[nvdec, android] proper detection and support for GPU decoder (#4068)

Detects Android MediaCodec FFmpeg decoders for H.264/VP8/VP9 when NVDEC GPU decoding is selected.
Required proper support of ffmpeg extradata, h264 frame dimensions and decoder frame handling.
Reenabled (uncommented) NVDEC Emulation selector on Android interface.

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4068

src/android/app/src/main/java/org/yuzu/yuzu_emu/features/settings/ui/SettingsFragmentPresenter.kt

@@ -269,7 +269,7 @@ class SettingsFragmentPresenter(
     // TODO(crueter): sub-submenus?
     private fun addGraphicsSettings(sl: ArrayList<SettingsItem>) {
         sl.apply {
-            // add(IntSetting.RENDERER_NVDEC_EMULATION.key)
+            add(IntSetting.RENDERER_NVDEC_EMULATION.key)
 
             add(IntSetting.RENDERER_RESOLUTION.key)
             add(IntSetting.RENDERER_VSYNC.key)

src/video_core/host1x/codecs/decoder.cpp

@@ -26,52 +26,39 @@ void Decoder::Decode() {
     }
 
     const auto packet_data = ComposeFrame();
-    // Send assembled bitstream to decoder.
-    if (!decode_api.SendPacket(packet_data)) {
-        return;
-    }
-
-    // Only receive/store visible frames.
-    if (vp9_hidden_frame) {
-        return;
+    FFmpeg::FrameOffsets offsets{};
+    offsets.hidden = vp9_hidden_frame;
+    offsets.interlaced = IsInterlaced();
+    if (offsets.interlaced) {
+        std::tie(offsets.luma, offsets.luma_bottom, offsets.chroma, offsets.chroma_bottom) =
+            GetInterlacedOffsets();
+    } else {
+        std::tie(offsets.luma, offsets.chroma) = GetProgressiveOffsets();
     }
 
-    // Receive output frames from decoder.
-    auto frame = decode_api.ReceiveFrame();
-
-    if (!frame) {
+    if (!decode_api.SendPacket(packet_data, offsets, GetFrameDimensions())) {
         return;
     }
 
-    if (IsInterlaced()) {
-        auto [luma_top, luma_bottom, chroma_top, chroma_bottom] = GetInterlacedOffsets();
-        auto frame_copy = frame;
-
-        if (!frame.get()) {
-            LOG_ERROR(HW_GPU,
-                      "Nvdec {} failed to decode interlaced frame for top {:#X} bottom 0x{:X}", id,
-                      luma_top, luma_bottom);
-        }
-
+    auto push = [&](u64 luma, std::shared_ptr<FFmpeg::Frame> frame) {
         if (UsingDecodeOrder()) {
-            host1x.frame_queue.PushDecodeOrder(id, luma_top, std::move(frame));
-            host1x.frame_queue.PushDecodeOrder(id, luma_bottom, std::move(frame_copy));
+            host1x.frame_queue.PushDecodeOrder(id, luma, std::move(frame));
         } else {
-            host1x.frame_queue.PushPresentOrder(id, luma_top, std::move(frame));
-            host1x.frame_queue.PushPresentOrder(id, luma_bottom, std::move(frame_copy));
+            host1x.frame_queue.PushPresentOrder(id, luma, std::move(frame));
         }
-    } else {
-        auto [luma_offset, chroma_offset] = GetProgressiveOffsets();
+    };
 
-        if (!frame.get()) {
-            LOG_ERROR(HW_GPU, "Nvdec {} failed to decode progressive frame for luma {:#X}", id,
-                      luma_offset);
+    while (auto result = decode_api.ReceiveFrame()) {
+        auto& [frame, o] = *result;
+        if (o.hidden || !frame) {
+            continue;
         }
-
-        if (UsingDecodeOrder()) {
-            host1x.frame_queue.PushDecodeOrder(id, luma_offset, std::move(frame));
+        if (o.interlaced) {
+            auto frame_copy = frame;
+            push(o.luma, std::move(frame));
+            push(o.luma_bottom, std::move(frame_copy));
         } else {
-            host1x.frame_queue.PushPresentOrder(id, luma_offset, std::move(frame));
+            push(o.luma, std::move(frame));
         }
     }
 }

src/video_core/host1x/codecs/decoder.h

@@ -45,6 +45,9 @@ protected:
     virtual std::tuple<u64, u64> GetProgressiveOffsets() = 0;
     virtual std::tuple<u64, u64, u64, u64> GetInterlacedOffsets() = 0;
     virtual bool IsInterlaced() = 0;
+    virtual std::optional<FFmpeg::FrameDimensions> GetFrameDimensions() {
+        return std::nullopt;
+    }
 
     FFmpeg::DecodeApi decode_api;
     Host1x::Host1x& host1x;

src/video_core/host1x/codecs/h264.cpp

@@ -50,6 +50,16 @@ bool H264::IsInterlaced() {
            current_context.h264_parameter_set.luma_bot_offset.Address() != 0;
 }
 
+std::optional<FFmpeg::FrameDimensions> H264::GetFrameDimensions() {
+    const auto& params = current_context.h264_parameter_set;
+    const s32 width = static_cast<s32>(params.pic_width_in_mbs) * 16;
+    const s32 height = static_cast<s32>(params.frame_height_in_mbs) * 16;
+    if (width <= 0 || height <= 0) {
+        return std::nullopt;
+    }
+    return FFmpeg::FrameDimensions{width, height};
+}
+
 std::span<const u8> H264::ComposeFrame() {
     host1x.gmmu_manager.ReadBlock(regs.picture_info_offset.Address(), &current_context, sizeof(H264DecoderContext));
     const s64 frame_number = current_context.h264_parameter_set.frame_number.Value();

src/video_core/host1x/codecs/h264.h

@@ -79,6 +79,7 @@ public:
     std::tuple<u64, u64> GetProgressiveOffsets() override;
     std::tuple<u64, u64, u64, u64> GetInterlacedOffsets() override;
     bool IsInterlaced() override;
+    std::optional<FFmpeg::FrameDimensions> GetFrameDimensions() override;
 
     std::string_view GetCurrentCodecName() const override {
         return "H264";

src/video_core/host1x/ffmpeg.cpp

@@ -4,6 +4,10 @@
 // SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
+#include <cstring>
+#include <string_view>
+#include <vector>
+
 #include "common/assert.h"
 #include "common/logging.h"
 #include "common/scope_exit.h"
@@ -83,6 +87,57 @@ std::string AVError(int errnum) {
     return errbuf;
 }
 
+#ifdef ANDROID
+// Match a 3- or 4-byte annex-B start code at `i`. Returns its length, or 0.
+size_t MatchStartCode(std::span<const u8> data, size_t i) {
+    const size_t n = data.size();
+    if (i + 3 < n && data[i] == 0 && data[i + 1] == 0 && data[i + 2] == 0 && data[i + 3] == 1) {
+        return 4;
+    }
+    if (i + 2 < n && data[i] == 0 && data[i + 1] == 0 && data[i + 2] == 1) {
+        return 3;
+    }
+    return 0;
+}
+
+// Pull SPS (NAL type 7) + PPS (NAL type 8) out of an annex-B frame into an
+// extradata buffer, each prefixed with a 4-byte start code. Eden synthesizes
+// these inline into the very first frame; h264_mediacodec wants them at open.
+std::vector<u8> ExtractH264AnnexBExtradata(std::span<const u8> packet) {
+    std::vector<u8> extradata;
+    const size_t size = packet.size();
+    size_t i = 0;
+    while (i < size) {
+        const size_t sc = MatchStartCode(packet, i);
+        if (sc == 0) {
+            ++i;
+            continue;
+        }
+        const size_t nal_start = i + sc;
+        if (nal_start >= size) {
+            break;
+        }
+        const u8 nal_type = packet[nal_start] & 0x1F;
+
+        size_t j = nal_start + 1;
+        while (j < size && MatchStartCode(packet, j) == 0) {
+            ++j;
+        }
+
+        if (nal_type == 7 || nal_type == 8) {
+            constexpr u8 start[4] = {0, 0, 0, 1};
+            extradata.insert(extradata.end(), start, start + sizeof(start));
+            extradata.insert(extradata.end(), packet.begin() + nal_start, packet.begin() + j);
+        } else if (nal_type == 1 || nal_type == 5) {
+            break;
+        }
+        i = j;
+    }
+    return extradata;
+}
+
+#endif
+
 }
 
 Packet::Packet(std::span<const u8> data) {
@@ -117,7 +172,26 @@ Decoder::Decoder(Tegra::Host1x::NvdecCommon::VideoCodec codec) {
             return AV_CODEC_ID_NONE;
         }
     }();
-    m_codec = avcodec_find_decoder(av_codec);
+
+#ifdef ANDROID
+    // FFmpeg exposes MediaCodec via dedicated decoders rather than as a
+    // hw_config on the regular ones.
+    if (Settings::values.nvdec_emulation.GetValue() == Settings::NvdecEmulation::Gpu) {
+        const char* mc_name = nullptr;
+        switch (av_codec) {
+        case AV_CODEC_ID_H264: mc_name = "h264_mediacodec"; break;
+        case AV_CODEC_ID_VP8:  mc_name = "vp8_mediacodec";  break;
+        case AV_CODEC_ID_VP9:  mc_name = "vp9_mediacodec";  break;
+        default: break;
+        }
+        if (mc_name) {
+            m_codec = avcodec_find_decoder_by_name(mc_name);
+        }
+    }
+#endif
+    if (!m_codec) {
+        m_codec = avcodec_find_decoder(av_codec);
+    }
 }
 
 bool Decoder::SupportsDecodingOnDevice(AVPixelFormat* out_pix_fmt, AVHWDeviceType type) const {
@@ -205,6 +279,9 @@ DecoderContext::DecoderContext(const Decoder& decoder) : m_decoder{decoder} {
     av_opt_set(m_codec_context->priv_data, "tune", "zerolatency", 0);
     m_codec_context->thread_count = 0;
     m_codec_context->thread_type &= ~FF_THREAD_FRAME;
+    // Forwarded into MediaCodec as KEY_LOW_LATENCY on Android.
+    m_codec_context->flags |= AV_CODEC_FLAG_LOW_DELAY;
+    m_codec_context->flags2 |= AV_CODEC_FLAG2_FAST;
 }
 
 DecoderContext::~DecoderContext() {
@@ -218,7 +295,19 @@ void DecoderContext::InitializeHardwareDecoder(const HardwareContext& context, A
     m_codec_context->pix_fmt = hw_pix_fmt;
 }
 
-bool DecoderContext::OpenContext(const Decoder& decoder) {
+bool DecoderContext::OpenContext(const Decoder& decoder, std::span<const u8> extradata) {
+    if (!extradata.empty()) {
+        av_freep(&m_codec_context->extradata);
+        m_codec_context->extradata = static_cast<u8*>(
+            av_mallocz(extradata.size() + AV_INPUT_BUFFER_PADDING_SIZE));
+        if (!m_codec_context->extradata) {
+            LOG_ERROR(HW_GPU, "Failed to allocate extradata");
+            return false;
+        }
+        std::memcpy(m_codec_context->extradata, extradata.data(), extradata.size());
+        m_codec_context->extradata_size = static_cast<int>(extradata.size());
+    }
+
     if (const int ret = avcodec_open2(m_codec_context, decoder.GetCodec(), nullptr); ret < 0) {
         LOG_ERROR(HW_GPU, "avcodec_open2 error: {}", AVError(ret));
         return false;
@@ -278,6 +367,12 @@ void DecodeApi::Reset() {
     m_hardware_context.reset();
     m_decoder_context.reset();
     m_decoder.reset();
+    m_opened = false;
+    m_needs_h264_extradata = false;
+    m_next_pts = 0;
+    while (!m_pending_offsets.empty()) {
+        m_pending_offsets.pop();
+    }
 }
 
 bool DecodeApi::Initialize(Tegra::Host1x::NvdecCommon::VideoCodec codec) {
@@ -293,23 +388,69 @@ bool DecodeApi::Initialize(Tegra::Host1x::NvdecCommon::VideoCodec codec) {
         m_hardware_context->InitializeForDecoder(*m_decoder_context, *m_decoder);
     }
 
-    // Open the decoder context.
+#ifdef ANDROID
+    // h264_mediacodec needs SPS/PPS in extradata at open. We pull them from
+    // the first frame's bitstream in SendPacket.
+    m_needs_h264_extradata = m_decoder->GetCodec() &&
+                             std::string_view(m_decoder->GetCodec()->name) == "h264_mediacodec";
+    if (m_needs_h264_extradata) {
+        return true;
+    }
+#endif
+
     if (!m_decoder_context->OpenContext(*m_decoder)) {
         this->Reset();
         return false;
     }
+    m_opened = true;
 
     return true;
 }
 
-bool DecodeApi::SendPacket(std::span<const u8> packet_data) {
+bool DecodeApi::SendPacket(std::span<const u8> packet_data, const FrameOffsets& offsets,
+                           std::optional<FrameDimensions> dimensions) {
+    if (!m_opened) {
+        std::vector<u8> extradata;
+#ifdef ANDROID
+        if (m_needs_h264_extradata) {
+            extradata = ExtractH264AnnexBExtradata(packet_data);
+            if (extradata.empty()) {
+                return true;
+            }
+            if (dimensions) {
+                auto* ctx = m_decoder_context->GetCodecContext();
+                ctx->width = dimensions->width;
+                ctx->height = dimensions->height;
+                ctx->coded_width = dimensions->width;
+                ctx->coded_height = dimensions->height;
+            }
+        }
+#endif
+        if (!m_decoder_context->OpenContext(*m_decoder, extradata)) {
+            this->Reset();
+            return false;
+        }
+        m_opened = true;
+    }
+    m_pending_offsets.push(offsets);
     FFmpeg::Packet packet(packet_data);
+    packet.GetPacket()->pts = m_next_pts;
+    packet.GetPacket()->dts = m_next_pts;
+    ++m_next_pts;
     return m_decoder_context->SendPacket(packet);
 }
 
-std::shared_ptr<Frame> DecodeApi::ReceiveFrame() {
-    // Receive raw frame from decoder.
-    return m_decoder_context->ReceiveFrame();
+std::optional<DecodeApi::DecodedFrame> DecodeApi::ReceiveFrame() {
+    auto frame = m_decoder_context->ReceiveFrame();
+    if (!frame) {
+        return std::nullopt;
+    }
+    FrameOffsets offsets{};
+    if (!m_pending_offsets.empty()) {
+        offsets = m_pending_offsets.front();
+        m_pending_offsets.pop();
+    }
+    return DecodedFrame{std::move(frame), offsets};
 }
 
 }

src/video_core/host1x/ffmpeg.h

@@ -179,7 +179,7 @@ public:
     ~DecoderContext();
 
     void InitializeHardwareDecoder(const HardwareContext& context, AVPixelFormat hw_pix_fmt);
-    bool OpenContext(const Decoder& decoder);
+    bool OpenContext(const Decoder& decoder, std::span<const u8> extradata = {});
     bool SendPacket(const Packet& packet);
     std::shared_ptr<Frame> ReceiveFrame();
 
@@ -198,6 +198,20 @@ private:
     bool m_decode_order{};
 };
 
+struct FrameOffsets {
+    bool interlaced{};
+    bool hidden{};
+    u64 luma{};
+    u64 chroma{};
+    u64 luma_bottom{};
+    u64 chroma_bottom{};
+};
+
+struct FrameDimensions {
+    s32 width{};
+    s32 height{};
+};
+
 class DecodeApi {
 public:
     YUZU_NON_COPYABLE(DecodeApi);
@@ -213,13 +227,23 @@ public:
         return m_decoder_context->UsingDecodeOrder();
     }
 
-    bool SendPacket(std::span<const u8> packet_data);
-    std::shared_ptr<Frame> ReceiveFrame();
+    bool SendPacket(std::span<const u8> packet_data, const FrameOffsets& offsets,
+                    std::optional<FrameDimensions> dimensions = std::nullopt);
+
+    struct DecodedFrame {
+        std::shared_ptr<Frame> frame;
+        FrameOffsets offsets;
+    };
+    std::optional<DecodedFrame> ReceiveFrame();
 
 private:
     std::optional<FFmpeg::Decoder> m_decoder;
     std::optional<FFmpeg::DecoderContext> m_decoder_context;
     std::optional<FFmpeg::HardwareContext> m_hardware_context;
+    bool m_opened{};
+    bool m_needs_h264_extradata{};
+    s64 m_next_pts{};
+    std::queue<FrameOffsets> m_pending_offsets;
 };
 
 } // namespace FFmpeg

src/video_core/host1x/nvdec.cpp

@@ -31,6 +31,7 @@ Nvdec::Nvdec(Host1x& host1x_, s32 id_, u32 syncpt)
 
 Nvdec::~Nvdec() {
     LOG_INFO(HW_GPU, "Destroying nvdec {}", id);
+    host1x.frame_queue.Close(id);
 }
 
 void Nvdec::ProcessMethod(u32 method, u32 argument) {

src/video_core/host1x/vic.cpp

@@ -137,7 +137,7 @@ void Vic::Execute() noexcept {
                         break;
                     }
                     Blend(config, slot_config, config.output_surface_config.out_pixel_format);
-                } else {
+                } else if (nvdec_id != -1) {
                     LOG_ERROR(HW_GPU, "Vic {} failed to get frame with offset {:#X}", id, luma_offset);
                 }
             }