Cannot connect Video pipe to FFmpeg

[mankouzhuya]

Describe the bug
Captura version: v8.0.0
print error msg 'Cannot connect Video pipe to FFmpeg' sometimes and the video file invalid only 1KB.
Captura
To Reproduce
Steps to reproduce the behavior:

1. start with commandline
2. kill the Captura process whit 'taskkill /pid %d -t -f' command
   the Captura console print error msg:
   System.Exception: Cannot connect Video pipe to FFmpeg\r\n
   at Captura.Models.FFmpegWriter.WriteFrame(IBitmapFrame Frame)\r\n
   at Captura.Models.WithPreviewWriter.WriteFrame(IBitmapFrame Image)\r\n
   at Screna.Recorder.DoWrite()

Desktop (please complete the following information):

• OS: win server 2016
• RAM: 4GB
• CPU: 2.5GHz(Intel(R) Xeon(R) Platinum 8163 CPU)
• Graphic Card:
• Captura Version: [v8.0.0]

[MathewSachin]

Please try the latest beta.
If this issue still happens on the latest beta reopen the open and also provide the command line arguments used to start captura.

[mankouzhuya]

commandline： captura-cli start --cursor --encoder ffmpeg:0 - f test.mp4
when i run the commandline with v9.0_beta4。the console print 'NullReferenceException'。
details：
Captura v9.0.0
(c) 2020 Mathew Sachin

Video Buffer Allocated: 2160000
System.NullReferenceException: Object reference not set to an instance of an object.
at SharpDX.MediaFoundation.Sample.GetBufferByIndex(Int32 dwIndex)
at Captura.MfColorConverter.Convert(Texture2D Texture, Byte[] Output)
at Captura.Models.FFmpegWriter.WriteFrame(IBitmapFrame Frame)
at Captura.Models.WithPreviewWriter.WriteFrame(IBitmapFrame Image)
at Screna.Recorder.AddFrame(IBitmapFrame Frame)
at Screna.Recorder.FrameWriter(TimeSpan Timestamp)
at System.Threading.Tasks.Task`1.InnerInvoke()
at System.Threading.Tasks.Task.Execute()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at Screna.Recorder.d__20.MoveNext()
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