SeamlessStreaming
Meta's massively multilingual streaming translator: near-real-time speech translation across ~100 input languages at around two seconds of latency, open weights included.
About
SeamlessStreaming (December 2023, part of Meta's Seamless Communication suite, paper arXiv 2312.05187) is the streaming sibling of SeamlessM4T v2. It adds simultaneous speech-to-speech and speech-to-text translation on top of the v2 architecture, with the key change being EMMA — Efficient Monotonic Multihead Attention — as the policy that decides, token by token, whether to emit a translation or wait for more audio. Meta's headline numbers: streaming ASR over 96 languages, simultaneous translation from ~101 speech input languages, text output in ~96, speech output in 36, all at roughly two seconds of latency with accuracy close to the offline model. The 2.5B-parameter checkpoint is on Hugging Face with the code, under Meta's CC-BY-NC research license. It is the most language-covering open simultaneous translator available, and the natural open-weight reference point for anything real-time in this space.
Specs
Context window
Pricing
Free quota
API access
Weights
Released
Benchmarks
- ~2s latency at near-offline accuracy across ~100 languages (provider-reported, arXiv 2312.05187)\n- Community evaluations exist but vary by setup; no single canonical independent benchmark
Provider-reported unless a source says otherwise. Benchmarks are marketing-adjacent by nature — treat them as directional.
Use cases
Trust score — 8/10
Scored 8/10 (TIER verified, metrics-v1). Evidence: peer-reviewed paper trail (arXiv 2312.05187), open weights on Hugging Face, actively maintained Meta research repo. Strengths: widest language coverage of any open simultaneous translator (~100 in, 36 speech out), ~2s latency, reproducible. Docked for: (1) CC-BY-NC license blocks commercial use; (2) the 2.5B checkpoint needs a real GPU (small variant trades quality); (3) headline accuracy figures are Meta's own. License: CC-BY-NC 4.0.
How the trust score is built
Full methodology →- Adoption · stars/downloads, log-scaled vs peers
- 8.0/10
- Maintenance · recency, releases, issue load
- 7.0/10
- Openness · license + docs
- 7.0/10
- Manual review · sanity read + red-flag check
- 8.0/10
- · 2.5B params; ~101 speech input languages, 36 speech output, ~2s latency (provider-reported)
- · EMMA simultaneous policy on top of SeamlessM4T v2 (arXiv 2312.05187)
- · Open weights on Hugging Face; CC-BY-NC blocks commercial use
- · 2.5B checkpoint needs a real GPU; small variant trades quality