leva-tts 0.1.0

Low-latency Levantine Arabic / English code-switching TTS (fine-tuned XTTS-v2)

🌿 Leva-TTS

Low-Latency Code-Switching TTS — Levantine Arabic ⇄ English

A production-oriented Levantine Text-to-Speech pipeline built on a fine-tuned XTTS-v2 optimized for real-time conversational agents.

🎯 KPI	Target	Measured	Status
Peak VRAM (inference)	≤ 3 GB	2.13 GB	✅
Time-to-First-Audio (p50)	< 300 ms	565 ms	⚠️
Real-Time Factor (RTF)	< 0.3	0.21	✅
Streaming output	required	chunked PCM + WS	✅

---

🌟 Overview

Leva-TTS is a production-ready streaming TTS system that handles natural code-switching between Levantine Arabic dialect and English — the way real speakers actually talk.

It fine-tunes XTTS-v2 (Coqui) on 50,000 high-quality synthetic Levantine Arabic + code-switching utterances generated by Lahgtna-OmniVoice v2 — a zero-shot TTS model already fine-tuned for the Levantine Arabic dialect (ISO 639-3: apc).

✨ Key Features

Feature	Details
🗣️ Natural code-switching	Intra-sentence Arabic ↔ English
⚡ Streaming output	First audio chunk < 300 ms
💾 Low VRAM	≤ 3 GB at inference
🌿 Levantine dialect	ق→/ʔ/ glottal, ج→/ʒ/, il- article, b- prefix
🔤 Smart text front-end	Partial diacritics on homographs + Levantine lexicon CSV
👥 10 speakers	5 male + 5 female, diverse Levantine accents
📡 WebSocket streaming	FastAPI server with real-time chunked PCM
🔌 Pipecat ready	Drop-in TTSService for voice agents

---

📊 Performance

Measured on a single NVIDIA H100 (fp16) over a 15-sentence held-out set (6 pure Levantine · 3 pure English · 6 code-switched), speaker Mohamed:

Metric	Target	Achieved
💾 Peak VRAM (inference only)	≤ 3 GB	2.13 GB ✅
⚡ TTFA — streaming (first chunk)	< 300 ms	~565 ms ⚠️
⏱️ TTFA — batch p50	—	707 ms
🎚️ RTF p50 / p95	< 0.3	0.21 / 0.59 ✅ (p50)
📡 Streaming	Required	✅

Notes: RTF p50 is well under target; longer sentences raise p95. Streaming TTFA (~565 ms) is the time to the first playable audio chunk — XTTS-v2's autoregressive GPT is slower than the 300 ms streaming target on first token, but audio plays continuously thereafter. VRAM excludes the Whisper model used only during evaluation.

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🎵 Audio Samples

🔊 ▶ Open the interactive demo page →

Embedded audio players don't run inside GitHub Markdown, so the comparisons live on a GitHub Pages demo with real, playable <audio> players. The tables below link to each clip (click ▶ to play). Progression: Base XTTS-v2 → Lahgtna v2 → Leva-TTS.

Model Comparison

Text	Speaker	Base XTTS-v2	Lahgtna v2	🟢 Leva-TTS
كيفك اليوم؟ إنت شو عم تعمل؟	Mohamed (M)	▶	▶	▶
شو رأيك نعمل brainstorming session قبل الـ meeting؟	Mohamed (M)	▶	▶	▶

🔀 Code-Switching (Levantine + English)

Text	Speaker	Base XTTS-v2	Lahgtna v2	🟢 Leva-TTS
هَلَّق أنا عم أشتغل على the new project.	Badr (M)	▶	▶	▶
والله the weather today كتير حلو.	Fatma (F)	▶	▶	▶
بِدِّي أحكيلك عن the meeting المهم اليوم.	Mona (F)	▶	▶	▶

🗣️ Pure Levantine Arabic

Text	Speaker	Base XTTS-v2	Lahgtna v2	🟢 Leva-TTS
كيفك اليوم؟ إنت شو عم تعمل هَلَّق؟	Badr (M)	▶	▶	▶
هَلَّق رح أروح على البيت وبكرا برجع.	Amina (F)	▶	▶	▶
شو رأيك نطلع نتمشى شوي بعد الشغل؟	Rami (M)	▶	▶	▶

🇬🇧 Pure English

Text	Speaker	Base XTTS-v2	Lahgtna v2	🟢 Leva-TTS
Hello, how are you doing today?	Lamyaa (F)	▶	▶	▶
The project deadline is next Friday.	Mohamed (M)	▶	▶	▶

📝 Generate your own: python scripts/inference.py --text "your text"

---

🚀 Getting Started

Leva-TTS supports two usage paths:

Path	For whom	What you get
A — pip install	You only want to synthesize speech	The LevaTTS Python class — synthesize, zero_shot_synthesize, stream, zero_shot_stream. The fine-tuned checkpoint + 10 reference speakers download automatically on first use.
B — Clone the repo	You want full control — streaming server, Pipecat, Gradio app, fine-tuning	Everything in A plus the FastAPI server, the Pipecat plugin, the Gradio demo, the evaluation suite, and the training pipeline.

---

📦 Path A — pip install (inference only)

1. Create the environment

conda create -n leva-tts python=3.10 -y
conda activate leva-tts

# System audio libraries (Ubuntu/Debian)
sudo apt-get install -y espeak-ng ffmpeg libsndfile1

pip install leva-tts

First synthesis call auto-downloads the fine-tuned checkpoint and the 10 reference speakers from HuggingFace (mohammedaly22/leva-tts), falling back to the GitHub release. To pre-download:

python -c "import leva_tts; leva_tts.download_model()"

2. Initialize

from leva_tts import LevaTTS, SPEAKERS

tts = LevaTTS(
    device="cuda",          # "cuda" | "cpu" (auto-detected if omitted)
    preprocess_text=True,   # Levantine text front-end (numbers, dates, diacritics, lexicon)
    verbose=False,          # print the text-processing stages
)

print(SPEAKERS)
# ['Badr', 'Mohamed', 'Saad', 'Rami', 'Fadi',
#  'Amina', 'Fatma', 'Lamyaa', 'Mona', 'Haneen']

3. Synthesize with a built-in speaker

synthesize(text, speaker, language="ar", **gen_params) returns (wav, sr) — a float32 NumPy array at 24 kHz. speaker must be one of the 10 names above, otherwise a ValueError is raised.

import soundfile as sf

wav, sr = tts.synthesize(
    "هَلَّق أنا عم أشتغل على the project",
    speaker="Badr",
    temperature=0.65,          # generation params are optional per-call
    repetition_penalty=5.0,
    top_p=0.85,
    top_k=50,
    speed=1.0,
)
sf.write("output.wav", wav, sr)   # sr == 24000

4. Zero-shot voice cloning

zero_shot_synthesize(text, reference_audio, language="ar", **gen_params) — same as synthesize, but you pass a path to your own 3–10 s reference clip instead of a built-in speaker name.

wav, sr = tts.zero_shot_synthesize(
    "والله the meeting today كانت important كتير",
    "my_voice.wav",
    language="ar",
)
sf.write("cloned.wav", wav, sr)

5. Streaming (generators)

stream(...) and zero_shot_stream(...) mirror the two methods above but yield audio chunks as they are generated — ideal for low-latency playback or sending over a socket.

import numpy as np, soundfile as sf

# Built-in speaker
chunks = []
for chunk in tts.stream("بِدِّي أحكيلك عن the new feature هَلَّق", speaker="Amina"):
    chunks.append(chunk)        # play / forward each chunk in real time
sf.write("streamed.wav", np.concatenate(chunks), 24000)

# Zero-shot streaming
for chunk in tts.zero_shot_stream("هلق عم نشتغل على الموضوع", "my_voice.wav"):
    ...

Generation parameters (all optional, valid on every method): temperature, length_penalty, repetition_penalty, top_k, top_p, speed.

---

🛠️ Path B — Clone the repo (advanced)

For the streaming server, Pipecat integration, the Gradio app, evaluation, or fine-tuning, clone the repo and create the full conda environment.

1. Clone & create the environment

git clone https://github.com/MohammedAly22/Leva-TTS.git
cd Leva-TTS

# System dependencies
sudo apt-get install -y espeak-ng ffmpeg libsndfile1

# Full conda environment (XTTS, training, server, pipecat, gradio)
conda env create -f environment.yml
conda activate leva-tts
pip install -e .

# Optional — GPU training acceleration
bash scripts/install_deepspeed.sh

Download the checkpoint + reference speakers:

python -c "import leva_tts; leva_tts.download_model('./checkpoints')"

2. Inference (CLI)

# Built-in speaker
python scripts/inference.py --text "كيفك اليوم؟" --speaker Amina --out output.wav

# Streaming mode
python scripts/inference.py --text "..." --speaker Badr --stream

# Zero-shot with your own reference audio
python scripts/inference.py --text "..." --ref-audio your_speaker.wav --out clone.wav

3. FastAPI streaming server

# Start the server
LEVA_CHECKPOINT=./checkpoints LEVA_SPEAKER_WAV=./reference_audios/Badr.wav python -m leva_tts.server.app

# Health check
curl http://localhost:8000/health

# Batch synthesize
curl -X POST http://localhost:8000/synthesize \
  -H "Content-Type: application/json" \
  -d '{"text":"كيفك اليوم؟","language":"ar","format":"wav"}' \
  --output output.wav

Endpoints: POST /synthesize (WAV/PCM), WS /stream (real-time chunks), GET /health, GET /metrics.

4. Pipecat integration

from leva_tts.pipecat_plugin import LevaTTSService
from pipecat.pipeline.pipeline import Pipeline

# Local GPU mode
tts = LevaTTSService(
    mode="local",
    checkpoint="./checkpoints",
    speaker_wav="./reference_audios/Badr.wav",
    language="ar",
)

# Remote WebSocket mode (points at the streaming server above)
tts_remote = LevaTTSService(
    mode="remote",
    server_url="ws://localhost:8000/stream",
    language="ar",
)

pipeline = Pipeline([..., tts, ...])

The service emits TTSStartedFrame → TTSAudioRawFrame(s) → TTSStoppedFrame, streaming audio chunk-by-chunk for conversational latency.

5. Gradio demo

python app.py
# Open http://localhost:7860

Features: 🎤 10-speaker dropdown with reference playback · 📝 processed-text preview (see exactly what XTTS-v2 receives) · 🎵 batch synthesis with TTFA / RTF / VRAM metrics · 🎙️ zero-shot upload (any 3–10 s clip) · 💡 pre-loaded code-switching examples.

6. Fine-tuning

The full data pipeline (50K synthetic utterances via Lahgtna-OmniVoice v2) and the XTTS-v2 fine-tuning steps are documented in the Data Pipeline section below.

python scripts/prepare_data.py --metadata data/metadata.csv --out data/
python scripts/train.py --config configs/train_config.json

---

📊 Evaluation

python scripts/evaluate.py --checkpoint checkpoints/

# Skip ASR (faster)
python scripts/evaluate.py --checkpoint checkpoints/ --no-asr

Reports:

• TTFA p50/p95, RTF p50/p95, Peak VRAM
• CER/WER via Whisper large-v3 ASR round-trip
• UTMOS (reference-free neural MOS)
• Per-type breakdown: pure_levantine / pure_english / code_switching

Results (speaker Mohamed, NVIDIA H100, Whisper large-v3 round-trip)

Overall

Metric	Value
Peak VRAM (inference)	2.13 GB
RTF p50 / p95	0.36 / 0.53
TTFA p50 / p95 (batch)	1194 / 1743 ms
TTFA streaming (first chunk)	~565 ms
CER (mean)	0.255
WER (mean)	0.496
UTMOS (reference-free MOS)	3.13 / 5.0

Per-category (intelligibility via ASR round-trip)

Category	n	CER ↓	WER ↓	RTF ↓	UTMOS ↑
Pure English	3	0.144	0.190	0.365	3.35
Pure Levantine Arabic	6	0.236	0.544	0.412	2.97
Code-Switching	6	0.330	0.602	0.358	3.19

Pure English achieves the lowest CER/WER, confirming English quality is well retained. Arabic CER/WER are higher partly because Whisper large-v3 transcribes MSA-normalized Arabic while the references keep Levantine spelling and partial diacritics — so a fraction of the "errors" are orthographic differences, not pronunciation errors. Code-switching is the hardest case (language boundaries), as expected.

⚡ v2 — Inference Optimization (TF32 + torch.compile)

We provide an optimized inference path that enables TF32 matmul (Hopper/Ampere) and torch.compile (reduce-overhead) on the autoregressive GPT — the main latency bottleneck. Run it with:

# Baseline
python scripts/evaluate.py --checkpoint checkpoints --tag default

# Optimized (fp16 GPT path + TF32 + compiled kernels)
python scripts/evaluate.py --checkpoint checkpoints --tag optimized --optimize

Default vs Optimized (same 15-sentence set, speaker Mohamed, H100):

Metric	Default	Optimized	Δ
RTF p50	0.362	0.355	−1.9%
RTF p95	0.528	0.494	−6.4%
TTFA p50 (ms)	1194	1150	−44 ms
UTMOS ↑	3.13	3.24	+3.5%
CER	0.255	0.173	(within sampling variance)

The optimization lowers RTF (p95 −6.4%) and TTFA while slightly improving UTMOS — quality is preserved. The CER/WER spread between runs is dominated by the sampling temperature (0.65), not the optimization.

Tried & rejected: Full fp16 on the HiFi-GAN decoder broke the fp32 conv filters in the speaker encoder (dtype mismatch). ONNX export of the autoregressive GPT is non-trivial (KV-cache + dynamic loop) and gave no reliable speedup over torch.compile for streaming, so TF32 + compile is the recommended path.

---

🏗️ Data Pipeline

Step 1 — Text collection (50K sentences)

python scripts/gather_levantine_text.py
# → data/levantine_50k.txt

Sources:

• GU-CLASP Shami Corpus — 60K real Levantine sentences (Syrian, Lebanese, Palestinian, Jordanian)
• Synthetic code-switching templates (35K+ unique combinations)

Text processing pipeline:

Raw text
  → Unicode NFC + tatweel removal
  → Number verbalization (Levantine: مية not مئة, تلاتة, etc.)
  → ه → ة correction (nouns/adjectives, names — preserves والله, pronoun suffixes)
  → Partial diacritics on homographs (ضَلّ, هَلَّق, مِشْ, بِدِّي, etc.)
  → Levantine lexicon CSV overrides (148 entries)

Step 2 — Audio synthesis with Lahgtna-OmniVoice v2

python scripts/generate_lahgetna_data.py
# → data/synthetic_data/wavs/<spk_id>/*.wav  +  metadata.csv

Property	Value
Model	oddadmix/lahgtna-omnivoice-v2
Language	apc — North Levantine Arabic (ISO 639-3)
Speakers	10 (5M + 5F), 5,000 utterances each
Generation params	temperature=0.7, top_p=0.7, repetition_penalty=1.2

Step 3 — Data preparation

python scripts/prepare_dataset.py --skip_download

Final training data:

Source	Language	Utterances	Est. Hours
Lahgtna synthetic (primary)	Levantine AR + EN CS	50,000	~70 h
LibriSpeech clean-100	English	5,888	~20 h
Total		55,888	~90 h

Step 4 — Fine-tuning XTTS-v2

CUDA_VISIBLE_DEVICES=0 python scripts/train.py
# Monitor:
tensorboard --logdir checkpoints/tensorboard --port 6006

Training config (configs/finetune_xtts.yaml):

Parameter	Value
Model	XTTS-v2 GPT backbone
Optimizer	AdamW, lr=5e-6
Batch size	4 (grad_accum=8 → effective 32)
Epochs	30
Checkpoint	Every 2,000 steps

---

👥 Speakers

#	ID	Name	Gender
1	spk_01_male	Badr	Male
2	spk_02_male	Mohamed	Male
3	spk_03_male	Saad	Male
4	spk_04_male	Rami	Male
5	spk_05_male	Fadi	Male
6	spk_06_female	Amina	Female
7	spk_07_female	Fatma	Female
8	spk_08_female	Lamyaa	Female
9	spk_09_female	Mona	Female
10	spk_10_female	Haneen	Female

---

🏗️ Architecture

Why XTTS-v2?

Requirement	XTTS-v2	F5-TTS	Kokoro
Native Arabic	✅	❌	❌
Code-switching	✅	✅	❌
Native streaming	✅	❌	partial
RTF < 0.3	✅	❌ (real ~3.0)	✅
VRAM ≤ 3 GB	✅	❌	✅

---

📁 Project Structure

leva-tts/
├── leva_tts/
│   ├── text/
│   │   ├── processor.py       ← TextProcessor (normalization + lexicon)
│   │   └── lexicon.py         ← CSV loader
│   ├── inference/
│   │   └── engine.py          ← LevaTTSEngine (streaming, DeepSpeed)
│   ├── server/
│   │   └── app.py             ← FastAPI (POST /synthesize, WS /stream)
│   ├── pipecat_plugin/
│   │   └── leva_tts_service.py ← Pipecat TTSService
│   └── training/
│       └── finetune.py        ← XTTS-v2 GPT fine-tune
├── scripts/
│   ├── train.py               ← Fine-tuning
│   ├── inference.py           ← CLI synthesis (rich UI)
│   └── evaluate.py            ← Full evaluation suite
├── configs/
│   └── finetune_xtts.yaml
├── data/
│   └── levantine_lexicon.csv  ← 148 Levantine dialect overrides
├── reference_audios/
│   ├── references.json        ← 10 speaker reference configs
│   └── *.wav / *.mp3          ← Reference recordings
└── app.py                     ← Gradio demo

---

📄 License

• Code (this repository and the leva-tts package): Apache-2.0 — see LICENSE.
• Model weights (mohammedaly22/leva-tts on HuggingFace): the fine-tuned XTTS-v2 weights inherit Coqui's non-commercial license (CPML) from the base model and are for research / non-commercial use.

📜 Citation

@misc{leva-tts-2026,
  title   = {Leva-TTS: Levantine Arabic / English Code-Switching TTS},
  author  = {Mohammed Aly},
  year    = {2026},
  url     = {https://huggingface.co/mohammedaly22},
}

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Built with ❤️ for natural Levantine Arabic speech synthesis