Adds a streaming multi-segment pipeline on top of the Hexagon talker + ONNX
CP backend. First audio arrives at ~20s (vs ~65s for the full phrase
non-streamed) on the Baer 16.56s reference (3-segment split). Voice cloning
is preserved per segment because each segment now ships its own full prefill.
Changes:
* Qwen3TtsEngine.generateFromEmbedsHexagonStreaming(path, onSegmentReady)
reads single- or multi-segment embeds, runs prefill + generation + VQ
decode + BigVGAN per segment, and fires the callback with each
segment's ShortArray the moment it's ready. Saves per-segment WAVs
(kazeia_stream_seg{N}.wav) plus the concatenated kazeia_stream_full.wav
for offline inspection. Extracted the common generation loop into
runHexSegmentFromEmbeds(prefill, trailing, idx) so single-segment and
streaming paths share exactly the same code (no quality drift between
modes). Added hexReset() between segments so segment 2's prefill logits
don't contain segment 1's KV state.
* vqDecode buffer overrun fix: when the talker samples CODEC_EOS as cb0
it stores a vocab id > CODEBOOK_SIZE, which vqDecode then used as a
codebook row index — reading past the 2048-row buffer. The short Baer
probe never hit this; longer phrases do. Clamp any out-of-vocab code
to 0 at allCodebooks build time.
* KazeiaService: new stream_pipeline intent extra wires the callback
to an AudioTrack MODE_STREAM instance, writing each segment's audio as
soon as it comes back. Logs time-to-first-audio.
* prepare_tts_segments.py: the previous version only captured 1-token
decode calls and substituted a generic 9-embed "prefill_base" pulled
from an unrelated single-segment file — dropping the per-segment
xvector conditioning AND the text-encoded embeddings, so Hexagon
produced garbled mixed speech for segments 2..N. Now captures the
multi-token prefill call too (like prepare_tts_voiceclone.py) so each
segment is self-contained.
Limitation (documented, not fixed in this commit): RTF ~4.4 > 1 on the
Snapdragon 8 Elite with current config means each segment takes longer to
generate than it takes to play, so audible gaps between segments remain.
Removing the gaps requires either (a) producer/consumer parallelism across
two coroutines (doesn't help if RTF stays > 1), or (b) faster CP (the
~180ms/step ONNX MLAS CP is the bottleneck; Hexagon HMX has a known NaN bug
and the .pte path contends with Hexagon talker on the DSP).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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