re[Openal] ading data

[Chris Robinson]

On Sunday 18 May 2008 10:09:06 pm bonanza wrote:
> is the size (ALsizei size)  not the same as  the offset in
> int offset;
> alGetSourcei(Source, AL_BYTE_OFFSET, &offset); ???

Measuring the size by constantly reading and using the largest offset may not 
always work. Once the mixer is done reading from the buffer (ie. it's byte 
pointer is at the end), its automatically put into a stopped state. And once 
the source is stopped, the reported offset will be 0.

Also, the byte offset in particulatr may not be reliable because the 
implementation is free to convert the data into a playable format (eg. 
converts 8-bit to 16-bit). The sample offset may also be affected (eg. 
resamples 32khz to 48khz).

The best way to "follow" the current playing position is to read the seconds 
offset:

ALfloat stime;
alGetSourcef(Source, AL_SEC_OFFSET, &stime);
int offset = (int)(stime*freq) * channels * bytes_per_sample;

where 'channels' and 'bytes_per_sample' are derived from the format (eg. 
AL_FORMAT_MONO16 has channels=1 and bytes_per_sample=2).