Creating a wave file

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Creating a wave file

Postby PatD » March 16th, 2007, 10:56 am

Hello.

I dynamically receive wave buffers from an ISDN board. I would like to create a wave file with this buffers.
I tried to use a TWaveStorage object and used BegingRewrite, Write, EndWrite and ConvertToPCM methods but it does not work.
By debugging your code, I saw that this functions do nothing because fIo is 0. I did not find how to initialize it.

Thanks for your help.
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Postby Kambiz » March 16th, 2007, 2:13 pm

It means BeginRewrite fails to initialize RIFF format.

Could you please post a sample code here, so that we can find what's going wrong.
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Postby PatD » March 16th, 2007, 4:48 pm

Here's the code :

WAVEFORMATEX sWaveFormat;
TWaveStorage *pWave=NULL;

sWaveFormat.wFormatTag=WAVE_FORMAT_PCM;
sWaveFormat.nChannels=1;
sWaveFormat.nSamplesPerSec=8000;
sWaveFormat.nAvgBytesPerSec=8000;
sWaveFormat.nBlockAlign=8;
sWaveFormat.wBitsPerSample=8;
sWaveFormat.cbSize=sizeof(WAVEFORMATEX);
pWave->Wave->BeginRewrite(&sWaveFormat);

pWave->Wave->Write(pBfr, dwGot);

if (!pWave->Wave->EndRewrite())
Msg(919, "EndRewrite");
if (!pWave->Wave->ConvertToPCM(Mono8Bit8000Hz))
Msg(919, "ConvertToPCM");
pWave->Wave->Seek(0, soFromBeginning);
pWave->Wave->SaveToFile(pszRecordFile);

In WaveStorage.pas, the code is :

function TWave.BeginRewrite(pWaveFormat: PWaveFormatEx): Boolean;
begin
Result := False;
if fIO <> 0 then
begin
fDirty := True;
fIO := CreateStreamWaveAudio(Self, pWaveFormat, fCkRIFF, fCkData);
Result := (fIO <> 0);
end;
end;

I don't see where fIO may be initialized.
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Postby Kambiz » March 16th, 2007, 5:14 pm

Oops, it's my mistake! :oops:

Code: Select all
if fIO <> 0 then

must be
Code: Select all
if fIO = 0 then


Sorry for this inconvenience.
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Postby PatD » March 26th, 2007, 5:57 pm

I made the change in WaveStorage.pas. Now, when I call TWave.Write, I get an infinite loop (have a look at the attached stack.gif file).

TWave.Write calls mmioWrite that produces a call to mmIOStreamProc wich executes the following :

MMIOM_WRITEFLUSH:
try
Stream.Seek(lpmmIOInfo^.lDiskOffset, SEEK_SET);
Result := Stream.Write(Pointer(lParam1)^, lParam2);
lpmmIOInfo^.lDiskOffset := Stream.Seek(0, SEEK_CUR);
except
Result := -1;
end

In this function, Stream.Write calls back TWave.Write, and so on....

I use C++Builder 6.
Attachments
Stack.gif
Stack.gif (7.47 KiB) Viewed 1867 times
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Postby Kambiz » March 27th, 2007, 12:13 am

Are you using the latest version (v1.80)?
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Postby PatD » March 27th, 2007, 2:05 pm

No, I was using version 1.70.

With version 1.80, it works.

Thanks a lot.
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