Ffmpeg record video, stop (vb.net, step on the pit, class library - 10)

Many tutorials on the Internet , About FFmpeg Recording video , To install Screen Capturer Recorder,

We don't need to install a big lump of things

1、 Still want to download 、 install

  But we only need to use one of them 2 A component

 audio_sniffer It's in the catalog ：Screen Capturer Recorder\vendor\virtual-audio

Select the corresponding components according to the needs of the system , We use it by default Not x64 Of , namely x32

Extract these two after installation Selected The file can be uninstalled

Do one thing before using , stay 2 Create an application manifest file in each project , If you have only one project , All you need is an application manifest file . hold

  Replace the second line of the comment section   "-->" Later （ I have replaced ） such , The main program will run as an administrator , With Restart as administrator visual studio. The purpose is register Those two components , Give Way FFmpeg distinguish , Do not change the name of the component .（ Be sure to use the administrator identity ）

register Code for ：

Public Class RegDll
    Public Function RegRec()
        VideoProcess.SharedP("C:\WINDOWS\system32\cmd.exe", "/c /q regsvr32 /u " & Application.StartupPath & "\screen-capture-recorder.dll", True)
        VideoProcess.SharedP("C:\WINDOWS\system32\cmd.exe", "/c /q regsvr32 " & Application.StartupPath & "\screen-capture-recorder.dll", True)

        VideoProcess.SharedP("C:\WINDOWS\system32\cmd.exe", "/c /q regsvr32 /u " & Application.StartupPath & "\audio_sniffer.dll", True)
        VideoProcess.SharedP("C:\WINDOWS\system32\cmd.exe", "/c /q regsvr32 " & Application.StartupPath & "\audio_snifferr.dll", True)
    End Function

Public Shared Function SharedP(s As String, Arguments As String, nowindow As Boolean)
        Dim p As New Process
        p.StartInfo.FileName = s
        p.StartInfo.Arguments = Arguments
        p.StartInfo.UseShellExecute = False
        p.StartInfo.RedirectStandardError = True
        p.StartInfo.CreateNoWindow = nowindow
        p.Start()
        p.WaitForExit()
        p.StandardError.ReadToEnd()
        Return p.StandardError.ReadToEnd()
        p.Close()
        p.Dispose()
    End Function


End Class

notes ： You can register with sharedP Written in the same class , my sharedP It's written in VideoProcess Class

The main form first registers these two components , In order to use for others , It can simplify the operation , Let the program register itself , Can be in Form_Load Sign up for , The perform RegRec function （function, You can change to sub）

2、 On the premise of registration , We're not here FFmpeg Tested , There must be

FFmpeg -list_devices true -f dshow -i dummy

 3、 Write 2 A process , It doesn't have to be a function , Because there is no value to return

 Public PRec As New Process

Public Function StartRecordVid(ffmpeg As String, out As String)
        PRec.StartInfo.FileName = "cmd"
        PRec.StartInfo.Arguments = "/c " & ffmpeg & " -f dshow -i audio=" & Chr(34) & " Microphone array  (Conexant SmartAudio HD)" & Chr(34) & " -f dshow -i audio=" & Chr(34) & "virtual-audio-capturer" & Chr(34) & " -filter_complex amix=inputs=2:duration=first:dropout_transition=0 -f dshow -i video=" & Chr(34) & "screen-capture-recorder" & Chr(34) & " -pix_fmt yuv420p " & out & " -y"
        PRec.StartInfo.UseShellExecute = False
        PRec.StartInfo.CreateNoWindow = true
        'PRec.StartInfo.RedirectStandardOutput = True
        'PRec.StartInfo.RedirectStandardError = True
        PRec.StartInfo.RedirectStandardInput = True
        PRec.Start()
        PRec.EnableRaisingEvents = True

    End Function
    Public Function EndRecordVid()
        PRec.StandardInput.WriteLine("q")
        PRec.StandardInput.AutoFlush = True
        PRec.Close()
        PRec.Dispose()
    End Function

You need to use    "    have access to chr(34) Instead of

It is worth noting that ： Because I didn't think carefully when watching others' tutorials , Cause to execute first StartRecordVid Function time ,PRec already close + dispose 了 , So that when the call stops StandardInput This error has not been redirected

This is the wrong code ：

Public Function StartRecordVid(ffmpeg As String, out As String)
        PRec.StartInfo.FileName = "cmd"
        PRec.StartInfo.Arguments = "/c " & ffmpeg & " -f dshow -i audio=" & Chr(34) & " Microphone array  (Conexant SmartAudio HD)" & Chr(34) & " -f dshow -i audio=" & Chr(34) & "virtual-audio-capturer" & Chr(34) & " -filter_complex amix=inputs=2:duration=first:dropout_transition=0 -f dshow -i video=" & Chr(34) & "screen-capture-recorder" & Chr(34) & " -pix_fmt yuv420p " & out & " -y"
        PRec.StartInfo.UseShellExecute = False
        PRec.StartInfo.CreateNoWindow = true
        'PRec.StartInfo.RedirectStandardOutput = True
        'PRec.StartInfo.RedirectStandardError = True
        PRec.StartInfo.RedirectStandardInput = True
        PRec.Start()
        PRec.EnableRaisingEvents = True
         PRec.Close()
        PRec.Dispose()

    End Function
    Public Function EndRecordVid()
        PRec.StandardInput.WriteLine("q")
        PRec.StandardInput.AutoFlush = True
       
    End Function

This is a pit , Don't step on it

Last ： Don't forget to FFmpeg All processes end the task ,

 Public Function EndRecordVid()
        PRec.StandardInput.WriteLine("q")
        PRec.StandardInput.AutoFlush = True
       ' PRec.Close()
        'PRec.Dispose()
        PRec.Kill()
    End Function

Join in kill Instructions , In order to move the video , Unwanted close and dispose 了 .