Race timer sets DVR filenames to the heat you flew, e.g. hdz_0042-WinterCup-Mains-A-R5-H1.mp4

[bob9]

Summary

Lets a race timer name the next DVR recording (e.g. WinterCup-Mains-A-R5-H1) by sending a new MSP_SET_DVR_NAME (0x030F) message through the ELRS backpack.

• elrs.c handles the new MSP command and hands the payload to dvr_set_race_label().
• dvr.c stores a filename-safe copy of the label (alnum kept, spaces become -, everything else dropped) with a 5-minute TTL so a recording made well after the heat doesn't inherit the race's name; an empty payload clears it. The label is written to the record conf on every update so a stale value never survives.
• The record process (record/) appends -label to the stock filename, just before the extension, for both naming modes — hdz_0042-WinterCup-Mains-A-R5-H1.mp4 (contiguous) or 20260718-141502-WinterCup-Mains-A-R5-H1.mp4 (date). Snapshot .jpg previews and split segments share the name. Because the stock prefix and index position are untouched, the existing contiguous file counter handles labelled names with no changes.

Labels are capped at 43 chars (REC_labelMAXLEN 44) — the worst case (date naming + label + .mp4) is 63 chars, still inside the playback list's 64-char name buffer. Over-long labels are silently truncated at both entry points (MSP payload and record conf), never rejected.

Additive only — recordings without a label are named exactly as before.

Related PRs

• Forward MSP_ELRS_BACKPACK_SET_DVR_NAME to the goggles ExpressLRS/Backpack#232 — companion firmware PR: the VRX backpack forwards MSP_ELRS_BACKPACK_SET_DVR_NAME to the goggles over the serial link, which is what delivers this message.

• Send RTC time from the TX backpack to the VRX backpack over ESP-NOW ExpressLRS/Backpack#231 — syncs the backpack/goggle RTC so the named recordings also carry correct timestamps.

• Automatically sync backpack time from the handset (real timestamps on goggle DVR) + lua memory optimisations ExpressLRS/Lua-Scripts#18 — the ELRS Lua script now seeds that clock automatically whenever it connects to the TX module.

• Let pilots switch between Raceband and Lowband via the ELRS backpack #614 — lets pilots switch between Raceband and Lowband via the backpack; part of the same integration, independent of this PR.

• Send handset time to the TX backpack to set its RTC ExpressLRS/ExpressLRS#3701 — TX-module side of that time sync: forwards the handset time to the backpack.

[bob9]

Pushed a follow-up commit that changes how the label lands in the filename, after trying the first cut at a race meet on paper.

Originally a label switched recordings to a separate YYYY-MM-DD-NNNN-label scheme. That reinvented naming the goggles already do and needed a second index scanner to keep the counter contiguous. Now the label is simply appended to whatever the stock naming produces — hdz_0042-WinterCup-Mains-A-R5-H1.mp4, or the same with a date-naming prefix — so a pilot's card sorts exactly as it always has, labelled and plain recordings interleaved in recording order. The extra scanner is deleted; the diff got 48 lines smaller.

Also raised the label cap from 32 to 43 chars so the race description can carry the meeting name properly. 43 is the exact budget: worst case is date naming (15) + dash + label + .mp4 = 63, one under the playback list's 64-char name buffer. Over-long labels truncate silently at both entry points rather than being rejected.

Description updated to match.