SC

Ultrafast sitting classification. 32x24 pixels is sufficient for estimating the state of the whole human body.

output_.mp4

Variant	Size	F1	CPU inference latency	ONNX
P	115 KB	0.8923	0.13 ms	Download
N	176 KB	0.9076	0.24 ms	Download
T	279 KB	0.8935	0.31 ms	Download
S	494 KB	0.9168	0.39 ms	Download
C	875 KB	0.9265	0.47 ms	Download

Data sample

1	2	3	4

Setup

git clone https://github.com/PINTO0309/SC.git && cd SC
curl -LsSf https://astral.sh/uv/install.sh | sh
uv sync
source .venv/bin/activate

Inference

uv run python demo_sc.py \
-pm sc_c_32x24.onnx \
-v 0 \
-ep cuda \
-dlr -dnm -dgm -dhm -dhd

uv run python demo_sc.py \
-pm sc_c_32x24.onnx \
-v 0 \
-ep tensorrt \
-dlr -dnm -dgm -dhm -dhd

Dataset Preparation

• AVA Actions Download (v2.2) - CC BY 4.0 license https://research.google.com/ava/download.html

uv run python 01_download_ava_videos.py

uv run python 03_renumber_files.py
uv run python 04_data_prep.py

uv run python 04_data_prep.py \
--timestamp-stride 32 \
--image-dir ./data/images \
--annotation-file ./data/annotation.txt \
--histogram-file ./data/image_size_hist.png \
--class-ratio-file ./data/class_ratio.png \
--balance-classes \
--dry-run

uv run python 04_data_prep.py \
--timestamp-stride 1 \
--image-dir ./data/images \
--annotation-file ./data/annotation.txt \
--histogram-file ./data/image_size_hist.png \
--class-ratio-file ./data/class_ratio.png \
--balance-classes

python 04_data_prep.py \
--timestamp-stride 1 \
--image-dir ./data/images \
--annotation-file ./data/annotation.txt \
--histogram-file ./data/image_size_hist.png \
--class-ratio-file ./data/class_ratio.png \
--balance-classes \
--resume-existing \
--start-index 198727

uv run python 05_make_parquet.py \
--embed-images \
--overwrite

uv run python 06_merge_parquet.py dataset1.parquet dataset2.parquet \
--output dataset.parquet \
--overwrite

uv run python 06_merge_parquet.py dataset1.parquet dataset2.parquet \
--output dataset.parquet \
--overwrite

Training Pipeline

• Use the images located under dataset/output/002_xxxx_front_yyyyyy together with their annotations in dataset/output/002_xxxx_front.csv.

• Every augmented image that originates from the same still_image stays in the same split to prevent leakage.

• The training loop relies on BCEWithLogitsLoss plus class-balanced pos_weight to stabilise optimisation under class imbalance; inference produces sigmoid probabilities. Use --train_resampling weighted to switch on the previous WeightedRandomSampler behaviour, or --train_resampling balanced to physically duplicate minority classes before shuffling.

• Training history, validation metrics, optional test predictions, checkpoints, configuration JSON, and ONNX exports are produced automatically.

• Per-epoch checkpoints named like sc_epoch_0001.pt are retained (latest 10), as well as the best checkpoints named sc_best_epoch0004_f1_0.9321.pt (also latest 10).

• The backbone can be switched with --arch_variant. Supported combinations with --head_variant are:

  --arch_variant	Default (--head_variant auto)	Explicitly selectable heads	Remarks
  baseline	avg	avg, avgmax_mlp	When using transformer/mlp_mixer, you need to adjust the height and width of the feature map so that they are divisible by --token_mixer_grid (if left as is, an exception will occur during ONNX conversion or inference).
  inverted_se	avgmax_mlp	avg, avgmax_mlp	When using transformer/mlp_mixer, it is necessary to adjust --token_mixer_grid as above.
  convnext	transformer	avg, avgmax_mlp, transformer, mlp_mixer	For both heads, the grid must be divisible by the feature map (default 3x2 fits with 30x48 input).

• The classification head is selected with --head_variant (avg, avgmax_mlp, transformer, mlp_mixer, or auto which derives a sensible default from the backbone).

• Pass --rgb_to_yuv_to_y to convert RGB crops to YUV, keep only the Y (luma) channel inside the network, and train a single-channel stem without modifying the dataloader.

• Alternatively, use --rgb_to_lab or --rgb_to_luv to convert inputs to CIE Lab/Luv (3-channel) before the stem; these options are mutually exclusive with each other and with --rgb_to_yuv_to_y.

• Mixed precision can be enabled with --use_amp when CUDA is available.

• Resume training with --resume path/to/sc_epoch_XXXX.pt; all optimiser/scheduler/AMP states and history are restored.

• Loss/accuracy/F1 metrics are logged to TensorBoard under output_dir, and tqdm progress bars expose per-epoch progress for train/val/test loops.

Baseline depthwise-separable CNN:

SIZE=32x24
uv run python -m sc train \
--data_root data/dataset.parquet \
--output_dir runs/sc_${SIZE} \
--epochs 100 \
--batch_size 256 \
--train_ratio 0.9 \
--val_ratio 0.1 \
--train_resampling balanced \
--image_size ${SIZE} \
--base_channels 32 \
--num_blocks 4 \
--arch_variant baseline \
--seed 42 \
--device auto \
--use_amp

Inverted residual + SE variant (recommended for higher capacity):

SIZE=32x24
uv run python -m sc train \
--data_root data/dataset.parquet \
--output_dir runs/sc_is_s_${SIZE} \
--epochs 100 \
--batch_size 256 \
--train_ratio 0.9 \
--val_ratio 0.1 \
--train_resampling balanced \
--image_size ${SIZE} \
--base_channels 32 \
--num_blocks 4 \
--arch_variant inverted_se \
--head_variant avgmax_mlp \
--seed 42 \
--device auto \
--use_amp

ConvNeXt-style backbone with transformer head over pooled tokens:

SIZE=32x24
uv run python -m sc train \
--data_root data/dataset.parquet \
--output_dir runs/sc_convnext_${SIZE} \
--epochs 100 \
--batch_size 256 \
--train_ratio 0.9 \
--val_ratio 0.1 \
--train_resampling balanced \
--image_size ${SIZE} \
--base_channels 32 \
--num_blocks 4 \
--arch_variant convnext \
--head_variant transformer \
--token_mixer_grid 2x2 \
--seed 42 \
--device auto \
--use_amp

• Outputs include the latest 10 sc_epoch_*.pt, the latest 10 sc_best_epochXXXX_f1_YYYY.pt (highest validation F1, or training F1 when no validation split), history.json, summary.json, optional test_predictions.csv, and train.log.
• After every epoch a confusion matrix and ROC curve are saved under runs/sc/diagnostics/<split>/confusion_<split>_epochXXXX.png and roc_<split>_epochXXXX.png.
• --image_size accepts either a single integer for square crops (e.g. --image_size 48) or HEIGHTxWIDTH to resize non-square frames (e.g. --image_size 64x48).
• Add --resume <checkpoint> to continue from an earlier epoch. Remember that --epochs indicates the desired total epoch count (e.g. resuming --epochs 40 after training to epoch 30 will run 10 additional epochs).
• Launch TensorBoard with:

  tensorboard --logdir runs/sc

ONNX Export

uv run python -m sc exportonnx \
--checkpoint runs/sc_is_s_32x24/sc_best_epoch0049_f1_0.9939.pt \
--output sc_s.onnx \
--opset 17

• The saved graph exposes images as input and prob_pointing as output (batch dimension is dynamic); probabilities can be consumed directly.
• After exporting, the tool runs onnxsim for simplification and rewrites any remaining BatchNormalization nodes into affine Mul/Add primitives. If simplification fails, a warning is emitted and the unsimplified model is preserved.

Arch

Ultra-lightweight classification model series

1. VSDLM: Visual-only speech detection driven by lip movements - MIT License
2. OCEC: Open closed eyes classification. Ultra-fast wink and blink estimation model - MIT License
3. PGC: Ultrafast pointing gesture classification - MIT License
4. SC: Ultrafast sitting classification - MIT License
5. PUC: Phone Usage Classifier is a three-class image classification pipeline for understanding how people interact with smartphones - MIT License
6. HSC: Happy smile classifier - MIT License
7. WHC: Waving Hand Classification - MIT License
8. UHD: Ultra-lightweight human detection - MIT License

Citation

If you find this project useful, please consider citing:

@software{hyodo2025sc,
  author    = {Katsuya Hyodo},
  title     = {PINTO0309/SC},
  month     = {11},
  year      = {2025},
  publisher = {Zenodo},
  doi       = {10.5281/zenodo.17625710},
  url       = {https://github.com/PINTO0309/sc},
  abstract  = {Ultrafast sitting classification.},
}

Acknowledgements

• AVA Actions Download (v2.2) - CC BY 4.0 License
• https://github.com/PINTO0309/PINTO_model_zoo/tree/main/472_DEIMv2-Wholebody34: Apache 2.0 License

  @software{DEIMv2-Wholebody34,
    author={Katsuya Hyodo},
    title={Lightweight human detection models generated on high-quality human data sets. It can detect objects with high accuracy and speed in a total of 28 classes: body, adult, child, male, female, body_with_wheelchair, body_with_crutches, head, front, right-front, right-side, right-back, back, left-back, left-side, left-front, face, eye, nose, mouth, ear, collarbone, shoulder, solar_plexus, elbow, wrist, hand, hand_left, hand_right, abdomen, hip_joint, knee, ankle, foot.},
    url={https://github.com/PINTO0309/PINTO_model_zoo/tree/main/472_DEIMv2-Wholebody34},
    year={2025},
    month={10},
    doi={10.5281/zenodo.17625710}
  }

• https://github.com/PINTO0309/bbalg: MIT License