使用视频环回设备伪造网络摄像头？

我想使用循环播放的视频剪辑作为Google+环聊中的网络摄像头源。我安装了v4l2loopback并创建了一个视频环回设备。但是我还没有弄清楚如何将视频帧写入设备。给定的示例是：

gst-launch videotestsrc ! v4l2sink device=/dev/video1

因此，在阅读了gst-launch的手册页并尝试了解发生了什么之后，我做了微弱的尝试：

sudo gst-launch-0.10 filesrc location=/home/briankb/Videos/darthvaderdancing.mp4 ! v4l2sink device=/dev/video0

结果是：

Setting pipeline to PAUSED ...
libv4l2: error getting pixformat: Invalid argument
Pipeline is PREROLLING ...
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...

(gst-launch-0.10:12622): GStreamer-CRITICAL **: gst_caps_get_structure: assertion `GST_IS_CAPS (caps)' failed
New clock: GstSystemClock

(gst-launch-0.10:12622): GStreamer-CRITICAL **: gst_structure_get_name: assertion `structure != NULL' failed
Caught SIGSEGV accessing address (nil)
#0  0x00007fc1890f0b03 in poll () from /lib/x86_64-linux-gnu/libc.so.6
#1  0x00007fc18962bff6 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2  0x00007fc18962c45a in g_main_loop_run ()
#3  0x00007fc189b5c4cb in gst_bus_poll ()
#4  0x0000000000404587 in ?? ()
#5  0x0000000000403c34 in ?? ()
#6  0x00007fc18902b76d in __libc_start_main ()
#7  0x00000000004043bd in ?? ()
#8  0x00007fff88253ed8 in ?? ()
#9  0x000000000000001c in ?? ()
#10 0x0000000000000006 in ?? ()
#11 0x00007fff882548c4 in ?? ()
#12 0x00007fff882548d4 in ?? ()
#13 0x00007fff882548dc in ?? ()
#14 0x00007fff88254904 in ?? ()
#15 0x00007fff88254906 in ?? ()
#16 0x00007fff8825490f in ?? ()
#17 0x0000000000000000 in ?? ()
Spinning.  Please run 'gdb gst-launch 12622' to continue debugging, Ctrl-C to quit, or Ctrl-\ to dump core.

我正在尝试使用29.97 fps，320x240并在mp4容器（来自Youtube）中的h264视频的剪辑。