StereoDepth

StereoDepth node calculates the disparity/depth from the stereo camera pair (2x MonoCamera/ColorCamera).

How to place it

Python

C++

pipeline = dai.Pipeline()
stereo = pipeline.create(dai.node.StereoDepth)

dai::Pipeline pipeline;
auto stereo = pipeline.create<dai::node::StereoDepth>();

Inputs and Outputs

               ┌───────────────────┐
               │                   │ confidenceMap
               │                   ├─────────────►
               │                   │rectifiedLeft
               │                   ├─────────────►
left           │                   │   syncedLeft
──────────────►│-------------------├─────────────►
               │                   │   depth [mm]
               │                   ├─────────────►
               │    StereoDepth    │    disparity
               │                   ├─────────────►
right          │                   │   syncedRight
──────────────►│-------------------├─────────────►
               │                   │rectifiedRight
               │                   ├─────────────►
inputConfig    │                   |     outConfig
──────────────►│-------------------├─────────────►
               └───────────────────┘

Inputs

Outputs

Debug outputs

Internal block diagram of StereoDepth node

../../_images/depth_diagram.png

On the diagram, red rectangle are firmware settings that are configurable via the API. Gray rectangles are settings that that are not yet exposed to the API. We plan on exposing as much configurability as possible, but please inform us if you would like to see these settings configurable sooner.

If you click on the image, you will be redirected to the webapp. Some blocks have notes that provide additional technical information.

Currently configurable blocks

Stereo Mode

Depth Filters

Mesh files

Confidence Threshold

Left-Right Check

Extended Disparity

Subpixel Disparity

Left-Right Check or LR-Check is used to remove incorrectly calculated disparity pixels due to occlusions at object borders (Left and Right camera views are slightly different).

  1. Computes disparity by matching in R->L direction

  2. Computes disparity by matching in L->R direction

  3. Combines results from 1 and 2, running on Shave: each pixel d = disparity_LR(x,y) is compared with disparity_RL(x-d,y). If the difference is above a threshold, the pixel at (x,y) in the final disparity map is invalidated.

You can use debugDispLrCheckIt1 and debugDispLrCheckIt2 debug outputs for debugging/fine-tuning purposes.

Extended disparity mode allows detecting closer distance objects for the given baseline. This increases the maximum disparity search from 96 to 191, meaning the range is now: [0..190]. So this cuts the minimum perceivable distance in half, given that the minimum distance is now focal_length * base_line_dist / 190 instead of focal_length * base_line_dist / 95.

  1. Computes disparity on the original size images (e.g. 1280x720)

  2. Computes disparity on 2x downscaled images (e.g. 640x360)

  3. Combines the two level disparities on Shave, effectively covering a total disparity range of 191 pixels (in relation to the original resolution).

You can use debugExtDispLrCheckIt1 and debugExtDispLrCheckIt2 debug outputs for debugging/fine-tuning purposes.

Subpixel mode improves the precision and is especially useful for long range measurements. It also helps for better estimating surface normals.

Besides the integer disparity output, the Stereo engine is programmed to dump to memory the cost volume, that is 96 levels (disparities) per pixel, then software interpolation is done on Shave, resulting a final disparity with 3 fractional bits, resulting in significantly more granular depth steps (8 additional steps between the integer-pixel depth steps), and also theoretically, longer-distance depth viewing - as the maximum depth is no longer limited by a feature being a full integer pixel-step apart, but rather 1/8 of a pixel. In this mode, stereo cameras perform: 94 depth steps * 8 subpixel depth steps + 2 (min/max values) = 754 depth steps

For comparison of normal disparity vs. subpixel disparity images, click here.

Depth Filtering / Depth Post-Processing is performed at the end of the depth pipeline. It helps with noise reduction and overall depth quality.

Median

Speckle

Temporal

Spatial

Threshold

Decimation

This is a non-edge preserving Median filter, which can be used to reduce noise and smoothen the depth map. Median filter is implemented in hardware, so it’s the fastest filter.

enum dai::MedianFilter

Median filter config for disparity post-processing

Values:

enumerator MEDIAN_OFF
enumerator KERNEL_3x3
enumerator KERNEL_5x5
enumerator KERNEL_7x7

Speckle Filter is used to reduce the speckle noise. Speckle noise is a region with huge variance between neighboring disparity/depth pixels, and speckle filter tries to filter this region.

struct dai::RawStereoDepthConfig::PostProcessing::SpeckleFilter

Speckle filtering. Removes speckle noise.

Public Members

bool enable = false

Whether to enable or disable the filter.

std::uint32_t speckleRange = 50

Speckle search range.

Temporal Filter is intended to improve the depth data persistency by manipulating per-pixel values based on previous frames. The filter performs a single pass on the data, adjusting the depth values while also updating the tracking history. In cases where the pixel data is missing or invalid, the filter uses a user-defined persistency mode to decide whether the missing value should be rectified with stored data. Note that due to its reliance on historic data the filter may introduce visible blurring/smearing artifacts, and therefore is best-suited for static scenes.

struct dai::RawStereoDepthConfig::PostProcessing::TemporalFilter

Temporal filtering with optional persistence.

Public Types

enum PersistencyMode

Persistency algorithm type.

Values:

enumerator PERSISTENCY_OFF
enumerator VALID_8_OUT_OF_8
enumerator VALID_2_IN_LAST_3
enumerator VALID_2_IN_LAST_4
enumerator VALID_2_OUT_OF_8
enumerator VALID_1_IN_LAST_2
enumerator VALID_1_IN_LAST_5
enumerator VALID_1_IN_LAST_8
enumerator PERSISTENCY_INDEFINITELY

Public Members

bool enable = false

Whether to enable or disable the filter.

PersistencyMode persistencyMode = PersistencyMode::VALID_2_IN_LAST_4

Persistency mode. If the current disparity/depth value is invalid, it will be replaced by an older value, based on persistency mode.

float alpha = 0.4f

The Alpha factor in an exponential moving average with Alpha=1 - no filter. Alpha = 0 - infinite filter. Determines the extent of the temporal history that should be averaged.

std::int32_t delta = 0

Step-size boundary. Establishes the threshold used to preserve surfaces (edges). If the disparity value between neighboring pixels exceed the disparity threshold set by this delta parameter, then filtering will be temporarily disabled. Default value 0 means auto: 3 disparity integer levels. In case of subpixel mode it’s 3*number of subpixel levels.

Spatial Edge-Preserving Filter will fill invalid depth pixels with valid neighboring depth pixels. It performs a series of 1D horizontal and vertical passes or iterations, to enhance the smoothness of the reconstructed data. It is based on this research paper.

struct dai::RawStereoDepthConfig::PostProcessing::SpatialFilter

1D edge-preserving spatial filter using high-order domain transform.

Public Members

bool enable = false

Whether to enable or disable the filter.

std::uint8_t holeFillingRadius = 2

An in-place heuristic symmetric hole-filling mode applied horizontally during the filter passes. Intended to rectify minor artefacts with minimal performance impact. Search radius for hole filling.

float alpha = 0.5f

The Alpha factor in an exponential moving average with Alpha=1 - no filter. Alpha = 0 - infinite filter. Determines the amount of smoothing.

std::int32_t delta = 0

Step-size boundary. Establishes the threshold used to preserve “edges”. If the disparity value between neighboring pixels exceed the disparity threshold set by this delta parameter, then filtering will be temporarily disabled. Default value 0 means auto: 3 disparity integer levels. In case of subpixel mode it’s 3*number of subpixel levels.

std::int32_t numIterations = 1

Nubmer of iterations over the image in both horizontal and vertical direction.

Threshold Filter filters out all disparity/depth pixels outside the configured min/max threshold values.

class depthai.RawStereoDepthConfig.PostProcessing.ThresholdFilter

Threshold filtering. Filters out distances outside of a given interval.

property maxRange

Maximum range in depth units. Depth values over this value are invalidated.

property minRange

Minimum range in depth units. Depth values under this value are invalidated.

Decimation Filter will sub-samples the depth map, which means it reduces the depth scene complexity and allows other filters to run faster. Setting decimationFactor to 2 will downscale 1280x800 depth map to 640x400.

struct dai::RawStereoDepthConfig::PostProcessing::DecimationFilter

Decimation filter. Reduces the depth scene complexity. The filter runs on kernel sizes [2x2] to [8x8] pixels.

Public Types

enum DecimationMode

Decimation algorithm type.

Values:

enumerator PIXEL_SKIPPING
enumerator NON_ZERO_MEDIAN
enumerator NON_ZERO_MEAN

Public Members

std::uint32_t decimationFactor = 1

Decimation factor. Valid values are 1,2,3,4. Disparity/depth map x/y resolution will be decimated with this value.

DecimationMode decimationMode = DecimationMode::PIXEL_SKIPPING

Decimation algorithm type.

Mesh files (homography matrix) are generated using the camera intrinsics, distortion coeffs, and rectification rotations. These files helps in overcoming the distortions in the camera increasing the accuracy and also help in when wide FOV lens are used.

Note

Currently mesh files are generated only for stereo cameras on the host during calibration. The generated mesh files are stored in depthai/resources which users can load to the device. This process will be moved to on device in the upcoming releases.

void dai::node::StereoDepth::loadMeshFiles(const dai::Path &pathLeft, const dai::Path &pathRight)

Specify local filesystem paths to the mesh calibration files for ‘left’ and ‘right’ inputs.

When a mesh calibration is set, it overrides the camera intrinsics/extrinsics matrices. Overrides useHomographyRectification behavior. Mesh format: a sequence of (y,x) points as ‘float’ with coordinates from the input image to be mapped in the output. The mesh can be subsampled, configured by setMeshStep.

With a 1280x800 resolution and the default (16,16) step, the required mesh size is:

width: 1280 / 16 + 1 = 81

height: 800 / 16 + 1 = 51

void dai::node::StereoDepth::loadMeshData(const std::vector<std::uint8_t> &dataLeft, const std::vector<std::uint8_t> &dataRight)

Specify mesh calibration data for ‘left’ and ‘right’ inputs, as vectors of bytes. Overrides useHomographyRectification behavior. See loadMeshFiles for the expected data format

void dai::node::StereoDepth::setMeshStep(int width, int height)

Set the distance between mesh points. Default: (16, 16)

  • Confidence threshold: Stereo depth algorithm searches for the matching feature from right camera point to the left image (along the 96 disparity levels). During this process it computes the cost for each disparity level and chooses the minimal cost between two disparities and uses it to compute the confidence at each pixel. Stereo node will output disparity/depth pixels only where depth confidence is below the confidence threshold (lower the confidence value means better depth accuracy).

  • LR check threshold: Disparity is considered for the output when the difference between LR and RL disparities is smaller than the LR check threshold.

StereoDepthConfig &dai::StereoDepthConfig::setConfidenceThreshold(int confThr)

Confidence threshold for disparity calculation

Parameters

  • confThr: Confidence threshold value 0..255

StereoDepthConfig &dai::StereoDepthConfig::setLeftRightCheckThreshold(int threshold)

Parameters

  • threshold: Set threshold for left-right, right-left disparity map combine, 0..255

Limitations

  • Median filtering is disabled when subpixel mode is set to 4 or 5 bits.

  • For RGB-depth alignment the RGB camera has to be placed on the same horizontal line as the stereo camera pair.

Stereo depth FPS

Stereo depth mode

FPS for 1280x720

FPS for 640x400

Standard mode

60

110

Left-Right Check

55

105

Subpixel Disparity

45

105

Extended Disparity

54

105

Subpixel + LR check

34

96

Extended + LR check

26

62

All stereo modes were measured for depth output with 5x5 median filter enabled. For 720P, mono cameras were set to 60 FPS and for 400P mono cameras were set to 110 FPS.

Usage

Python

C++

pipeline = dai.Pipeline()
stereo = pipeline.create(dai.node.StereoDepth)

# Better handling for occlusions:
stereo.setLeftRightCheck(False)
# Closer-in minimum depth, disparity range is doubled:
stereo.setExtendedDisparity(False)
# Better accuracy for longer distance, fractional disparity 32-levels:
stereo.setSubpixel(False)

# Define and configure MonoCamera nodes beforehand
left.out.link(stereo.left)
right.out.link(stereo.right)

dai::Pipeline pipeline;
auto stereo = pipeline.create<dai::node::StereoDepth>();

// Better handling for occlusions:
stereo->setLeftRightCheck(false);
// Closer-in minimum depth, disparity range is doubled:
stereo->setExtendedDisparity(false);
// Better accuracy for longer distance, fractional disparity 32-levels:
stereo->setSubpixel(false);

// Define and configure MonoCamera nodes beforehand
left->out.link(stereo->left);
right->out.link(stereo->right);

Reference

Python

C++

class depthai.node.StereoDepth

StereoDepth node. Compute stereo disparity and depth from left-right image pair.

class Connection

Connection between an Input and Output

class Id

Node identificator. Unique for every node on a single Pipeline

class PresetMode

Preset modes for stereo depth.

Members:

HIGH_ACCURACY : Prefers accuracy over density. More invalid depth values, but less outliers.

HIGH_DENSITY : Prefers density over accuracy. Less invalid depth values, but more outliers.

property name
Properties

alias of depthai.StereoDepthProperties

property confidenceMap

Outputs ImgFrame message that carries RAW8 confidence map. Lower values means higher confidence of the calculated disparity value. RGB alignment, left-right check or any postproccessing (e.g. median filter) is not performed on confidence map.

property debugDispCostDump

Outputs ImgFrame message that carries cost dump of disparity map. Useful for debugging/fine tuning.

property debugDispLrCheckIt1

Outputs ImgFrame message that carries left-right check first iteration (before combining with second iteration) disparity map. Useful for debugging/fine tuning.

property debugDispLrCheckIt2

Outputs ImgFrame message that carries left-right check second iteration (before combining with first iteration) disparity map. Useful for debugging/fine tuning.

property debugExtDispLrCheckIt1

Outputs ImgFrame message that carries extended left-right check first iteration (downscaled frame, before combining with second iteration) disparity map. Useful for debugging/fine tuning.

property debugExtDispLrCheckIt2

Outputs ImgFrame message that carries extended left-right check second iteration (downscaled frame, before combining with first iteration) disparity map. Useful for debugging/fine tuning.

property depth

Outputs ImgFrame message that carries RAW16 encoded (0..65535) depth data in depth units (millimeter by default).

Non-determined / invalid depth values are set to 0

property disparity

RAW8 encoded (0..95) for standard mode; RAW8 encoded (0..190) for extended disparity mode; RAW16 encoded for subpixel disparity mode: - 0..760 for 3 fractional bits (by default) - 0..1520 for 4 fractional bits - 0..3040 for 5 fractional bits

Type

Outputs ImgFrame message that carries RAW8 / RAW16 encoded disparity data

enableDistortionCorrection(self: depthai.node.StereoDepth, arg0: bool) → None

Equivalent to useHomographyRectification(!enableDistortionCorrection)

getAssetManager(*args, **kwargs)

Overloaded function.

  1. getAssetManager(self: depthai.Node) -> depthai.AssetManager

Get node AssetManager as a const reference

  1. getAssetManager(self: depthai.Node) -> depthai.AssetManager

Get node AssetManager as a const reference

getInputRefs(*args, **kwargs)

Overloaded function.

  1. getInputRefs(self: depthai.Node) -> List[depthai.Node.Input]

Retrieves reference to node inputs

  1. getInputRefs(self: depthai.Node) -> List[depthai.Node.Input]

Retrieves reference to node inputs

getInputs(self: depthai.Node) → List[depthai.Node.Input]

Retrieves all nodes inputs

getMaxDisparity(self: depthai.node.StereoDepth) → float

Useful for normalization of the disparity map.

Returns

Maximum disparity value that the node can return

getName(self: depthai.Node) → str

Retrieves nodes name

getOutputRefs(*args, **kwargs)

Overloaded function.

  1. getOutputRefs(self: depthai.Node) -> List[depthai.Node.Output]

Retrieves reference to node outputs

  1. getOutputRefs(self: depthai.Node) -> List[depthai.Node.Output]

Retrieves reference to node outputs

getOutputs(self: depthai.Node) → List[depthai.Node.Output]

Retrieves all nodes outputs

getParentPipeline(*args, **kwargs)

Overloaded function.

  1. getParentPipeline(self: depthai.Node) -> depthai.Pipeline

  2. getParentPipeline(self: depthai.Node) -> depthai.Pipeline

property id

Id of node

property initialConfig

Initial config to use for StereoDepth.

property inputConfig

Input StereoDepthConfig message with ability to modify parameters in runtime. Default queue is non-blocking with size 4.

property left

Input for left ImgFrame of left-right pair

Default queue is non-blocking with size 8

loadMeshData(self: depthai.node.StereoDepth, dataLeft: List[int], dataRight: List[int]) → None

Specify mesh calibration data for ‘left’ and ‘right’ inputs, as vectors of bytes. Overrides useHomographyRectification behavior. See loadMeshFiles for the expected data format

loadMeshFiles(self: depthai.node.StereoDepth, pathLeft: Path, pathRight: Path) → None

Specify local filesystem paths to the mesh calibration files for ‘left’ and ‘right’ inputs.

When a mesh calibration is set, it overrides the camera intrinsics/extrinsics matrices. Overrides useHomographyRectification behavior. Mesh format: a sequence of (y,x) points as ‘float’ with coordinates from the input image to be mapped in the output. The mesh can be subsampled, configured by setMeshStep.

With a 1280x800 resolution and the default (16,16) step, the required mesh size is:

width: 1280 / 16 + 1 = 81

height: 800 / 16 + 1 = 51

property outConfig

Outputs StereoDepthConfig message that contains current stereo configuration.

property rectifiedLeft

Outputs ImgFrame message that carries RAW8 encoded (grayscale) rectified frame data.

property rectifiedRight

Outputs ImgFrame message that carries RAW8 encoded (grayscale) rectified frame data.

property right

Input for right ImgFrame of left-right pair

Default queue is non-blocking with size 8

setBaseline(self: depthai.node.StereoDepth, arg0: float) → None

Override baseline from calibration. Used only in disparity to depth conversion. Units are centimeters.

setConfidenceThreshold(self: depthai.node.StereoDepth, arg0: int) → None

Confidence threshold for disparity calculation

Parameter confThr:

Confidence threshold value 0..255

setDefaultProfilePreset(self: depthai.node.StereoDepth, arg0: depthai.node.StereoDepth.PresetMode) → None

Sets a default preset based on specified option.

Parameter mode:

Stereo depth preset mode

setDepthAlign(*args, **kwargs)

Overloaded function.

  1. setDepthAlign(self: depthai.node.StereoDepth, align: depthai.RawStereoDepthConfig.AlgorithmControl.DepthAlign) -> None

Parameter align:

Set the disparity/depth alignment: centered (between the ‘left’ and ‘right’ inputs), or from the perspective of a rectified output stream

  1. setDepthAlign(self: depthai.node.StereoDepth, camera: depthai.CameraBoardSocket) -> None

Parameter camera:

Set the camera from whose perspective the disparity/depth will be aligned

setEmptyCalibration(self: depthai.node.StereoDepth) → None

Specify that a passthrough/dummy calibration should be used, when input frames are already rectified (e.g. sourced from recordings on the host)

setExtendedDisparity(self: depthai.node.StereoDepth, enable: bool) → None

Disparity range increased from 0-95 to 0-190, combined from full resolution and downscaled images.

Suitable for short range objects. Currently incompatible with sub-pixel disparity

setFocalLength(self: depthai.node.StereoDepth, arg0: float) → None

Override focal length from calibration. Used only in disparity to depth conversion. Units are pixels.

setFocalLengthFromCalibration(self: depthai.node.StereoDepth, arg0: bool) → None

Whether to use focal length from calibration intrinsics or calculate based on calibration FOV. Default value is true.

setInputResolution(*args, **kwargs)

Overloaded function.

  1. setInputResolution(self: depthai.node.StereoDepth, width: int, height: int) -> None

Specify input resolution size

Optional if MonoCamera exists, otherwise necessary

  1. setInputResolution(self: depthai.node.StereoDepth, resolution: Tuple[int, int]) -> None

Specify input resolution size

Optional if MonoCamera exists, otherwise necessary

setLeftRightCheck(self: depthai.node.StereoDepth, enable: bool) → None

Computes and combines disparities in both L-R and R-L directions, and combine them.

For better occlusion handling, discarding invalid disparity values

setMedianFilter(self: depthai.node.StereoDepth, arg0: depthai.MedianFilter) → None
Parameter median:

Set kernel size for disparity/depth median filtering, or disable

setMeshStep(self: depthai.node.StereoDepth, width: int, height: int) → None

Set the distance between mesh points. Default: (16, 16)

setNumFramesPool(self: depthai.node.StereoDepth, arg0: int) → None

Specify number of frames in pool.

Parameter numFramesPool:

How many frames should the pool have

setOutputDepth(self: depthai.node.StereoDepth, arg0: bool) → None
setOutputKeepAspectRatio(self: depthai.node.StereoDepth, keep: bool) → None

Specifies whether the frames resized by setOutputSize should preserve aspect ratio, with potential cropping when enabled. Default true

setOutputRectified(self: depthai.node.StereoDepth, arg0: bool) → None
setOutputSize(self: depthai.node.StereoDepth, width: int, height: int) → None

Specify disparity/depth output resolution size, implemented by scaling.

Currently only applicable when aligning to RGB camera

setPostProcessingHardwareResources(self: depthai.node.StereoDepth, arg0: int, arg1: int) → None

Specify allocated hardware resources for stereo depth. Suitable only to increase post processing runtime.

Parameter numShaves:

Number of shaves.

Parameter numMemorySlices:

Number of memory slices.

setRectification(self: depthai.node.StereoDepth, enable: bool) → None

Rectify input images or not.

setRectifyEdgeFillColor(self: depthai.node.StereoDepth, color: int) → None

Fill color for missing data at frame edges

Parameter color:

Grayscale 0..255, or -1 to replicate pixels

setRectifyMirrorFrame(self: depthai.node.StereoDepth, arg0: bool) → None

DEPRECATED function. It was removed, since rectified images are not flipped anymore. Mirror rectified frames, only when LR-check mode is disabled. Default true. The mirroring is required to have a normal non-mirrored disparity/depth output.

A side effect of this option is disparity alignment to the perspective of left or right input: false: mapped to left and mirrored, true: mapped to right. With LR-check enabled, this option is ignored, none of the outputs are mirrored, and disparity is mapped to right.

Parameter enable:

True for normal disparity/depth, otherwise mirrored

setRuntimeModeSwitch(self: depthai.node.StereoDepth, arg0: bool) → None

Enable runtime stereo mode switch, e.g. from standard to LR-check. Note: when enabled resources allocated for worst case to enable switching to any mode.

setSubpixel(self: depthai.node.StereoDepth, enable: bool) → None

Computes disparity with sub-pixel interpolation (3 fractional bits by default).

Suitable for long range. Currently incompatible with extended disparity

setSubpixelFractionalBits(self: depthai.node.StereoDepth, subpixelFractionalBits: int) → None

Number of fractional bits for subpixel mode. Default value: 3. Valid values: 3,4,5. Defines the number of fractional disparities: 2^x. Median filter postprocessing is supported only for 3 fractional bits.

property syncedLeft

Passthrough ImgFrame message from ‘left’ Input.

property syncedRight

Passthrough ImgFrame message from ‘right’ Input.

useHomographyRectification(self: depthai.node.StereoDepth, arg0: bool) → None

Use 3x3 homography matrix for stereo rectification instead of sparse mesh generated on device. Default behaviour is AUTO, for lenses with FOV over 85 degrees sparse mesh is used, otherwise 3x3 homography. If custom mesh data is provided through loadMeshData or loadMeshFiles this option is ignored.

Parameter useHomographyRectification:

true: 3x3 homography matrix generated from calibration data is used for stereo rectification, can’t correct lens distortion. false: sparse mesh is generated on-device from calibration data with mesh step specified with setMeshStep (Default: (16, 16)), can correct lens distortion. Implementation for generating the mesh is same as opencv’s initUndistortRectifyMap function. Only the first 8 distortion coefficients are used from calibration data.

class dai::node::StereoDepth : public dai::NodeCRTP<Node, StereoDepth, StereoDepthProperties>

StereoDepth node. Compute stereo disparity and depth from left-right image pair.

Public Types

enum PresetMode

Preset modes for stereo depth.

Values:

enumerator HIGH_ACCURACY

Prefers accuracy over density. More invalid depth values, but less outliers.

enumerator HIGH_DENSITY

Prefers density over accuracy. Less invalid depth values, but more outliers.

Public Functions

StereoDepth(const std::shared_ptr<PipelineImpl> &par, int64_t nodeId)
StereoDepth(const std::shared_ptr<PipelineImpl> &par, int64_t nodeId, std::unique_ptr<Properties> props)
void setEmptyCalibration()

Specify that a passthrough/dummy calibration should be used, when input frames are already rectified (e.g. sourced from recordings on the host)

void loadMeshFiles(const dai::Path &pathLeft, const dai::Path &pathRight)

Specify local filesystem paths to the mesh calibration files for ‘left’ and ‘right’ inputs.

When a mesh calibration is set, it overrides the camera intrinsics/extrinsics matrices. Overrides useHomographyRectification behavior. Mesh format: a sequence of (y,x) points as ‘float’ with coordinates from the input image to be mapped in the output. The mesh can be subsampled, configured by setMeshStep.

With a 1280x800 resolution and the default (16,16) step, the required mesh size is:

width: 1280 / 16 + 1 = 81

height: 800 / 16 + 1 = 51

void loadMeshData(const std::vector<std::uint8_t> &dataLeft, const std::vector<std::uint8_t> &dataRight)

Specify mesh calibration data for ‘left’ and ‘right’ inputs, as vectors of bytes. Overrides useHomographyRectification behavior. See loadMeshFiles for the expected data format

void setMeshStep(int width, int height)

Set the distance between mesh points. Default: (16, 16)

void setInputResolution(int width, int height)

Specify input resolution size

Optional if MonoCamera exists, otherwise necessary

void setInputResolution(std::tuple<int, int> resolution)

Specify input resolution size

Optional if MonoCamera exists, otherwise necessary

void setOutputSize(int width, int height)

Specify disparity/depth output resolution size, implemented by scaling.

Currently only applicable when aligning to RGB camera

void setOutputKeepAspectRatio(bool keep)

Specifies whether the frames resized by setOutputSize should preserve aspect ratio, with potential cropping when enabled. Default true

void setMedianFilter(dai::MedianFilter median)

Parameters

  • median: Set kernel size for disparity/depth median filtering, or disable

void setDepthAlign(Properties::DepthAlign align)

Parameters

  • align: Set the disparity/depth alignment: centered (between the ‘left’ and ‘right’ inputs), or from the perspective of a rectified output stream

void setDepthAlign(CameraBoardSocket camera)

Parameters

  • camera: Set the camera from whose perspective the disparity/depth will be aligned

void setConfidenceThreshold(int confThr)

Confidence threshold for disparity calculation

Parameters

  • confThr: Confidence threshold value 0..255

void setRectification(bool enable)

Rectify input images or not.

void setLeftRightCheck(bool enable)

Computes and combines disparities in both L-R and R-L directions, and combine them.

For better occlusion handling, discarding invalid disparity values

void setSubpixel(bool enable)

Computes disparity with sub-pixel interpolation (3 fractional bits by default).

Suitable for long range. Currently incompatible with extended disparity

void setSubpixelFractionalBits(int subpixelFractionalBits)

Number of fractional bits for subpixel mode. Default value: 3. Valid values: 3,4,5. Defines the number of fractional disparities: 2^x. Median filter postprocessing is supported only for 3 fractional bits.

void setExtendedDisparity(bool enable)

Disparity range increased from 0-95 to 0-190, combined from full resolution and downscaled images.

Suitable for short range objects. Currently incompatible with sub-pixel disparity

void setRectifyEdgeFillColor(int color)

Fill color for missing data at frame edges

Parameters

  • color: Grayscale 0..255, or -1 to replicate pixels

void setRectifyMirrorFrame(bool enable)

DEPRECATED function. It was removed, since rectified images are not flipped anymore. Mirror rectified frames, only when LR-check mode is disabled. Default true. The mirroring is required to have a normal non-mirrored disparity/depth output.

A side effect of this option is disparity alignment to the perspective of left or right input: false: mapped to left and mirrored, true: mapped to right. With LR-check enabled, this option is ignored, none of the outputs are mirrored, and disparity is mapped to right.

Parameters

  • enable: True for normal disparity/depth, otherwise mirrored

void setOutputRectified(bool enable)

Enable outputting rectified frames. Optimizes computation on device side when disabled. DEPRECATED. The outputs are auto-enabled if used

void setOutputDepth(bool enable)

Enable outputting ‘depth’ stream (converted from disparity). In certain configurations, this will disable ‘disparity’ stream. DEPRECATED. The output is auto-enabled if used

void setRuntimeModeSwitch(bool enable)

Enable runtime stereo mode switch, e.g. from standard to LR-check. Note: when enabled resources allocated for worst case to enable switching to any mode.

void setNumFramesPool(int numFramesPool)

Specify number of frames in pool.

Parameters

  • numFramesPool: How many frames should the pool have

float getMaxDisparity() const

Useful for normalization of the disparity map.

Return

Maximum disparity value that the node can return

void setPostProcessingHardwareResources(int numShaves, int numMemorySlices)

Specify allocated hardware resources for stereo depth. Suitable only to increase post processing runtime.

Parameters

  • numShaves: Number of shaves.

  • numMemorySlices: Number of memory slices.

void setDefaultProfilePreset(PresetMode mode)

Sets a default preset based on specified option.

Parameters

  • mode: Stereo depth preset mode

void setFocalLengthFromCalibration(bool focalLengthFromCalibration)

Whether to use focal length from calibration intrinsics or calculate based on calibration FOV. Default value is true.

void useHomographyRectification(bool useHomographyRectification)

Use 3x3 homography matrix for stereo rectification instead of sparse mesh generated on device. Default behaviour is AUTO, for lenses with FOV over 85 degrees sparse mesh is used, otherwise 3x3 homography. If custom mesh data is provided through loadMeshData or loadMeshFiles this option is ignored.

Parameters

  • useHomographyRectification: true: 3x3 homography matrix generated from calibration data is used for stereo rectification, can’t correct lens distortion. false: sparse mesh is generated on-device from calibration data with mesh step specified with setMeshStep (Default: (16, 16)), can correct lens distortion. Implementation for generating the mesh is same as opencv’s initUndistortRectifyMap function. Only the first 8 distortion coefficients are used from calibration data.

void enableDistortionCorrection(bool enableDistortionCorrection)

Equivalent to useHomographyRectification(!enableDistortionCorrection)

void setBaseline(float baseline)

Override baseline from calibration. Used only in disparity to depth conversion. Units are centimeters.

void setFocalLength(float focalLength)

Override focal length from calibration. Used only in disparity to depth conversion. Units are pixels.

Public Members

StereoDepthConfig initialConfig

Initial config to use for StereoDepth.

Input inputConfig = {*this, "inputConfig", Input::Type::SReceiver, false, 4, {{DatatypeEnum::StereoDepthConfig, false}}}

Input StereoDepthConfig message with ability to modify parameters in runtime. Default queue is non-blocking with size 4.

Input left = {*this, "left", Input::Type::SReceiver, false, 8, true, {{DatatypeEnum::ImgFrame, true}}}

Input for left ImgFrame of left-right pair

Default queue is non-blocking with size 8

Input right = {*this, "right", Input::Type::SReceiver, false, 8, true, {{DatatypeEnum::ImgFrame, true}}}

Input for right ImgFrame of left-right pair

Default queue is non-blocking with size 8

Output depth = {*this, "depth", Output::Type::MSender, {{DatatypeEnum::ImgFrame, false}}}

Outputs ImgFrame message that carries RAW16 encoded (0..65535) depth data in depth units (millimeter by default).

Non-determined / invalid depth values are set to 0

Output disparity = {*this, "disparity", Output::Type::MSender, {{DatatypeEnum::ImgFrame, false}}}

Outputs ImgFrame message that carries RAW8 / RAW16 encoded disparity data: RAW8 encoded (0..95) for standard mode; RAW8 encoded (0..190) for extended disparity mode; RAW16 encoded for subpixel disparity mode:

  • 0..760 for 3 fractional bits (by default)

  • 0..1520 for 4 fractional bits

  • 0..3040 for 5 fractional bits

Output syncedLeft = {*this, "syncedLeft", Output::Type::MSender, {{DatatypeEnum::ImgFrame, false}}}

Passthrough ImgFrame message from ‘left’ Input.

Output syncedRight = {*this, "syncedRight", Output::Type::MSender, {{DatatypeEnum::ImgFrame, false}}}

Passthrough ImgFrame message from ‘right’ Input.

Output rectifiedLeft = {*this, "rectifiedLeft", Output::Type::MSender, {{DatatypeEnum::ImgFrame, false}}}

Outputs ImgFrame message that carries RAW8 encoded (grayscale) rectified frame data.

Output rectifiedRight = {*this, "rectifiedRight", Output::Type::MSender, {{DatatypeEnum::ImgFrame, false}}}

Outputs ImgFrame message that carries RAW8 encoded (grayscale) rectified frame data.

Output outConfig = {*this, "outConfig", Output::Type::MSender, {{DatatypeEnum::StereoDepthConfig, false}}}

Outputs StereoDepthConfig message that contains current stereo configuration.

Output debugDispLrCheckIt1 = {*this, "debugDispLrCheckIt1", Output::Type::MSender, {{DatatypeEnum::ImgFrame, false}}}

Outputs ImgFrame message that carries left-right check first iteration (before combining with second iteration) disparity map. Useful for debugging/fine tuning.

Output debugDispLrCheckIt2 = {*this, "debugDispLrCheckIt2", Output::Type::MSender, {{DatatypeEnum::ImgFrame, false}}}

Outputs ImgFrame message that carries left-right check second iteration (before combining with first iteration) disparity map. Useful for debugging/fine tuning.

Output debugExtDispLrCheckIt1 = {*this, "debugExtDispLrCheckIt1", Output::Type::MSender, {{DatatypeEnum::ImgFrame, false}}}

Outputs ImgFrame message that carries extended left-right check first iteration (downscaled frame, before combining with second iteration) disparity map. Useful for debugging/fine tuning.

Output debugExtDispLrCheckIt2 = {*this, "debugExtDispLrCheckIt2", Output::Type::MSender, {{DatatypeEnum::ImgFrame, false}}}

Outputs ImgFrame message that carries extended left-right check second iteration (downscaled frame, before combining with first iteration) disparity map. Useful for debugging/fine tuning.

Output debugDispCostDump = {*this, "debugDispCostDump", Output::Type::MSender, {{DatatypeEnum::ImgFrame, false}}}

Outputs ImgFrame message that carries cost dump of disparity map. Useful for debugging/fine tuning.

Output confidenceMap = {*this, "confidenceMap", Output::Type::MSender, {{DatatypeEnum::ImgFrame, false}}}

Outputs ImgFrame message that carries RAW8 confidence map. Lower values means higher confidence of the calculated disparity value. RGB alignment, left-right check or any postproccessing (e.g. median filter) is not performed on confidence map.

Public Static Attributes

static constexpr const char *NAME = "StereoDepth"

Private Members

PresetMode presetMode = PresetMode::HIGH_DENSITY
std::shared_ptr<RawStereoDepthConfig> rawConfig

Disparity

Disparity refers to the distance between two corresponding points in the left and right image of a stereo pair.

../../_images/disparity_explanation.jpeg

When calculating the disparity, each pixel in the disparity map gets assigned a confidence value 0..255 by the stereo matching algorithm, as:

  • 0 - maximum confidence that it holds a valid value

  • 255 - minimum confidence, so there is more chance that the value is incorrect

(this confidence score is kind-of inverted, if say comparing with NN)

For the final disparity map, a filtering is applied based on the confidence threshold value: the pixels that have their confidence score larger than the threshold get invalidated, i.e. their disparity value is set to zero. You can set the confidence threshold with stereo.initialConfig.setConfidenceThreshold().

Measuring real-world object dimensions

Because the depth map contains the Z distance, objects in parallel with the camera are measured accurately standard. For objects not in parallel, the Euclidean distance calculation can be used. Please refer to the below:

../../_images/Euclidian_distance_fig.png

When running eg. the RGB & MobilenetSSD with spatial data example, you could calculate the distance to the detected object from XYZ coordinates (SpatialImgDetections) using the code below (after code line 143 of the example):

distance = math.sqrt(detection.spatialCoordinates.x ** 2 + detection.spatialCoordinates.y ** 2 + detection.spatialCoordinates.z ** 2) # mm

Got questions?

We’re always happy to help with code or other questions you might have.

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