EncoderConfig: introduce GetMaxBFrameCount

The default value for B Frame count is 3 but some
implementation does not support B frames.
Set the value to the max B Frame count supported
by the implementation if it exceeds the value.

Signed-off-by: Stéphane Cerveau <scerveau@igalia.com>

Author: dabrain34

vk_video_encoder/libs/VkVideoEncoder/VkEncoderConfig.h

@@ -618,6 +618,8 @@ struct EncoderConfig : public VkVideoRefCountBase {
     virtual int8_t InitDpbCount() { return 16; };
 
     virtual bool InitRateControl();
+
+    virtual uint8_t GetMaxBFrameCount() { return 0;}
 };
 
 // Create codec configuration for H.264 encoder

vk_video_encoder/libs/VkVideoEncoder/VkEncoderConfigH264.cpp

@@ -369,6 +369,7 @@ VkResult EncoderConfigH264::InitDeviceCapabilities(const VulkanDeviceContext* vk
         std::cout << "\t\t\t" << "maxExtent: " << videoCapabilities.maxCodedExtent.width  << " x " << videoCapabilities.maxCodedExtent.height << std::endl;
         std::cout << "\t\t\t" << "maxDpbSlots: " << videoCapabilities.maxDpbSlots << std::endl;
         std::cout << "\t\t\t" << "maxActiveReferencePictures: " << videoCapabilities.maxActiveReferencePictures << std::endl;
+        std::cout << "\t\t\t" << "maxBPictureL0ReferenceCount: " << h264EncodeCapabilities.maxBPictureL0ReferenceCount << std::endl;
     }
 
     return VK_SUCCESS;

vk_video_encoder/libs/VkVideoEncoder/VkEncoderConfigH264.h

@@ -184,6 +184,8 @@ struct EncoderConfigH264 : public EncoderConfig {
     // 2. First h.264 determine the rate control parameters
     virtual bool InitRateControl();
 
+    virtual uint8_t GetMaxBFrameCount() { return h264EncodeCapabilities.maxBPictureL0ReferenceCount; }
+
     bool GetRateControlParameters(VkVideoEncodeRateControlInfoKHR *rcInfo,
                                   VkVideoEncodeRateControlLayerInfoKHR *pRcLayerInfo,
                                   VkVideoEncodeH264RateControlInfoKHR *rcInfoH264,

vk_video_encoder/libs/VkVideoEncoder/VkEncoderConfigH265.cpp

@@ -89,6 +89,7 @@ VkResult EncoderConfigH265::InitDeviceCapabilities(const VulkanDeviceContext* vk
         std::cout << "\t\t\t" << "maxExtent: " << videoCapabilities.maxCodedExtent.width  << " x " << videoCapabilities.maxCodedExtent.height << std::endl;
         std::cout << "\t\t\t" << "maxDpbSlots: " << videoCapabilities.maxDpbSlots << std::endl;
         std::cout << "\t\t\t" << "maxActiveReferencePictures: " << videoCapabilities.maxActiveReferencePictures << std::endl;
+        std::cout << "\t\t\t" << "maxBPictureL0ReferenceCount: " << h265EncodeCapabilities.maxBPictureL0ReferenceCount << std::endl;
     }
 
     return VK_SUCCESS;

vk_video_encoder/libs/VkVideoEncoder/VkEncoderConfigH265.h

@@ -158,6 +158,8 @@ struct EncoderConfigH265 : public EncoderConfig {
     // 2. First h.265 determine the rate control parameters
     virtual bool InitRateControl();
 
+    virtual uint8_t GetMaxBFrameCount() { return h265EncodeCapabilities.maxBPictureL0ReferenceCount; }
+
     bool GetRateControlParameters(VkVideoEncodeRateControlInfoKHR *rcInfo,
                                   VkVideoEncodeRateControlLayerInfoKHR *pRcLayerInfo,
                                   VkVideoEncodeH265RateControlInfoKHR *rcInfoH265,

vk_video_encoder/libs/VkVideoEncoder/VkVideoEncoder.cpp

@@ -359,6 +359,11 @@ VkResult VkVideoEncoder::InitEncoder(VkSharedBaseObj<EncoderConfig>& encoderConf
     // specific GOP structure. For example it may not support B-frames.
     // gopStructure.Init() should be called after  encoderConfig->InitDeviceCapabilities().
     m_encoderConfig->gopStructure.Init(m_encoderConfig->numFrames);
+    if (encoderConfig->GetMaxBFrameCount() < m_encoderConfig->gopStructure.GetConsecutiveBFrameCount()) {
+        std::cout << "Max consecutive B frames: " << (uint32_t)encoderConfig->GetMaxBFrameCount() << " lower than the configured one: " << (uint32_t)m_encoderConfig->gopStructure.GetConsecutiveBFrameCount() << std::endl;
+        std::cout << "Fallback to the max value: " << (uint32_t)m_encoderConfig->gopStructure.GetConsecutiveBFrameCount() << std::endl;
+        m_encoderConfig->gopStructure.SetConsecutiveBFrameCount(encoderConfig->GetMaxBFrameCount());
+    }
     std::cout << std::endl << "GOP frame count: " << (uint32_t)m_encoderConfig->gopStructure.GetGopFrameCount();
     std::cout << ", IDR period: " << (uint32_t)m_encoderConfig->gopStructure.GetIdrPeriod();
     std::cout << ", Consecutive B frames: " << (uint32_t)m_encoderConfig->gopStructure.GetConsecutiveBFrameCount();