TProcess gstreamer thread wont killed
lazarus / 32-Linux

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af0815 · 2020-01-13 14:48

I want to start gstreamer and make one picture. After this the
gstreamer pipeline should be shut down.

My problem is, the gstreamer pipeline is still exists and every try
there is a new one. Actual the sample works with installed gstreamer
and a USB V4L Kamera.

How can i shutdown the pipeline too ?!

BTW: V4L is not possible because the cameras are only working with
gstreamer (GigE, USB3,...).

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TFormVideoTmp.SnapShot();const  BUF_SIZE = 2048; // Buffer size for
reading the output in chunks var  AProcess: TProcess;  BytesRead:
longint;  Buffer: array[1..BUF_SIZE] of byte;  i,found: Integer; 
line: String;  finish: boolean;begin  AProcess :=
TProcess.Create(nil);   AProcess.Executable := '/bin/sh'; 
AProcess.Parameters.Add('-c');  AProcess.Parameters.Add('/usr/bin/gst-
launch-1.0 -v v4l2src ! identity silent=false ! jpegenc ! filesink
location=/tmp/test.jpg');//  AProcess.Parameters.Add('/usr/bin/gst-
launch-1.0 -v tcambin ! identity silent=false ! jpegenc ! filesink
location=/tmp/test.jpg');  AProcess.Options := [poUsePipes]; 
AProcess.Execute;  finish := false;  repeat    BytesRead :=
AProcess.Output.Read(Buffer, BUF_SIZE);    Line := '';    for i := 1
to BytesRead do begin      Line := Line + chr(Buffer[i]);    end;   
found := Pos('dts',Line);    if (found > 0) and (BytesRead >
(found+4+18)) then begin      finish:= true;    end;    if (BytesRead
= 0) then begin      finish:= true;    end;  until finish;  // Stop if
no more data is available or dts found  if AProcess.Terminate(0) then 
  writeln('Teminate ok')  else    writeln('Terminate NOK'); 
AProcess.Free;end;

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marcov · 2020-01-13 15:03

Probably never block on reads, that leaves you free to terminate.
(e.g. when you termine it is complete.

Best is to look at  FPC 3.2 or 3.3.1 sources, processbody.inc
procedure readinputstream. Note how it continuously checks the bytes
to read using P.NumBytesAvailable

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function TP
rocessnamemacro.ReadInputStream(p:TInputPipeStream;data:TStream;MaxLoo
ps:integer=10):boolean;const  BufSize = 4096;var  Buffer:
array[0..BufSize - 1] of byte;  ReadBytes: integer;  Available :
integer;begin  Available:=P.NumBytesAvailable;  result:=Available>0; 
if not result then    Exit;  while (available > 0) and (MaxLoops>0)
do  begin    ReadBytes := Output.Read({%H-}Buffer,
min(BufSize,Available));    data.Write(Buffer, ReadBytes);   
Available:=P.NumBytesAvailable;    dec(MaxLoops);  end;end;

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af0815 · 2020-01-13 15:25

This is not my problem with the block on read.

I have changed the line a little to
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i   AProcess
:= TProcess.Create(nil);  AProcess.Executable :=
'/home/andi/data/start'; and a start with
Code: Text  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
#!/bin/sh/usr/bin/gst-launch-1.0 -v tcambin ! identity silent=false !
jpegenc ! filesink location=/tmp/test.jpg On commandline it work like
expected. But i see gst-launch-1.0 itself fork and gstreamer have
another processID. Normally one more than the reportedID from
TProcess.

I think this is my problem, gst-launch is shut down, but gstreamer did
not see this signal.

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marcov · 2020-01-13 16:48

Well, then the question is what does gstreamer need to shutdown? 
Maybe a bit of stracing helps.

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af0815 · 2020-01-13 17:35

Quote from: marcov on January 13, 2020, 05:48:53 pm Maybe a bit of
stracing helps.
I found only entries to ST Racing, but nothing about stracing. Can you
give me a more desciptive advice ?

I should send a cntrl-c (=SIGINT) to the gst-launch before terminate?
How can i send it with TProcess ?!

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marcov · 2020-01-13 17:51

Try to type

man strace

on the cmdline. It is a tool to dump syscalls.

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af0815 · 2020-01-14 06:17

Ok, i have done it, the result:
Quote.....
futex(0x557d38f59728, FUTEX_WAIT_PRIVATE, 2, NULL) = 0
read(3, "W", 1)                         = 1
futex(0x557d38f59728, FUTEX_WAKE_PRIVATE, 1) = 0
write(14, "\1\0\0\0\0\0\0\0",         = 8
futex(0x557d392a6dd0, FUTEX_WAKE_PRIVATE, 2147483647) = 0
write(14, "\1\0\0\0\0\0\0\0",         = 8
write(14, "\1\0\0\0\0\0\0\0",         = 8
write(1, "/GstPipeline:pipeline0/GstIdenti"...,
248/GstPipeline:pipeline0/GstIdentity:identity0: last-message = chain 
 ******* (identity0:sink) (25165824 bytes, dts: 0:00:05.304566315,
pts: 0:00:05.304566315, duration: none, offset: -1, offset_end: -1,
flags: 00000000 , meta: none) 0x7f9dcc03c140
) = 248
write(14, "\1\0\0\0\0\0\0\0",         = 8
poll([{fd=3, events=POLLIN}, {fd=14, events=POLLIN}], 2, -1) = 1
([{fd=14, revents=POLLIN}])
read(14, "\5\0\0\0\0\0\0\0", 16)        = 8
poll([{fd=3, events=POLLIN}, {fd=14, events=POLLIN}], 2, -1^C) = ?
ERESTART_RESTARTBLOCK (Interrupted by signal)
strace: Process 2333 detached

andi@DebLap:~$ handling interrupt.
Interrupt: Stopping pipeline ...
Execution ended after 0:00:06.429844722
Setting pipeline to PAUSED ...
Setting pipeline to READY ...
Setting pipeline to NULL ...
Freeing pipeline ...

Ctrl-C should be uses to shut down the pipeline (^C) = ?
ERESTART_RESTARTBLOCK (Interrupted by signal))

But a send a sending of SIGINT to TProcess nothing change, the
pipeline (and TProcess) is still running
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i     repeat 
  BytesRead := AProcess.Output.Read(Buffer, BUF_SIZE);    Line := ''; 
  for i := 1 to BytesRead do begin      Line := Line +
chr(Buffer[i]);    end;    writeln(Line);    found :=
Pos('dts',Line);    if (found > 0) and (BytesRead > (found+4+18)) then
begin      writeln(copy(Line,found+4,18));     
writeln('+++++++++++++');      if fpkill(AProcess.Handle,SIGINT)=0
then        writeln('SIGINT ok')      else        writeln('SIGINT
NOK');    end;    if (BytesRead = 0) then begin     
writeln('-------------');      finish:= true;    end;  until finish;
 // Stop if no more data is available or dts found

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trev · 2020-01-14 06:42

Have you tried using  gst-launch  with the -e argument?

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af0815 · 2020-01-14 07:34

Quote from: trev on January 14, 2020, 07:42:02 amHave you tried using 
gst-launch  with the -e argument?
-e is not a valid argument
Quotegst-launch-1.0 accepts the following options:
--help
Print help synopsis and available FLAGS

-v, --verbose
Output status information and property notifications

-q, --quiet
Do not print any progress information

-m, --messages
Output messages posted on the pipeline's bus

-t, --tags
Output tags (also known as metadata)

-o FILE, --output=FILE
Save XML representation of pipeline to FILE and exit

-f, --no_fault
Do not install a fault handler

-T, --trace
Print memory allocation traces. The feature must be enabled at compile
time to work.Source:
https://gstreamer.freedesktop.org/documentation/tools/gst-
launch.html?gi-language=c

Actual i use a workaround and search for the PID of gst-launch and
send the SIGINT direct to the process instead of sending to TProcess.
It looks the SIGINT is eaten by the basic process, controlled by
TProcess and never send to the childs.

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
IsCommandRunning(cmd:String):THandle;var  t:TProcess; 
s,s1:TStringList;  erg: integer;  h1,h2,h3:string;begin  Result:=0; 
t:=tprocess.create(nil);  t.Executable:='ps'; 
t.Parameters.Add('-C'+cmd);  t.Options:=[poUsePipes,poWaitonexit]; 
try    t.Execute;    s:=tstringlist.Create;    try     
s.LoadFromStream(t.Output);      if s.Count > 1 then begin        //
Zeile 0 = Text        h1:= s[1];        s1:=TStringList.Create;      
try          s1.Delimiter:=#32;          s1.StrictDelimiter:=true;   
     s1.DelimitedText:= trim(s[1]);          h2:= s1[0];          erg
:= 0;          if s1.Count > 1 then           
TryStrToInt(s1[0],erg);          Result:=erg;        finally         
s1.free;        end;      end;    finally      s.free;    end; 
finally    t.Free;  end;end; if the Handle is 0 the process was not
found.