Index-Echo-S2ST-9B-FP4 released as NVFP4 quantized speech translation model

IndexTeam released Index-Echo-S2ST-9B-FP4, an NVFP4 (W4A4) quantization of the Index-Echo-S2ST-9B speech-to-speech translation model, with only its text LLM backbone quantized. Perplexity rose from 3.8218 to 3.9650 (+3.75%) on a fixed corpus, while zh→en and en→zh outputs were semantically equivalent, and full FP4 speedup requires an NVIDIA Blackwell GPU.