TiBLA-PP-DocLayout-L

Permissive (Apache-2.0) alternative in TiBLA (Tibetan Book Layout Analysis) — a PP-DocLayout-L detector for the page layout of modern Tibetan books (headers, text area, footers, footnotes). It matches the primary RT-DETR-l checkpoint at an Apache-2.0 license.

• Base model / provenance: PP-DocLayout-L (PaddleOCR / PaddleDetection, an RT-DETR-L detector), fine-tuned on the leak-free v4 tam2col split of TiBLAD.
• License: Apache-2.0.
• Dataset: BDRC/TiBLAD
• Paper: buda-base/papers (papers/2026-tibetan-book-layout) — arXiv link forthcoming
• Code: github.com/buda-base/tibla

Task

A 4-class detector — header, text-area, footer, footnote — kept as four classes at training time. Evaluation folds them into a 3-class canonical scheme: header+footer are combined into one header-footer class (matched individually, merged losslessly afterwards), text-area is merged to a single page/column envelope as a post-processing step (two boxes only on genuine two-column pages), and footnote is left as-is. All numbers below are in that canonical space, on the leak-free TiBLAD v4 833-page test set, unified scorer (pycocotools bbox mAP 0.50:0.05:0.95; F1 by greedy IoU≥0.5 at the best-mean-F1 operating point).

Files

• inference/ — the exported PaddlePaddle inference model (inference.pdiparams, inference.yml, inference.json), re-exported for Paddle 3.0.0.
• best_model.pdparams — the trainable fine-tuned weights.
• infer.py — batch inference helper (YOLO-format output).

Inference

# pip install paddlepaddle==3.0.0 paddlex
from paddlex import create_model

model = create_model(model_name="PP-DocLayout-L", model_dir="inference")
for res in model.predict("page.jpg", threshold=0.61):  # recommended global conf
    res.print()          # boxes with label in {header, text-area, footnote, footer}
    res.save_to_img("out/")

A ready-made infer.py (batch, YOLO-format output) is included in this repo. Recommended global operating confidence: 0.61 (the validation-selected best-mean-F1 point).

Evaluation (TiBLAD v4, 833-page test)

metric	TiBLA-RTDETR	TiBLA-PP-DocLayout-L	TiBLA-RFDETR
license	AGPL-3.0	Apache-2.0	Apache-2.0
base model	RT-DETR-l (Ultralytics)	PP-DocLayout-L (PaddleOCR, RT-DETR-L)	RF-DETR-L (Roboflow)
mean F1 (canonical 3-class)	0.952	0.955	0.921
header-footer F1	0.954	0.953	0.947
text-area F1	0.999	0.998	0.996
footnote F1	0.902	0.914	0.821
mean [email protected]	0.974	0.959	0.925
mean AP@[0.50:0.95]	0.786	0.781	0.667
shared-class mAP@[.50:.95] (DocLayNet-aligned)	0.650	0.641	0.604
Hidden Trespass — header/footer	0.009	0.004	0.021
Hidden Trespass — footnote	0.043	0.037	0.178
COTe (Trespass)	0.975 (0.001)	0.978 (0.000)	0.974 (0.002)
operating confidence	0.64	0.61	0.47

"operating confidence" is the single global best-mean-F1 confidence, selected on the leak-free validation split and frozen for test (no test-set tuning). COCO AP rows are threshold-free (all detections above the fixed 0.05 floor).

Hidden Trespass = peripheral (header/footer/footnote) ground-truth area that survives in the actual OCR body crop C = E \ P, where E is the predicted text-area envelope and P is the union of the predicted peripheral boxes the pipeline subtracts; area-based, micro-averaged over the test set. Lower is better (less peripheral text bled into the OCR region). Formal definition in the paper.

Which checkpoint to pick

checkpoint	license	mean F1	shared mAP	footnote HT
TiBLA-RTDETR (primary)	AGPL-3.0	0.952	0.650	0.043
TiBLA-PP-DocLayout-L	Apache-2.0	0.955	0.641	0.037
TiBLA-RFDETR	Apache-2.0	0.921	0.604	0.178

RT-DETR-l leads on mAP, shared-class mAP and the 5-seed mean F1 (0.961 ± 0.009), but its weights are AGPL-3.0 (Ultralytics). If you need a permissive license, PP-DocLayout-L is an Apache-2.0 match (statistically on par on F1); RF-DETR is a lighter PyTorch-native Apache-2.0 option.

Citation

@misc{tibla2026,
  title        = {TiBLA: Tibetan Book Layout Analysis},
  author       = {Buddhist Digital Resource Center (BDRC)},
  year         = {2026},
  howpublished = {\url{https://github.com/buda-base/tibla}},
  note         = {arXiv link forthcoming}
}