hwopus: Leverage multistream API for decoding regular Opus packets

After doing a little more reading up on the Opus codec, it turns out
that the multistream API that is part of libopus can handle regular
packets. Regular packets are just a degenerate case of multistream Opus
packets, and all that's necessary is to pass the number of streams as 1
and  provide a basic channel mapping, then everything works fine for
that case.

This allows us to get rid of the need to use both APIs in the future
when implementing multistream variants in a follow-up PR, greatly
simplifying the code that needs to be written.

src/core/hle/service/audio/hwopus.cpp

@@ -8,6 +8,7 @@
 #include <vector>
 
 #include <opus.h>
+#include <opus_multistream.h>
 
 #include "common/assert.h"
 #include "common/logging/log.h"
@@ -18,12 +19,12 @@
 namespace Service::Audio {
 namespace {
 struct OpusDeleter {
-    void operator()(void* ptr) const {
+    void operator()(OpusMSDecoder* ptr) const {
-        operator delete(ptr);
+        opus_multistream_decoder_destroy(ptr);
     }
 };
 
-using OpusDecoderPtr = std::unique_ptr<OpusDecoder, OpusDeleter>;
+using OpusDecoderPtr = std::unique_ptr<OpusMSDecoder, OpusDeleter>;
 
 struct OpusPacketHeader {
     // Packet size in bytes.
@@ -33,7 +34,7 @@ struct OpusPacketHeader {
 };
 static_assert(sizeof(OpusPacketHeader) == 0x8, "OpusHeader is an invalid size");
 
-class OpusDecoderStateBase {
+class OpusDecoderState {
 public:
     /// Describes extra behavior that may be asked of the decoding context.
     enum class ExtraBehavior {
@@ -49,22 +50,13 @@ public:
         Enabled,
     };
 
-    virtual ~OpusDecoderStateBase() = default;
-
-    // Decodes interleaved Opus packets. Optionally allows reporting time taken to
-    // perform the decoding, as well as any relevant extra behavior.
-    virtual void DecodeInterleaved(Kernel::HLERequestContext& ctx, PerfTime perf_time,
-                                   ExtraBehavior extra_behavior) = 0;
-};
-
-// Represents the decoder state for a non-multistream decoder.
-class OpusDecoderState final : public OpusDecoderStateBase {
-public:
     explicit OpusDecoderState(OpusDecoderPtr decoder, u32 sample_rate, u32 channel_count)
         : decoder{std::move(decoder)}, sample_rate{sample_rate}, channel_count{channel_count} {}
 
+    // Decodes interleaved Opus packets. Optionally allows reporting time taken to
+    // perform the decoding, as well as any relevant extra behavior.
     void DecodeInterleaved(Kernel::HLERequestContext& ctx, PerfTime perf_time,
-                           ExtraBehavior extra_behavior) override {
+                           ExtraBehavior extra_behavior) {
         if (perf_time == PerfTime::Disabled) {
             DecodeInterleavedHelper(ctx, nullptr, extra_behavior);
         } else {
@@ -135,7 +127,7 @@ private:
 
         const int frame_size = (static_cast<int>(raw_output_sz / sizeof(s16) / channel_count));
         const auto out_sample_count =
-            opus_decode(decoder.get(), frame, hdr.size, output.data(), frame_size, 0);
+            opus_multistream_decode(decoder.get(), frame, hdr.size, output.data(), frame_size, 0);
         if (out_sample_count < 0) {
             LOG_ERROR(Audio,
                       "Incorrect sample count received from opus_decode, "
@@ -158,7 +150,7 @@ private:
     void ResetDecoderContext() {
         ASSERT(decoder != nullptr);
 
-        opus_decoder_ctl(decoder.get(), OPUS_RESET_STATE);
+        opus_multistream_decoder_ctl(decoder.get(), OPUS_RESET_STATE);
     }
 
     OpusDecoderPtr decoder;
@@ -168,7 +160,7 @@ private:
 
 class IHardwareOpusDecoderManager final : public ServiceFramework<IHardwareOpusDecoderManager> {
 public:
-    explicit IHardwareOpusDecoderManager(std::unique_ptr<OpusDecoderStateBase> decoder_state)
+    explicit IHardwareOpusDecoderManager(OpusDecoderState decoder_state)
         : ServiceFramework("IHardwareOpusDecoderManager"), decoder_state{std::move(decoder_state)} {
         // clang-format off
         static const FunctionInfo functions[] = {
@@ -190,35 +182,51 @@ private:
     void DecodeInterleavedOld(Kernel::HLERequestContext& ctx) {
         LOG_DEBUG(Audio, "called");
 
-        decoder_state->DecodeInterleaved(ctx, OpusDecoderStateBase::PerfTime::Disabled,
+        decoder_state.DecodeInterleaved(ctx, OpusDecoderState::PerfTime::Disabled,
-                                         OpusDecoderStateBase::ExtraBehavior::None);
+                                        OpusDecoderState::ExtraBehavior::None);
     }
 
     void DecodeInterleavedWithPerfOld(Kernel::HLERequestContext& ctx) {
         LOG_DEBUG(Audio, "called");
 
-        decoder_state->DecodeInterleaved(ctx, OpusDecoderStateBase::PerfTime::Enabled,
+        decoder_state.DecodeInterleaved(ctx, OpusDecoderState::PerfTime::Enabled,
-                                         OpusDecoderStateBase::ExtraBehavior::None);
+                                        OpusDecoderState::ExtraBehavior::None);
     }
 
     void DecodeInterleaved(Kernel::HLERequestContext& ctx) {
         LOG_DEBUG(Audio, "called");
 
         IPC::RequestParser rp{ctx};
-        const auto extra_behavior = rp.Pop<bool>()
+        const auto extra_behavior = rp.Pop<bool>() ? OpusDecoderState::ExtraBehavior::ResetContext
-                                        ? OpusDecoderStateBase::ExtraBehavior::ResetContext
+                                                   : OpusDecoderState::ExtraBehavior::None;
-                                        : OpusDecoderStateBase::ExtraBehavior::None;
 
-        decoder_state->DecodeInterleaved(ctx, OpusDecoderStateBase::PerfTime::Enabled,
+        decoder_state.DecodeInterleaved(ctx, OpusDecoderState::PerfTime::Enabled, extra_behavior);
-                                         extra_behavior);
     }
 
-    std::unique_ptr<OpusDecoderStateBase> decoder_state;
+    OpusDecoderState decoder_state;
 };
 
 std::size_t WorkerBufferSize(u32 channel_count) {
     ASSERT_MSG(channel_count == 1 || channel_count == 2, "Invalid channel count");
-    return opus_decoder_get_size(static_cast<int>(channel_count));
+    constexpr int num_streams = 1;
+    const int num_stereo_streams = channel_count == 2 ? 1 : 0;
+    return opus_multistream_decoder_get_size(num_streams, num_stereo_streams);
+}
+
+// Creates the mapping table that maps the input channels to the particular
+// output channels. In the stereo case, we map the left and right input channels
+// to the left and right output channels respectively.
+//
+// However, in the monophonic case, we only map the one available channel
+// to the sole output channel. We specify 255 for the would-be right channel
+// as this is a special value defined by Opus to indicate to the decoder to
+// ignore that channel.
+std::array<u8, 2> CreateMappingTable(u32 channel_count) {
+    if (channel_count == 2) {
+        return {{0, 1}};
+    }
+
+    return {{0, 255}};
 }
 } // Anonymous namespace
 
@@ -259,9 +267,15 @@ void HwOpus::OpenOpusDecoder(Kernel::HLERequestContext& ctx) {
     const std::size_t worker_sz = WorkerBufferSize(channel_count);
     ASSERT_MSG(buffer_sz >= worker_sz, "Worker buffer too large");
 
-    OpusDecoderPtr decoder{static_cast<OpusDecoder*>(operator new(worker_sz))};
+    const int num_stereo_streams = channel_count == 2 ? 1 : 0;
-    if (const int err = opus_decoder_init(decoder.get(), sample_rate, channel_count)) {
+    const auto mapping_table = CreateMappingTable(channel_count);
-        LOG_ERROR(Audio, "Failed to init opus decoder with error={}", err);
+
+    int error = 0;
+    OpusDecoderPtr decoder{
+        opus_multistream_decoder_create(sample_rate, static_cast<int>(channel_count), 1,
+                                        num_stereo_streams, mapping_table.data(), &error)};
+    if (error != OPUS_OK || decoder == nullptr) {
+        LOG_ERROR(Audio, "Failed to create Opus decoder (error={}).", error);
         IPC::ResponseBuilder rb{ctx, 2};
         // TODO(ogniK): Use correct error code
         rb.Push(ResultCode(-1));
@@ -271,7 +285,7 @@ void HwOpus::OpenOpusDecoder(Kernel::HLERequestContext& ctx) {
     IPC::ResponseBuilder rb{ctx, 2, 0, 1};
     rb.Push(RESULT_SUCCESS);
     rb.PushIpcInterface<IHardwareOpusDecoderManager>(
-        std::make_unique<OpusDecoderState>(std::move(decoder), sample_rate, channel_count));
+        OpusDecoderState{std::move(decoder), sample_rate, channel_count});
 }
 
 HwOpus::HwOpus() : ServiceFramework("hwopus") {