justdata

A TensorFlow-native data pipeline library with a modality-neutral core and first-class computer vision and acoustic recipes. justdata.core owns loading, adapter, preset, metadata, padding, and seeded execution machinery; justdata.vision owns image schemas, transforms, augmentations, corruptions, tasks, and vision presets. justdata.acoustic owns audio schemas, decoding, resampling, segmentation, frontends, augmentations, corruptions, DCASE helpers, stats, metadata/JAX helpers, and acoustic presets.

Installation
Architecture
Data Pipeline Stages
Supervised Learning — Training Pipelines
Automatic Augmentation Policies: RandAugment, TrivialAugment, and TrivialAugmentWide
Supervised Learning — Validation Pipelines
The timm ImageNet Recipes (ResNet Strikes Back: A1/A2/A3)
Self-Supervised Learning Pipeline (DINOv2)
Registry System
Presets and Smart Merging
Acoustic Pipelines
Dataset Adapters
Mini-C Corruption Benchmark
Audio Corruption Benchmark
Usage
Development

Installation

pip install justdata

Requirements: Python 3.11–3.13, TensorFlow ≥ 2.18.1, TensorFlow Datasets ≥ 4.9.9. Install optional modality extras with justdata[vision] for Hugging Face vision datasets, justdata[wilds] for WILDS image classification datasets, or justdata[acoustic] for audio dataset/source dependencies.

Architecture

justdata is structured around a fixed, four-stage pipeline abstraction. The currently supported vision tasks, classification and segmentation, each expose exactly four composable functions. Object detection and depth estimation are future scope and are not registered capabilities.

(preprocess_fn, augment_fn, late_augment_fn, postprocess_fn)

These are assembled by justdata.core.load_ds into the following execution graph:

fetch_ds -> adapter -> preprocess -> cache -> augment -> shuffle -> postprocess -> batch -> late_augment -> pad -> prefetch

The strict ordering reflects the execution domain requirements articulated throughout this document: format normalization occurs before the optional preprocessing cache; spatial and photometric distortions precede tensor conversion and normalization; and batch-level operations (Mixup, CutMix, random erasing) occur after batching on the GPU. An optional model-input cache can be inserted after deterministic postprocessing and before batching; for training it must be explicitly opted in and is placed before shuffle so epoch order is not frozen.

Core Public API

Function	Description
`justdata.core.fetch_ds(dataset_names, splits_info, data_dir)`	Raw dataset loading through registered source loaders. Returns a `tf.data.Dataset` in canonical schema.
`justdata.core.load_ds(...)`	Full pipeline for training or evaluation. Handles caching, augmentation, shuffling, batching, and prefetching.
`justdata.vision.minic.create_minic_datasets(...)`	Constructs Mini-C corruption benchmark datasets from a shared preprocessed base dataset.
`justdata.acoustic.corruptions.create_audio_corruption_datasets(...)`	Constructs acoustic corruption benchmark datasets from a shared preprocessed base dataset.
`justdata.acoustic.dcase2025.make_source_dataset(...)`	Builds DCASE Task 1 source-domain datasets with split-safety checks.

Import justdata.vision before resolving built-in vision datasets or pipelines. Hugging Face vision datasets are referenced with the hf: prefix (e.g., hf:cifar10), and WILDS image classification datasets are referenced with the wilds: prefix (e.g., wilds:camelyon17).

Data Pipeline Stages

Stage 1: Preprocessing (before cache)

Format normalization is performed before the optional decoded-dataset cache. Operations include rank fixing (2D -> 3D), CHW -> HWC transposition, grayscale -> RGB expansion, and RGBA -> RGB projection. The output shape is forced to [None, None, 3].

Stage 2: Augmentation (per-sample, training only)

Per-sample spatial and photometric augmentations are applied after the optional cache stage, ensuring that each training epoch receives independently sampled augmentations. All augmentation functions use tf.random.split for stateless randomization, enabling full reproducibility.

Stage 3: Postprocessing (every sample)

Resize, channel-wise normalization to zero mean and unit standard deviation, and optional HWC -> CHW transposition. This stage runs unconditionally for both training and evaluation.

Set cache_model_inputs=True with model_input_cache_path to cache these resized, normalized tensors on local SSD. For dataset_type="train", also set allow_train_model_input_cache=True and use it only when the training view is deterministic; stochastic crops or photometric augmentation will be materialized into the cache on first fill.

Stage 4: Late Augmentation (per-batch, training only)

Batch-level operations—Mixup, CutMix, and random erasing—are applied after batching. These operations are strictly training-only and require a formed batch to operate across the sample dimension.

Supervised Learning — Training Pipelines

To ensure mathematical correctness, the training pipeline is strictly segregated by execution domain. Spatial and photometric distortions are applied to [0, 255] image tensors (PIL-equivalent domain) before zero-mean tensor normalization.

1. Image Domain Augmentations

Geometric Augmentations

CIFAR-10/100: RandomCrop(32, padding=4, padding_mode='zeros') -> RandomHorizontalFlip(p=0.5).
ImageNet-1K: RandomResizedCrop(size=224) (or 256). Scale: (0.08, 1.0), Aspect ratio: (0.75, 1.33), Interpolation: Bicubic. -> RandomHorizontalFlip(p=0.5).

Photometric Augmentations (Mutually Exclusive Branches)

The photometric augmentation strategy is architecture-dependent and the two branches are mutually exclusive.

Modern Branch (ViT / ConvNeXt): Apply RandAugment(num_ops=2, magnitude=9), TrivialAugment, or TrivialAugmentWide (see the Automatic Augmentation Policies section for full specifications). Color Jitter is explicitly disabled to prevent redundant and destructive color space distortion.
Legacy Branch (ResNet): Apply ColorJitter(brightness=0.4, contrast=0.4, saturation=0.4, hue=0.1). RandAugment is disabled.

2. Tensor Domain

Conversion & Scaling: ToImage() -> ToDtype(float32, scale=True). Maps [0, 255] -> [0.0, 1.0].
Normalization:
- CIFAR-10: mean=(0.4914, 0.4822, 0.4465), std=(0.2023, 0.1994, 0.2010)
- CIFAR-100: mean=(0.5071, 0.4867, 0.4408), std=(0.2675, 0.2565, 0.2761)
- ImageNet-1K: mean=(0.485, 0.456, 0.406), std=(0.229, 0.224, 0.225)
Random Erasing (Cutout): Applied to the normalized tensor. p=0.25, scale=(0.02, 0.33), ratio=(0.3, 3.3).

3. Mini-Batch Domain

Applied across the batch dimension during training.

Repeated Augmentation (RA): Enabled for ViTs. Typically 3 repetitions per sample per mini-batch.
Mixup & CutMix: Controlled by mixup_prob=1.0 (probability of batch mixing) and switch_prob=0.5 (probability of selecting CutMix over Mixup).
- Mixup: $\tilde{x} = \lambda x_i + (1 - \lambda) x_j$, where $\lambda \sim \mathrm{Beta}(0.8,, 0.8)$.
- CutMix: Replaces a rectangular bounding box region; $\lambda \sim \mathrm{Beta}(1.0,, 1.0)$.
- Note: The $\alpha$ values (0.8 and 1.0) reflect the DeiT baseline. Mixup/CutMix parameters are strictly recipe-dependent; see the A1/A2/A3 section for ResNet-specific variations.
Label Smoothing: Cross-entropy loss modification with $\varepsilon = 0.1$.

Automatic Augmentation Policies: RandAugment, TrivialAugment, and TrivialAugmentWide

justdata provides native TensorFlow implementations of three closely related automatic augmentation policies: RandAugment (Cubuk et al., 2020), TrivialAugment (Müller & Hutter, 2021), and TrivialAugmentWide (Müller & Hutter, 2021). All three are registered under the augment_strategy registry and share a common operation pool and magnitude discretization framework.

1. Pipeline Position and Domain Constraints

To guarantee deterministic reproduction of published results, all three policies are applied exclusively in the image domain (integer uint8 tensors, pixel values $\in [0, 255]$), before tensor conversion to floating-point and channel-wise normalization. The canonical execution order within the per-sample augmentation stage is:

Random Resized Crop (or Random Pad Crop for CIFAR)
RandAugment / TrivialAugment / TrivialAugmentWide
Random Horizontal Flip (integrated into the crop strategy)
ToTensor — scales to float $[0.0, 1.0]$ (postprocessing stage)
Normalize — subtracts dataset mean, divides by standard deviation (postprocessing stage)

Applying photometric and geometric distortions prior to floating-point conversion ensures that operations such as Posterize and Solarize, which are defined on integer pixel arithmetic, remain numerically well-founded, and that fill values for geometric operations are expressed in the same integer domain as the source image.

2. The RA Operation Space ($K = 14$)

All three algorithms draw from the RA augmentation space, a fixed pool of $K = 14$ operations. The pool is partitioned into two subsets based on magnitude dependency.

Magnitude-Independent Operations (3 ops)

These operations ignore the sampled magnitude $m$ entirely.

Operation	Description
`Identity`	Returns the image unmodified.
`AutoContrast`	Linearly scales the pixel intensity histogram so that the darkest pixel maps to 0 and the brightest to 255.
`Equalize`	Equalizes the image histogram per channel using a cumulative distribution function.

Magnitude-Dependent Operations (11 ops)

These operations scale their physical intensity as a function of the sampled magnitude index $m$.

Sign randomization. For all geometric operations (Rotate, ShearX, ShearY, TranslateX, TranslateY) and all color enhancement operations (Brightness, Color, Contrast, Sharpness), the direction of the applied transformation is randomized bidirectionally. Given a raw physical magnitude $v$ computed from $m$, the applied value is:

$$v' = v \cdot s, \quad s \sim \mathcal{U}{-1, +1}$$

This sign randomization is sampled independently per operation per sample, using a stateless seed derived from the layer's random state.

Geometric fill. When pixels are shifted outside the image boundary by Rotate, ShearX, ShearY, TranslateX, or TranslateY, the vacated regions are filled with a constant value (default: 128). Geometric operations use the implementation's fixed nearest-neighbor interpolation for images.

For segmentation pipelines, these geometric operations reuse the same sampled parameters for the image and segmentation map. The image uses bilinear interpolation, while the map uses nearest-neighbor interpolation and preserves its integer dtype. Vacated map pixels use the configurable mask_fill_value (default 255), which must be treated as an ignore label by the training loss. Photometric operations continue to affect only the image.

Solarize semantics. Solarize inverts all pixel values that are greater than or equal to the computed threshold $\tau$. Formally, for each pixel $p$:

$$p' = \begin{cases} 255 - p & \text{if } p \geq \tau \ p & \text{otherwise} \end{cases}$$

where $\tau = 255 \cdot (1 - m / B)$. At $m = 0$, the threshold is 255 (no pixels inverted); at $m = B$, the threshold is 0 (all pixels inverted).

3. Magnitude Discretization and Physical Mappings

The magnitude scale is a 31-bin discrete framework with bin indices $m \in {0, 1, \ldots, 30}$ and $B = 30$ (the maximum bin index). This parameterization is the native scale of the torchvision (v0.13+) implementation of both RandAugment and TrivialAugmentWide.

The table below specifies the physical mapping formula and the operation-specific bound for each of the two spaces. $W$ and $H$ denote the input image width and height at the moment the augmentation is applied.

Operation	Sign Rand.	Physical Mapping	Standard Bound (RA / TA)	Wide Bound (TA-Wide)
Rotate	Yes	$(m / B) \cdot \text{MaxDeg} \cdot s$	30.0°	135.0°
TranslateX	Yes	$(m / B) \cdot \text{MaxPx}_X \cdot s$	$(150 / 331) \times W$	32.0 px
TranslateY	Yes	$(m / B) \cdot \text{MaxPx}_Y \cdot s$	$(150 / 331) \times H$	32.0 px
ShearX	Yes	$(m / B) \cdot \text{MaxShear} \cdot s$	0.3	0.99
ShearY	Yes	$(m / B) \cdot \text{MaxShear} \cdot s$	0.3	0.99
Brightness	Yes	$1.0 + (m / B) \cdot \text{MaxDelta} \cdot s$	0.9	0.99
Color	Yes	$1.0 + (m / B) \cdot \text{MaxDelta} \cdot s$	0.9	0.99
Contrast	Yes	$1.0 + (m / B) \cdot \text{MaxDelta} \cdot s$	0.9	0.99
Sharpness	Yes	$1.0 + (m / B) \cdot \text{MaxDelta} \cdot s$	0.9	0.99
Posterize	No	$8 - \mathrm{round}!\left((m / B) \cdot \text{MaxBits}\right)$	MaxBits = 4 (min 4 bits retained)	MaxBits = 6 (min 2 bits retained)
Solarize	No	$255.0 \cdot (1 - m / B)$	threshold down to 0	threshold down to 0
Identity	—	—	—	—
AutoContrast	—	—	—	—
Equalize	—	—	—	—

Note on TranslateX / TranslateY: Translation is a deliberate exception to the "wider bounds" pattern. The TA-Wide space specifies a fixed ceiling of 32 px for both axes. For any image dimension exceeding approximately 71 px, the Standard RA space—whose ceiling scales proportionally with the image dimension—admits a larger maximum translation than the Wide space.

4. Algorithm Specifications

4.1 RandAugment (RA)

RandAugment (Cubuk et al., 2020) reduces the search space of AutoAugment from $\mathcal{O}(K^N)$ policies to two scalar hyperparameters: the number of sequential operations $N$ and the global magnitude $M$.

Procedure. Given a training image $x$:

Independently sample $N$ operation indices $k_1, \ldots, k_N$ uniformly at random with replacement from the pool of $K$ operations.
For each selected operation $T_{k_i}$, map the fixed global magnitude $M$ to a physical parameter via the operation-specific formula in the table above, applying sign randomization where applicable.
Apply the operations sequentially: $x \leftarrow T_{k_N}(\cdots T_{k_1}(x))$.

The magnitude $M$ is expressed on the 31-bin scale ($M \in {0, \ldots, 30}$) used throughout justdata. An optional magnitude perturbation $\sigma > 0$ samples the effective level per layer from $\mathcal{N}(M, \sigma^2)$, clipped to $[0, B]$.

API parameters (augment_strategy = "rand_augment" or direct call to rand_augment):

Parameter	Type	Default	Description
`num_layers`	`int`	2	Number of operations $N$ applied per image.
`magnitude`	`float`	9.0	Global magnitude $M$ on the 31-bin scale.
`magnitude_std`	`float`	0.0	Per-layer Gaussian magnitude noise $\sigma$. Set to 0.5 to replicate `timm` stochastic magnitude.
`prob_to_apply`	`float \| None`	`None`	If set, each layer is skipped with probability $1 - p$.
`rotate_max`	`float`	30.0	Maximum rotation angle in degrees.
`shear_max`	`float`	0.3	Maximum shear coefficient (Standard RA space).
`enhance_max`	`float`	0.9	Maximum delta for brightness, color, contrast, sharpness.
`posterize_max_bits`	`int`	4	Bits removed at maximum magnitude; min retained = $8 - \text{MaxBits}$.
`translate_const`	`float`	100.0	Absolute translate ceiling in pixels. For Standard RA, set to $(150/331) \times \text{image_width}$.
`exclude_ops`	`list[str] \| None`	`None`	Operations to exclude from the sampling pool.

Published optimal hyperparameters and 31-bin scale conversion. The original paper (Cubuk et al., 2020) reports hyperparameters on an 11-level scale ($M_{\text{paper}} \in {0, \ldots, 10}$). To replicate those results using the 31-bin scale employed by justdata, apply the conversion $m = M_{\text{paper}} \times 3$.

Dataset	Architecture	$N$	$M_{\text{paper}}$	$m$ (31-bin)
CIFAR-10	WideResNet-28-2	3	4	12
CIFAR-10	WideResNet-28-10	3	5	15
CIFAR-10	PyramidNet + ShakeDrop	3	7	21
CIFAR-10	Shake-Shake	3	9	27
ImageNet-1K	ResNet-50	2	9	27
ImageNet-1K	EfficientNet-B7	2	—	28†

†The EfficientNet-B7 value was reported on an extended scale beyond 10; cross-verify against the target codebase before use. The torchvision default of magnitude=9 on the 31-bin scale corresponds to moderate augmentation and is not equivalent to the paper's $M_{\text{paper}} = 9$.

4.2 TrivialAugment (TA)

TrivialAugment (Müller & Hutter, 2021) eliminates hyperparameter search entirely by selecting a single operation and sampling its magnitude uniformly at random from the full discrete range on each forward pass.

Procedure. Given a training image $x$:

Sample one operation index $k \sim \mathcal{U}{1, \ldots, K}$ uniformly from the 14-op RA pool.
Sample a magnitude $m \sim \mathcal{U}{0, 1, \ldots, 30}$ uniformly from the full 31-bin range.
Map $m$ to a physical parameter via the Standard bounds in the table above, applying sign randomization where applicable.
Apply the single operation: $x \leftarrow T_k(x)$.

The proportional translate ceiling is computed dynamically as $(150 / 331) \times W$ (image width), matching the Standard RA space definition.

API: augment_strategy = "trivial_augment". Accepts translate_const (float, optional; computed from image width if not supplied) and exclude_ops (list of strings, optional).

4.3 TrivialAugmentWide (TA-Wide)

TrivialAugmentWide (Müller & Hutter, 2021) is the native torchvision variant of TrivialAugment. It uses the same zero-hyperparameter, single-operation protocol as baseline TA, but operates over the Wide magnitude bounds, substantially expanding the geometric and photometric search range.

Procedure. Identical to TrivialAugment, with two differences:

The Wide physical bounds from the table above are applied in place of the Standard bounds.
The translate ceiling is a fixed 32 px (not image-proportional).

Wide bounds summary:

Transformation	Standard RA / TA	TA-Wide
Rotation range	±30°	±135°
Shear range (X and Y)	±0.3	±0.99
Enhancement delta (Brightness, Color, Contrast, Sharpness)	±0.9	±0.99
Posterize (minimum bits retained)	4	2
Translation (fixed ceiling)	$(150/331) \times \text{dim}$	32 px

API: augment_strategy = "trivial_augment_wide". Accepts exclude_ops (list of strings, optional). The wide bounds are fixed by design and cannot be overridden via kwargs; to use custom bounds, call rand_augment directly with num_layers=1 and the desired parameters.

5. Algorithm Comparison

Property	RandAugment	TrivialAugment	TrivialAugmentWide
Operations applied per image	$N$ (tunable, with replacement)	1 (fixed)	1 (fixed)
Magnitude $m$	Fixed global $M$, constant across ops	Sampled: $m \sim \mathcal{U}{0, \ldots, 30}$	Sampled: $m \sim \mathcal{U}{0, \ldots, 30}$
Hyperparameter search required	Grid search over $(N, M)$	None	None
Transformation bounds	Standard RA space	Standard RA space	Wide space
Translate ceiling	Configurable (default 100 px)	$(150/331) \times W$ (image-proportional)	32 px (fixed)
Reference implementation	`torchvision`	`automl/trivialaugment`	`torchvision`
`justdata` registry key	`rand_augment`	`trivial_augment`	`trivial_augment_wide`

6. Non-RA Operations

The following internal primitives exist in the implementation but are excluded from the fixed 14-op RA pool and cannot be selected through RandAugment, TrivialAugment, or TrivialAugmentWide. The public exclude_ops parameter can remove operations from the pool; it cannot add these primitives.

Operation	Notes
`Invert`	Inverts all pixel values: $p' = 255 - p$.
`Cutout`	Erases a random square patch (fill with constant). Superseded by the `random_erasing` late-augmentation stage.
`SolarizeAdd`	Additive solarization variant.
`Grayscale`	Converts to single-channel luminance and broadcasts to RGB.

Supervised Learning — Validation Pipelines

Validation pipelines are strictly deterministic. The objective shifts from regularization to feature preservation and scale alignment.

CIFAR-10 / CIFAR-100 Standard Validation

Because CIFAR images are inherently 32×32 and contain minimal background, spatial cropping destroys the primary subject.

Pipeline: ToImage() -> ToDtype(float32, scale=True) -> Normalize (training-set statistics as above).

ImageNet-1K Standard Baseline (The 0.875 Rule)

For standard supervised models and baseline linear probing, the canonical 0.875 crop ratio discards peripheral background.

Pipeline: Resize(256, interpolation=Bicubic) -> CenterCrop(224) -> ToImage() -> ToDtype(float32, scale=True) -> Normalize.

ImageNet-1K Modern Recipes (FixRes Strategy)

Modern recipes correct train-test resolution discrepancies by manipulating the validation crop percentage (crop_pct).

A3 (Light) Validation: Train at 160×160, validate at 224×224. Resize shorter edge to ≈236, then CenterCrop(224).
A1 / A2 (Heavy/Moderate) Validation: Default test at 224×224 (crop_pct=1.0, so Resize(224) -> CenterCrop(224)). Accuracy improves further via FixRes evaluation at 288×288 (Resize(288) -> CenterCrop(288)) as demonstrated in the RSB paper.

The `timm` ImageNet Recipes (ResNet Strikes Back: A1/A2/A3)

The "ResNet Strikes Back" (RSB) recipes dynamically scale augmentation intensity and training schedules to match model capacity.

Crucial context: These recipes were designed specifically for ResNet-family architectures. ViTs typically use distinct recipes (e.g., DeiT, BEiT) with different Mixup $\alpha$, optimizers (AdamW), and loss functions. While the principle of scaling augmentation with model capacity generalizes, the specific hyperparameters below do not transfer directly to ViTs.

Parameter	A1 (Heavy)	A2 (Moderate)	A3 (Light)
Target Architecture	Large ResNets (e.g., ResNet-152/200) or high compute	ResNet-50 (standard)	ResNet-50 (fast) or smaller (e.g., ResNet-18)
Training Resolution	224	224	160 (FixRes strategy)
Test Resolution	224 (scales to 288 via FixRes)	224	224
Epochs	600	300	100
Optimizer	LAMB	LAMB	LAMB
LR Schedule	Cosine with warmup	Cosine with warmup	Cosine with warmup
Loss Function	BCE (per-class binary)	BCE	CE (standard)
RandAugment	$m \approx 7$, $n = 2$	$m \approx 6$, $n = 2$	$m \approx 6$, $n = 2$
Random Erasing	`p=0.35`	`p=0.25`	Disabled (`p=0.0`)
Repeated Aug (RA)	Enabled (3×)	Enabled (3×)	Disabled
Mixup $\alpha$	0.2	0.2	0.1
CutMix $\alpha$	1.0	1.0	1.0
Stochastic Depth	Capacity-dependent (e.g., 0.05+)	0.0	0.0
EMA	Yes	Yes	No (or lighter)
Weight Decay	0.02	0.02	0.02

Note: RandAugment parameter $n$ defaults to 2 per the original specification, though exact magnitude strings fluctuate across timm versions.

Self-Supervised Learning Pipeline (DINOv2)

DINOv2 employs a Teacher-Student knowledge distillation framework operating on multi-crop asymmetry to force the learning of semantic invariance over low-level frequency matching.

Multi-Crop Geometric Strategy

Global Crops (Context): 2 crops at 224×224. Scale: (0.32, 1.0). Passed to both Teacher and Student.
Local Crops (Detail): 8 crops at 96×96 (default). Use 98×98 ($14 \times 7$) to avoid positional embedding interpolation when using ViT-14 backbones. Scale: (0.05, 0.32). Passed to Student only.

Asymmetric Pipeline Implementation

The per-crop asymmetry is structurally enforced by three distinct Compose pipelines rather than conditional branching within a single block. Each source image passes through all three pipelines to produce the full 10-crop suite.

global_transform_1: Global Crop 1. Enforces strict blurring (p=1.0), disables solarization (p=0.0).
global_transform_2: Global Crop 2. Minimizes blurring (p=0.1), enables solarization (p=0.2).
local_transform: The 8 Local Crops. Moderate blurring (p=0.5), disables solarization (p=0.0).

Execution Order and Domain Separation (Per Crop)

Step	Operation	Parameters / Per-Crop Asymmetry	Domain
1	`RandomResizedCrop`	Aspect ratio (0.75, 1.33), Bicubic interpolation.	Image
2	`RandomHorizontalFlip`	`p=0.5` (all crops)	Image
3	`ColorJitter`	`p=0.8` (all crops). `b=0.4, c=0.4, s=0.2, h=0.1`	Image
4	`RandomGrayscale`	`p=0.2` (all crops)	Image
5	`GaussianBlur`	$\sigma \sim \mathrm{Uniform}(0.1, 2.0)$, dynamic kernel. Global 1: `p=1.0` · Global 2: `p=0.1` · Local: `p=0.5`	Image
6	`Solarization`	Invert pixels $> 128$. Global 1: `p=0.0` · Global 2: `p=0.2` · Local: `p=0.0`	Image
7	Convert & Scale	`ToImage()` -> `ToDtype(float32, scale=True)`	Image -> Tensor
8	`Normalize`	ImageNet `mean` and `std`.	Tensor (zero-mean)

SSL Downstream Evaluation

Image-Level Classification (Linear Probing / $k$-NN): Standard supervised inference transforms: Resize(256, Bicubic) -> CenterCrop(224) -> ToImage() -> ToDtype(float32) -> Normalize. Features are extracted from the [CLS] token or a concatenation of [CLS] and average-pooled patch tokens.

Dense Tasks (Segmentation / Depth Validation — Patch Alignment): To avoid dropping boundary pixels or forcing complex interpolation during dense evaluation, images are resized to the target scale and padded (reflection or zero) on the bottom and right edges such that both height and width are exact multiples of the ViT patch size (e.g., 14). This is implemented in justdata.vision.transforms.pad_to_patch_multiple.

Registry System

All extensible components in justdata use a decorator-based registry pattern with thread-safe lookups.

Registry	Decorator	Lookup
Crop strategies	`@register_crop_strategy(name)`	`justdata.vision.augmentations.get_crop_strategy(name)`
Augment strategies	`@register_augment_strategy(name)`	`justdata.vision.augmentations.get_augment_strategy(name)`
Corruptions	`@register_corruption(name, descriptor=...)`	`justdata.vision.corruptions.apply_corruption(...)`
Dataset adapters	`@register_adapter(dataset_name)`	`justdata.core.get_adapter(dataset_name)`
Source loaders	`@register_source_loader(prefix)`	`justdata.core.get_source_loader(dataset_name)`
Pipelines	`@register_pipeline("modality/task")`	`justdata.core.get_pipeline(...)`
Dataset metadata	`register_dataset(name, task_type, modality=...)`	`justdata.core.get_dataset_info(name)`
Audio frontends	`@register_audio_frontend(name)`	`justdata.acoustic.get_audio_frontend(name)`
Audio components	`@register_audio_*` decorators	`justdata.acoustic.get_audio_`, `list_audio_`, `has_audio_*`

get_pipeline is the high-level resolver: it infers the task type from the dataset name, merges preset defaults with user-supplied kwargs (via smart merge; see below), and invokes the appropriate pipeline factory.

Built-in crop strategies: random_resized, random_resized_hvflip, random_pad, random_hflip, resize_random_hflip, random_rot90_hflip.

Built-in augment strategies: rand_augment, trivial_augment, trivial_augment_wide, color_jitter, none.

Crop-specific parameters are passed through aug_kwargs["crop_kwargs"]. size, seed, interpolation, padding, and pad_mode remain controlled by the existing top-level augmentation fields and are rejected inside crop_kwargs, avoiding ambiguous precedence. For example, the FMoW M1 crop is fully declarative:

pipeline = get_pipeline(
    dataset="wilds:fmow",
    aug_kwargs={
        "enable": True,
        "image_size": 224,
        "crop_type": "random_resized_hvflip",
        "interpolation": "bicubic",
        "crop_kwargs": {
            "scale": (0.85, 1.0),
            "ratio": (0.90, 1.10),
            "horizontal_flip_probability": 0.5,
            "vertical_flip_probability": 0.5,
        },
    },
)

The acoustic package registers audio decoders, resamplers, channel strategies, segment strategies, frontends, augmentations, normalizations, eval views, postprocessors, and corruptions. Use list_audio_* helpers to inspect registered acoustic components.

Presets and Smart Merging

justdata.vision.presets stores dataset-specific default kwargs for all four vision pipeline stages. The vision _default preset (ImageNet statistics, 224px, RandAugment) serves as the fallback for vision only.

Available presets:

Preset	Description
`_default`	ImageNet-1K statistics, 224px, RandAugment, modern branch
`cifar`	32px, TrivialAugmentWide, CIFAR-10 normalization, no resizing
`cifar100`	32px, TrivialAugmentWide, CIFAR-100 normalization
`imagenet_resnet`	ImageNet statistics, legacy branch with ColorJitter
`imagenet_a1`	RSB A1: heavy augmentation, BCE loss, 600 epochs
`imagenet_a2`	RSB A2: moderate augmentation, BCE loss, 300 epochs
`imagenet_a3`	RSB A3: light augmentation, CE loss, 160px training
`dinov2`	Asymmetric multi-crop SSL pipeline
`wilds:*`	WILDS benchmark defaults; matching `_strong` presets are opt-in

merge_with_presets(dataset, user_kwargs) implements a smart merge: user-supplied kwargs that are identical to the _default preset values are treated as "not explicitly overridden," allowing dataset-specific preset values to take precedence. Only kwargs that genuinely differ from the defaults are considered intentional user overrides.

Resolved presets are serializable and hashable across modalities. Use get_resolved_preset(name) from justdata.vision.presets, justdata.acoustic.presets, or justdata.core.presets to obtain an object with .to_json() and .hash(). Hashes use canonical JSON with sorted keys and a 16-character SHA-256 prefix.

Acoustic presets are typed with AudioPreset and nested frozen config dataclasses for preprocessing, segmentation, frontends, labels, normalization, train augment settings, eval views, layout, and metadata policy. The justdata.audio namespace is a compatibility alias for justdata.acoustic.

See docs/presets.md for acoustic preset contracts, including EfficientAT/DyMN, PaSST, and CED.

Automatic preset resolution

When a vision dataset has a registered preset (e.g., cifar10 -> cifar, cifar100 -> cifar100), get_pipeline automatically applies it. Vision datasets without a dedicated preset fall back to the vision _default.

import justdata.vision
from justdata.core.registry import get_pipeline

# cifar10 automatically gets the 'cifar' preset (32px, TrivialAugmentWide, CIFAR-10 stats)
pipeline = get_pipeline(dataset="cifar10")

Applying a named preset to any dataset

The dataset argument in get_pipeline drives preset lookup, not just task inference. To apply a specific named preset to a dataset that does not have its own preset (e.g., using imagenet_a3 for imagenette), pass it as preset:

import justdata.vision
from justdata.core.loader import load_ds
from justdata.core.registry import get_pipeline

# Resolve the A3 (RSB light) pipeline for imagenette
pipeline = get_pipeline(
    dataset="imagenette",
    preset="imagenet_a3",       # drives preset lookup: 160px train, 224px val, RandAugment m=6
)

train_ds, N = load_ds(
    dataset_names_arg=["imagenette"],  # actual dataset to load
    splits_arg={"imagenette": ["train"]},
    dataset_type="train",
    batch_size=128,
    seed=42,
    pipeline=pipeline,
    num_classes=10,
    cache_dataset=False,
)

The validation pipeline uses the same preset name; the A3 preset's FixRes strategy (train_image_size=160, val_resize_size=236) is applied automatically:

# The same pipeline can be used for validation; `load_ds` automatically sets `is_training=False` based on `dataset_type`
# and applies the deterministic center-crop resize (FixRes 236 → CenterCrop 224)
val_ds, N = load_ds(
    dataset_names_arg=["imagenette"],
    splits_arg={"imagenette": ["validation"]},
    dataset_type="validation",
    batch_size=256,
    seed=0,
    pipeline=pipeline,
    num_classes=10,
    cache_dataset=False,
)

Acoustic Pipelines

Import justdata.acoustic before resolving built-in acoustic datasets or pipelines. Acoustic samples use the canonical keys waveform, sample_rate, optional label, features, duration, and metadata.

import justdata.acoustic
from justdata.core.loader import load_ds
from justdata.core.registry import get_pipeline

pipeline = get_pipeline(
    dataset="dcase2025_task1",
    preset="dcase2025_task1_efficientat_32k_1s",
)

ds, n = load_ds(
    dataset_names_arg=["dcase2025:task1"],
    splits_arg={"dcase2025:task1": ["dev_train_25"]},
    dataset_type="train",
    batch_size=64,
    seed=0,
    pipeline=pipeline,
    num_classes=10,
    cache_dataset=False,
    data_dir="/path/to/dcase",
    metadata_mode="numeric_only",
    as_numpy=True,
)

Modality documentation:

docs/vision.md: vision schema, four stages, preset contracts, metadata modes, Mini-C, and parity matrix.
docs/acoustic.md: canonical schema, four stages, metadata modes, golden tests, corruption benchmark, and parity matrix.
docs/dcase2025.md: DCASE Task 1 source/target helpers and split safety.
docs/presets.md: vision and acoustic preset selection and hashable contracts.
docs/golden_tests.md: optional golden compatibility test workflow.

Examples are split by modality under examples/vision/ and examples/acoustic/. Each directory includes loading, Hugging Face source, statistics, and corruption benchmark examples.

Dataset Adapters

Core adapters normalize raw records into the modality-specific schema expected by a selected pipeline. justdata.core itself is schema-neutral, and the identity adapter is applied when no dataset-specific adapter is registered.

Vision adapter

Vision pipelines expect image, optional label, and task-specific fields such as mask.

from justdata.core.adapters import register_adapter

@register_adapter("my_dataset")
def my_adapter(sample):
    return {"image": sample["img"], "label": sample["class_id"]}

Acoustic adapter

Acoustic pipelines expect waveform, sample_rate, and an optional label.

from justdata.core.adapters import register_adapter

@register_adapter("my_audio_dataset")
def my_audio_adapter(sample):
    result = {
        "waveform": sample["audio"],
        "sample_rate": sample["sampling_rate"],
    }
    if "target" in sample:
        result["label"] = sample["target"]
    return result

Mini-C Corruption Benchmark

create_minic_datasets constructs finalized corruption evaluation datasets by forking from a preprocessed RGB dataset. Corruption runs after decoding and rank/channel normalization, but before resize, float conversion, normalization, batching, and padding. Pass cache_dataset=True with an explicit disk path when avoiding source re-reads across corruptions is worth the storage cost; otherwise the base remains streaming.

The original Mini-C family names remain pinned to their 1.0.0 behavior:

Name	Version 1 implementation
`blur`	Defocus blur with a disk kernel and alias Gaussian filter
`noise`	Additive Gaussian noise using the legacy absolute standard deviations
`digital`	Nearest-neighbor pixelation
`weather`	Synthetic snow

Five exact-name TensorFlow-native operators are also available at version 1.0.0: gaussian_blur, gaussian_noise, jpeg_compression, contrast_reduction, and brightness_reduction. Their immutable descriptors contain the severity table, domains, dtype/shape contract, seed policy, clipping and rounding policy, backend identity, and codec/filter settings. Use get_corruption_descriptor(name, version) or list_corruption_descriptors() to serialize and fingerprint these semantics.

For a caller-owned scientific seed, use exact version dispatch directly:

import tensorflow as tf

from justdata.vision.corruptions import (
    apply_corruption,
    get_corruption_descriptor,
)

descriptor = get_corruption_descriptor("gaussian_noise", "1.0.0")
corrupted = apply_corruption(
    decoded_rgb_uint8,
    name=descriptor.name,
    version=descriptor.version,
    severity=3,
    seed=tf.constant([123, 456], dtype=tf.int32),
)

The complete seed is supplied by the caller; no global RNG is read. [email protected] uses TensorFlow Philox. The JPEG descriptor fixes encode and decode options and is repeatable for a fixed TensorFlow/codec build, but does not claim byte identity across unrelated TensorFlow or codec versions.

import justdata.vision
from justdata.core.registry import get_pipeline
from justdata.vision.minic import create_minic_datasets

pipeline = get_pipeline(dataset="imagenet")

datasets, n = create_minic_datasets(
    corruption_types=["gaussian_noise", "jpeg_compression", "blur"],
    severity=3,
    dataset_names_arg=["imagenet2012"],
    splits_arg={"imagenet2012": ["validation"]},
    dataset_type="validation",
    batch_size=256,
    seed=0,
    pipeline=pipeline,
    num_classes=1000,
)

With metadata_mode="full", finalized samples include corruption, corruption_version, corruption_identity, corruption_identity_hash, severity, and corruption_domain. numeric_only retains the numeric identity hash and severity; none removes metadata according to the shared core contract. The dataset helper preserves legacy enumeration-position seed salting. Consumers with their own sample-level PRNG lineage should call apply_corruption directly.

Audio Corruption Benchmark

create_audio_corruption_datasets mirrors Mini-C for acoustic evaluation. It applies deterministic severity 1-5 corruptions in the waveform or spectrogram domain, attaches corruption metadata, runs the normal postprocessing stage, and preserves padding_mask.

import justdata.acoustic
from justdata.acoustic.corruptions.datasets import create_audio_corruption_datasets
from justdata.core.registry import get_pipeline

pipeline = get_pipeline(
    dataset="dcase2025_task1",
    preset="dcase2025_task1_efficientat_32k_1s",
)

datasets, n = create_audio_corruption_datasets(
    corruption_types=["additive_white_noise", "clipping"],
    severity=3,
    base_dataset="dcase2025:task1",
    preset="dcase2025_task1_efficientat_32k_1s",
    split="dev_test",
    pipeline=pipeline,
    batch_size=64,
    seed=0,
    num_classes=10,
    metadata_mode="numeric_only",
)

Usage

Basic Classification Pipeline

import justdata.vision
from justdata.core.loader import load_ds
from justdata.core.registry import get_pipeline

pipeline = get_pipeline(dataset="cifar10")

train_ds, N = load_ds(
    dataset_names_arg=["cifar10"],
    splits_arg={"cifar10": ["train"]},
    dataset_type="train",
    batch_size=128,
    seed=42,
    pipeline=pipeline,
    num_classes=10,
    # CIFAR-10 is small enough for an intentional memory cache.
    cache_dataset=True,
)

Reusable, Explicitly Seeded Epochs

Use return_raw_ds=True to prepare the source, pipeline, preprocessing, cache, and filters once, then materialize the complete remaining training pipeline for each epoch:

prepared_train, tools = load_ds(
    dataset_names_arg=["cifar10"],
    splits_arg={"cifar10": ["train"]},
    dataset_type="train",
    batch_size=128,
    seed=0,
    pipeline=pipeline,
    num_classes=10,
    cache_dataset=False,
    deterministic=True,
    return_raw_ds=True,
)

for epoch in range(num_epochs):
    train_iterator, n_batches = tools["finalize_epoch"](
        prepared_train,
        seed=derive_epoch_seed(epoch),
        as_numpy=True,
    )
    train_one_epoch(train_iterator)

finalize_epoch applies standard augmentation, shuffle, postprocessing, batching, late augmentation, padding, and prefetching. The epoch seed is split into standard- and late-augmentation seeds, with source and batch indices folded in. Shuffle uses the epoch seed with reshuffling disabled on the materialized dataset. With deterministic=True, repeating a seed therefore reproduces the epoch independently of previous iterator creation or consumption, including when the returned TensorFlow dataset is iterated more than once.

With cache_dataset=False, source samples, preprocessing, and filters still run on every iteration; only loader and graph preparation are reused. A fresh NumPy iterator is created by each finalize_epoch(..., as_numpy=True) call.

finalize_epoch rejects cache_model_inputs=True when training or evaluation augmentation is enabled because that downstream cache intentionally freezes the first sampled augmented views. Existing one-shot load_ds and finalize_fn behavior is unchanged.

Loading a Hugging Face Dataset

train_ds, n_batches = load_ds(
    dataset_names_arg=["hf:cifar10"],
    splits_arg={"hf:cifar10": ["train"]},
    cache_dataset=False,
    ...
)

load_ds returns the dataset and its batch cardinality. The cardinality is a Python integer when TensorFlow can determine it and None for unknown or infinite pipelines.

For remote/downloaded sources, data_dir is a cache root. justdata namespaces source-owned caches under it: tfds/, hf/vision/, hf/acoustic/, wilds/, and zenodo/. If omitted, the root is ~/.cache/justdata.

Loader caches are separate from source-owned caches. cache_dataset/cache_path caches decoded, preprocessed samples before augmentation. Loader caching is off by default, so datasets remain streaming when cache_dataset is omitted. Set cache_dataset=True with an empty cache_path to opt into memory caching, or provide a nonempty path to cache on the filesystem. Large datasets should use an explicit disk path or remain uncached. cache_model_inputs and model_input_cache_path cache resized, normalized model inputs before batching. Use different paths for the two cache stages. This default changes performance, not output values.

Loading a WILDS Dataset

WILDS image classification datasets use the wilds: source prefix. Source options such as FMoW temporal split schemes live in the dataset string; when using a splits_arg dictionary, reuse that exact string as the key. Downloads are disabled by default (download=false). To download through WILDS under data_dir/wilds, add download=true to the dataset string. Use & between query options, not a second ?. The automatic presets are benchmark-faithful: Camelyon17 96 px, FMoW 224 px, iWildCam 448 px, and RxRx1 256 px with per-image channel standardization. Use preset="wilds:fmow_strong" or another _strong name to opt into stronger training augmentation.

local_ssd = "/local_ssd/justdata"
wilds_ds = "wilds:fmow?split_scheme=time_after_2016&download=true"
pipeline = get_pipeline(dataset="wilds:fmow")

train_ds, N = load_ds(
    dataset_names_arg=[wilds_ds],
    splits_arg={wilds_ds: ["train"]},
    dataset_type="train",
    batch_size=32,
    seed=42,
    pipeline=pipeline,
    num_classes=62,
    data_dir=f"{local_ssd}/sources",
    cache_dataset=True,
    cache_path=f"{local_ssd}/decoded/fmow-train",
    cache_model_inputs=True,
    model_input_cache_path=f"{local_ssd}/model-inputs/fmow-train-224",
    allow_train_model_input_cache=True,
    metadata_mode="numeric_only",
)

FMoW source inventories can opt into authoritative sequence identity and acquisition time without changing the default WILDS signature:

from justdata.core import fetch_ds

fmow = (
    "wilds:fmow?split_scheme=official&version=1.1&download=false"
    "&source_metadata=location_id,timestamp"
)
inventory = fetch_ds([fmow], {fmow: ["train", "id_val", "id_test", "val"]})

for sample in inventory.as_numpy_iterator():
    source = sample["metadata"]["wilds_source"]
    location_id = source["location_id"]  # UTF-8 bytes
    timestamp = source["timestamp"]      # UTF-8 bytes

The option accepts only location_id and timestamp. JustData maps every emitted wilds_index through WILDS' authoritative full_idxs mapping: location_id is the exact original FMoW sequence-directory basename, and timestamp preserves the source timezone-aware ISO-8601 text. Invalid fields, target-equivalent fields, missing source columns, or unreliable mappings fail closed. The wilds_source mapping is absent without the opt-in; it is retained by metadata_mode="full" and removed by numeric_only.

The base wilds:fmow preset has no stochastic per-sample training augmentation, so train model-input caching is safe when explicitly opted in. Do not use train model-input caching with wilds:fmow_strong unless freezing the first pass of stochastic augmentation is intentional.

Applying a Named Preset

To use a specific preset for any dataset, pass the preset name as preset:

# Load imagenette with the RSB A3 (light) recipe: 160px training, RandAugment m=6, Mixup α=0.1
pipeline = get_pipeline(
    dataset="imagenette",
    preset="imagenet_a3",  # apply the A3 preset to the imagenette task
)

train_ds, N = load_ds(
    dataset_names_arg=["imagenette"],
    splits_arg={"imagenette": ["train"]},
    dataset_type="train",
    batch_size=128,
    seed=42,
    pipeline=pipeline,
    num_classes=10,
    cache_dataset=False,
)

Overriding Preset Parameters

pipeline = get_pipeline(
    dataset="imagenet",
    aug_kwargs={"augment_type": "trivial_augment"},  # overrides preset default
)

DINOv2 SSL Pipeline

pipeline = get_pipeline(
    preset="dinov2",
    pipeline_name="vision/classification",
)

Development

This project uses devenv (Nix-based) with uv for Python dependency management.

devenv shell        # enter the development environment
direnv allow        # approve automatic devenv activation once
uv sync             # install/update dependencies
uv run pytest       # run all tests
uv run ruff check . # run lint checks
uv run ruff format --check .  # check formatting
uv run pytest tests/path/to/test_file.py::test_name  # run a single test

The project targets Python 3.12 (see .python-version). LD_LIBRARY_PATH is configured by devenv for native libraries.

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examples		examples
src/justdata		src/justdata
tests		tests
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.gitignore		.gitignore
.gitlab-ci.yml		.gitlab-ci.yml
.python-version		.python-version
AGENTS.md		AGENTS.md
LICENSE		LICENSE
README.md		README.md
devenv.lock		devenv.lock
devenv.nix		devenv.nix
devenv.yaml		devenv.yaml
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uv.lock		uv.lock

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