Gloss-Based Pipeline for Spoken to Signed Language Translation

a text-to-gloss-to-pose-to-video pipeline for spoken to signed language translation.

• Demos available for:

  • 🇩🇪 Swiss German Sign Language 🇨🇭
  • 🇫🇷 French Sign Language of Switzerland🇨🇭
  • 🇮🇹 Italian Sign Language of Switzerland 🇨🇭

• Paper available on arxiv, presented at AT4SSL 2023.

Install

pip install spoken-to-signed

Then, to download a lexicon, run:

download_lexicon \
  --name <signsuisse> \
  --directory <path_to_directory>

Usage

For language codes, we use the IANA Language Subtag Registry. Our pipeline provides multiple scripts.

To quickly demo it using a dummy lexicon, either open it in Colab:

or run it locally with some installation steps first:

git clone https://github.com/ZurichNLP/spoken-to-signed-translation
cd spoken-to-signed-translation

pip install .

text_to_gloss_to_pose \
  --text "Kleine Kinder essen Pizza in Zürich." \
  --glosser "simple" \
  --lexicon "assets/dummy_lexicon" \
  --spoken-language "de" \
  --signed-language "sgg" \
  --pose "quick_test.pose"

Text-to-Gloss Translation

This script translates input text into gloss notation.

text_to_gloss \
  --text <input_text> \
  --glosser <simple|spacylemma|rules|nmt> \
  --spoken-language <de|fr|it> \
  --signed-language <sgg|ssr|slf>

Text-to-Gloss-to-Pose Translation

This script translates input text into gloss notation, then converts the glosses into a pose file.

text_to_gloss_to_pose \
  --text <input_text> \
  --glosser <simple|spacylemma|rules|nmt> \
  --lexicon <path_to_directory> \
  --spoken-language <de|fr|it> \
  --signed-language <sgg|ssr|slf> \
  --pose <output_pose_file_path>.pose

Words missing from the lexicon are fingerspelled letter-by-letter by default; pass --disable-fingerspelling to skip them instead.

Add --coverage-info to print how each token was matched, color-coded in the terminal (green: lexicon, yellow: language backup, orange: fingerspelling, red: unmatched), or --coverage-stats <file.json> to save the same per-token information as JSON.

Text-to-Gloss-to-Pose-to-Video Translation

This script translates input text into gloss notation, converts the glosses into a pose file, and then transforms the pose file into a video.

Note: Video generation requires the pose-to-video package with pix2pix and upscaler:

pip install 'pose-to-video[pix2pix,simple_upscaler] @ git+https://github.com/sign-language-processing/pose-to-video'

text_to_gloss_to_pose_to_video \
  --text <input_text> \
  --glosser <simple|spacylemma|rules|nmt> \
  --lexicon <path_to_directory> \
  --spoken-language <de|fr|it> \
  --signed-language <sgg|ssr|slf> \
  --video <output_video_file_path>.mp4

HTTP service

pip install '.[server]'
MODEL_VERSION=local hypercorn spoken_to_signed.server:app --bind 0.0.0.0:8080

POST /senses-to-gloss accepts an unmodified WSD document (including dependency heads and sentence boundaries). English → ASL rules run without an LLM or API key. Set WORDNET_URL to the WordNet API for semantic time-frame ordering.

{
  "spoken_language": "en",
  "signed_language": "ase",
  "senses": {
    "tokens": [
      {"word": "What", "lemma": "what", "pos": "PRON", "dep": "attr", "head": 1},
      {"word": "is", "lemma": "be", "pos": "AUX", "dep": "ROOT", "head": 1},
      {"word": "your", "lemma": "your", "pos": "PRON", "dep": "poss", "head": 3},
      {"word": "name", "lemma": "name", "pos": "NOUN", "dep": "nsubj", "head": 1},
      {"word": "?", "lemma": "?", "pos": "PUNCT", "dep": "punct", "head": 1}
    ],
    "synsets": [],
    "entities": [],
    "sentences": [{"start_token": 0, "end_token": 4}]
  }
}

Returns sentences in your name What ? order and indexes: [[2, 3, 0, 4]], plus an auditable changes list and notes describing conservative fallbacks. Indexes refer to grouped candidates, not raw tokens. Each candidate carries its original inclusive start_token/end_token, exact-span senses/entities, morphology, and source annotations for lookup/fallback. sentence and notes also travel with each candidate so flattening does not erase boundaries or limitations. Unknown words survive for fingerspelling. Standalone punctuation is retained as PUNCT candidates for downstream SignWriting rendering or pose boundaries.

Overlapping spans prefer the widest meaning (earlier on ties); constituent senses are never treated as senses of the whole phrase. No dictionary lookup happens here. WSD sentence boundaries are authoritative; malformed trees/spans return 422. Concrete calendar DATE spans with WSD ent_iob B/I boundaries remain one candidate, even without a Wikidata link. Relative phrases retain their lexical senses and temporal rules. Source tokens retain their text and annotations for date realization; ambiguous date order is not guessed here. Without WORDNET_URL, temporal ordering is skipped with a note. Configured WordNet failures return 503, not a silently different translation. Pin the WordNet deployment alongside this service for reproducibility. TODO: batch API and batch semantic lookups. The service checks the pinned OMW resource at startup. Requests are limited to 2 MiB and 1,024 tokens/annotations. All semantic traversals in a request share a 10-second budget, checked between lookups; an in-flight lookup has a 5-second socket timeout. This bounds ordinary slow-service chains, not adversarial slow-drip responses; WordNet must be a trusted internal service.

The Python entry point is spoken_to_signed.text_to_gloss.senses.senses_to_gloss. Rules produce a lexical plan, not fluent ASL: nonmanuals, spatial grammar and aspect realization remain downstream work. See rules, evidence and evaluation. /tokens-to-gloss and the HTTP glosser selector were removed; existing Python token/GPT APIs remain available for comparisons. Callers must upgrade their WSD schema.

POST /gloss-to-pose accepts already ordered tokens and the same language fields, returning binary application/pose. It uses the existing lookup and concatenation, excluding pos: "PUNCT". Optional: fingerspelling=true, anonymize=false, source (PostgreSQL video-ID prefix). Configure LEXICON_PATH for CSV or DATABASE_URL for PostgreSQL (takes precedence); without either, pose requests return 503. For PostgreSQL, install .[server,postgres,gcs] and use a read-only role. The optional SQLPoseLookup backend migrates the old models captions-table lookup and reads gs://sign-mt-poses; it is not dictionary-api synset lookup. Glosser/health requests need no database. See /docs for the full API schema.

docker build --build-arg MODEL_VERSION=local -t spoken-to-signed .
docker run --rm -p 8080:8080 spoken-to-signed

Releases publish ghcr.io/sign-language-processing/spoken-to-signed-translation:<tag>. The image includes PostgreSQL/GCS dependencies. PORT defaults to 8080; Hypercorn supports HTTP/1.1 and HTTP/2 (h2c). Configure HTTP/2 upstream in the gateway too. /health returns version; successful API responses include X-Model-Tag, set by MODEL_VERSION (baked into release images), with a suffix identifying the configured WordNet URL or offline mode. Changing WordNet resources at the same URL requires a new MODEL_VERSION to invalidate downstream caches. Deploy internally; auth and caching belong to the gateway. Caller routing and the old caption-maintenance job still need migrating before retiring the function in models.

Methodology

The pipeline consists of three main components:

1. Text-to-Gloss Translation

   Transforms the input (spoken language) text into a sequence of glosses.

• Simple lemmatizer,
• Spacy lemmatizer: more accurate, but slower lemmatization, covering fewer languages than simple,
• Rule-based word reordering and dropping component and
• Neural machine translation system.

2. Gloss-to-Pose Conversion

• Lookup: Uses a lexicon of signed languages to convert the sequence of glosses into a sequence of poses.
• Pose Concatenation: The poses are then cropped, concatenated, and smoothed, creating a pose representation for the input sentence.

3. Pose-to-Video Generation

   Transforms the processed pose video back into a synthesized video using an image translation model.

Supported Languages

Online Playgrounds

We have two available:

• sign.mt is a web interface of a translation system.
• research.sign.mt is an overview of sign language processing literature.

Citation

If you find this work useful, please cite our paper:

@inproceedings{moryossef2023baseline,
  title={An Open-Source Gloss-Based Baseline for Spoken to Signed Language Translation},
  author={Moryossef, Amit and M{\"u}ller, Mathias and G{\"o}hring, Anne and Jiang, Zifan and Goldberg, Yoav and Ebling, Sarah},
  booktitle={2nd International Workshop on Automatic Translation for Signed and Spoken Languages (AT4SSL)},
  year={2023},
  month={June},
  url={https://github.com/ZurichNLP/spoken-to-signed-translation},
  note={Available at: \url{https://arxiv.org/abs/2305.17714}}
}