[Openal] AL_FORMAT Types and Meanings

[Ümit Uzun]

Hi All,

I have needed to control every channel manually so I have injected
Framework.cpp of OpenAL SDK.
I added

template<typename T> T *LoadData(const T *data, int size, const char
*channels, short channelType)
{
    size /= sizeof(T);

    T *multData = new T[size * channelType];

    for(int i = 0; i < size; i++)
    {
        for(int k = 0; k < channelType; k++)
        {
            multData[i * channelType + k] = channels[k] == '1' ? data[i] :
0;
        }
    }

    return multData;
}

const char *channels; // For example 110010
// Find channelType by counting channels value for example 5.1's channelType
== 6
short channelType;
for(channelType = 0; channels[channelType] != NULL; channelType++);
if(fmt.wBitsPerSample == 16)   // assumes 16-bit short
{
    ALshort *data = LoadData((const ALshort*)pData, iDataSize, channels,
channelType);
    switch(channelType)
    {
    case 2:
    alBufferData(uiBufferID, alGetEnumValue("AL_FORMAT_MONO16"), data,
iDataSize * channelType, iFrequency);
    break;
    case 4:
    alBufferData(uiBufferID, alGetEnumValue("AL_FORMAT_QUAD16"), data,
iDataSize * channelType, iFrequency);
    break;
    case 6:
    alBufferData(uiBufferID, alGetEnumValue("AL_FORMAT_51CHN16"), data,
iDataSize * channelType, iFrequency);
    break;
    case 7:
    alBufferData(uiBufferID, alGetEnumValue("AL_FORMAT_61CHN16"), data,
iDataSize * channelType, iFrequency);
    break;
    case 8:
    alBufferData(uiBufferID, alGetEnumValue("AL_FORMAT_71CHN16"), data,
iDataSize * channelType, iFrequency);
    break;
    }
    delete[] data;
}

instead of
alBufferData(uiBufferID, eBufferFormat, pData, iDataSize, iFrequency);
command.

With this changing I can specify each channel for related buffer's will be
played.
I specify each sounds channel value by;
<!-- Channels Enum for 5.1 123456   -->
<!--   1 : Front Left      Speaker  -->
<!--   2 : Front Right     Speaker  -->
<!--   3 : Front Center    Speaker  -->
<!--   4 : Low   Frequency Speaker  -->
<!--   5 : Back  Left      Speaker  -->
<!--   6 : Back  Right     Speaker  -->

In LoadData template function I create the multData sound buffer data in
this sequence. I mean for example we have 16 bit sampled 5.1 sound which
will be played only front left(this sound's channels:100000) I send the raw
pData sound buffer to LoadData function and multiplex this sound data for 6
channel in given sequence order. Create new multData array for 6 channel and
start to set this sound array firstly Front Left and Front Right and so on.
So do you think this operation right or now?

With all those changing I want to control channels. Because I have some
sounds which only must played on rear left channel and some sounds only
front right and etc.
Do you think this approach is suitable?

And another question I want to handle 2.0 speaker like 5.1 and as you can
see I use AL_FORMAT_MONO16 for 2 channel. Do you think it's right or not?
Should I use AL_FORMAT_STEREO16? Or which enumeration do I need?

If I am so complex, please ask me question to lead you right direction.
Regards.

Ümit Uzun
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