Advanced Encoder Configuration

Advanced H.264 Encoder Configuration

The OpenH264 library provides extensive configuration options to fine-tune the H.264 encoding process. This section details the advanced configuration parameters available through the TagEncParamExt structure, demonstrating how to customize encoding behavior for various scenarios.

Table of Contents

• Configuration Parameters
• Basic Settings
• Spatial Layer Settings
• Advanced Settings
• Quality Enhancements
• Usage Example

Configuration Parameters

The TagEncParamExt structure encapsulates a wide range of encoding parameters. Below is a breakdown of key fields and their significance:

Basic Settings

Parameter	Type	Description	Example
iUsageType	EUsageType	Specifies the usage scenario, such as real-time camera video (CAMERA_VIDEO_REAL_TIME), screen capture, etc.	EUsageType.CAMERA_VIDEO_REAL_TIME
iPicWidth	int	Sets the width of the input video frames in pixels.	iPicWidth = 1280
iPicHeight	int	Sets the height of the input video frames in pixels.	iPicHeight = 720
iTargetBitrate	int	Defines the desired bitrate for the encoded video in bits per second.	iTargetBitrate = 1000000 (1 Mbps)
iTemporalLayerNum	int	Specifies the number of temporal layers for scalable video coding (SVC).	iTemporalLayerNum = 1 (no temporal scalability)
iSpatialLayerNum	int	Specifies the number of spatial layers for scalable video coding (SVC).	iSpatialLayerNum = 1 (no spatial scalability)
iRCMode	RC_MODES	Sets the rate control mode, such as constant bitrate (RC_BITRATE_MODE).	RC_MODES.RC_BITRATE_MODE

Spatial Layer Settings

(sSpatialLayers[0])

Parameter	Type	Description	Example
iVideoWidth	int	Sets the width of the spatial layer, if spatial scalability is enabled.	iVideoWidth = 0
iVideoHeight	int	Sets the height of the spatial layer, if spatial scalability is enabled.	iVideoHeight = 0
fFrameRate	float	Specifies the target frame rate for the spatial layer.	fFrameRate = 60
iSpatialBitrate	int	Sets the bitrate for the spatial layer.	iSpatialBitrate = 1000000
uiProfileIdc	EProfileIdc	Defines the H.264 profile, such as High profile (PRO_HIGH).	EProfileIdc.PRO_HIGH
uiLevelIdc	int	Sets the H.264 level.	uiLevelIdc = 0
iDLayerQp	int	Sets the QP value for the layer.	iDLayerQp = 0

Advanced Settings

Parameter	Type	Description	Example
iComplexityMode	ECOMPLEXITY_MODE	Controls the encoder's complexity, affecting encoding speed and quality.	ECOMPLEXITY_MODE.HIGH_COMPLEXITY
uiIntraPeriod	int	Sets the interval between intra (I) frames.	uiIntraPeriod = 300
iNumRefFrame	int	Specifies the number of reference frames used for motion estimation.	iNumRefFrame = 0
eSpsPpsIdStrategy	EParameterSetStrategy	Defines the strategy for handling Sequence Parameter Sets (SPS) and Picture Parameter Sets (PPS).	EParameterSetStrategy.SPS_LISTING_AND_PPS_INCREASING
bPrefixNalAddingCtrl	bool	Control prefix nal adding.	bPrefixNalAddingCtrl = false
bEnableSSEI	bool	Enable Supplemental Enhancement Information.	bEnableSSEI = true
bSimulcastAVC	bool	Enable simulcast AVC.	bSimulcastAVC = false
iPaddingFlag	int	Padding flag.	iPaddingFlag = 0
iEntropyCodingModeFlag	int	Entropy coding mode flag (0: CAVLC, 1: CABAC).	iEntropyCodingModeFlag = 1 (CABAC)
bEnableFrameSkip	bool	Enables frame skipping.	bEnableFrameSkip = false
iMaxBitrate	int	Sets the maximum bitrate.	iMaxBitrate = 0
iMinQp	int	Sets the minimum quantization parameter.	iMinQp = 0
iMaxQp	int	Sets the maximum quantization parameter.	iMaxQp = 51
uiMaxNalSize	int	Maximum NAL unit size.	uiMaxNalSize = 0
bEnableLongTermReference	bool	Enables long-term reference frames.	bEnableLongTermReference = true
iLTRRefNum	int	Sets the number of long-term reference frames.	iLTRRefNum = 1
iLtrMarkPeriod	int	Sets the marking period for long-term reference frames.	iLtrMarkPeriod = 180
iMultipleThreadIdc	int	Controls multi-threading.	iMultipleThreadIdc = 1
bUseLoadBalancing	bool	Enables load balancing.	bUseLoadBalancing = true

Quality Enhancements

Parameter	Type	Description	Example
bEnableDenoise	bool	Enables denoising.	bEnableDenoise = false
bEnableBackgroundDetection	bool	Enables background detection.	bEnableBackgroundDetection = true
bEnableAdaptiveQuant	bool	Enables adaptive quantization.	bEnableAdaptiveQuant = true
bEnableSceneChangeDetect	bool	Enables scene change detection.	bEnableSceneChangeDetect = true
bIsLosslessLink	bool	Enables lossless link.	bIsLosslessLink = false
bFixRCOverShoot	bool	Fixes rate control overshoot.	bFixRCOverShoot = true
iIdrBitrateRatio	int	IDR frame bitrate ratio.	iIdrBitrateRatio = 400
fMaxFrameRate	float	Maximum frame rate.	fMaxFrameRate = 30

Usage Example

encoder = new H264Encoder();
var param = encoder.GetDefaultParameters();

param.iUsageType = EUsageType.CAMERA_VIDEO_REAL_TIME;
param.iPicWidth = w;
param.iPicHeight = h;
param.iTargetBitrate = 1000000;
param.iTemporalLayerNum = 1;
param.iSpatialLayerNum = 1;
param.iRCMode = RC_MODES.RC_BITRATE_MODE;

param.sSpatialLayers[0].iVideoWidth = 0;
param.sSpatialLayers[0].iVideoWidth = 0;
param.sSpatialLayers[0].fFrameRate = 60;
param.sSpatialLayers[0].iSpatialBitrate = 1000000;
param.sSpatialLayers[0].uiProfileIdc = EProfileIdc.PRO_HIGH;
param.sSpatialLayers[0].uiLevelIdc = 0;
param.sSpatialLayers[0].iDLayerQp = 0;

param.iComplexityMode = ECOMPLEXITY_MODE.HIGH_COMPLEXITY;
param.uiIntraPeriod = 300;
param.iNumRefFrame = 0;
param.eSpsPpsIdStrategy = EParameterSetStrategy.SPS_LISTING_AND_PPS_INCREASING;
param.bPrefixNalAddingCtrl = false;
param.bEnableSSEI = true;
param.bSimulcastAVC = false;
param.iPaddingFlag = 0;
param.iEntropyCodingModeFlag = 1;
param.bEnableFrameSkip = false;
param.iMaxBitrate = 0;
param.iMinQp = 0;
param.iMaxQp = 51;
param.uiMaxNalSize = 0;
param.bEnableLongTermReference = true;
param.iLTRRefNum = 1;
param.iLtrMarkPeriod = 180;
param.iMultipleThreadIdc = 1;
param.bUseLoadBalancing = true;

param.bEnableDenoise = false;
param.bEnableBackgroundDetection = true;
param.bEnableAdaptiveQuant = true;
param.bEnableSceneChangeDetect = true;
param.bIsLosslessLink = false;
param.bFixRCOverShoot = true;
param.iIdrBitrateRatio = 400;
param.fMaxFrameRate = 30;

encoder.Initialize(param);