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Zhro
Asked: 2021-03-27 18:18:05 +0800 CST

仅在指定第二遍时，FFmpeg 错误“请求的比特率太低”何时出现？

  • 772

我正在尝试ffmpeg在 Windows 上使用 mpeg4 对文件进行编码，并且效果很好：

ffmpeg.exe -y -i input.avi -c:v mpeg4 -q:v 3 -s 640x448 output.avi

除非我尝试使用两遍编码：

ffmpeg.exe -y -i input.avi -c:v mpeg4 -q:v 3 -s 640x448 -pass 1 -an -f avi NUL
ffmpeg.exe -y -i input.avi -c:v mpeg4 -q:v 3 -s 640x448 -pass 2 output.avi

第一遍很好，但第二遍抛出错误：

Input #0, matroska,webm, from 'input.avi':
  Metadata:
    encoder         : libebml-0.7.5 & libmatroska-0.7.7
    creation_time   : 2012-05-28T14:59:33.000000Z
  Duration: 00:01:11.40, start: 0.000000, bitrate: 2101 kb/s
  Stream #0:0(eng): Video: vp8 (VP80 / 0x30385056), yuv420p(progressive), 1280x896, SAR 1:1 DAR 10:7, 15 fps, 15 tbr, 1k
 tbn, 1k tbc (default)
  Stream #0:1(eng): Audio: vorbis, 22050 Hz, stereo, fltp (default)
Stream mapping:
  Stream #0:0 -> #0:0 (vp8 (native) -> mpeg4 (native))
  Stream #0:1 -> #0:1 (vorbis (native) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
[mpeg4 @ 000001d795b8f5c0] requested bitrate is too low

为什么当我尝试使用两遍编码时这只是一个问题？

第一次通过的完整日志：

ffmpeg version 2021-03-21-git-75fd3e1519-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-fontc
onfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-lzma --enable-libsnappy --enable-zlib --enab
le-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enabl
e-sdl2 --enable-libdav1d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enabl
e-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 --en
able-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwb
enc --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-chr
omaprint
  libavutil      56. 71.100 / 56. 71.100
  libavcodec     58.135.100 / 58.135.100
  libavformat    58. 77.100 / 58. 77.100
  libavdevice    58. 14.100 / 58. 14.100
  libavfilter     7.111.100 /  7.111.100
  libswscale      5. 10.100 /  5. 10.100
  libswresample   3. 10.100 /  3. 10.100
  libpostproc    55. 10.100 / 55. 10.100
Input #0, matroska,webm, from 'input.avi':
  Metadata:
    encoder         : libebml-0.7.5 & libmatroska-0.7.7
    creation_time   : 2012-05-28T14:59:33.000000Z
  Duration: 00:01:11.40, start: 0.000000, bitrate: 2101 kb/s
  Stream #0:0(eng): Video: vp8 (VP80 / 0x30385056), yuv420p(progressive), 1280x896, SAR 1:1 DAR 10:7, 15 fps, 15 tbr, 1k
 tbn, 1k tbc (default)
  Stream #0:1(eng): Audio: vorbis, 22050 Hz, stereo, fltp (default)
Stream mapping:
  Stream #0:0 -> #0:0 (vp8 (native) -> mpeg4 (native))
Press [q] to stop, [?] for help
Output #0, avi, to 'NUL':
  Metadata:
    ISFT            : Lavf58.77.100
  Stream #0:0(eng): Video: mpeg4 (FMP4 / 0x34504D46), yuv420p(tv, bt470bg/unknown/unknown, progressive), 640x448 [SAR 1:
1 DAR 10:7], q=2-31, 200 kb/s, 15 fps, 15 tbn (default)
    Metadata:
      encoder         : Lavc58.135.100 mpeg4
    Side data:
      cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: N/A
frame= 1071 fps=719 q=3.0 Lsize=   13267kB time=00:01:11.40 bitrate=1522.1kbits/s speed=47.9x
video:13236kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.236026%

第二遍的完整日志：

ffmpeg version 2021-03-21-git-75fd3e1519-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-fontc
onfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-lzma --enable-libsnappy --enable-zlib --enab
le-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enabl
e-sdl2 --enable-libdav1d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enabl
e-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 --en
able-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwb
enc --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-chr
omaprint
  libavutil      56. 71.100 / 56. 71.100
  libavcodec     58.135.100 / 58.135.100
  libavformat    58. 77.100 / 58. 77.100
  libavdevice    58. 14.100 / 58. 14.100
  libavfilter     7.111.100 /  7.111.100
  libswscale      5. 10.100 /  5. 10.100
  libswresample   3. 10.100 /  3. 10.100
  libpostproc    55. 10.100 / 55. 10.100
Input #0, matroska,webm, from 'input.avi':
  Metadata:
    encoder         : libebml-0.7.5 & libmatroska-0.7.7
    creation_time   : 2012-05-28T14:59:33.000000Z
  Duration: 00:01:11.40, start: 0.000000, bitrate: 2101 kb/s
  Stream #0:0(eng): Video: vp8 (VP80 / 0x30385056), yuv420p(progressive), 1280x896, SAR 1:1 DAR 10:7, 15 fps, 15 tbr, 1k
 tbn, 1k tbc (default)
  Stream #0:1(eng): Audio: vorbis, 22050 Hz, stereo, fltp (default)
Stream mapping:
  Stream #0:0 -> #0:0 (vp8 (native) -> mpeg4 (native))
  Stream #0:1 -> #0:1 (vorbis (native) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
[mpeg4 @ 000001d795b8f5c0] requested bitrate is too low
video ffmpeg

1 个回答

  1. Best Answer

    如果要执行多次传递，请使用-b:v，而不是-q:v/ 。-qscale:v

    来自 FFmpeg 开发人员之一：

    我认为同时拥有-q:vand-pass选项没有意义。

    多遍编码旨在实现一定的平均比特率，并在整个文件上对其进行管理，以便为需要更多比特的部分提供更多比特。

    该-q:v选项设置量化器值（对于任何给定的帧，它与质量级别直接相关），并且不允许编码器选择设置比特率。

    如果您关心生成文件的总大小，则需要使用-b:v设置平均比特率并-pass尽可能有效地使用它。如果没有，你设置-q:v并只做一次传球。

    使用 VBR qscale 时，来自请求的比特率太低

    • 0

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