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Step 7.5b4a: player volume (Spotify app slider), applied after the ring

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- player: volume 0..100 %, amplitude = (v/100)^3 (about -18 dB at 50 %,
  0 = mute), applied in the TX pull callback after the ring so a change
  is heard at once (the ring holds 4 s); ramped over one packet to avoid
  zipper noise. Spotify VOLUME events (0..65535) set it.
- Docs: pipeline order ring -> volume/gain, curve described.
- Verified from a Mac: RMS followed the slider immediately (100 % about
  -10 dBFS; steps to about -24.5 and -28 dBFS match the cubic curve for
  ~57 % / ~50 %); user: "sounds about right". Mute at 0 % not yet
  confirmed (check via /api/player/volume later).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
Ben Nicholson
2026-09-25 18:52:57 +10:00
parent 4a38254660
commit cd747aec40
2 changed files with 40 additions and 3 deletions
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docs/hardware-and-design-notes.md
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@@ -17,7 +17,8 @@ Core AES67 parts (PTP, TX, SDP/SAP, network/VLAN, syslog, web UI base, config sc
- Sources: Waveshare wiki (waveshare.com/wiki/ESP32-P4-ETH), ESPHome device page (devices.esphome.io/devices/waveshare-esp32-p4-eth), espp board docs (esp-cpp.github.io/espp/dev_boards/waveshare/esp32_p4_eth.html).
## Project pipeline
source (cspot Spotify Connect | HLS player) -> decode (Vorbis/AAC/MP3) -> SRC 44.1k->48k -> volume/gain -> PSRAM ring buffer -> aes67_tx pull callback
source (cspot Spotify Connect | HLS player) -> decode (Vorbis/AAC/MP3) -> SRC 44.1k->48k -> PSRAM ring buffer -> volume/gain -> aes67_tx pull callback
- Volume is applied after the ring (in the pull callback) so a change is heard at once, not one ring length (4 s) later; ramped over one packet to avoid zipper noise. Curve: amplitude = (volume/100)^3 (about -18 dB at 50 %, 0 = mute). The built-in test tone (mode "tone") is not affected.
- Spotify Connect: cspot (feelfreelinux/cspot), needs Premium, zeroconf via mDNS (on the internet interface when VLAN split). Spotify occasionally changes auth for 3rd-party clients — expect breakage risk.
- HLS: HTTPS (mbedTLS), m3u8 parse (master->media playlist), segment fetch, TS demux or fMP4/ADTS, AAC decode (esp_audio_codec / esp-gmf).
- Stereo L24/48k at 1 ms is about 3 Mbit/s on the wire; 100 Mb has plenty of headroom.