Reading Progress from Command Prompt

[Arokh]

I use a Cmd Prompt app (AVDump) which hashes and gets info from a video file (~200MB), which of course takes some time.

While the App processes the file, it prints the progress into the cmd prompt,

which I want to read into my App.

 

Now I already achieved to read the line necessary from the cmd prompt,

but with a huge delay, to be more exact, after the hashing is done.

 

Since AVDump drives the CPU usage to 100%, I thought lowering the priority would solve the problem but it didn't.

 

Here is the code I use:

Public Class AVDump
   Dim CmdOutPut As IO.StreamReader
   Dim CmdProcess As New Process
   Dim Reader As New Threading.Thread(AddressOf ReadProgress)

   Private Sub ReadProgress()
       Do Until CmdProcess.HasExited
           Debug.Print(CmdOutPut.ReadLine)
       Loop
   End Sub

   Public Sub StartAVDump(ByVal CmdLine As String)
       CmdProcess.StartInfo.FileName = My.Application.Info.DirectoryPath & "\AVDump\avdump.exe"
       CmdProcess.StartInfo.RedirectStandardOutput = True
       CmdProcess.StartInfo.UseShellExecute = False

       CmdProcess.Start()
       CmdProcess.PriorityClass = ProcessPriorityClass.BelowNormal

       CmdOutPut = CmdProcess.StandardOutput

       Reader.Start()
   End Sub
End Class

 

Is there any way to get the progress in realtime?

 

The aguments to AVDump:

"-log:log.xml -ay " & Chr(34) & "[VIDEOFILE(AVI;MPG;MP4;MKV;OGM)]" & Chr(34)

[MrPaul]

StreamReader may buffer

 

The StreamReader class may be performing internal buffering. Rather than using CmdOutPut.ReadLine followed by Debug.Print, perhaps you could try using CmdOutPut.Read followed by Debug.Write (as the line seperators would also transfer):

 

Private Sub ReadProgress() 
   Dim buff As Char()
   Dim numRead As Integer

   buff = New Char(4096) 'Default stream buffer size

   Do Until CmdProcess.HasExited 
       'Attempt to read some text
       numRead = CmdOutPut.Read(buff, 0, buff.Length)

       If (numRead > 0) Then
           'Write text to Debug
           Debug.Write(New String(buff, 0, numRead))
       End If
   Loop 
End Sub

 

Good luck :)

[Arokh]

Unfortunately, this didn't solve the problem.

Although I had to change the code a little, but I guess it is the same:

Dim buff(4096) As Char
Dim numRead As Integer

Do Until CmdProcess.HasExited
...

The Procedure "stops" on numRead = CmdOutPut.Read(buff, 0, buff.Length)

until the Hashing of the file is complete.

 

After that it outputs the first line printed

(which should have been printed directly after the cmd prompt was started)

till the last or somewhere in the middle,

since the cmd is closed right after the hashing is done

and HasExited is true before all the old lines could be printed.

 

So I guess that means the StreamReader is still buffering.

I also tried to lower the CharArray with no luck.

Any other ideas?

 

And I forgot to say that in addition to the heavy load on the CPU the cmd prompt outputs ~4 lines per second.

But it is not important to get all of them, if I could get the lines in realtime this way.

[MrPaul]

Reading directly from Stream

 

You could try reading directly from the Stream which the StreamReader is reading from:

 

'Import System.IO, System.Text and System.Threading

Private Sub ReadProgress()
   Dim buff As Byte()
   Dim numRead As Integer

   buff = New Byte(4095) 'Default stream buffer size

   Do Until CmdProcess.HasExited
       'Attempt to read some text
       numRead = CmdOutPut.BaseStream.Read(buff, 0, buff.Length)

       While (numRead > 0)
           'Write text to Debug
           Debug.Write(Encoding.Default.GetString(buff, 0, numRead))
           'Attempt to read more text
           numRead = CmdOutPut.BaseStream.Read(buff, 0, buff.Length)
       End While

       Thread.Sleep(1) 'Don't hog the CPU
   Loop
End Sub

 

Try it and see. Good luck :)

[kurf]

Re: Reading directly from Stream

 

you could also try and sleep the thread for 0(zero) which will cause it to yeild and it will help stop the hammering on the processor