ffmpeg - 通过 UTP 上的 USB 使用 FFmpeg 进行网络摄像头录制

Question

我正在尝试使用 FFmpeg 录制我的网络摄像头。
我用这一行列出了设备:

ffmpeg -list_devices true -f dshow -i dummy

我用这个测试设置:

ffplay -loglevel verbose -f dshow -rtbufsize 100M -video_size 1280x720 -framerate 60 -video_device_number 0 -audio_device_number 0 -i video="C922 Pro Stream Webcam":audio="Microphone (C922 Pro Stream Web"

第一个命令输出:

ffmpeg version n4.4-10-g75c3969292 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 10-win32 (GCC) 20210408
  configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-w64-mingw32- --arch=x86_64 --target-os=mingw32 --enable-gpl --enable-version3 --disable-debug --disable-w32threads --enable-pthreads --enable-iconv --enable-libxml2 --enable-zlib --enable-libfreetype --enable-libfribidi --enable-gmp --enable-lzma --enable-fontconfig --enable-libvorbis --enable-opencl --enable-libvmaf --enable-vulkan --enable-amf --enable-libaom --enable-avisynth --enable-libdav1d --enable-libdavs2 --enable-ffnvcodec --enable-cuda-llvm --enable-libglslang --enable-libgme --enable-libass --enable-libbluray --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --enable-libmfx --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librav1e --enable-librubberband --enable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --enable-libvidstab --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-libs=-lgomp
  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
[dshow @ 000000000035a000] DirectShow video devices (some may be both video and audio devices)
[dshow @ 000000000035a000]  "C922 Pro Stream Webcam"
[dshow @ 000000000035a000]     Alternative name "@device_pnp_\\?\usb#vid_046d&pid_085c&mi_00#9&1da24ac&0&0000#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\global"
[dshow @ 000000000035a000] DirectShow audio devices
[dshow @ 000000000035a000]  "Microphone (C922 Pro Stream Web"
[dshow @ 000000000035a000]     Alternative name "@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\Microphone (C922 Pro Stream Web"
[dshow @ 000000000035a000]  "Microphone (Realtek High Defini"
[dshow @ 000000000035a000]     Alternative name "@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\Microphone (Realtek High Defini"
dummy: Immediate exit requested

第二个是这样的:

ffplay version n4.4-10-g75c3969292 Copyright (c) 2003-2021 the FFmpeg developers
  built with gcc 10-win32 (GCC) 20210408
  configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-w64-mingw32- --arch=x86_64 --target-os=mingw32 --enable-gpl --enable-version3 --disable-debug --disable-w32threads --enable-pthreads --enable-iconv --enable-libxml2 --enable-zlib --enable-libfreetype --enable-libfribidi --enable-gmp --enable-lzma --enable-fontconfig --enable-libvorbis --enable-opencl --enable-libvmaf --enable-vulkan --enable-amf --enable-libaom --enable-avisynth --enable-libdav1d --enable-libdavs2 --enable-ffnvcodec --enable-cuda-llvm --enable-libglslang --enable-libgme --enable-libass --enable-libbluray --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --enable-libmfx --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librav1e --enable-librubberband --enable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --enable-libvidstab --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-libs=-lgomp
  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
Initialized direct3d renderer.
    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0   
    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0   
    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0   
    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0   
    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0   
    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0   
    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0   
    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0   
    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0   
dshow passing through packet of type video size   170103 timestamp 2074640340000 orig timestamp 2074640336004 graph timestamp 2074640340000 diff 3996 C922 Pro Stream Webcam
    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0   
dshow passing through packet of type video size   166381 timestamp 2074640500000 orig timestamp 2074640502670 graph timestamp 2074640500000 diff -2670 C922 Pro Stream Webcam
    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0   
dshow passing through packet of type video size   173348 timestamp 2074640820000 orig timestamp 2074640816017 graph timestamp 2074640820000 diff 3983 C922 Pro Stream Webcam
    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0   
...

但是，如果我使用 USB 电缆延长器(USB over UTP - 这个东西由两部分组成:第一个有一个公头，第二个是一个母头 USB A，它们通过 RJ45 socket 和 Cat5e UTP 电缆连接)，它根本不起作用。第一个命令打印相同:

ffmpeg version n4.4-10-g75c3969292 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 10-win32 (GCC) 20210408
  configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-w64-mingw32- --arch=x86_64 --target-os=mingw32 --enable-gpl --enable-version3 --disable-debug --disable-w32threads --enable-pthreads --enable-iconv --enable-libxml2 --enable-zlib --enable-libfreetype --enable-libfribidi --enable-gmp --enable-lzma --enable-fontconfig --enable-libvorbis --enable-opencl --enable-libvmaf --enable-vulkan --enable-amf --enable-libaom --enable-avisynth --enable-libdav1d --enable-libdavs2 --enable-ffnvcodec --enable-cuda-llvm --enable-libglslang --enable-libgme --enable-libass --enable-libbluray --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --enable-libmfx --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librav1e --enable-librubberband --enable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --enable-libvidstab --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-libs=-lgomp
  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
[dshow @ 000000000039a000] DirectShow video devices (some may be both video and audio devices)
[dshow @ 000000000039a000]  "C922 Pro Stream Webcam"
[dshow @ 000000000039a000]     Alternative name "@device_pnp_\\?\usb#vid_046d&pid_085c&mi_00#9&1da24ac&0&0000#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\global"
[dshow @ 000000000039a000] DirectShow audio devices
[dshow @ 000000000039a000]  "Microphone (C922 Pro Stream Web"
[dshow @ 000000000039a000]     Alternative name "@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\Microphone (C922 Pro Stream Web"
[dshow @ 000000000039a000]  "Microphone (Realtek High Defini"
[dshow @ 000000000039a000]     Alternative name "@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\Microphone (Realtek High Defini"
dummy: Immediate exit requested

但第二个因“无法设置视频选项”而失败:

ffplay version n4.4-10-g75c3969292 Copyright (c) 2003-2021 the FFmpeg developers
  built with gcc 10-win32 (GCC) 20210408
  configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-w64-mingw32- --arch=x86_64 --target-os=mingw32 --enable-gpl --enable-version3 --disable-debug --disable-w32threads --enable-pthreads --enable-iconv --enable-libxml2 --enable-zlib --enable-libfreetype --enable-libfribidi --enable-gmp --enable-lzma --enable-fontconfig --enable-libvorbis --enable-opencl --enable-libvmaf --enable-vulkan --enable-amf --enable-libaom --enable-avisynth --enable-libdav1d --enable-libdavs2 --enable-ffnvcodec --enable-cuda-llvm --enable-libglslang --enable-libgme --enable-libass --enable-libbluray --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --enable-libmfx --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librav1e --enable-librubberband --enable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --enable-libvidstab --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-libs=-lgomp
  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
Initialized direct3d renderer.
    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0   

[dshow @ 00000000004de180] Could not set video options
video=C922 Pro Stream Webcam:audio=Microphone (C922 Pro Stream Web: I/O error

可能是什么问题？是延长线吗？ FFmpeg 对 USB 数据线(和延长线)有什么要求？

Answer 1

这不是软件/配置问题 - 它纯粹是电气问题。我假设您有无源 USB 以太网适配器，它只转换接线而不接触信号本身。 5-10 米是您对这种电缆所能期望的最大实际长度(我使用 iPhone 和 Mac Mini 进行了测试)。
Active USB over Ethernet 适配器可能会有所帮助。它们以完全不同的方式工作，并且对主机和访客设备都是完全透明的——不需要额外的配置。
有关 USB 电缆限制的详细信息，请参阅此答案 https://superuser.com/a/64747/416084