[Coco] OVCC project update.

Walter Zambotti zambotti at iinet.net.au
Thu Aug 16 21:05:14 EDT 2018

So the audio/sound component of direct/x/sound is the last component to be
converted to SDL.


In comparison to the graphics conversion it has been challenging.  Where the
graphics models between directx and sdl are similar enough that the
conversion was straight forward the audio models are considerably different.


Direct Sound has devices and devices are allocated sound buffers. The user
has sound samples stored in memory. The user copies his sound sample from
memory to a sound buffer.  Basically a memory to memory copy.  It was up to
VCC to figure out what and where to copy.  So in VCC there were a lot of
buffer pointers maintained and logic to maintain a circular buffer.


SDL however has sound devices and sound queues (not buffers).  The user has
samples stored in memory. The user just submits the sample to the queue.
There's no concept of manipulating the sound buffers after that stage.


So all the VCC sound buffer logic seems irrelevant.  So my SDL sound
interface has very little code.


In VCC whenever something is written to the sound register at FF22 (from
memory) that value is also recorded in a small buffer (array) and once every
1/60 sec that small buffer is sent to the direct sound interface to place in
the next position in the sound device's circular buffer.


In SDL all I can do with that small buffer is queue it to the SDL sound


So I have written the SDL sound code that I believe will work and I now
begin to debug it. 


So keep your fingers crossed that that is all I need to do (queue it) !!!





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