avi @ 00000245f2e7d640] Stream #0: not enough frames to estimate rate; consider increasing probesize
Guessed Channel Layout for Input Stream #0.1 : stereo
Input #0,avi,from '1.avi':
  Duration: 00:00:02.00,start: 0.000000,bitrate: 3983150 kb/s
  Stream #0:0: Video: rawvideo,bgra,1920x1080,4014784 kb/s,60 fps,60 tbr,60 tbn,60 tbc
  Stream #0:1: Audio: pcm_s16le ([1][0][0][0] / 0x0001),48000 Hz,stereo,s16,1536 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> vp8 (libvpx))
  Stream #0:1 -> #0:1 (pcm_s16le (native) -> opus (libopus))
Press [q] to stop,[?] for help
[libvpx @ 00000245f2e8ecc0] v1.10.0-24-g8b3e575a4
[libvpx @ 00000245f2e8ecc0] Neither bitrate nor constrained quality specified,using default CRF of 32 and bitrate of 256kbit/sec
[libvpx @ 00000245f2e8ecc0] Transparency encoding with auto_alt_ref does not work
Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate,rate,width or height
Conversion Failed!

解决方法

最简单的命令是：

ffmpeg -i input.avi output.webm

• 默认情况下将使用视频编码器 libvpx-vp9。
• libvpx-vp9 支持 alpha，因此默认情况下会保留 alpha。
• 有关详细信息，请参阅FFmpeg Wiki: VP9。

,

我用来解决的命令：

ffmpeg -i "1.avi" -c:v libvpx -b:v 2000k -pix_fmt yuva420p -auto-alt-ref 0 "1.webm"

"1.avi" - input.avi "1.webm" - out.webm

简单命令：

ffmpeg -i input.avi output.webm