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Peter's report: the phone runs hot, uses a lot of battery, playback takes a
moment to start, and intelligent skipping has never done anything.
**The hot phone and the dead detection were one bug.** The candidate search
correlated 117 window positions against the whole of the other clip,
re-transforming that unchanged clip every time -- 199 seconds per episode end,
measured on a desktop, so minutes more on a phone. FingerprintWorker is a plain
WorkManager worker, Android stops one at ten minutes, and nothing was persisted
until a comparison returned. So it was killed mid-flight, saved nothing, and was
re-enqueued to start over, forever. IntroOutroDetectorScaleTest is the tripwire
whose absence allowed this: the unit tests ran on 300-sample clips while
production ran on 1,920,000.
Fixed coarse-to-fine, plus AudioCorrelation.prepareTarget so the target clip is
transformed once per search rather than 117 times. 10.6x, and a test asserts the
chosen reference window is byte-identical to what a full-resolution search picks.
**Midroll detection could never have run at all.** decodeFull buffered a whole
episode at its native rate -- 434MB for a 13-minute episode, no largeHeap -- to
produce 6MB of 8kHz mono. It threw OutOfMemoryError into a swallowing
runCatching and the episode was then marked checked forever. MonoResampler now
streams the decode so the peak allocation is the output, and maxDecodableMs skips
a longer episode before spending anything and without marking it checked.
**Detection is moving to a server**, Peter's call, in Go to match podkit and
doot. server/ holds the ported core, verified three ways because this is the
second port of this maths and the first shipped a normalization bug: numpy's
literals extracted mechanically from AudioCorrelationTest, the FFT against a
direct DFT, and the whole correlation path against a brute-force Pearson.
On four real Radiolab episodes it confirms the intro on 4 of 4, at 48.0s, 8.65s,
8.65s and 65.15s -- the varying pre-roll, observed in working code at last.
skips.SelfCheck verifies located segments against *each other* rather than
against the reference, which is a different claim: correlation is not transitive,
so two segments can each clear 0.6 against a reference and be unrelated. It
rejected the outro on its first real run (r=0.746), withholding offsets that
would have ended three episodes early. Offsets are published only when they
verify.
Also: the episode screen gets a working scrubber with ad-break marks and a
declared-versus-measured length readout, queue rows open the episode instead of
doing nothing, PrepareTrace logs playback-start timing against episode length
for the still-open pause question, and -PphoneOnly drops the emulator's CPython
from a sideload build (114MB -> 99MB).
Full history and numbers in docs/detection-findings.md.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018AwnALZL6bD4VBtATDVv3B
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Peter asked how expensive it would be to check before dropping them. Checking
turned out to be cheaper than arguing about it, so here is the answer from his
own 61 subscriptions rather than from general knowledge.
Every feed's newest episode was fetched far enough to read its entire ID3 tag
-- the declared size from the header, not a guessed window, which matters
because several are multi-megabyte (Cruising the Waves carries 10MB of cover
art) and a first pass with a 400KB window left thirteen of them inconclusive.
ID3v2.2's 3-byte frame headers needed handling separately from v2.3/2.4's
4-byte ones, which is what made Dan Carlin's feeds look truncated at first.
Not one of the 61 carries a CHAP frame. The frames present are all artwork and
metadata: APIC, TALB, TIT2 and friends. Exactly one show publishes chapters at
all -- Wards Way Podcast -- and it does so as Podcasting 2.0 JSON, which has
been supported since the skip work landed.
So CHAP is dropped rather than deferred. The two survey scripts are kept under
tools/ so this can be rerun in a minute if a new subscription ever suggests
otherwise, rather than re-derived.
Two things fell out of the survey worth writing down. A feed can carry two
chapters elements per item -- the podcastindex one with a url and a podlove one
without; Buzzsprout emits both. The parser takes the first non-null url so it
is unaffected, but a last-wins read would silently lose chapters. And the one
show with chapters marks none of them toc:false, so ad-chapter skipping -- on
by default as of this morning -- currently has nothing to act on anywhere in
the library. It is correct and idle, waiting for a publisher who marks breaks.
Documentation and tooling only; no behaviour change.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018AwnALZL6bD4VBtATDVv3B
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