Encoding Parameters

level

Sets the level for encoding. If level=0 the encoder will automatically determine the level based on picture size, frame rate and bitrate. If specified, the level will be used.

When a non-zero level is specified, the encoder will use it regardless of the encoder parameters.

profile

Sets the profile for encoding. The valid profiles for H.264 and H.265 are shown below.

Any profile can be used for 8 bit encoding, but only the 10 bit profiles (main10 for H.265 and high10 for h.264) may be used for 10 bit encoding.

high-tier

Sets the tier for AV1 and H.265 encoding. 

av1OpLevel

Specifies level for each AV1 operating point. This parameter takes up to 4 integer (E.g. 51 for level 5.1) or decimal values separated by commas, each value indicating the level for an operating point, starting from operating 0 to the highest. When this parameter is not specified or set to 0, firmware will automatically determine the level for each AV1 operating point.

This parameter is generally used only for AV1 spatial layers encoding. When this parameter is specified, the number of comma separated values must match with the number of spatial layers specified by spatialLayers parameter. A sample ffmpeg command is as follows:

ffmpeg -loglevel info -vsync 0 -i base_layer.mp4 -i enhancement_layer.mp4 -filter_complex "[0:v][1:v]interleave=2" -r 50 -c:v av1_ni_quadra_enc -xcoder-params "spatialLayers=2:spatialLayersRefBaseLayer=1:RcEnable=1:spatialLayerBitrate=10000000,1000000:av1OpLevel=5.0,5.1:intraPeriod=120" -y out.mp4

hrdEnable

Enable hypothetical reference decoder (HRD) compliance.

When enabled this parameter will:

1. Update the HRD parameters in the VUI

2. Send the pic timing sei messages in the bitstream

3. Send the buffering period sei messages in the bitstream

4. Automatically set RcEnable = 1 if RcEnable is not already enabled 

enableAUD

Specifies whether to include Access Unit Delimiters (AUD) or not.

Required For:

AUDs are required for DolbyVision compatibility, or when placing bitstreams in transport streams.

dolbyVisionProfile

Configures the Netint encoder as a 3rd party encoder with the Dolby Encoding Engine. Overrides VUI colour parameters as per DolbyVision profile 5 requirements (video_format=1 (full-range), colour_primaries=transfer_characteristics=matrix_coeffs=2 (unspecified), chroma_loc_info_present_flag=0) and enables AUD and HRD.

maxCLL

Specifies parameters for HDR Content Light Level Info as per CEA 861.3. Specified as a string with format “%hu,%hu” where %hu are unsigned 16 bit integers. The first value is the maximum content light level (or 0 if no maximum is indicated), the second value is the maximum picture average light level (or 0). For example, for MaxCLL=1000 nits, MaxFALL=400 nits: max-cll =“1000,400”. Note that this string value will need to be escaped or quoted to protect against shell expansion on many platforms. When this parameter is specified, it will be used in preference to content light level info side data of FFmpeg AVFrame.

masterDisplay

Specifies parameters for the HDR Mastering Display Colour Volume SEI as per SMPTE ST 2086. Specified as a string with format: “G(%hu,%hu)B(%hu,%hu)R(%hu,%hu)WP(%hu,%hu)L(%u,%u)” where %hu are unsigned 16bit integers and %u are unsigned 32bit integers. The SEI includes X,Y display primaries for RGB channels and white point (WP) in units of 0.00002 and max,min luminance (L) values in units of 0.0001 nits

For example for a P3D65 1000-nits monitor, where

G(x=0.265, y=0.690), B(x=0.150, y=0.060), R(x=0.680, y=0.320), WP(x=0.3127, y=0.3290), L(max=1000, min=0.0001): “G(13250,34500)B(7500,3000)R(34000,16000)WP(15635,16450)L(10000000,1)”

Note that this string value will need to be escaped or quoted to protect against shell expansion on many platforms. When this parameter is specified, it will be used in preference to mastering display info side data of FFmpeg AVFrame.

enableAllSeiPassthru

All custom SEI types will be passed through if this is enabled. Also, when enabled, the firmware SEI will be disabled.

useLowDelayPocType

When enabled, the encoder will use picture_order_count_type=2 in the H.264 SPS, this tells the decoders all frames are in sequence, this typically results in a lower decoding delay. This feature is only supported for H.264 when all frames are reference frames, i.e, when using gop presets gopPresetIdx=1, 3, 7, and 9. For custom gop (gopPresetIdx 0), this feature is only supported for custom gop size 1. By default, this feature is disabled, and the encoder uses picture_order_count_type=0, which is compatible with all gops.

confWinTop

Conformance top window size. This is the number of pixel rows at the top of the picture that should not be displayed when decoding. This is in addition to any cropping info that may already be included on the AVFrame to be encoded.

confWinBot

Conformance bottom window size. This is the number of pixel rows at the bottom of the picture that should not be displayed when decoding. This is in addition to any cropping info that may already be included on the AVFrame to be encoded.

confWinLeft

Conformance left window size. This is the number of pixel columns at the left side of the picture that should not be displayed when decoding. This is in addition to any cropping info that may already be included on the AVFrame to be encoded

confWinRight

Conformance right window size. This is the number of pixel columns at the right side of the picture that should not be displayed when decoding. This is in addition to any cropping info that may already be included on the AVFrame to be encoded

repeatHeaders

Specifies whether the encoder repeats the VPS/SPS/PPS headers on all I frames. Or if intra refresh is enabled, headers are repeated on P frames at IntraRefreshMinPeriod.

For HDR/HDR10+ streams, the static HDR SEIs (content light level info, mastering display colour volume, and alternative transfer characterics) if present are also repeated. Repeated headers permit a bitstream to be decoded mid-stream. It also provides error resilience, in case packets were lost during transmission.

prefTRC

Specifies the HLG preferred transfer characteristics value. If this parameter is present, the encoder will include an alternative transfer characteristics metadata in the bitstream with the preferred transfer characteristics field set to the value of this parameter. If the parameter is not present, the SEI will not be present. The alternative transfer characteristics metadata is required by ETSI for HLG and specifies an alternative transfer characteristic from that provided in the VUI.

sliceMode

Enable multi-slice encoding. Must be used in conjunction with parameter sliceArg.

sliceArg

If sliceMode is enabled, this represents the number of CTU/MB rows in each slice. Value must be between 1 and number of CTU/MB rows in the picture. The number of rows is calculated by height/64 (H.265) or by height/16 (H.264).

sliceNum = (ctbPerCol + sliceArg - 1) / sliceArg.

need to keep sliceNum <= 256, if sliceNum > 256, sliceArg will increase one automatically until sliceNum <= 256

entropyCodingMode

Selects the entropy coding mode used in the encoding process. Note that CABAC is only compatible with H.264 Main, High, and High10 profiles and is disabled for other profiles.

framerate

The numerator of the frame rate. This works in conjunction with frameRateDenom to support fractional framerates. The frameRate is used by the encoder for rate control (when enabled) and to set the VUI timing information. If not specified, the frameRate passed in from FFmpeg (or 3rd party application) is used. This parameter is intended for integrating directly with libxcoder.

frameRateDenom

The encoder frame rate denominator that supports fraction frame rate together with frameRate. The frame rate would then be frameRate / frameRateDenom, e.g. frameRate=30000 and frameRateDenom=1001 represents frame rate of 30000/1001=29.97. This parameter is intended for integrating directly with libxcoder.

colorPri

Specifies one of the VUI color description parameters: color_primaries. The supported values are defined as AVColorPrimaries in FFmpeg, and ni_color_primaries_t in libxcoder. If colorPri, colorTrc, or colorSpc is not equal to 2 (unspecified), the relevant VUI parameters are added to the sequence header.

colorTrc

Specifies one of the VUI color description parameters: transfer_characteristics. The supported values are defined as AVColorTransferCharacteristic in FFmpeg, and ni_color_transfer_characteristic_t in libxcoder. If colorPri, colorTrc, or colorSpc is not equal to 2 (unspecified), the relevant VUI parameters are added to the sequence header.

colorSpc

Specifies one of the VUI color description parameters: matrix_coeffs. The supported values are defined as AVColorSpace in FFmpeg, and ni_color_space_t in libxcoder. If colorPri, colorTrc, or colorSpc is not equal to 2 (unspecified), the relevant VUI parameters are added to the sequence header.

sarNum, sarDenom

Specifies the VUI sample aspect ratio aspect_ratio_idc, as sarNum : sarDenom. When sarNum is 0, aspect_ratio_idc is not included in VUI. When sarNum is greater than 0, the aspect_ratio_idc is included in VUI. This parameter is intended for integrating directly with libxcoder.

videoFullRangeFlag

Specifies the VUI video_full_range_flag parameter value. When it is 1, the relevant VUI parameters are added to the sequence header.

av1ErrorResilientMode

Specifies whether AV1 error resilient mode is enabled. AV1 error resilient mode allows the syntax of a frame to be parsed independently of previously decoded frames. Note that enabling AV1 error resilient mode may reduce compression efficiency. Also note that error resilient mode is only applicable to AV1, enabling this mode has no effect on other codecs.

disableAv1TimingInfo

By default, Quadra AV1 encoder signals timing info (refer to AV1 spec 5.5.3 Timing info syntax) in sequence header. When timing info is present, AV1 decoder model will assume default parameters (refer to AV1 spec E.3.1 Resource availability mode). This may cause decoders or video analyzing tools to report decoder model conformance issues, if the encoder rate control mode is not CBR mode, or if the rate control bitrate and buffer size settings are not confined to match with decoder model default parameters.

To avoid decoder model conformance issues, the user may set disableAv1TimingInfo to 1 to disable timing info. The downside of disabling timing info is that framerate information will not be available in the sequence header. However, this typically causes no harm since AV1's minimum viable format—the IVF container—provides framerate signaling, as do all multimedia containers like MP4 and AVI.

temporalLayersEnable

Enables temporal scalability with SVC (Scalable Video Coding). When enabled, temporal layers related syntax is added to bitstream. For temporal IDs assignments for each preset gop pattern, please refer to section 8.4.3.2 - Pre-defined GOP Structure.

ppsInitQp

Specifies h.264 pic_init_qp_minus26 or h.265 init_qp_minus26 in Picture Parameter Sets. When specified, every Picture Parameter Set in the h.264 or h.265 bitstream will signal the specified ppsInitQp value for init_qp_minus26 syntax - instead of setting init_qp_minus26 according to the initial QP value decided by firmware, which is the default behavior when user does not specify ppsInitQP.

spatialLayers

Specifies the number of spatial layers in AV1 encoding. Setting spatialLayers > 1 enables AV1 spatial scalability with multiple spatial layers. Quadra supports up to 4 spatial layers.

spatialLayersRefBaseLayer

When spatialLayersRefBaseLayer is enabled, each EL (Enhancement Layer) frame will refer to the BL (Base Layer) frame instead of the lower layer frame. Please refer to section “8.4.3.4 - AV1 Spatial Layers Gop Patterns” for illustrations of cross layer reference hierarchies when spatialLayersRefBaseLayer is enabled.

spatialLayerBitrate

Specifies the target bitrate of each AV1 spatial layer. This parameter takes up to 4 integer values separated by commas. When this parameter is specified, the rate control of each AV1 spatial layer is separated from each other and each conforms to its own target bitrate as specified with this parameter. This can guarantee that the base layer always remains the same when it’s encoded with different enhancement layers, as long as the encoding parameters are the same. This parameter can also be used in conjunction with spatialLayers=1 (single layer encoding), which alters single layer rate control and gop structure to match with the base layer of a multi-layers bitstream. When this parameter is specified, the number of comma separated values must match with the number of spatial layers. Also note that when this parameter is specified, the bitrate parameter will not take effects. A sample FFmpeg command is as follows:

ffmpeg -vsync 0 -i base_layer.mp4 -i enhancement_layer_1.mp4 -i enhancement_layer_2.mp4 -i enhancement_layer_3.mp4 -filter_complex "[0:v][1:v][2:v][3:v]interleave=4" -r 60 -c:v av1_ni_quadra_enc -xcoder-params rcEnable=1:bitrateMode=1:vbvBufferSize=2000:cuLevelRCEnable=1:intraPeriod=60:spatialLayers=4:spatialLayersRefBaseLayer=1:spatialLayerBitrate=5000000,2000000,1500000,1000000 out.mp4

As shown in the example command above, the first value (5000000) is the target bitrate for base layer, the second value (2000000) is the target bitrate for the first enhancement layer, and so on for the second and third enhancement layers.

enableTimecode

When enabled, set the pic_struct_present flag in VUI to 1. This is needed for properly inserting timecode data into the picture timing SEI in H264. See section 6.6.7.6 in the libxcoder API integration guide for more details on how to insert timecode data into SEI.

avccHvcc

When this flag is disabled, the encoder produces a byte stream where NALUs are sent sequentially, as specified by Annex B. Each NALU is preceded by a Start Code Prefix, which is not allowed to appear within the NALU itself.

When it is enabled, the firmware encoder generates the bitstream in AVCC/HVCC. The encoder generates [Codec]DecoderConfigurationBox followed by NALUs, where [Codec] can be either ‘AVC’ or ‘HEVC’. Refer to the table below for the syntax details. Each NALU, following this configuration box, is preceded by its length rather than a Start Code Prefix.

clearRefListModification

Clears ref_pic_list_modification_flag_l0 in H.264 P-slice headers and removes the associated reference-picture-list reordering commands. Only the slice header is rewritten; the coded slice data is left unchanged. This produces P slices that use the default reference-picture-list ordering.

This option modifies only H.264 P slices; B slices and all other slice types are left untouched. It is safe to use when each P slice uses a single reference picture, so that the reordering commands are redundant (they reproduce the default reference-picture list) and clearing them does not change how the stream decodes. Do not enable it for streams that use P slices with multiple reference pictures or long-term references, as removing the reordering may change which reference each P-slice macroblock predicts from and corrupt the decoded output.

When entropyCodingMode is 0 (CAVLC), the slice data is bit-shifted to close the gap left by the removed commands; when it is 1 (CABAC), the byte-aligned slice data is copied unchanged.

Libxcoder Application Features

lowDelay

Specifies whether or not to enable the low latency mode in encoding. When enabled, libxcoder increases its rate of polling the encoder and only permits buffering of a single frame to minimize the delay.

minFramesDelay

Specifies whether to enable the minimum encoding delay frames feature. When enabled, libxcoder increases its rate of polling the encoder and only permits buffering of the minimum frames to minimize the delay.

The minimum encoding delay depends on both the GOP size and the lookahead depth.

For example, when gopPresetIdx = 5 and lookaheadDepth = 4, the minimum encoding delay is 3 frames, meaning that the application must submit 4 input frames before the encoder produces the first output packet.

keepAliveTimeout

Specifies a session keep alive timeout value. This is a periodic request/response between libxcoder and XCoder firmware that when timed out, the session instance will be terminated by XCoder firmware. If this option is used in conjunction with FFmpeg command line option keep_alive_timeout then keepAliveTimeout overrides keep_alive_timeout.

zeroCopyMode

Enable or disable libxcoder zero copy feature. When zero copy is disabled, libxcoder copies YUV data from input frame buffer(s) to consecutive internal buffer before transferring data to device. This reduces overhead by triggering data transfer only once.

When zero copy is enabled, libxcoder transfers data directly from input frame buffer(s) (luma / chroma buffers can be inconsecutive) to device, which improves performance when encoding high resolution / large frames.

The default setting is auto mode, in which libxcoder decides whether to enable or disable zero copy based on input resolution – zero copy is enabled if input resolution >= 1080p, and disabled if input resolution < 1080p. Auto mode's zero copy enable / disable is based on performance test results, and therefore is the suggested setting.

ddrPriorityMode

Specifies the DDR memory priority mode. Only need set once at beginning, and it will reset to default automatic after current process finish.

statisticOutputLevel

Specify the information output for each frame, statisticOutputLevel = 1 will including the maximum and minimum MV of the macroblocks in the current frame, as well as the number of inter/intra macroblocks in the current frame and the frame size of the current frame. statisticOutputLevel = 6 will include 1-pass satd cost

disableAdaptiveBuffers

Specifies whether to disable adaptive buffers when bitstream sequence is changed. When disableAdaptiveBuffers=1 and width/height of pictures is different from previous width/height in sequence change, it will take a little time to re-configure encoder with new width/height.

Encode Algorithm and Features

preset

Selects a predefined set of encoding parameters to balance encoding speed and compression efficiency. Presets provide a convenient way to configure the encoder with optimized settings for specific use cases, prioritizing either speed or quality. When a preset is used, any additional encoding parameters specified will override the corresponding preset values except RcEnable. RcEnable is always set to 1 and crf to –1 (disabled) since preset is only supported in the CBR mode. If no preset is selected, the encoder applies no predefined parameter set.

The following are example ffmpeg commands:

ffmpeg -vsync 0 -i input.h264 -c:v h265_ni_quadra_enc -xcoder-params preset=medium output.mp4

ffmpeg -vsync 0 -i input.h264 -c:v h265_ni_quadra_enc -preset medium output.mp4

rdoLevel

Specifies the number of candidates to use for Rate Distortion Optimization. RDO is a method for improving video quality during compression. Lower values mean a lower quality but better performance, higher values mean more quality but less performance

EnableRdoQuant

Specifies whether to enable or disable RDO Quantization. RDOQ provides optimized quantization to further improve video quality, with the cost of lower performance

tuneBframeVisual

Specifies whether to enable or disable B-frame visual tuning. B-frame visual tuning helps mitigate subjective quality fluctuation, at the cost of lowered compression efficiency. When enabled, there are 2 modes available – setting tuneBframeVisual to 1 enables MEDIUM tuning mode, in which encoder tunes B-frame visual quality with minor loss in compression efficiency, and setting tuneBframeVisual to 2 enables HIGH tuning mode, in which encoder applies stronger tuning to B-frame visual quality with more compression efficiency loss

enable2PassGop

This parameter will affect the group of picture pattern for 2-pass encoding.

By default, it is disabled. Encoder has its own GOP for 2-pass mode when lookahead > 0. GOP will be different from what is described in gopPresetIdx.

When it is enabled, the 2-pass encoding’s GOP is consistent with GOP specified by gopPresetIdx.

For more details, please refer to Section 8.4.3.2 Pre-defined GOP Structure.

lookAheadDepth

Number of frames to lookahead while encoding. Lookahead can increase encoder quality at the expense of performance (approximately 25%) and delay. Note that the input video pixel width must be at least 144 pixels wide.

noMbTree

When lookahead is enabled, MB Tree / CU Tree is enabled by default. Use the noMbTree parameter to disable MB Tree / CU Tree feature. Because disabling MB Tree / CU Tree can reduce quality and compression efficiency, this setting is not recommended in most cases.

totalCuTreeDepth

In live streaming, cloud gaming, or other low delay scenarios, a high lookahead depth setting may not be acceptable due to the extended delay caused by lookahead. In scenarios where increasing lookahead depth is not an option, the user may set totalCuTreeDepth to a number greater than lookahead depth to improve quality. Currently this feature is only supported for gopPresetIdx 5, and the suggested value is lookahead depth + ½ gop size, E.g. for lookaheadDepth=4 and gopPresetIdx=5 (which has gop size 4), the suggested setting for totalCuTreeDepth is 4+(4/2)=6. Please also note enabling this feature will cause up to 9 ~ 10% performance degradation.

gopPresetIdx

Defines the Group Of Picture pattern.

By default, encoder uses Adaptive Gop, for which the encoder dynamically adjusts gop pattern while encoding based on statistics collected from previous frames (1-pass) or lookahead (2-pass).

If both coding parameters gopPresetIdx and lookaheadDepth are set, then the gop pattern is different from setting only the coding parameter gopPresetIdx. For details, please refer to Section 8.4.3 Custom Gop Structure.

For 2-pass encoding, the GOP is not only affected by this parameter, but also affected by parameter enable2PassGop. Please refer to it for more details.

intraPeriod

Key frame / IDR frame interval.

intraQP

Specifies intra frame quantization parameter.

When used for JPEG, the encoder scales the quantization table in the JPEG standard to produce bitstreams of different video quality.

intraQPDelta

Delta value added to the Intra frame QP. Can be used to lower the Intra Picture encoded size (higher QP) or to increase Intra quality relative to the Inter Pictures (lower QP) to get rid of intra flashing. Recommended value range is –12 to 12.

After intraQpDelta is applied, the intra frame QP is further adjusted by rate control, which means that the encoded bitstream may not contain the exact value of the user-defined delta depending on the source.

qLevel

JPEG only. Specifies the quantization scale to produce the different video qualities by scaling the quantization table. Higher values produce better quality.

minQP

Min QP for rate control.

maxQP

Max QP for rate control.

roiEnable

ROI (Region of interest), is a feature of the encoder that permits the quality of some regions to be improved at the expense of other regions. If rate control is disabled, the QPs are used directly for encoding, if rate control is enabled, the encoder scales the QPs as necessary to meet the bitrate target. When ROI is enabled, the ROI map can be updated, enabled, or disabled on a frame by frame basis.

For ROI map configuration, please refer to ni_quadra_roi in section 10 – Filters.

RoiDemoMode

Enables the ROI demo mode. When ROI is enabled (roiEnable=1), ROIDemoMode permits the ROI feature to be demonstrated using the standard FFmpeg command line, without additional application development. ROI demo mode is currently only supported on FFmpeg 3.4.2 and above. Demo mode 1 has QP=40 for the center 1/3, and QP=10 for outer 2/3. Demo mode 2 has opposite QP. In both cases ROI is enabled at frame 90 and disabled at frame 300.

cacheRoi

Enables caching of an ROI map. When ROI is enabled, the ROI map can be changed on a frame by frame basis. When cacheRoi is enabled at the same time, the currently available ROI map is cached and applied to the subsequent frames until a new map is supplied. It is only valid if ROI is enabled.

intraRefreshMode

Selects intra refresh macroblock update method. This method is not supported for 2-pass encode and the command will be rejected.

intraRefreshArg

Specifies the number of consecutive CTB or MB rows refreshed (to be encoded as Intra) per frame

If intra refresh cycle is 1 (meaning intra refresh must be completed in 1 frame), this defeats the purpose of intra refresh and therefore the encode command will be rejected. Intra refresh cycle can be calculated by

Intra refresh cycle = input picture height / (intraRefreshArg * 16 for h.264, or * 64 for 	h.265 and AV1)

For example, if h.265 input resolution is 640x480 and intraRefreshArg is 8, intra refresh cycle = ceil(480 / (64 * 8)) = 1, which is invalid setting and will be rejected

IntraRefreshMinPeriod

Intra refresh cycle starts at intra period, which is specified by intraPeriod or intraRefreshMinPeriod. If both intraRefreshMinPeriod and intraPeriod are specified, whichever comes later in the parameter string has higher priority.

IntraRefreshResetOnForceIDR

Intra refresh cycle will reset to restart on force IDR frame

longTermReferenceEnable

Enables the long term reference (LTR) feature. With long term reference enabled, an application can

1. Set LTR interval by longTermReferenceInterval, and/or

2. Set any frame as LTR on a frame by frame basis. For more detail refer to QUADRA libxcoder API Guide

3. Set number of LTRs (1 or 2) by longTermReferenceCount

LTR is only supported by low delay gop (i.e. all frames in sequence), namely gopPresetIdx=1, 3, 7, 9, or 0 (if custom gop has consecutive order frames). Also, LTR is not supported for 2-pass encode and the command will be rejected.

longTermReferenceInterval

When longTermReferenceEnable is enabled, assign longTermReferenceInterval > 0 will set frames as LTR periodically upon specified frame interval. If longTermReferenceInterval = 0, only IDR frames will be set as LTR

longTermReferenceCount

When longTermReferenceEnable is enabled, the number of LTRs (1 or 2) can be configured by longTermReferenceCount.

By default, Quadra preserves up to 2 LTRs. However, due to Quadra h.264 encoder limitation, some decoders may not be able to decode h.264 bitstream Quadra encoded with 2 LTRs, in which case longTermReferenceInterCount should be set to 1

longTermReferenceOldest

Specifies which long-term reference (LTR) frame takes priority when inter-frames use LTRs for prediction and two LTR frames are available.

Inter-frames use LTRs for prediction when the application invalidates short-term references (STRs) or when useLTRsOnly=1.

Priority is determined by display order:
Newest LTR: The most recent LTR in display order.
Oldest LTR: The earliest LTR in display order.

useLTRsOnly

Restricts every inter-frame prediction to the available long-term reference(s) (one or two LTRs). If insufficient LTRs are available, short-term references (STRs) are used as a fallback. When two LTRs are available, longTermReferenceOldest determines which LTR takes priority.

multicoreJointMode

Enables encoder multi-core mode where all 4 cores work together in parallel (a.k.a. joint mode). When disabled (default) the encoder instances use a single video core to encode. When enabled, encoder instances use all 4 video encoding cores in parallel. Recommended only for high resolution encoding with less than 4 instances e.g. 8K encode. When more than 4 encoding instances are used enabling this feature will lower performance due to extra synchronization overhead.

When multicoreJointMode is enabled, lowDelay and picSkip must be 0.

enableSSIM

When enabled, XCoder firmware will return SSIM values for Y, U, and V of each encoded frame in the ni_metadata_enc_bstream_t structure. The SSIM values are 4 decimal places multiplied by 10000. Divide by 10000 to get the original value.

getPsnrMode 

Specify whether to output PSNR. Hardware only support output psnr on y component for HEVC codec. For other codec or for UV component, the psnr should calculate on the SW. Enable this feature will reduce performance. 

intervalOfPsnr 

Specify the interval frame numbers for outputting PSNR. Its function is to reduce performance consumption, and this params affects the input frames. Therefore, if it is a non continuous frame output, the output interval may be slightly different from the value of intervalOfPsnr, depending on the gop size in the encoding.

getReconstructedMode 

Specify whether to get reconstructed frame from Hardware. Currently get reconstructed frame is supported for 8-bit YUV420p only. The workflow is like getPsnrMode.

ReconfDemoMode

Specifies demo mode. When enabled the specified demo mode reconfigures the encoding parameters while encoding is in progress. Must be used with ReconfFile. For example, “ReconfDemoMode=1:ReconfFile=reconf.txt”. The types of parameters that can be reconfigured by the demo mode are listed in Supported Values. The example command below shows how to enable the bitrate reconfiguration demo:

ffmpeg -vsync 0 -c:v h264_ni_quadra_dec -dec 0 -y -i Dinner_1920x1080p30_300.h264 -c:v h264_ni_quadra_enc -xcoder-params "bitrate=1000000:RcEnable=1:ReconfDemoMode=1:ReconfFile=reconf.txt" -enc 0 out.h264

The Long Term Reference (LTR) and the reference invalidation features are explained in detail in sections 8.4.1 Long Term Reference and 8.4.2 Reference Invalidation, respectively.

ReconfFile

Specifies the name of the reconf file from which the reconfiguration demo mode will read key and value information. Must be used with ReconfDemoMode. For example, ReconfDemoMode=1:ReconfFile=reconf.txt. The reconf file must be created in the same directory where the command is running. The file contains one line or multiple lines of key:value pairs.

The content of the reconf file for the different demo mode is shown in the examples below:

Bitrate (ReconfDemoMode 1)

At frame number 100, bitrate changes to 1000000 bps. Add multiple lines of key:value to change the bitrate over multiple frames.

Intra Period (ReconfDemoMode 2)

At frame number 100, force IDR frame (aka key frame) and changes intra period to 30. Add multiple lines of key:value pairs to change intra period over multiple frames.

VUI (ReconfDemoMode 3)

A VUI containing the 7 listed parameter changes at frame number 100.

Long Term Reference (LTR) frame setting (ReconfDemoMode 4)

Refer to the description of longTermReferenceEnable

Max & Min qp setting (ReconfDemoMode 6)

Long Term Reference (LTR) interval setting (ReconfDemoMode 7)

Refer to the description of longTermReferenceInterval

Frame reference invalidation (ReconfDemoMode 8)

Framerate (ReconfDemoMode 9)

MaxFrameSize parameter setting (ReconfDemoMode 10)

 Refer to the description of MaxFrameSize for required settings

CRF (ReconfDemoMode 14)

VBV (ReconfDemoMode 16)

MaxFrameSizeRatio (ReconfDemoMode 17)

SliceArg (ReconfDemoMode 18)

Set Long-Term Reference (LTR) and Invalidate Reference Frames (ReconfDemoMode 19)

Marks the current frame as an LTR and/or invalidates reference frames according to entries in a configuration file.

Prerequisite: This mode takes effect only when longTermReferenceEnable=1

Set Long-Term Reference (LTR) and Invalidate Reference Frames and configure the current frame to use LTR prediction (ReconfDemoMode 20)

Marks the current frame as an LTR, and/or invalidates reference frames, and/or configure the current frame to use LTR prediction, according to entries in a configuration file.

Prerequisite: This mode takes effect only when longTermReferenceEnable=1

enableAIEnhance

Embedded image enhancement models are utilized to improve the visual quality of videos during the transcoding process. Upon decoding the YUV hardware frames, they are transmitted to the Quadra AI Inference Engine, which generates enhanced frames of identical size and format, before passing them on to the encoder. Generally, this approach results in videos with superior visual quality.

AIEnhanceLevel

Specifies the adjust level of AI engine to AI enhance optimization. The higher means the AI engine would change more about the original picture and the PSNR may be lower.

enableHVSPlus

HVS+ utilizes Quadra's internal AI engine to enhance video quality during encoding by mimicking the human visual system. It optimizes video content through perceptual optimization, achieving a balanced performance between PSNR (Peak Signal-to-Noise Ratio) and VMAF (Video Multi-Method Assessment Fusion). This ensures that both objective and subjective quality metrics are met. HVS+ offers two preconfigured settings tailored to different types of video content, providing optimal enhancement for various genres.

HVSPlusLevel

Level 1 preserves the PSNR better in general. Level 2 is more towards improving the subject quality.

cropWidth

Specifies cropping width, must be even.

cropHeight

Specifies cropping height, must be even.

horOffset

Specifies horizontal cropping offset, must be even.

verOffset

Specifies vertical cropping offset, must be even.

motionContrainedMode

Enables Motion Constrained mode 1 (Performance mode), mode 2 (Quality mode), or mode 3 (Advanced Quality mode). When Motion Constrained mode is enabled, the encoder forces specific blocks to be encoded in intra mode to prevent motion vectors from crossing picture boundaries. This allows the encoded frame to be converted into HEVC or AV1 tiles and stitched together with other tiles to form a multi-tile bitstream without introducing visible decoding artifacts.

A common use case for this feature is multiview applications, where multiple video streams are displayed simultaneously on a single display device.

Please note that enabling Motion Constrained mode may negatively impact encoding performance and/or compression efficiency due to the additional motion estimation constraints:

• Mode 1 (Performance mode): No performance impact, but lower compression efficiency and quality.

• Mode 2 (Quality mode): Reduced encoding performance, but significantly better visual quality than mode 1 at the same bitrate.

• Mode 3 (Advanced Quality mode): Provides further quality optimization over mode 2, with a slight additional encoding performance cost.

Rate Control

RcEnable

Enables or disables rate control.

bitrate

Used when RcEnable is enabled (set to 1) or crf value is specified (crf value >= 0), otherwise it is ignored. The encoding bitrate is in bps.

bitrateMode

Decides rate control behavior when RcEnable is 1, cuLevelRCEnable is 1, and lookaheadDepth is 0 (NOTE - lookaheadDepth default value is 0).

When bitrateMode is 0 (default), encoder perceives bitrate as the maximum bitrate allowed, and therefore may produce bitrate lower than bitrate to achieve higher compression efficiency. When bitrateMode is 1, encoder perceives bitrate as the average bitrate target, and shall produce bitrate close to the target.

enableVFR

Specifies the variable framerate(VFR) encoding is support or not.

The VFR feature is disabled by default and the encoder rate control assumes that the framerate is constant. When enabled, the VFR feature uses the video timestamps to calculate the average framerate every second. Encoding a VFR stream without VFR enabled will likely result in the encoded bitrate being wrong.

For example, the framerate reported in a video container may be 25 fps, while the average framerate from the timestamps could be 20fps. Without VFR enabled, the average encoded bitrate in this case would be only 80% of the target.

Enabling the VFR feature also causes h.264 fixed_frame_rate_flag syntax to be set to 0.

vbvBufferSize

Specifies the size of the VBV buffer (Coded Picture Buffer or CPB) in milliseconds. This parameter determines if HRD (Hypothetical Reference Decoder) compliance is followed when RcEnable is 1, or if peak bitrate is constrained when crf >= 0. Setting vbvBufferSize to 0 disables HRD compliance or peak bitrate constraint.

 The CPB receives compressed NAL units from the bitstream, stores them temporarily, and removes them at the appropriate decoding time as defined by the HRD parameters. 

vbvBufferReencode

When vbvBufferReencode is set to 1, the encoder will re-encode frame(s) if their encoded bit count exceeds the VBV buffer limit, ensuring compliance with VBV (also known as HRD) constraints. Please note that re-encoding increases latency, so it is recommended only when strict adherence to VBV (HRD) conformance is required.

vbvMaxRate

The vbvMaxRate parameter sets the maximum bitrate limit during encoding in Constrained VBR mode and Capped CRF mode. Compared to ABR mode, in which vbvBufferSize and vbvMaxRate are both set to 0, and CBR mode, in which vbvBufferSize is set to valid non-zero values and vbvMaxRate is set to 0, Constrained VBR mode requires vbvBufferSize and vbvMaxRate both set to valid non-zero values. In Capped CRF mode, encoder implicitly takes bitrate as the maximum bitrate limit if vbvMaxRate is not set; otherwise, encoder will take vbvMaxRate as the maximum bitrate limit when it is set. Please refer to Section “8.3.4 CRF & Capped CRF Descriptions and Examples” for more details.

Constrained VBR mode sample FFmpeg command –

ffmpeg -c:v h264_ni_quadra_dec -i crowdrun_1920x1080.264 -c:v h264_ni_quadra_enc -xcoder-params "RcEnable=1:bitrate=3000000:vbvMaxRate=6000000:vbvBufferSize=1000" quadra.h264

fillerEnable

When enabled, the HRD compliance algorithm may insert filler NAL units to prevent VBV (CPB) buffer underflow. Filler insertion is supported in the following rate control modes:

• CBR mode

• Capped CRF mode (when vbvMinRate is specified)

If neither rcEnable nor crf is specified, setting fillerEnable=1 implicitly enables CBR rate control with HRD conformance. In this case:

• rcEnable is automatically set to 1

• vbvBufferSize is set to the default value of 3000

picSkip

When enabled, the HRD algorithm can skip pictures when the VBV (CPB) buffer overflows. HRD rate control is enabled when rcEnable is 1 and vbvBufferSize > 0.

If picSkip is enabled, and the maximum output size has been specified with either MaxFrameSize(Deprecated), MaxFrameSize_Bits or MaxFrameSize_Bytes, then the encoder will discard any frames whose output size exceeds the specified size.

skipFrameEnable

When enabled, the encoded frame will be forced to be a skip frame, meaning that all macroblocks are encoded as skip mode macroblocks when VBV buffer overflows.

maxConsecutiveSkipFrameNum

Specify the maximum number of consecutive skip frames. This parameter only takes effect when the skipFrameEnable is enabled.

skipFrameInterVal

Specify the insertion of a skip frame every skipFrameInterVal frame interval. This parameter only takes effect when the skipFrameEnable is enabled.

This parameter may improve the image quality of certain videos, but it may not have a significant effect on optimizing the quality of certain videos. Also, if the encoding frame rate is low or if the skipFrameInterVal is too small, there may be lag phenomenon. It is recommended that the value in the range of 7 to 10 for 30fps encoding.

stillImageDetectLevel

Specify the level of detection for static frames. Setting different levels is because the definition of static is sometimes very subjective, and different scenarios have slightly different requirements for static.

The levels are divided into two categories: 1-3 and 4-6. Levels 1-3 do not require additional resources and do not reduce performance, but their accuracy is not as high as levels 4-6.

The larger the value of level, the stricter the judgment of whether it is a static frame. When the level value is large, only when the image is completely still, it is judged as a static frame. When the level value is small, if there are very small changes in the image (such as a change area that may only be 1%-3% of the entire image), it will also be considered a still image.

sceneChangeDetectLevel

Specify the level of detection for scene change. Setting different levels is because the definition of static is sometimes very subjective, and different scenarios have slightly different requirements for scene change.

The levels are divided into two categories:1-5 and 6-10. Levels 1-5 do not require additional resources and do not reduce performance, but their accuracy is not as high as Levels 6-10.

The same as the above stillImageDetectLevel, the larger the value of level, the stricter the judgment of whether it is a scene change. When the level value is large, only the current frame is completely different from the before frame, will be considered a scene change. When the level is small, there is a significant difference between the current frame and the previous frame, it may be considered a scene change.

maxFrameSize -- DEPRECATED

Specifies the maximum allowable output byte count for any frame (please note the unit of maxFrameSize is in bytes). While encoding, the encoder will re-encode the frame with higher QP if the output byte count exceeds the maxFrameSize. This process will continue until the output byte count becomes less than maxFrameSize. If the QP has been increased to the maxQP but the output byte count still exceeds maxFrameSize, the encoder will either produce the output, or if picSkip is enabled, it will discard the output (see the picSkip parameter description).

Note that maxFrameSize is only valid if lowDelay is enabled. If lowDelay is disabled, maxFrameSize parameter will be rejected. If lowDelay is enabled, but maxFrameSize is not specified in the command line, libxcoder will set maxFrameSize to the default value, which is ½ of the input frame size.

This feature can also be used to limit the maximum frame size to a multiple of the average frame size, using the ratio keyword. For example, maxFrameSize=ratio[8] will limit the maximum frame size to be no more than 8 times the average frame size calculated by the libxcoder.

maxFrameSize_Bytes

Specifies the maximum allowable output byte count for any frame. The size specified with maxFrameSize_Bytes is bytes. While encoding, the encoder will re-encode the frame with higher QP if the output byte count exceeds maxFrameSize_Bytes. This process will continue until the output byte count becomes less than maxFrameSize_Bytes. If the QP has been increased to the maxQP but the output byte count still exceeds maxFrameSize_Bytes, the encoder will either produce the output, or if picSkip is enabled, it will discard the output (see the picSkip parameter description).

Note that maxFrameSize_Bytes is only valid if lowDelay is enabled. If lowDelay is disabled, the maxFrameSize_Bytes parameter will be rejected. If lowDelay is enabled, but maxFrameSize_Bytes is not specified in the command line, the libxcoder will set maxFrameSize_Bytes to the default value, which is ½ the input frame size.

This feature can also be used to limit the maximum frame size to a multiple of the average frame size, using the ratio keyword. For example, maxFrameSize_Bytes =ratio[8] will limit the maximum frame size to be no more than 8 times the average frame size calculated by the libxcoder.

maxFrameSize_Bits

Specifies the maximum allowable output bit count for any frame (please note the unit of maxFrameSize_Bits is in bits). While encoding, the encoder will re-encode the frame with a higher QP if the output bit count exceeds the maxFrameSize_Bits. This process will continue until the output bit count becomes less than the maxFrameSize_Bits. If the QP has been increased to the maxQP but the output bit count still exceeds maxFrameSize_Bits, the encoder will either produce the output, or if picSkip is enabled it will discard the output (see the picSkip parameter description).

Note that maxFrameSize_Bits is only valid if lowDelay is enabled. If lowDelay is disabled, maxFrameSize_Bits parameter will be rejected. If lowDelay is enabled, but maxFrameSize_Bits is not specified in the command line, libxcoder will set maxFrameSize_Bits to the default value, which is ½ of the input frame size.

This feature can also be used to limit the maximum frame size to a multiple of the average frame size, using the ratio keyword. For example, maxFrameSize_Bits =ratio[8] will limit the maximum frame size to be no more than 8 times the average frame size calculated by the libxcoder.

It is recommended to use maxFrameSize_Bytes only.

crf

This parameter enables Constant Rate Factor mode. CRF is a constant subjective quality mode as opposed to normal rate control which adjusts quality to maintain constant bitrate (CBR). On the other hand, it is not possible to predict the bitrate a CRF encode will come out to. CRF values range from 0 to 51, lower value indicates higher quality and higher value indicates lower quality. The recommended CRF value is 23.

CRF can also be used together with bitrate, vbvBufferSize, vbvMaxRate, vbvMinRate parameters to maintain a consistent quality level, while the maximum (and minimum) bitrate cap prevents the bitrate from exceeding a certain threshold – this mode is referred to as Capped CRF mode. For more details and examples of Capped CRF encode parameters, please refer to Section 8.3.4 “CRF & Capped CRF Examples”.

• CRF with lookaheadDepth 0 – supports gopPresetIdx -1 (adaptive gop), 0 (custom gop), 1, 4, 5, 8, 9

• CRF with lookaheadDepth > 0 – supports gopPresetIdx -1 (adaptive gop), 0 (custom gop), 4, 5, 8, 9

crfFloat

This parameter enables Constant Rate Factor mode. Supports floating-point numbers with 2 decimal places. CRF is a constant subjective quality mode as opposed to normal rate control which adjusts quality to maintain constant bitrate (CBR). On the other hand, it is not possible to predict the bitrate a CRF encode will come out to. CRF values range from 0.00 to 51.00, lower value indicates higher quality and higher value indicates lower quality. The recommended CRF value is 23.00.

CRF can also be used together with bitrate, vbvBufferSize, vbvMaxRate, vbvMinRate parameters to maintain a consistent quality level, while the maximum (and minimum) bitrate cap prevents the bitrate from exceeding a certain threshold – this mode is referred to as Capped CRF mode. For more details and examples of Capped CRF encode parameters, please refer to Section 8.3.4 “CRF & Capped CRF Examples”.

• CRF with lookaheadDepth 0 – supports gopPresetIdx -1 (adaptive gop), 0 (custom gop), 1, 4, 5, 8, 9

• CRF with lookaheadDepth > 0 – supports gopPresetIdx -1 (adaptive gop), 0 (custom gop), 4, 5, 8, 9

qpScaleEnable

The qpScaleEnable parameter enables the QP scaling algorithm in CRF mode, improving compression efficiency under limited lookahead conditions, such as in live-streaming scenarios.

crfMaxIframeEnable

The crfMaxIframeEnable parameter allows encoder to produce higher quality I-frames in Capped CRF mode (with lookahead enabled) to improve quality. The side effect is that I-frame bit count will be increased, which may not be ideal in scenarios where bitrate spike is unacceptable. When enabled, the user can select from mode 1 (MEDIUM, legacy) mode 2 (HIGH, legacy) mode 5 (MEDIUM) and mode 6 (HIGH) which offer different I-frame bits allocation policies, as described below –

enableSmoothCrf

The enableSmoothCrf parameter determines whether the size curve of the encoded stream will be smoothed when different crfFloat values are set to foloating-point type. Without enabling this parameter, the size of the encoded stream size may increase as the crfFloat value increases. If this parameter is enabled, the size of the encoded stream decreases as the crfFloat value increases.

vbvMinRate

The vbvMinRate parameter sets the minimum bitrate limit during encoding in Capped CRF mode. (NOTE – unlike vbvMaxRate parameter which takes effect in both Constrained VBR mode and Capped CRF mode, vbvMinRate only takes effect in Capped CRF mode.)

In Capped CRF mode, if vbvMinRate is not set, the encoder will not constrain bitrate by a minimum bitrate limit (only limit maximum bitrate). If vbvMinRate is set, the encoder will produce more bits to meet the minimum bitrate, which may also raise quality to be higher than the specified consistent quality level (which depends on crf parameter value) when bits required at specified quality level is lower than the minimum bitrate. Please refer to Section “8.3.4 CRF & Capped CRF Descriptions and Examples” for more details.

Capped CRF mode sample FFmpeg command with vbvMinRate –

ffmpeg -f rawvideo -pix_fmt yuv420p -s 1920x1080 -r 30.0 -i input1920x1080.yuv -c:v h265_ni_quadra_enc -xcoder-params "gopPresetIdx=5:RcEnable=0:crf=23:lookAheadDepth=10:vbvBufferSize=1000:bitrate= 3200000:vbvMinRate=1000000" output1920x1080.h265

qcomp

This parameter affects how much bitrate is given to important scenes as opposed to unimportant scenes for subjective quality. Only effective in CRF mode.

ipRatio

Modifies average I-frames bit count increase as compared to P-frames. Higher values increase the quality of I-frames generated. Only effective in CRF mode.

enableipRatio

Enable or disable the ipRatio when in CBR and VBR mode. This parameter only affect ipRatio in CBR and VBR mode. If crf is set, ipRatio always works, regardless of whether enableipRatio is enabled or not.

iFrameSizeRatio

Specifies the ratio of I frame size to default I frame size. The ratio of the frame size is not exactly the same as the specified ratio, they are just approximate. This is influenced by different bitrate control algorithms.

pbRatio

Modifies average B-frames bit count decrease as compared to P-frames. Higher values decrease the quality of B-frames generated. Only effective in CRF mode.

cplxDecay

This parameter affects how fast the past frames complexity decays when encoder decides current frame quantization based on complexity. Only effective in CRF mode.

chromaQpOffset

Offset of Cb/Cr chroma quantization from the luma quantization selected by rate control. This is a general way to specify encoder spending more or less bits on the chroma channel.

hvsQPEnable

Enable or disable block level QP adjustment for subjective quality enhancement.

hvsBaseMbComplexity

Base complexity of block level QP adjustment for subjective quality. A higher base complexity value will result in higher subjective quality, at the cost of increased bit count. In low target bitrate use case, increasing base complexity value may cause actual bitrate to be higher than the target bitrate. Default base complexity value is 15.

CuLevelRCEnable

Enable or disable coding unit level rate control.

tolCtbRcInter

Tolerance of CU level rate control for P-frames and B-frames (aka INTER frames). CU level rate control will enforce INTER frame bits limit within the range of: [ ExpectedBits * (1 – tolCtbRcInter), ExpectedBits * (1 + tolCtbRcInter)], except for -1 and 0 as described below:

• If tolCtbRcInter == -1, CU level rate control is disabled for INTER frames

• If tolCtbRcInter == 0, CU level rate control adjust INTER frames bits according to the current VBV buffer level. The total VBV buffer size can be configured by vbvBufferSize.

tolCtbRcIntra

Tolerance of CU level rate control for I-frames (aka INTRA frames). CU level rate control will enforce INTRA frame bits limit within the range of: [ ExpectedBits * (1 – tolCtbRcIntra), ExpectedBits * (1 + tolCtbRcIntra)], except for -1 and 0 as described below:

• If tolCtbRcIntra == -1, CU level rate control is disabled for I-frames

• If tolCtbRcIntra == 0, CU level rate control adjust I-frames bits according to the current VBV buffer level. The total VBV buffer size can be configured by vbvBufferSize.

rcQpDeltaRange

Max absolute value of CU/MB QP delta relative to frame QP in CTB RC.

It controls maximum range CU/MB QP is allowed to vary within a frame.

bitrateWindow

Specifies the bitrate window length in frames. Rate control allocates bits for one window and tries to match the target bitrate at the end of each window. This enforces an average target bit rate within the window interval, allowing encoder to adapt to changes of complexity on video input and variations on compression efficiency between frames. Typically window begins with an intra frame, but this is not mandatory.

By default bitrateWindow = intraPeriod

If intraPeriod = 0 (infinite period), bitrateWindow = 150

ctbRowQpStep

The maximum accumulated QP adjustment step per CTB Row allowed by CU level rate control. Increasing ctbRowQpStep helps reduce instant bitrate spike / overshoot, but it may also reduce compression efficiency. CU level rate control QP step per CTB is calculated by

QP_step_per_CTB = MIN((ctbRowQpStep / Ctb_per_Row),4)

If ctbRowQpStep == 0, Quadra will use pre-defined ctbRowQpStep value [4] for H.264 and [16] for HEVC.

enableAcqLimit

Whether to enable encoder to limit its upstream’s output buffering count. Enabling this option could prevent the upstream instance outputting more buffers than encoder needs.

customizeQpLevel

Specifies the level of the roi map. When customizeQpLevel > 0. Customize roi map will take effect after cutree in 2pass.

customizeQpMapFile

Specifies the name of the qp map file. It will take effect when ROI is enabled (roiEnable=1) and customizeQpLevel is 1. customizeQpMap is currently only supported on FFmpeg 3.4.2 and above. It supports qp info from 1 to 10, supports qp value from 0 to 63. The qp_info in roi block indicates the row number it chooses in customizeQpMapFile. And it will choose qp value in customizeQpMapFile table after rate control, the qp after rate control indicates the column number and qp_info indicates the row number. The qp map file must be created in the same directory where the command is running. The file contains one line or multiple lines of qp value map

enableCompensateQp

It only takes effect when maxframesize > 0. XCoder firmware will record the previous frame first qp and ssim when previous frame trigger re-encode because of maxframesize. And re-encode with lower qp for next frame if its ssim different from last time is greater than the threshold

adaptiveLamdaMode

This param is trying to optimize BD-rate for hevc encode with lookahead, It only takes effect when lookahead >= 4. XCoder firmware will adjust lambda of I frame based on the distortion ratio of I frame and P frame and adjust ipratio based on intra ratio and skip ratio in a gop

adaptiveCrfMode

It only takes effect in capped-crf mode in pass2. This param will adjust crf when qp is capped by vbvbuffer to reduce qp capped in later gop, it will also adjust vbvMaxRate, allow to get better quality in complex picture. Worse quality should be better than before.

intraCompensateMode

It only takes effect in crf mode in pass2. This param will compensate qp when frame intra ratio is high in pass1 encode, it will optimize subjective image quality in complex scenarios.