Parakeet CTC 1.1B
May 11, 2026 · View on GitHub
NVIDIA's nvidia/parakeet-ctc-1.1b
ported to transcribe.cpp. A 1.1B-parameter FastConformer-XL encoder with a
linear CTC head.
What it's for
Offline English speech-to-text with greedy CTC decoding. Output is lowercase, no punctuation (the upstream model card explicitly notes "lower case English alphabet"). Token- and word-level timestamps are available. Not a streaming model; does not translate.
This is the largest pure-CTC variant in the parakeet family and trades size for accuracy. NVIDIA reports a 0.04 percentage-point improvement on LibriSpeech test-clean over the 0.6B sibling.
See NVIDIA's model card for training data, intended use, and upstream evaluation methodology.
Licensed CC-BY-4.0. Ported from upstream commit
a707e81,
pinned 2026-05-10.
Download
| Quantization | Download | Size | WER (LibriSpeech test-clean) |
|---|---|---|---|
| F32 | parakeet-ctc-1.1b-F32.gguf | 4.25 GB | 1.85% |
| F16 | parakeet-ctc-1.1b-F16.gguf | 2.13 GB | 1.85% |
| Q8_0 | parakeet-ctc-1.1b-Q8_0.gguf | 1.26 GB | 1.85% |
| Q6_K | parakeet-ctc-1.1b-Q6_K.gguf | 1.04 GB | 1.85% |
| Q5_K_M | parakeet-ctc-1.1b-Q5_K_M.gguf | 929 MB | 1.84% |
| Q4_K_M | parakeet-ctc-1.1b-Q4_K_M.gguf | 818 MB | 1.90% |
WER is measured on the full LibriSpeech test-clean split (2620 utterances) with greedy CTC decoding and no external LM. F32 reference baseline: 1.85%. NVIDIA's self-reported number on the same split is 1.83% (from the HF model card).
Quick Start
cmake -B build
cmake --build build
build/bin/transcribe-cli \
-m models/parakeet-ctc-1.1b/parakeet-ctc-1.1b-Q8_0.gguf \
samples/jfk.wav
If your audio is not already 16 kHz mono WAV, convert it first:
ffmpeg -i input.mp3 -ar 16000 -ac 1 output.wav
Performance
Cells are wall-clock latency (mean over 3 iterations after 1 warmup),
with speedup over realtime in parentheses. Units: ms below 1 s, s
above (2 decimal places). Cells gated on Tctl < 55°C per backend.
Apple M4 Max
| Backend | Sample | Q8_0 | Q4_K_M |
|---|---|---|---|
| Metal | jfk (11.0s) | 91 ms (121×) | 93 ms (118×) |
| Metal | dots (35.3s) | 224 ms (158×) | 224 ms (158×) |
| CPU | jfk (11.0s) | 602 ms (18×) | 501 ms (22×) |
| CPU | dots (35.3s) | 2.04 s (17×) | 1.70 s (21×) |
macOS 26.4.1, transcribe.cpp a6c097e.
AMD Ryzen 7 4750U Pro
| Backend | Sample | Q8_0 | Q4_K_M |
|---|---|---|---|
| Vulkan | jfk (11.0s) | 825 ms (13×) | 822 ms (13×) |
| Vulkan | dots (35.3s) | 2.34 s (15×) | 2.33 s (15×) |
| CPU | jfk (11.0s) | 1.75 s (6×) | 1.38 s (8×) |
| CPU | dots (35.3s) | 6.08 s (6×) | 5.12 s (7×) |
Fedora 43, transcribe.cpp 57997dc. Vulkan device: AMD Radeon Graphics (RADV RENOIR).
Benchmark reproduction:
uv run scripts/bench/run.py \
--models parakeet-ctc-1.1b \
--quants q8_0,q4_k_m \
--samples jfk,dots \
--backends metal,cpu,vulkan \
--iters 3 --warmup 1 \
--name parakeet-ctc-1.1b-publication
Numerical Validation
transcribe.cpp is validated tensor-by-tensor against NeMo on samples/jfk.wav
via scripts/validate.py, sharing the parakeet family tolerance file. The
family-level forward map at
reports/porting/parakeet/forward-map.md
documents the per-stage divergence sources (fp64 STFT, mel amplification,
attenuation through the encoder).
| Field | Value |
|---|---|
| Reference | NeMo, nvidia/parakeet-ctc-1.1b |
| Dump script | scripts/dump_reference_parakeet_nemo.py |
| Manifest | tests/golden/parakeet/parakeet-ctc-1.1b.manifest.json |
| Command | uv run scripts/validate.py all --family parakeet --variant parakeet-ctc-1.1b |
Reproduction
Convert
uv run --project scripts/envs/parakeet \
scripts/convert-parakeet.py nvidia/parakeet-ctc-1.1b
Quantize
build/bin/transcribe-quantize \
models/parakeet-ctc-1.1b/parakeet-ctc-1.1b-F32.gguf \
models/parakeet-ctc-1.1b/parakeet-ctc-1.1b-Q8_0.gguf \
--quant Q8_0
Validate
uv run scripts/validate.py all --family parakeet --variant parakeet-ctc-1.1b