audio: support NGS2 PCM16 samplers and rear low-pass filters (#825)

* audio: support standard NGS2 PCM16 sampler playback

Extend the existing fixed-point PCM path to standard samplers, loops, and progress reporting. Apply voice events immediately and honor callback interruption during source advancement.

Reuse upstream rate and pitch handling. Add regression coverage for streaming, routing, callbacks, loops, and custom sampler controls; ngs2_sampler passes.

* audio: apply NGS2 rear low-pass filters

Handle rear low-pass FCQ controls at the output sample rate with per-channel history and channel masks. Preserve filter tails through streaming gaps and use the standard pi constant for coefficients.

Add regression coverage for frequency response, control layout, channel isolation, and starvation/refill continuity. Emulator build and both audio test suites pass.

* Preserve resampling phase for accepting voices

Only reset voice.sample_phase when there are no blocks and the voice does not accept blocks (change in src/libs/ngs2.cpp). Add TestResamplingPhaseAfterStarvation to tests to ensure sampler and custom sampler retain resampling phase and pending source advancement after starvation, and that SetupSampler still resets the phase. This prevents resampling phase loss during starvation/refill across sample rates.

* audio: correct sampler controls, lifecycle, and filter tails

---------

Co-authored-by: nmzik <Nmzik@mail.ru>

CMakeLists.txt

@@ -465,6 +465,13 @@ add_executable(audio_out2_port_tests EXCLUDE_FROM_ALL
 target_link_libraries(audio_out2_port_tests common fmt::fmt)
 target_include_directories(audio_out2_port_tests PRIVATE ${inc_headers})
 
+add_executable(ngs2_sampler_tests EXCLUDE_FROM_ALL
+	"${KYTY_TESTS_DIR}/Ngs2SamplerTests.cpp"
+	"${KYTY_SOURCE_DIR}/loader/timer.cpp"
+)
+target_link_libraries(ngs2_sampler_tests common fmt::fmt LibAtrac9)
+target_include_directories(ngs2_sampler_tests PRIVATE ${inc_headers})
+
 add_executable(save_data_memory_tests EXCLUDE_FROM_ALL
 	"${KYTY_TESTS_DIR}/SaveDataMemoryTests.cpp"
 )
@@ -555,6 +562,7 @@ if(BUILD_TESTING)
 	add_test(NAME kernel_file_system COMMAND $<TARGET_FILE:kernel_file_system_tests>)
 	add_test(NAME sync_on_address COMMAND $<TARGET_FILE:sync_on_address_tests>)
 	add_test(NAME audio_out2_port COMMAND $<TARGET_FILE:audio_out2_port_tests>)
+	add_test(NAME ngs2_sampler COMMAND $<TARGET_FILE:ngs2_sampler_tests>)
 	add_test(NAME save_data_memory COMMAND $<TARGET_FILE:save_data_memory_tests>)
 	add_test(NAME shader_recompiler_compute COMMAND $<TARGET_FILE:shader_recompiler_compute_tests>)
 	add_test(NAME shader_recompiler_alignbyte
@@ -620,6 +628,7 @@ if(BUILD_TESTING)
 		shader_recompiler_compute_tests
 		virtual_memory_allocation_tests
 		audio_out2_port_tests
+		ngs2_sampler_tests
 	)
 endif()