Four fixes from the second review, plus one bug they made visible.
isPCM16Wav tested only the bit depth, and go-audio's IsValidFile never looks at
the format tag, so a 16-bit WAVE_FORMAT_EXTENSIBLE (0xFFFE) upload was passed
through untouched where the old fold would have transcoded it. audio.cpp's WAV
reader accepts 16-bit only when the tag is 1, so such a file died with
"unsupported WAV encoding". Extensible is what many DAWs and Windows tools
write and music files are this endpoint's new headline input, so it is a
first-contact failure rather than a corner. The check now requires tag 1, with a
spec that fails against the old implementation.
Stem URLs are percent-escaped. A stem name is the model's own string and legally
contains a space, a '#', a '?' or a '%'; an unescaped '#' truncates the URL
before the request is even sent. The name field keeps the raw name.
sample_rate and response_format are applied to the stems as well as to dst.
Applying beat documenting: dst IS one of those stems, so leaving them alone
broke the "dst duplicates the selected stem" invariant the whole design rests
on, and both conversions are no-ops when unset. A stem whose conversion fails is
dropped from the header rather than advertised in the wrong shape.
Verifying that turned up why it had never been noticed: the two fields were
never bound at all. The request arrives as multipart/form-data and echo's binder
falls back to the FIELD NAME without a form tag, matching only
case-insensitively, so "SampleRate" never matched "sample_rate" and "Format"
never matched "response_format". Both were documented in the endpoint table and
silently ignored. Two form tags fix it, and with them the conversion is
observable end to end.
Docs: audio-transform.md now documents what LocalAI does to an upload before the
backend sees it, which backend gets the 16 kHz mono fold and why, params[stem],
and the X-Audio-Stems header with a worked example.
Also records the known limitation that the fold lookup is on the bare backend
name, so pinned variants (vulkan-localvqe) do not match, and points at
IsLlamaCppBackend as the suffix-tolerant precedent.
Assisted-by: Claude:claude-opus-5 [Claude Code]
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
b93e7bdfb3