[Openal-devel] LOKI_buffer_data_callback

[Steve Baker]

Олег "__ka" Андреев wrote:
> Excuse me, I'm new to OpenAL (and to English too =)).
> 
> First, is anyone implementing LOKI_buffer_data_callback and is this 
> functionality going to be proposed to OpenAL 1.2 (or some other) 
> specification. Or, at least, can we be sure, that any modern 
> implementation of OpenAL will have this extension.

The problems with data being unpacked by a callback are many:

1) It prevents the data being stored down in the hardware.

2) It forces the implementation to do unpacking, etc in the
    user-side driver.  You can't run user-code in any kind of
    kernel-level device driver.

3) Some popular languages (such as Java) can't implement callbacks.

4) Thread-safety.  It's likely that the unpack code would have to
    run in a parallel thread (at least on some implementations).  This
    tends to come to a suprise to naive users resulting in many subtle
    and exciting problems!

> Second, some people voice an opinion, that you should be able to read 
> data back from buffer. What should be returned, if you didn't pass data 
> via alBufferData, but with a callback. Will you return an error? Or will 
> you return the last saved chunk?

I would assume that the driver would call the callback to unpack the data
so you'd get unpacked data in your buffer - but there are other possibilities.

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