Reported on Discord by Netti93: with Tidal configured for "HiRes only"
and "Allow Quality Fallback" disabled, tracks were still downloading
successfully — as m4a 320kbps files. Some "successful" downloads were
less than half the file size of the same track pulled via Tidarr/tiddl
from the same Tidal account.
Root cause: Tidal's API silently degrades to the best quality your
account + the track + your region permits. Setting
`session.audio_quality = Quality.hi_res_lossless` and calling
`track.get_stream()` on a track that's only available in AAC returns
an AAC stream with no error. The downloader wrote the m4a file to
disk, the ~7MB size sailed past the 100KB stub threshold, and the
download reported success.
The pre-existing "verify quality wasn't silently downgraded" block
only LOGGED a warning when this happened; it did not fail the tier.
Two knock-on effects:
- Users with "HiRes only, no fallback" got m4a files anyway, which
defeats the setting entirely.
- The worker-level fallback chain (hires → lossless → high → low)
couldn't advance past the first tier, because every tier
"succeeded" at whatever Tidal happened to serve.
Fix: after `track.get_stream()`, compare `stream.audio_quality`
against the tier we asked for using a rank-based ordering:
LOW < HIGH < LOSSLESS < HI_RES < HI_RES_LOSSLESS
- Same tier or higher → accept (so the occasional Tidal upgrade
doesn't get rejected just because it's not an exact match).
- Lower tier → reject THIS tier. The loop `continue`s and the next
fallback tier is tried, or the whole download fails honestly
when the user has fallback disabled. The existing final-error
log already has a hint directing users to enable fallback if
they want automatic Lossless substitution.
- Unrecognized `audioQuality` value (e.g. a new Tidal tier we
haven't mapped) → reject conservatively, so the next fallback
tier gets a chance and the diagnostic log names the unknown
value.
Why the rank-based approach instead of strict equality:
Tidal's API doesn't technically promise an exact-tier match on
serving; on tracks that are flagged in its catalog as a higher
tier, it can serve higher than the session setting. Rejecting
higher-than-asked quality would be user-hostile. And the `HI_RES`
(legacy MQA) value — not in tidalapi's modern `Quality` enum but
possibly still present on old catalog entries — needs to rank
below `HI_RES_LOSSLESS`: users asking for true lossless HiRes
should reject MQA since MQA is a lossy format.
tidalapi's `Quality` enum is a `str` subclass whose VALUES (not
member names) match what the Tidal API returns in the
`audioQuality` field (e.g. `Quality.hi_res_lossless.value ==
'HI_RES_LOSSLESS'`, `Quality.low_320k.value == 'HIGH'`). Both
sides of the comparison are coerced to `str` before use, so the
check is robust to whichever tidalapi version exposes the served
quality as an enum or a plain string.
The check is extracted as `_verify_stream_tier(stream, q_info,
q_key) -> (ok, reason)` at module scope — a pure function with no
I/O, unit-tested independently. Ten tests: match, three upgrade
cases (LOSSLESS → HI_RES_LOSSLESS, LOSSLESS → HI_RES, LOW → any
higher), three downgrade cases (the reported HiRes → AAC, HiRes
Lossless → MQA HiRes, Lossless → AAC), one unrecognized-tier case,
and two defensive paths for older tidalapi builds without
`audio_quality` on the stream object and for QUALITY_MAP entries
that lack `tidal_quality` (e.g. tidalapi wasn't importable at
module load). Test stub updated to use uppercase `Quality` values
matching real tidalapi so case-sensitivity regressions get caught.
Also removed the old codec-string-based warning block — the new
tier check is strictly stronger, and keeping the warning around
would just be dead code waiting to drift out of sync.
Deliberately NOT tackling in this PR (documented as follow-ups):
- Bit-depth verification of HiRes FLAC files via mutagen. The
`stream.audio_quality` tier check catches the main "HiRes
requested, got AAC" case; bit-depth would only matter if Tidal
labeled a stream HI_RES_LOSSLESS but served a 16-bit FLAC
(`Stream.bit_depth` isn't reliable for this — tidalapi defaults
missing `bitDepth` fields to 16, so a trust-the-stream check
would spuriously reject valid HiRes whenever Tidal omits the
field). A proper fix runs mutagen post-download to inspect the
actual file, then decides whether to delete + retry the next
tier — a whole new failure mode with design trade-offs that
deserve their own PR. The support logs don't show this
happening.
- The "manual remap still says Not Found" symptom. Might be
downstream of this same bug (silent-AAC "success" hitting a
later rejection), might be a separate task-state issue. Not
guessing without logs from the retry path.
- Quality-aware stub threshold. 100KB is a reasonable floor for
real stub/preview detection and there's no evidence the
universal threshold is misfiring in the wild.
Field-verified status: desk-verified via unit tests and empirical
checks against a live tidalapi import (confirming the `Quality`
enum's str-subclass behavior). Not yet smoke-tested end-to-end
against a real Tidal account with a HiRes-only-no-fallback
setting — Netti93 or anyone else with that config should notice
either the fix working (non-HiRes tracks fail honestly with a
clear log line) or any regression before wider release.
Files:
- core/tidal_download_client.py — new `_verify_stream_tier` helper
and `_QUALITY_RANK` table at module scope, called in the
download loop after the stream is fetched and before any
bandwidth is spent. Removed the old inline codec-based warning
since the new check supersedes it.
- tests/test_tidal_stream_tier_verification.py — ten tests covering
match / upgrade / downgrade / unknown / defensive paths.
- tests/test_tidal_search_shortening.py — fake `Quality` values
brought in line with tidalapi's real values so both files share
a consistent stub regardless of pytest collection order.
- webui/static/helper.js — WHATS_NEW entry under 2.40 describing
the rank-based tier comparison.
Reported on Discord by Netti93 — the "same account works via
Tidarr" comparison narrowed the cause to SoulSync's download path
rather than an account/region issue.
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