Nvidia Parakeet Tdt ASR support

[Nenad Banfic (nenad1002)]

Add Parakeet TDT speech recognition model support
Adds end-to-end support for NVIDIA's Parakeet TDT ASR model in onnxruntime-genai.

Code here will support both v2 (English-only) and v3 (multilingual) model - both CPU and CUDA.

Note: Only for batch inference - can support any length of the audio.

What's included
New model type parakeet_tdt with encoder / decoder / joint ONNX subgraphs wired through Model::Create.

TDT decoding loop in src/models/parakeet.cpp: joint network emits [token_logits | duration_logits]; per-frame argmax over tokens and durations with the standard TDT constraints:
Blank + duration 0 is forbidden (prevents single-frame loop-hang).
max_symbols_per_frame cap forces a one-frame skip if the model wants to stay on a frame indefinitely.
Processor (src/models/parakeet_processor.cpp / .h): full-audio log-mel computed up front via the audio extension op; encoder consumes the mel in chunked fashion.
Config plumbing (src/config.h, src/config.cpp): adds tdt_durations, blank_id, max_symbols_per_frame, etc., matching the genai_config.json

Sample: examples/python/parakeet.py - minimal CLI to transcribe an audio file.
Tests:
C++: test/c_api_tests.cpp - model creation + decode smoke test.
Python: test/python/test_parakeet_tdt.py - end-to-end transcription on jfk.flac (short) and tedlium_long_120s.flac fixture (~2 MB) for long-audio coverage.

Long-audio handling: encoder is run on overlapping up to 10 s chunks with both left and right context (configurable via chunk_samples / left_context_samples / right_context_samples in genai_config.json.
Only the chunk-proper region is decoded; context frames just provide receptive field at boundaries. This keeps per-step latency bounded while supporting arbitrary-length audio alongside with much higher RTFx than for native true streaming models.

The model is multilingual at just 0.6B.
The original model link:
https://huggingface.co/nvidia/parakeet-tdt-0.6b-v3

[Copilot]

Pull request overview

Adds end-to-end support for NVIDIA’s Parakeet TDT ASR model to onnxruntime-genai, integrating it into the existing Model/State/Generator pipeline and exposing a Python example and tests.

Changes:

• Introduces a new parakeet_tdt model type with encoder/decoder/joiner sessions and a TDT decoding loop.
• Adds a Parakeet processor that decodes audio and computes full-utterance normalized log-mel features.
• Extends config parsing to support Parakeet-specific parameters and adds C++/Python E2E tests plus a Python CLI example.

Reviewed changes

Copilot reviewed 15 out of 16 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
test/python/test_parakeet_tdt.py	New Python pytest E2E coverage for Parakeet transcription + optional WER checks.
test/python/test_onnxruntime_genai_e2e.py	Runs Parakeet E2E via the new examples/python/parakeet.py script.
test/python/conftest.py	Adds a pytest fixture for locating the Parakeet TDT test model directory.
test/c_api_tests.cpp	Adds C API smoke tests for model creation and non-empty transcription on sample audios.
src/models/parakeet.h	Declares Parakeet TDT model/state/config structures.
src/models/parakeet.cpp	Implements chunked encoder execution + TDT token/duration decoding and one-hot logits output.
src/models/parakeet_processor.h	Declares a processor to decode audio and produce mel features + SOS input_ids.
src/models/parakeet_processor.cpp	Implements audio decode + Nemo-style mel extraction + per-feature normalization.
src/models/model.h	Wires in Parakeet processor header for multimodal processor creation.
src/models/model.cpp	Registers parakeet_tdt model creation and processor factory mapping.
src/models/model_type.h	Adds ModelType::IsTDT() detection for parakeet_tdt.
src/config.h	Adds Parakeet config fields (durations, context samples, norm eps, decoder IO names).
src/config.cpp	Parses new Parakeet config fields from genai_config.json.
examples/python/parakeet.py	New CLI example to transcribe an audio file with Parakeet TDT.
cmake/deps.txt	Updates the onnxruntime-extensions dependency revision.

[Copilot]

Pull request overview

Copilot reviewed 21 out of 22 changed files in this pull request and generated no new comments.