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I was dabbling with ffprobe (ffmpeg might be affected as well) calling it from the command-line in a Lazarus program, using TProcess, only to notice that I didn't get any output back from the command-line call.
Low and behold, for some reason odd ffprobe actually doesn't use stdout but stderr.
The code below shows how I call ffprobe and catch it's output in Lazarus:
procedure TForm1.Button1Click(Sender: TObject);
var fExec, Args : string;
begin
fExec := './ffprobe';
Args := '';
with TProcess.Create(self) do
begin
CurrentDirectory := '.';
Options := [poUsePipes];
CommandLine := fExec + ' ' + Args;
Execute;
Memo1.Lines.LoadFromStream(Stderr); // use the Stderr property instead of the Output property
end;
end;
This should be cross platform, with the exception of course on how ffprobe is called in the fExec string (patch and such).
Don't forget to add Process to your Uses clause.
I stand corrected:
1) The default info from ffprobe (version, libs, etc) goes through stderr.
2) The movie informatie however comes through stdout.
Note: Output can be pretty extensive. If that's the case consider having Lazarus wait by changing line 9 to:
Options := [poWaitOnExit,poUsePipes];
In the end I used this for both MacOS X and Windows:
{$IFDEF DARWIN} // Mac
fExec := ProgramDirectory+'ffprobe';
{$ENDIF}
{$IFDEF WINDOWS} // Windows
fExec := 'ffprobe.exe';
{$ENDIF}
MyShell := TProcess.Create(self);
ShellResult := TStringList.Create;
MemStream := TMemoryStream.Create;
BytesRead := 0;
with MyShell do
begin
Options:=[poUsePipes];
ShowWindow:=swoHIDE;
Executable:=fExec;
Parameters.Add('-show_format');
Parameters.Add('-show_streams');
Parameters.Add('-v');
Parameters.Add('quiet');
Parameters.Add('-print_format');
Parameters.Add('ini');
Parameters.Add(movieFile);
Execute;
end;
while MyShell.Running do
begin
MemStream.SetSize(BytesRead + READ_BYTES);
NumBytes := MyShell.Output.Read((MemStream.Memory + BytesRead)^, READ_BYTES);
if NumBytes > 0 then
begin
Inc(BytesRead, NumBytes);
end
else
begin
Sleep(100);
end;
end;
repeat
// make sure we have room
MemStream.SetSize(BytesRead + READ_BYTES);
// try reading it
NumBytes := MyShell.Output.Read((MemStream.Memory + BytesRead)^, READ_BYTES);
if NumBytes > 0 then
begin
Inc(BytesRead, NumBytes);
end;
until NumBytes <= 0;
MemStream.SetSize(BytesRead);
ShellResult.LoadFromStream(MemStream);
MemStream.Free;
MyShell.Free;