尝试使用 FFMPEG 将 webm 视频缩放到其分辨率的 50%，但不断出现错误（顺便说一句，视频具有透明度）
Trying to scale a webm video to 50% of its resolution using FFMPEG but keep getting an error (video has transparency btw)
我正在尝试使用这行命令缩小具有透明度的 webm 视频（基于此 Whosebug 问题中的答案@ ）：
ffmpeg -c:v libvpx -i in.webm -c:v libvpx -vf scale=400:416 -auto-alt-ref 0 out.webm
但我不断收到错误消息（例如）：
[libvpx @ 00000128eb6123c0] Invalid sync code 310042.
[libvpx @ 00000128eb6123c0] Failed to decode frame: Bitstream not supported by this decoder
Cannot determine format of input stream 0:0 after EOF
完整日志（我删除了大量带有“...”的完全相同的消息）：
ffmpeg version 2021-02-02-git-2367affc2c-full_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-libsnappy --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libdav1d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-libass --enable-frei0r --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-libglslang --enable-vulkan --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
libavutil 56. 64.100 / 56. 64.100
libavcodec 58.120.100 / 58.120.100
libavformat 58. 65.101 / 58. 65.101
libavdevice 58. 11.103 / 58. 11.103
libavfilter 7.101.100 / 7.101.100
libswscale 5. 8.100 / 5. 8.100
libswresample 3. 8.100 / 3. 8.100
libpostproc 55. 8.100 / 55. 8.100
[libvpx @ 00000128eb6123c0] v1.9.0-146-gebb5ffc1d
[libvpx @ 00000128eb6123c0] Invalid sync code 310042.
[libvpx @ 00000128eb6123c0] Failed to decode frame: Bitstream not supported by this decoder
[libvpx @ 00000128eb6123c0] Invalid sync code 007a49.
[libvpx @ 00000128eb6123c0] Failed to decode frame: Bitstream not supported by this decoder
[libvpx @ 00000128eb6123c0] Invalid sync code 01f096.
[libvpx @ 00000128eb6123c0] Failed to decode frame: Bitstream not supported by this decoder
...
...
...
[libvpx @ 00000128eb6123c0] Invalid sync code 01f096.
[libvpx @ 00000128eb6123c0] Failed to decode frame: Bitstream not supported by this decoder
[libvpx @ 00000128eb6123c0] Invalid sync code 01f096.
[libvpx @ 00000128eb6123c0] Failed to decode frame: Bitstream not supported by this decoder
[libvpx @ 00000128eb6123c0] Invalid sync code 01f096.
[libvpx @ 00000128eb6123c0] Failed to decode frame: Bitstream not supported by this decoder
[libvpx @ 00000128eb6123c0] Invalid sync code 01f096.
[matroska,webm @ 00000128eb60f040] decoding for stream 0 failed
[matroska,webm @ 00000128eb60f040] Could not find codec parameters for stream 0 (Video: vp8 (libvpx), none(progressive), 800x832): unspecified pixel format
Consider increasing the value for the 'analyzeduration' (0) and 'probesize' (5000000) options
Input #0, matroska,webm, from 'in.webm':
Metadata:
encoder : libwebm-0.2.1.0
creation_time : 2017-12-02T12:06:12.000000Z
Duration: 00:00:10.00, start: 0.000000, bitrate: 2592 kb/s
Stream #0:0(eng): Video: vp8, none(progressive), 800x832, SAR 1:1 DAR 25:26, 30 fps, 30 tbr, 1k tbn, 1k tbc (default)
Metadata:
alpha_mode : 1
[libvpx @ 00000128eb612a40] v1.9.0-146-gebb5ffc1d
Stream mapping:
Stream #0:0 -> #0:0 (vp8 (libvpx) -> vp8 (libvpx))
Press [q] to stop, [?] for help
[libvpx @ 00000128eb612a40] Failed to decode frame: Bitstream not supported by this decoder
Error while decoding stream #0:0: Invalid data found when processing input
[libvpx @ 00000128eb612a40] Failed to decode frame: Bitstream not supported by this decoder
Error while decoding stream #0:0: Invalid data found when processing input
[libvpx @ 00000128eb612a40] Failed to decode frame: Bitstream not supported by this decoder
...
...
...
Error while decoding stream #0:0: Invalid data found when processing input
[NULL @ 00000128eb6123c0] Invalid sync code 01f096.
[libvpx @ 00000128eb612a40] Failed to decode frame: Bitstream not supported by this decoder
Error while decoding stream #0:0: Invalid data found when processing input
[NULL @ 00000128eb6123c0] Invalid sync code 01f096.
[libvpx @ 00000128eb612a40] Failed to decode frame: Bitstream not supported by this decoder
Error while decoding stream #0:0: Invalid data found when processing input
[NULL @ 00000128eb6123c0] Invalid sync code 009c96.
[libvpx @ 00000128eb612a40] Failed to decode frame: Bitstream not supported by this decoder
Error while decoding stream #0:0: Invalid data found when processing input
Cannot determine format of input stream 0:0 after EOF
Error marking filters as finished
Conversion failed!
ffmpeg -i input.webm 的日志：
ffmpeg version 2021-02-02-git-2367affc2c-full_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-libsnappy --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libdav1d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-libass --enable-frei0r --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-libglslang --enable-vulkan --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
libavutil 56. 64.100 / 56. 64.100
libavcodec 58.120.100 / 58.120.100
libavformat 58. 65.101 / 58. 65.101
libavdevice 58. 11.103 / 58. 11.103
libavfilter 7.101.100 / 7.101.100
libswscale 5. 8.100 / 5. 8.100
libswresample 3. 8.100 / 3. 8.100
libpostproc 55. 8.100 / 55. 8.100
Input #0, matroska,webm, from 'input.webm':
Metadata:
encoder : libwebm-0.2.1.0
creation_time : 2017-12-02T12:06:12.000000Z
Duration: 00:00:10.00, start: 0.000000, bitrate: 2592 kb/s
Stream #0:0(eng): Video: vp9 (Profile 0), yuv420p(tv), 800x832, SAR 1:1 DAR 25:26, 30 fps, 30 tbr, 1k tbn, 1k tbc (default)
Metadata:
alpha_mode : 1
At least one output file must be specified
使用
ffmpeg -c:v libvpx-vp9 -i in.webm -c:v libvpx -vf scale=400:416 -auto-alt-ref 0 out.webm
输入视频是VP9，而libvpx解码器是VP8。
如果你想要 VP9 流，对输出做同样的事情。
我正在尝试使用这行命令缩小具有透明度的 webm 视频（基于此 Whosebug 问题中的答案@
ffmpeg -c:v libvpx -i in.webm -c:v libvpx -vf scale=400:416 -auto-alt-ref 0 out.webm
但我不断收到错误消息（例如）：
[libvpx @ 00000128eb6123c0] Invalid sync code 310042.
[libvpx @ 00000128eb6123c0] Failed to decode frame: Bitstream not supported by this decoder
Cannot determine format of input stream 0:0 after EOF
完整日志（我删除了大量带有“...”的完全相同的消息）：
ffmpeg version 2021-02-02-git-2367affc2c-full_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-libsnappy --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libdav1d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-libass --enable-frei0r --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-libglslang --enable-vulkan --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
libavutil 56. 64.100 / 56. 64.100
libavcodec 58.120.100 / 58.120.100
libavformat 58. 65.101 / 58. 65.101
libavdevice 58. 11.103 / 58. 11.103
libavfilter 7.101.100 / 7.101.100
libswscale 5. 8.100 / 5. 8.100
libswresample 3. 8.100 / 3. 8.100
libpostproc 55. 8.100 / 55. 8.100
[libvpx @ 00000128eb6123c0] v1.9.0-146-gebb5ffc1d
[libvpx @ 00000128eb6123c0] Invalid sync code 310042.
[libvpx @ 00000128eb6123c0] Failed to decode frame: Bitstream not supported by this decoder
[libvpx @ 00000128eb6123c0] Invalid sync code 007a49.
[libvpx @ 00000128eb6123c0] Failed to decode frame: Bitstream not supported by this decoder
[libvpx @ 00000128eb6123c0] Invalid sync code 01f096.
[libvpx @ 00000128eb6123c0] Failed to decode frame: Bitstream not supported by this decoder
...
...
...
[libvpx @ 00000128eb6123c0] Invalid sync code 01f096.
[libvpx @ 00000128eb6123c0] Failed to decode frame: Bitstream not supported by this decoder
[libvpx @ 00000128eb6123c0] Invalid sync code 01f096.
[libvpx @ 00000128eb6123c0] Failed to decode frame: Bitstream not supported by this decoder
[libvpx @ 00000128eb6123c0] Invalid sync code 01f096.
[libvpx @ 00000128eb6123c0] Failed to decode frame: Bitstream not supported by this decoder
[libvpx @ 00000128eb6123c0] Invalid sync code 01f096.
[matroska,webm @ 00000128eb60f040] decoding for stream 0 failed
[matroska,webm @ 00000128eb60f040] Could not find codec parameters for stream 0 (Video: vp8 (libvpx), none(progressive), 800x832): unspecified pixel format
Consider increasing the value for the 'analyzeduration' (0) and 'probesize' (5000000) options
Input #0, matroska,webm, from 'in.webm':
Metadata:
encoder : libwebm-0.2.1.0
creation_time : 2017-12-02T12:06:12.000000Z
Duration: 00:00:10.00, start: 0.000000, bitrate: 2592 kb/s
Stream #0:0(eng): Video: vp8, none(progressive), 800x832, SAR 1:1 DAR 25:26, 30 fps, 30 tbr, 1k tbn, 1k tbc (default)
Metadata:
alpha_mode : 1
[libvpx @ 00000128eb612a40] v1.9.0-146-gebb5ffc1d
Stream mapping:
Stream #0:0 -> #0:0 (vp8 (libvpx) -> vp8 (libvpx))
Press [q] to stop, [?] for help
[libvpx @ 00000128eb612a40] Failed to decode frame: Bitstream not supported by this decoder
Error while decoding stream #0:0: Invalid data found when processing input
[libvpx @ 00000128eb612a40] Failed to decode frame: Bitstream not supported by this decoder
Error while decoding stream #0:0: Invalid data found when processing input
[libvpx @ 00000128eb612a40] Failed to decode frame: Bitstream not supported by this decoder
...
...
...
Error while decoding stream #0:0: Invalid data found when processing input
[NULL @ 00000128eb6123c0] Invalid sync code 01f096.
[libvpx @ 00000128eb612a40] Failed to decode frame: Bitstream not supported by this decoder
Error while decoding stream #0:0: Invalid data found when processing input
[NULL @ 00000128eb6123c0] Invalid sync code 01f096.
[libvpx @ 00000128eb612a40] Failed to decode frame: Bitstream not supported by this decoder
Error while decoding stream #0:0: Invalid data found when processing input
[NULL @ 00000128eb6123c0] Invalid sync code 009c96.
[libvpx @ 00000128eb612a40] Failed to decode frame: Bitstream not supported by this decoder
Error while decoding stream #0:0: Invalid data found when processing input
Cannot determine format of input stream 0:0 after EOF
Error marking filters as finished
Conversion failed!
ffmpeg -i input.webm 的日志：
ffmpeg version 2021-02-02-git-2367affc2c-full_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-libsnappy --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libdav1d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-libass --enable-frei0r --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-libglslang --enable-vulkan --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
libavutil 56. 64.100 / 56. 64.100
libavcodec 58.120.100 / 58.120.100
libavformat 58. 65.101 / 58. 65.101
libavdevice 58. 11.103 / 58. 11.103
libavfilter 7.101.100 / 7.101.100
libswscale 5. 8.100 / 5. 8.100
libswresample 3. 8.100 / 3. 8.100
libpostproc 55. 8.100 / 55. 8.100
Input #0, matroska,webm, from 'input.webm':
Metadata:
encoder : libwebm-0.2.1.0
creation_time : 2017-12-02T12:06:12.000000Z
Duration: 00:00:10.00, start: 0.000000, bitrate: 2592 kb/s
Stream #0:0(eng): Video: vp9 (Profile 0), yuv420p(tv), 800x832, SAR 1:1 DAR 25:26, 30 fps, 30 tbr, 1k tbn, 1k tbc (default)
Metadata:
alpha_mode : 1
At least one output file must be specified
使用
ffmpeg -c:v libvpx-vp9 -i in.webm -c:v libvpx -vf scale=400:416 -auto-alt-ref 0 out.webm
输入视频是VP9，而libvpx解码器是VP8。
如果你想要 VP9 流，对输出做同样的事情。