Making MOSS fit: the codec and the chunk budget

The HQ4 generator occupied about 6.24 GiB and the codec about 3.31 GiB. A one-shot path reached roughly 13 GiB and ran out of memory; 0.8-second streaming chunks kept the resident stack near 9.55 GiB on the 12 GB RTX 3060.

Fitting the complete pipeline

Moving the final stage

For native-voice inputs of 45, 143 and 193 characters, wall time changed from 35.4/40.8/51.0 seconds to 26.4/32.4/37.7. The three-sentence case changed from 53.9 to 38.0. Codec decode fell from 10.3–18.6 seconds to 2.6–3.9.

Native waveform correlations ranged from about 0.9965 to 0.99993. The female-reference path also changed encoding and had a much lower correlation, so it cannot inherit the native-voice fidelity result.

The boundary that mattered

A 256-step ceiling needs a text budget. A 231-character fragment truncated at the ceiling; punctuation-aware chunks around a 200-character budget finished. FlashAttention2 was slower in the tested setup, around 241 ms per step versus 177 with SDPA, and changed the take. SDPA remained the qualified choice.

The useful outcome is a fitting pipeline with an explicit input limit. A smaller chunk is an acceptance rule, not just a speed preference.

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.