A faithful decoder can still be the slower pipeline

Two different questions

The complete community 6-bit MLX route had a 1.359-second warm median and RTF 0.225. The ordinary CoreML/ONNX Python adapter measured 4.974 seconds and RTF 0.749. Their payloads were 0.524 and 3.331 GiB respectively, with process RSS peaks of 1.181 and 4.963 GiB.

The diagnostic did not rank the application

In a separate controlled-noise experiment, the alternative decoder stayed much closer to the original waveform: log-mel difference around 0.141 dB versus 1.308, and waveform cosine 0.997428 versus 0.795194. That diagnostic altered randomness in four outputs; it is not a shipping whole-pipeline result.

Complete-generation voice cosine was nearly tied around 0.966 and 0.965. Small ASR counts, an imperfect evaluator and three sentences cannot settle perceived quality.

What comes next

Keep MLX for the tested speed requirement, then test the proposed decoder swap directly. Published headline speedups on another machine and another token budget cannot be compared as if they measured this workload.

Evidence and publication boundary

This is an edited account of the recorded experiment. The linked archive is private; the methods, aggregate findings and limits are included above. Reference recordings, raw conversations, authentication material and workstation configuration are excluded.

• Source record 1