cellAudio: Fix audio channel order

[capriots]

Documentation says samples have the order Front L, Front R, Center, LFE, Surround L, Surround R, Rear L, Rear R

Fixes #5818

[Megamouse]

This pull request seems incomplete.
The buffers apply to all audio backends, but i haven't seen any adjustments there.

[Megamouse]

The following code might be correct.
Just seems weird to swap the buffer positions like that.

[capriots]

The PCM samples games put into the buffer definitely have the order I specified above, so the names should stay like this. out_buffer names should be swapped too if you don't like my solution.
Swapping the channels universally in cellAudio seemed like the best solution since pretty much everywhere else the rear channels come first.

Xaudio2's default channel order is L, R, C, LFE, RL, RR, SL, SR (https://docs.microsoft.com/en-us/windows/win32/xaudio2/xaudio2-default-channel-mapping)

Same with OpenAL (page 141: https://www.openal.org/documentation/OpenAL_Programmers_Guide.pdf)

For PulseAudio the same order is manually specified

rpcs3/rpcs3/Emu/Audio/Pulse/PulseBackend.cpp

Lines 36 to 66 in 78bcb0f

	pa_channel_map channel_map;
	if (m_channels == 2)
	{
	channel_map.channels = 2;
	channel_map.map[0] = PA_CHANNEL_POSITION_FRONT_LEFT;
	channel_map.map[1] = PA_CHANNEL_POSITION_FRONT_RIGHT;
	}
	else if (m_channels == 6)
	{
	channel_map.channels = 6;
	channel_map.map[0] = PA_CHANNEL_POSITION_FRONT_LEFT;
	channel_map.map[1] = PA_CHANNEL_POSITION_FRONT_RIGHT;
	channel_map.map[2] = PA_CHANNEL_POSITION_FRONT_CENTER;
	channel_map.map[3] = PA_CHANNEL_POSITION_LFE;
	channel_map.map[4] = PA_CHANNEL_POSITION_REAR_LEFT;
	channel_map.map[5] = PA_CHANNEL_POSITION_REAR_RIGHT;
	}
	else
	{
	channel_map.channels = 8;
	channel_map.map[0] = PA_CHANNEL_POSITION_FRONT_LEFT;
	channel_map.map[1] = PA_CHANNEL_POSITION_FRONT_RIGHT;
	channel_map.map[2] = PA_CHANNEL_POSITION_FRONT_CENTER;
	channel_map.map[3] = PA_CHANNEL_POSITION_LFE;
	channel_map.map[4] = PA_CHANNEL_POSITION_REAR_LEFT;
	channel_map.map[5] = PA_CHANNEL_POSITION_REAR_RIGHT;
	channel_map.map[6] = PA_CHANNEL_POSITION_SIDE_LEFT;
	channel_map.map[7] = PA_CHANNEL_POSITION_SIDE_RIGHT;
	}
	ss.channels = channel_map.channels;

No clue about ALSA but the output was wrong there too.

I guess you could do the swapping in the backends instead, there seems to be manual channel mapping support in all of them.

[Megamouse]

The thing is, I wrote some of that code and I couldn't believe that the channels were swapped.
But i remember now that rear channels usually come first.
I also remember that the PS3 does it differently.
I could've sworn I had them ordered properly back then.
Maybe I didn't want to change them unless proven wrong.

Anyway, good job finding the issue (maybe they were typos).
I'll take a look later and confirm again just to be sure.
Haven't had time to look at the code so far.