The VideoLAN Forums

Posted: **06 Oct 2013 13:37**

I get floating point error from libvlccore when using libvlc_audio_set_volume while playback, no crash if playback is stopped. On 2.0.x there is no problem. Tested on Win8x86 and Win7x64.

Maybe parameters changed and somebody forgot to update documentation?

Posted: **07 Oct 2013 14:17**

You might need to provide more information. I'm not having any problem. I'm using:
libvlc_audio_set_volume(vlcPlayer, vol);
...where vol is int from 0 to 200.

It's compiled using 32-bit libvlc, running in WinXP (32bit) and Win7 (32 and 64bit).

Posted: **07 Oct 2013 15:12**

I'm doing exactly the same as you.

libvlc_audio_set_volume : function(p_media_player : Plibvlc_media_player_t; volume : Integer) : Integer; cdecl;

All worked on 1.1.x and 2.0.x, but with 2.1.0 I get floating point error from module libvlccore.dll when calling libvlc_audio_set_volume with any value >0 while playback is active.
I'm using delphi7 and this wrapper - https://code.google.com/p/utlibvlc/

BTW what lang/compiler are you using?

Posted: **07 Oct 2013 16:14**

I guess you can look into the delphi wrapper, then. I'm writing in C.

Posted: **07 Oct 2013 16:26**

MSVC or QT ? I tested a C# .NET 3.5 wrapper in MSVC and it crashes with the same floating point error.
But my friend compiled demo QtVLC by QT-Creator and it worked without errors.

The thing is call to function is exactly the same everywhere...

BTW function libvlc_audio_set_volume always returns 0 in my situation

Posted: **07 Oct 2013 17:07**

I don't use a "wrapper". My code is C/C++. I'm not having any problem with libvlc_audio_set_volume() calls during playback.

Posted: **07 Oct 2013 17:32**

Posted: **08 Oct 2013 05:26**

Here is my code. No wrappers, just direct calls. It can be easy rewritten to any language:

Code: Select all

program Test;

function  AllocConsole:LongBool; stdcall; external 'kernel32.dll';

function  libvlc_new(argc:integer; args:ppchar):pointer; cdecl; external 'libvlc.dll';
function  libvlc_media_new_path(vlc: pointer; mrl : pchar):pointer;cdecl; external 'libvlc.dll';
function  libvlc_media_player_new_from_media(media: pointer): pointer; cdecl; external 'libvlc.dll';
procedure libvlc_media_player_play(mediaplayer: pointer); cdecl; external 'libvlc.dll';
procedure libvlc_audio_set_volume(mediaplayer: pointer; volume:integer); cdecl; external 'libvlc.dll';

var
  args:array of pchar;
  fn:string;
  v:integer;
  p_libvlc,p_media,p_player:pointer;
begin
  AllocConsole;
  SetLength(args,5);
  args[0]:=pchar('--plugin-path=..\plugins');
  args[1]:=pchar('--no-osd');
  args[2]:=pchar('--no-media-library');
  args[3]:=pchar('--no-video-title-show');
  args[4]:=nil;
  p_libvlc:=libvlc_new(System.Length(args)-1,@args[0]);
  if p_libvlc=nil then begin WriteLn('p_libvlc is nil');ReadLn;Halt;end;
  fn:='e:\bla-bla.avi'; // whatever
  p_media:=libvlc_media_new_path(p_libvlc,pchar(fn));
  if p_media=nil then begin WriteLn('p_media is nil');ReadLn;Halt;end;
  p_player:=libvlc_media_player_new_from_media(p_media);
  if p_player=nil then begin WriteLn('p_player is nil');ReadLn;Halt;end;
  libvlc_media_player_play(p_player);
  WriteLn('Press ENTER when video playback starts');
  ReadLn;
  v:=30;
  libvlc_audio_set_volume(p_player,v); // crash right here with error 207 (floating point) from libvlccore
  WriteLn('Vol 30');
  ReadLn;
  v:=50;
  libvlc_audio_set_volume(p_player,v);
  WriteLn('Vol 50');
  WriteLn('Press ENTER to end');
  ReadLn;
end.

Comiled binary and source here - http://rghost.ru/49230940
Works with 1.1.x and 2.0.x, crashes 2.1.x and 2.2.x (nightly)

audio.c (libvlc)

Code: Select all

int libvlc_audio_set_volume( libvlc_media_player_t *mp, int volume )
{
    float vol = volume / 100.f;
    if (vol < 0.f)
    {
        libvlc_printerr( "Volume out of range" );
        return -1;
    }

    int ret = -1;
    audio_output_t *aout = GetAOut( mp );
    if( aout != NULL )
    {
        ret = aout_VolumeSet( aout, vol );
        vlc_object_release( aout );
    }
    return ret;
}

output.c (libvlccore)

Code: Select all

int aout_VolumeSet (audio_output_t *aout, float vol)
{
    aout_owner_t *owner = aout_owner (aout);

    assert (vol >= 0.f);
    vlc_mutex_lock (&owner->req.lock);
    owner->req.volume = vol;
    vlc_mutex_unlock (&owner->req.lock);

    if (aout_OutputTryLock (aout) == 0)
        aout_OutputUnlock (aout);
    return 0;
}

I don't get how can that assert from second function happen when there is an "if" with same condition in first one?

Posted: **13 Oct 2013 14:37**

Same Problem with set audio volume in delphi:
I can reproduce the failure with the provided sample console program from r21514
Is there a need to do additional calls bevore using set audio volume (set audio mute works fine though)..

Posted: **27 Oct 2013 09:43**

The same here with Win7 64bit and Delphi 5. (Exception EInvalidOp)
If this error happens the stream freezes and if I call libvlc_media_player_stop() my program hangs up.

Posted: **13 Nov 2013 10:33**

There is no crash with "aout=waveout", so the problem in only with directsound.

I went through binaries from nightlies.videolan.org and that's what I've found:
vlc-2.1.0-git-20130204-0002-win32 - works ok like old 2.0.x
vlc-2.1.0-git-20130211-0003-win32 - crashes like 2.1.0 release

I've read diff report on difference between 20130204 and 20130211 sources.
There are some changes in modules\audio_output\directx.c about type of "directx-volume" variable, it changed from integer to float (and we have floating point error, remember?).

Anyway I took plugins\audio_output\libdirectsound_plugin.dll from vlc-2.1.0-20130204-0002 and put into vlc-2.1.0-release and I have no crash, everything works.
So that's temporary solution. Dll can be downloaded here.

Posted: **13 Nov 2013 19:46**

Nice workaround, thx for finding it out!

Posted: **18 Nov 2013 23:42**

That's only temporary. Finding the real fix would be nice.

Posted: **19 Nov 2013 18:47**

Sorry, I don't have enough knowledge of C/C++ and VLC architecture to understand massive changes in directx.c between those two dates.
I understood that type of volume level variable was changed, but that led to many other changes, and I can't debug VLC code from delphi to get exact crash line.

Posted: **19 Apr 2014 17:02**

Delphi Solution:

Some of drivers cause floating point
errors, which are converted to exceptions. These exceptions can be disabled with the
SetExceptionMask function of the Math unit, as follows:

SetExceptionMask([exInvalidOp, exDenormalized, exZeroDivide,
exOverflow, exUnderflow, exPrecision]); //<= default c runtime fpu exception handling

Then You can use libvlc_audio_set_volume without exception.

Posted: **05 Mar 2015 13:30**

Problem with DirectSound is still present in VLC 2.2

Posted: **05 Mar 2015 15:14**

This rather looks like a bug in the Delphi wrapper that you are using. Maths exception handling is the most likely problem.

Posted: **18 Mar 2015 19:45**

I'm not using any wrapper, just direct calls to dll functions. So the bug is delphi itself.

My solution is:

Code: Select all

Set8087CW((Get8087CW and $FFC0) or $003F);

It must be the same that celeburdi recomended.

[SOLVED]

But still there in an unsafe floating point operation somewhere in libdirectsound...

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