PSG and SCC/SCC+ message queues are required.

[mori0091]

What's happen? Please describe the problem you met.

The opll_buf.h provides a message queue (FIFO) to write to the OPLL registers.

On the other hand, ay_3_8910.h and scc_buf.h provide the PSG and SCC/SCC+ register caches. These assume that the sound driver only writes the most recent register values each frame. However, the sound driver may write to the same register more than once in a frame.

For example, when playing very short pulses or very short mutes, the sound driver may write to PSG register No.7 or the SCC/SCC+ channel mask register two or more times in the same frame.

Describe the solution you'd like

PSG and SCC/SCC+ also require a message queue (FIFO) API.

Describe alternatives you've considered

Also, sound drivers may write to the PSG, SCC/SCC+, and OPLL registers in various orders. Therefore, a unified message queue API may be needed for these sound chips.

Additional context

(none)

[mori0091]

The following tasks are in progress

• [x] Implement unified message queues for PSG, SCC/SCC+ and OPLL.
• [x] Modify the libmsx audio replayer to use the new message queue instead of ay_3_8910.h, scc_buf.h and opll_buf.h. (This is BREAKING CHANGE! If there is a decoder implementation for libmsx audio replayer, it should be also modified.)
• [x] Adapt SNDDRV to it as well.
• [x] Implement a new decoder for libmsx audio replayer and a VGM file conversion tool for it.

[mori0091]

sample/la0_demo cannot be built because there is no song data.

If you have some VGM files, you can try the following method

• Convert your VGM files to bgm.la0 or sfx.la0 using the tools/vgm2la tool.
• Put the bgm.la0 or sfx.la0 in sample/la0_demo/resources/.
• Then do make clean all in the sample/la0_demo/ folder.
• So la0_demo.rom file will be made in sample/la0_demo/bin/.

[mori0091]

I need some redistributable VGM files (.vgm or .vgz)

I would like to bundle sample song data with libmsx. If anyone has redistributable VGM files (.vgm or .vgz), please provide them.