当我尝试将视频播放到虚拟摄像头时，它可以工作，但是当我尝试将网络摄像头播放到虚拟摄像头时，它什么也不做。
我做什么：
将视频播放到虚拟相机：
ffmpeg -re -i "yt.mkv" -map 0:v -f v4l2 "/dev/video2"
然后 ^C
将网络摄像头播放到虚拟摄像头：
ffmpeg -i "/dev/video0" -map 0:v -f v4l2 "/dev/video2"
当我执行最后一个命令时会发生什么：什么都没有发生。播放的视频的最后一帧只是停留在那里，冻结了。
当我使用ffplay /dev/video2它时输出：
[video4linux2,v4l2 @ 0x7fdcf4000b80] Dequeued v4l2 buffer contains 460800 bytes, but 1382400 were expected. Flags: 0x00000001.
我可以播放 2 个不同的视频，所以我不知道为什么它不起作用
我怎样才能让它工作？
编辑：日志
第一个命令
ffmpeg version 4.1.6-1~deb10u1 Copyright (c) 2000-2020 the FFmpeg developers
built with gcc 8 (Debian 8.3.0-6)
configuration: --prefix=/usr --extra-version='1~deb10u1' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
libavutil 56. 22.100 / 56. 22.100
libavcodec 58. 35.100 / 58. 35.100
libavformat 58. 20.100 / 58. 20.100
libavdevice 58. 5.100 / 58. 5.100
libavfilter 7. 40.101 / 7. 40.101
libavresample 4. 0. 0 / 4. 0. 0
libswscale 5. 3.100 / 5. 3.100
libswresample 3. 3.100 / 3. 3.100
libpostproc 55. 3.100 / 55. 3.100
Input #0, matroska,webm, from 'yt.mkv':
Metadata:
ENCODER : Lavf58.20.100
Duration: 00:00:43.28, start: -0.007000, bitrate: 2025 kb/s
Stream #0:0(eng): Audio: opus, 48000 Hz, stereo, fltp (default)
Metadata:
DURATION : 00:00:43.281000000
Stream #0:1: Video: h264 (Main), yuv420p(tv, bt709, progressive), 1280x720 [SAR 1:1 DAR 16:9], 60 fps, 60 tbr, 1k tbn, 120 tbc (default)
Metadata:
HANDLER_NAME : ISO Media file produced by Google Inc.
DURATION : 00:00:43.234000000
Stream mapping:
Stream #0:1 -> #0:0 (h264 (native) -> rawvideo (native))
Press [q] to stop, [?] for help
Output #0, video4linux2,v4l2, to '/dev/video2':
Metadata:
encoder : Lavf58.20.100
Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 663552 kb/s, 60 fps, 60 tbn, 60 tbc (default)
Metadata:
HANDLER_NAME : ISO Media file produced by Google Inc.
DURATION : 00:00:43.234000000
encoder : Lavc58.35.100 rawvideo
frame= 27 fps=0.0 q=-0.0 size=N/A time=00:00:00.45 bitrate=N/A speed=0.887x
第二个 ：
ffmpeg version 4.1.6-1~deb10u1 Copyright (c) 2000-2020 the FFmpeg developers
built with gcc 8 (Debian 8.3.0-6)
configuration: --prefix=/usr --extra-version='1~deb10u1' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
libavutil 56. 22.100 / 56. 22.100
libavcodec 58. 35.100 / 58. 35.100
libavformat 58. 20.100 / 58. 20.100
libavdevice 58. 5.100 / 58. 5.100
libavfilter 7. 40.101 / 7. 40.101
libavresample 4. 0. 0 / 4. 0. 0
libswscale 5. 3.100 / 5. 3.100
libswresample 3. 3.100 / 3. 3.100
libpostproc 55. 3.100 / 55. 3.100
Input #0, video4linux2,v4l2, from '/dev/video0':
Duration: N/A, start: 13203.980211, bitrate: 110592 kb/s
Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 640x360, 110592 kb/s, 30 fps, 30 tbr, 1000k tbn, 1000k tbc
Stream mapping:
Stream #0:0 -> #0:0 (rawvideo (native) -> rawvideo (native))
Press [q] to stop, [?] for help
Output #0, video4linux2,v4l2, to '/dev/video2':
Metadata:
encoder : Lavf58.20.100
Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 640x360, q=2-31, 82944 kb/s, 30 fps, 30 tbn, 30 tbc
Metadata:
encoder : Lavc58.35.100 rawvideo
frame= 222 fps= 32 q=-0.0 Lsize=N/A time=00:00:07.40 bitrate=N/A dup=117 drop=0 speed=1.06x
ffplay-
ffplay version 4.1.6-1~deb10u1 Copyright (c) 2003-2020 the FFmpeg developers
built with gcc 8 (Debian 8.3.0-6)
configuration: --prefix=/usr --extra-version='1~deb10u1' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
libavutil 56. 22.100 / 56. 22.100
libavcodec 58. 35.100 / 58. 35.100
libavformat 58. 20.100 / 58. 20.100
libavdevice 58. 5.100 / 58. 5.100
libavfilter 7. 40.101 / 7. 40.101
libavresample 4. 0. 0 / 4. 0. 0
libswscale 5. 3.100 / 5. 3.100
libswresample 3. 3.100 / 3. 3.100
libpostproc 55. 3.100 / 55. 3.100
Input #0, video4linux2,v4l2, from '/dev/video2':B sq= 0B f=0/0
Duration: N/A, start: 893.874176, bitrate: 82944 kb/s
Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 640x360, 82944 kb/s, 30 fps, 30 tbr, 1000k tbn, 1000k tbc
[video4linux2,v4l2 @ 0x7f5f30000b80] Dequeued v4l2 buffer contains 348160 bytes, but 345600 were expected. Flags: 0x00000001.
[video4linux2,v4l2 @ 0x7f5f30000b80] Dequeued v4l2 buffer contains 348160 bytes, but 345600 were expected. Flags: 0x00000001.
答案1
尝试：
ffmpeg -f v4l2 -i /dev/video0 -f v4l2 /dev/video2