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[Schlichter]

Is there any possibility to normalize audio tracks, i.e. setting their peak level to 100% or 0 dB, without changing the channel's volume?

Thanks for your suggestions

H.Schlichter

[Ian @ un4seen]

If you want to normalize a track, you'll need to pre-scan it to find the peak (which could take a while), and then adjust the gain/volume accordingly during playback, eg. using a DSP function. Assuming 16-bit sample data, something like this...

int GetPeak(DWORD channel)
{
int a, c, peak=0;
short buf[50000];
BASS_ChannelSetPosition(channel, 0); // make sure to start from the start
while (BASS_ChannelIsActive(channel)) { // not reached the end yet
c=BASS_ChannelGetData(channel, buf, sizeof(buf)); // decode some data
for (a=0; a<c/2; a++) // scan the data for the peak
if (peak<abs(buf)) peak=abs(buf); // new highest peak
}
if (peak>32767) peak=32767;
return peak;
}

void CALLBACK NormalizeDSP(HDSP handle, DWORD channel, void *buffer, DWORD length, DWORD peak)
{
short *s=buffer;
int a;
for (a=0; a<length/2; a++)
s[a]=s[a]*32767/peak; // apply normalization
}

...

HSTREAM decoder=BASS_StreamCreateFile(FALSE, filename, 0, 0, BASS_STREAM_DECODE); // create decoder to pre-scan
int peak=GetPeak(decoder); // get the peak
BASS_StreamFree(decoder); // free the decoder

stream=BASS_StreamCreateFile(FALSE, filename, 0, 0, 0); // create the playback channel
BASS_ChannelSetDSP(stream, NormalizeDSP, peak, 0); // set the normalization DSP on it
BASS_ChannelPlay(stream, 0); // start playing

Another (slightly simpler) option is to use BASS_ChannelGetLevel to find the peaks, instead of BASS_ChannelGetData.

int GetPeak(DWORD channel)
{
int peak=0;
BASS_ChannelSetPosition(channel, 0); // make sure to start from the start
while (BASS_ChannelIsActive(channel)) { // not reached the end yet
DWORD level=BASS_ChannelGetLevel(channel);
int left=LOWORD(level), right=HIWORD(level); // extract left & right peaks
if (peak<left) peak=left;
if (peak<right) peak=right;
}
if (peak>32767) peak=32767;
return peak;
}

[Schlichter]

Pretty much simple, if one knows...
Thank you very much for your support.

H.Schlichter

[se]

Sorry for this question if it seems stupid.

I did understand that normalizing a channel can be done in reference to another channel.
for example 2 audio files played one after the other, and we don't want to have one played with a higher level than the first one.

In this sample you are just referring to a unique file, to normalize it.

Do I miss the point on the absolute level in dB?

best
and thank you for all the new updates I didn't play with! very exciting indeed!

[Schlichter]

The highest possible (digital) level of an audio track is 32767, equivalent to 0 dB. The peak level of any audio track is measured to this value.

Naturally you can normalize an audio track to another one.

H.Schlichter

[prl]

I'm having problem with the System.Windows.Forms.Control.Right() property. It turns out to be a read only and can't be initialized to any value, in this example HiWord(level). How do I solve this problem? 

[radio42]

Don't know what you are doing...but...the "System.Windows.Forms.Control.Right":
gets the distance, in pixels, between the right edge of the control and the left edge of its container's client area.
So why would you set that to a level value.

The value of the "Right" property is equal to the sum of the "Left" property value and the "Width" property value.
The "Right" property is read-only. You can change this property value indirectly by changing the value of the "Left" or "Width" properties or calling the "SetBounds", "SetBoundsCore", "UpdateBounds", or "SetClientSizeCore" methods.

Or take a look to the .Net documentation...as I copied the above text from there :-)

[prl]

thank you so much radio. I'm really not that good in programming but I'll try to work it out. :-)

[prl]

thank you so much radio. I'm really not that good in programming but I'll try to work it out. :-)

Also, I overlooked the right in the example above. I thought it was a SystemForms.Control object. All along it was just a variable declared as an int. hehehe... sorry.

[Nicolás]

Hi, i need some example for normalizing audio but in VB please!!..

Realy thanks!

[IsraelMS]

Hello members! Sorry my english, I'm braziliam.

I need an example in Delphi. please help me.

Thanks.

Israel

[Chris]

try this

function ScanPeak(const FileName: string): integer;
var
  a, c, Peak: Integer;
  buf: array[0..20000] of SmallInt;
  Channel: DWORD;
begin
  peak := 0;
  Bass_SetDevice(0);
  Channel := BASS_StreamCreateFile(false, PChar(FileName), 0, 0, BASS_STREAM_DECODE);
  if Channel = 0 then
    exit;
  while (BASS_ChannelIsActive(channel) <> 0) do
  begin
    c := BASS_ChannelGetData(channel, @buf, 40000);
    c := c div 2;
    for a := 0 to c do
      if (peak < Abs(buf[a])) then
peak := abs(buf[a]);
  end;
  BASS_StreamFree(channel);
  Result := Peak;
end;

Chris

[Nicolás]

Hi, i need help, i'm programming this in VB.net, but i have the "peak value" that work's good but when i try to put this line;:

            Bass.BASS_ChannelSetDSP(strm, NormalizeDSP, peak, 0)

I haven't the NormalizeDSP function in VB, somebody can help me??

¿¿¿¿¿NormalizeDSP in VB???

¿¿¿ void CALLBACK NormalizeDSP(HDSP handle, DWORD channel, void *buffer, DWORD length, DWORD peak)

What is handle,*buffer, etc.  please HELP!!  Thanks

[radio42]

Here is a VB.Net translation of Ian's original NormalizeDSP code:

Private _peakValue As Integrer = 1
Private _sampleData As Short() = Nothing

' a DSP callback - which will apply a gain factor
Private Sub NormalizeDSP(handle As Integer, channel As Integer,
                   buffer As IntPtr, length As Integer, user As IntPtr)
  If _peakValue = 1f Or length = 0 Or buffer = IntPtr.Zero Then
      Return
   End If

  ' length is in bytes, so the number of 16-bit values to process is length/1
  Dim l2 As Integer = length / 2

  ' increase the data buffer as needed
  If _sampleData Is Nothing Or _sampleData.Length < l2 Then
    _sampleData = New Single(l2) {}
  End If

  ' copy from unmanaged to managed memory
  Marshal.Copy(buffer, _sampleData, 0, l2)

  ' apply the gain, assuming 16-bit (no clipping)
  Dim a As Integer
  For a = 0 To l2 - 1
    _sampleData(a) = _sampleData(a) * 32737/_peakValue
  Next a

  ' copy back from unmanaged to managed memory
  Marshal.Copy(_sampleData, 0, buffer, l2)
End Sub

[Nicolás]

Hi Radio42, Thank you very much.

Now i have the function, but, when i put the line;:

Bass.BASS_ChannelSetDSP(strm, NormalizeDSP, peak, 0) ' for apply normalization

I need to put the variables in::. Bass.BASS_ChannelSetDSP(strm, NormalizeDSP(X,X,X,X,X), peak, 0)

Where are these variables?

[Nicolás]

And one more...

When i put variables in these line::. Bass.BASS_ChannelSetDSP(strm, NormalizeDSP(X,X,X,X,X), peak, 0)

I have then next error: "Expression does not produce a value"

Thanks

[radio42]

PLease take a look to the BASS and BASS.NET doc - there are a lot of VB.Net examples included:

Private _myDSPProc As DSPPROC ' make it global, so that the GC can not remove it
...
_myDSPProc = New DSPPROC(AddressOf NormalizeDSP)
Bass.BASS_ChannelSetDSP(_stream, _myDSPProc, IntPtr.Zero, 0)
...

Replace "_stream" with your stream handle as returned by "BASS_StreamCreateFile"

[Nicolás]

Ok thanks again, but.. i have a similar problem, now in the line::

_myDSPProc = New DSPPROC(AddressOf NormalizeDSP)

becouse in the AddressOf "NormalizeDSP" i have the error:

"Method Private Sub Normalize(handle...... does not have the same signature as Delegate Sub DSPROC(handle as....


Thanks

[radio42]

Then you are using an old version of BASS/BASS.NET - which version are you using?
And please, please also consult the documentation!

[Nicolás]

I-m using Bass.Net 2.3.0.2 Version,

Please give your e/mail, for send you my code via email ok__ thanks man