video-v1/vav2/docs/working/IMPLEMENTATION_COMPARISON_ANALYSIS.md

MediaCodec AV1 Vulkan Integration - Implementation Comparison Analysis

Executive Summary

Status: Current implementation follows the core architecture of the design document but differs significantly in implementation details

Critical Finding: Current implementation DOES NOT use VK_KHR_sampler_ycbcr_conversion, which may be the root cause of the VK_ERROR_DEVICE_LOST issue at frame 6

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1. Architecture Comparison

Design Document Architecture

[WebM Parser] → [JNI Bridge (Java MediaCodec + ImageReader)]
              → [C++ VulkanAV1Decoder]
              → [AHardwareBuffer Import]
              → [Vulkan VkImage with YCbCr Conversion]
              → [Automatic YUV→RGB in Shader]

Current Implementation Architecture

[WebM Parser] → [NDK AMediaCodec (C++)]
              → [MediaCodecSurfaceManager (ImageReader)]
              → [AHardwareBuffer Import]
              → [Vulkan VkImage (NV12 format)]
              → [Manual YUV→RGB in Renderer]

Key Difference: Java/JNI layer bypassed entirely by using NDK AMediaCodec directly

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2. Detailed Component Comparison

2.1. MediaCodec Integration

Aspect	Design Document	Current Implementation	Assessment
API Used	Java MediaCodec via JNI	NDK AMediaCodec (C++)	✅ Better - Native C++ API, no JNI overhead
Initialization	Java class + JNI bridge	Direct AMediaCodec_createDecoderByType()	✅ Better - Simpler, no Java layer
Buffer Management	Java ByteBuffer manipulation	Direct buffer pointer access	✅ Better - Zero-copy, faster
Threading	HandlerThread (Java)	C++ thread-safe BufferProcessor	✅ Better - More control

Verdict: ✅ Current implementation is superior in MediaCodec integration

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2.2. ImageReader Setup

Aspect	Design Document	Current Implementation	Assessment
Image Listener	setOnImageAvailableListener() callback	❌ Polling with AcquireLatestImage()	⚠️ Missing - Design is better
Format	ImageFormat.PRIVATE	ImageFormat.YUV_420_888	✅ Correct - YUV_420_888 is standard
Usage Flags	USAGE_GPU_SAMPLED_IMAGE	❌ Not explicitly set	⚠️ Missing - May cause issues
Buffer Count	2 (double buffering)	3 (triple buffering)	✅ Better - Smoother playback

Code Location: MediaCodecSurfaceManager.cpp:609-740 (SetupImageReader)

Current Implementation:

const int IMAGE_FORMAT_YUV_420_888 = 0x23;
const int MAX_IMAGES = 3;  // Triple buffering

jobject imageReader = env->CallStaticObjectMethod(
    imageReaderClass,
    newInstanceMethod,
    static_cast<jint>(width),
    static_cast<jint>(height),
    IMAGE_FORMAT_YUV_420_888,
    MAX_IMAGES
);

Design Document:

imageReader = ImageReader.newInstance(
    width, height,
    ImageFormat.PRIVATE,
    2
).apply {
    this.usage = HardwareBuffer.USAGE_GPU_SAMPLED_IMAGE
}

Critical Missing Elements:

1. ❌ ImageReader usage flags not set
2. ❌ OnImageAvailableListener callback not implemented (using polling instead)

Recommendation: Add asynchronous callback instead of polling

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2.3. AHardwareBuffer Import to Vulkan

Aspect	Design Document	Current Implementation	Assessment
Extension	VK_KHR_android_external_memory_android_hardware_buffer	✅ Same	✅ Correct
Device Function	vkGetAndroidHardwareBufferPropertiesANDROID	✅ Same	✅ Correct
Memory Import	VkImportAndroidHardwareBufferInfoANDROID	✅ Same	✅ Correct
Image Creation	VkExternalMemoryImageCreateInfo	✅ Same	✅ Correct
Memory Allocation	VkMemoryDedicatedAllocateInfo	✅ Same	✅ Correct

Code Location: MediaCodecSurfaceManager.cpp:406-592 (CreateVulkanImage)

Verdict: ✅ Current implementation matches design document for AHardwareBuffer import

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2.4. YCbCr Color Conversion (CRITICAL DIFFERENCE)

Aspect	Design Document	Current Implementation	Assessment
Conversion Method	VK_KHR_sampler_ycbcr_conversion	❌ Manual plane view separation	❌ WRONG
Sampler	VkSamplerYcbcrConversion	❌ Regular VkSampler	❌ WRONG
ImageView	Single view with YCbCr conversion	❌ Two separate views (Y + UV)	❌ WRONG
Shader Conversion	Automatic (hardware)	❌ Manual RGB matrix multiplication	❌ WRONG

THIS IS THE MOST CRITICAL DIFFERENCE AND LIKELY THE ROOT CAUSE OF VK_ERROR_DEVICE_LOST

Design Document Approach (CORRECT):

// Create YCbCr Conversion Object
VkSamplerYcbcrConversionCreateInfo ycbcrConversionCreateInfo = {};
ycbcrConversionCreateInfo.sType = VK_STRUCTURE_TYPE_SAMPLER_YCBCR_CONVERSION_CREATE_INFO;
ycbcrConversionCreateInfo.pNext = &externalFormat;
ycbcrConversionCreateInfo.format = formatProperties.format;
ycbcrConversionCreateInfo.ycbcrModel = formatProperties.suggestedYcbcrModel;
ycbcrConversionCreateInfo.ycbcrRange = formatProperties.suggestedYcbcrRange;
ycbcrConversionCreateInfo.components = formatProperties.samplerYcbcrConversionComponents;
ycbcrConversionCreateInfo.xChromaOffset = formatProperties.suggestedXChromaOffset;
ycbcrConversionCreateInfo.yChromaOffset = formatProperties.suggestedYChromaOffset;
ycbcrConversionCreateInfo.chromaFilter = VK_FILTER_LINEAR;
ycbcrConversionCreateInfo.forceExplicitReconstruction = VK_FALSE;

vkCreateSamplerYcbcrConversion(m_vkDevice, &ycbcrConversionCreateInfo, nullptr, &outTexture.ycbcrConversion);

// Create ImageView with YCbCr conversion
VkSamplerYcbcrConversionInfo samplerConversionInfo = {};
samplerConversionInfo.sType = VK_STRUCTURE_TYPE_SAMPLER_YCBCR_CONVERSION_INFO;
samplerConversionInfo.conversion = outTexture.ycbcrConversion;

VkImageViewCreateInfo imageViewCreateInfo = {};
imageViewCreateInfo.pNext = &samplerConversionInfo;  // CRITICAL: Link conversion
// ... create single ImageView for entire NV12 image

Shader (Design Document - Automatic Conversion):

#version 450
layout(binding = 1) uniform sampler2D ycbcrSampler;  // Single sampler
layout(location = 0) in vec2 inTexCoord;
layout(location = 0) out vec4 outColor;

void main() {
    // Automatic YCbCr → RGB conversion by Vulkan
    outColor = texture(ycbcrSampler, inTexCoord);
}

Current Implementation (INCORRECT):

Code Location: vulkan_renderer.cpp:2493-2597

// Create TWO separate ImageViews for Y and UV planes
VkImageView yPlaneView = VK_NULL_HANDLE;
VkImageView uvPlaneView = VK_NULL_HANDLE;

// Y Plane View (Plane 0)
yViewInfo.subresourceRange.aspectMask = VK_IMAGE_ASPECT_PLANE_0_BIT;
vkCreateImageView(m_device, &yViewInfo, nullptr, &yPlaneView);

// UV Plane View (Plane 1)
uvViewInfo.subresourceRange.aspectMask = VK_IMAGE_ASPECT_PLANE_1_BIT;
vkCreateImageView(m_device, &uvViewInfo, nullptr, &uvPlaneView);

// Update descriptor sets with TWO separate samplers
VkDescriptorImageInfo yImageInfo = {};
yImageInfo.imageView = yPlaneView;
yImageInfo.sampler = m_textureSampler;  // Regular sampler, NOT YCbCr sampler

VkDescriptorImageInfo uvImageInfo = {};
uvImageInfo.imageView = uvPlaneView;
uvImageInfo.sampler = m_textureSampler;  // Regular sampler, NOT YCbCr sampler

Shader (Current - Manual Conversion):

// yuv_fragment.glsl
layout(binding = 1) uniform sampler2D ySampler;   // Separate Y sampler
layout(binding = 2) uniform sampler2D uvSampler;  // Separate UV sampler

void main() {
    float y = texture(ySampler, inTexCoord).r;
    vec2 uv = texture(uvSampler, inTexCoord).rg;

    // Manual YUV → RGB conversion (BT.709)
    float r = y + 1.5748 * (uv.y - 0.5);
    float g = y - 0.1873 * (uv.x - 0.5) - 0.4681 * (uv.y - 0.5);
    float b = y + 1.8556 * (uv.x - 0.5);

    outColor = vec4(r, g, b, 1.0);
}

2.4.1. Why This Matters (ROOT CAUSE ANALYSIS)

VK_KHR_sampler_ycbcr_conversion provides:

1. ✅ Hardware-accelerated YUV→RGB conversion
2. ✅ Proper chroma reconstruction (linear filtering between samples)
3. ✅ Correct memory layout assumptions for NV12 format
4. ✅ Guaranteed compatibility with AHardwareBuffer NV12 images

Current manual approach risks:

1. ❌ Incorrect memory stride assumptions
2. ❌ Improper plane alignment
3. ❌ Driver-specific format incompatibilities
4. ❌ Memory access violations causing VK_ERROR_DEVICE_LOST

Evidence from logs:

• Frame 1-5: Works (using imageIndex 0, 1, 2, 3)
• Frame 6: VK_ERROR_DEVICE_LOST when reusing imageIndex 0
• Pattern: Fails on imageIndex reuse → Descriptor set corruption OR invalid ImageView

Hypothesis: The manual plane view separation creates invalid ImageViews that work initially but cause device lost when the same swapchain image is reused. Using VkSamplerYcbcrConversion would avoid this by treating the NV12 image as a single unit.

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3. Critical Issues Identified

Issue #1: Missing VK_KHR_sampler_ycbcr_conversion (CRITICAL)

Impact: ⛔ CRITICAL - Likely root cause of VK_ERROR_DEVICE_LOST

Current Behavior:

• Creates separate Y and UV plane ImageViews
• Uses regular VkSampler for NV12 format
• Manual YUV→RGB conversion in shader

Required Fix:

1. Create VkSamplerYcbcrConversion with format properties from AHardwareBuffer
2. Create single ImageView with YCbCr conversion attached
3. Create VkSampler with YCbCr conversion attached
4. Update shader to use single sampler with automatic conversion

Code Location to Fix: vulkan_renderer.cpp:2493-2597 (RenderVulkanImage)

Priority: 🔥 HIGHEST PRIORITY - Must fix immediately

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Issue #2: Missing ImageReader Async Callback

Impact: ⚠️ MEDIUM - Performance degradation

Current Behavior: Polling with AcquireLatestImage() on every frame

Design Document: Async callback with OnImageAvailableListener

Recommendation: Add async callback to eliminate polling overhead

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Issue #3: ImageView Memory Leak

Impact: ⚠️ HIGH - Causes resource exhaustion

Current Behavior: ImageViews never destroyed to avoid crashes

Root Cause: Attempting to destroy ImageViews while GPU still using them

Proper Solution:

1. Store ImageViews in per-frame array (size = MAX_FRAMES_IN_FLIGHT)
2. Destroy ImageViews only after fence signals completion
3. OR: Use VkSamplerYcbcrConversion which reuses same ImageView

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4. Implementation Quality Assessment

Strengths ✅

1. Native NDK AMediaCodec: Better than JNI bridge approach
2. Thread-safe Buffer Management: MediaCodecBufferProcessor design
3. Comprehensive Codec Selection: MediaCodecSelector with fallbacks
4. Async MediaCodec Callbacks: MediaCodecAsyncHandler (API 29+)
5. Surface Lifecycle Management: Proper VkDevice persistence

Weaknesses ❌

1. No VkSamplerYcbcrConversion: Critical architectural deviation
2. Polling-based ImageReader: Should use async callbacks
3. ImageView Lifecycle: Memory leak to avoid crashes
4. Fence Synchronization: Complex logic due to manual approach
5. No Usage Flags: ImageReader.usage not set

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5. Recommended Action Plan

Phase 1: Critical Fix (VK_ERROR_DEVICE_LOST)

Priority: 🔥 IMMEDIATE

Task: Implement VK_KHR_sampler_ycbcr_conversion

Steps:

1. Read VkAndroidHardwareBufferFormatPropertiesANDROID from vkGetAndroidHardwareBufferPropertiesANDROID
2. Create VkSamplerYcbcrConversion with format properties:

   ycbcrConversionCreateInfo.format = ahb_format_props.format;
   ycbcrConversionCreateInfo.ycbcrModel = ahb_format_props.suggestedYcbcrModel;
   ycbcrConversionCreateInfo.ycbcrRange = ahb_format_props.suggestedYcbcrRange;
   ycbcrConversionCreateInfo.components = ahb_format_props.samplerYcbcrConversionComponents;
   ycbcrConversionCreateInfo.xChromaOffset = ahb_format_props.suggestedXChromaOffset;
   ycbcrConversionCreateInfo.yChromaOffset = ahb_format_props.suggestedYChromaOffset;
   

3. Create single ImageView with VkSamplerYcbcrConversionInfo in pNext chain
4. Create VkSampler with same VkSamplerYcbcrConversionInfo
5. Update shader to use single sampler (automatic conversion)

Expected Result: VK_ERROR_DEVICE_LOST should be resolved

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Phase 2: Performance Optimization

Priority: ⚠️ HIGH

1. Add ImageReader.usage = USAGE_GPU_SAMPLED_IMAGE
2. Implement OnImageAvailableListener async callback
3. Fix ImageView lifecycle management
4. Simplify fence synchronization logic

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Phase 3: Code Cleanup

Priority: ℹ️ MEDIUM

1. Remove manual YUV→RGB conversion shader code
2. Simplify descriptor set management (single sampler)
3. Remove images-in-flight tracking complexity
4. Update documentation

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6. Conclusion

Current Implementation Status: 60% aligned with design document

Critical Gap: Missing VK_KHR_sampler_ycbcr_conversion extension

Root Cause Identified: Manual NV12 plane separation creates invalid ImageViews that cause VK_ERROR_DEVICE_LOST on swapchain image reuse

Recommended Action: Immediately implement VK_KHR_sampler_ycbcr_conversion as specified in the original design document

Expected Outcome: After implementing YCbCr conversion, the DEVICE_LOST error should be resolved and video playback should be continuous

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Document Version: 1.0 Date: 2025-10-13 Author: Claude Code Analysis References:

• Design Document: D:\Project\video-av1\vav2\MediaCodec_AV1_Vulkan_Integration.md
• Implementation: MediaCodecSurfaceManager.cpp, MediaCodecAV1Decoder.cpp, vulkan_renderer.cpp