feat: Auto as the default transport (#112)

[compot-dev]

Closes #112 (the second half; the first half — the transport in use — came with #117).

• A slot that has never stored a transport (new install, a slot filled for the first time) now uses Auto: UDP, falling back to TCP when UDP is refused, brings no video (feat: RTSP over UDP unicast, with fallback to TCP (#67) #70) or brings packets but no decodable frames (fix: Auto falls back to TCP when UDP delivers packets but no frame decodes (#113) #125, Multi-view over UDP (Auto): cells receive but decode nothing on key frames #113). The URL dialog preselects Auto for such a slot.
• Stored choices stay as they are (existing installs keep their TCP/UDP/… per slot); an unknown stored value still means TCP. A shared link without the transport extra keeps the slot's setting, as before.
• Transport.Mode.stored() + unit test; READMEs (EN/RU/ZH): Auto marked as the default in the URL dialog text and in the transport table.

Device check: a fresh slot on Aceline-1 shows Auto in the dialog and plays over UDP (or TCP (auto) after a fallback); existing TCP slots unchanged.

[compot-dev]

/review

[qodo-free-for-open-source-projects]

Code Review by Qodo

🐞 Bugs (0) 📘 Rule violations (0) 📎 Requirement gaps (0) 🎨 UX issues (0) 🔗 Cross-repo conflicts (0) 📜 Skill insights (0)

1. New single-view slots can stay black ✓ Resolved

Description

RtspSession.receiveUdp() stops waiting for video when RtspClient.processVideo() accepts a
well-formed RTP packet, even if NalAssembler has not emitted a complete key frame. If UDP
repeatedly loses pieces of key frames while other video packets keep arriving, neither the
first-video timeout nor the inactivity watchdog switches the newly defaulted slot to TCP; the
decoded-frame stall check exists only for multi-view cells.

Code

android/app/src/main/java/com/openipc/decoder/Decoder.java[519]

+            mTransports[i] = Transport.Mode.stored(pref.getString("transport_" + i, null));

Evidence

An absent transport preference now selects Auto and starts UDP. NalAssembler.assemble() returns
true for valid RTP even when a fragmented NAL is incomplete, and RtspClient.processVideo() passes
that result to the session. receiveUdp() then clears its first-video flag and updates the
last-packet time, disabling both existing fallback conditions; unlike QuadCell, the single-view
client has no decoded-frame stall check.

android/app/src/main/java/com/openipc/decoder/Decoder.java[515-519]
android/app/src/main/java/com/openipc/decoder/NalAssembler.java[91-110]
android/app/src/main/java/com/openipc/decoder/RtspClient.java[119-137]
android/app/src/main/java/com/openipc/decoder/RtspSession.java[656-683]
android/app/src/main/java/com/openipc/decoder/QuadCell.java[358-382]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
New single-view slots use Auto, but receiving valid RTP without decodable frames prevents the UDP-to-TCP fallback.
## Fix Focus Areas
- android/app/src/main/java/com/openipc/decoder/Decoder.java[518-519]
- android/app/src/main/java/com/openipc/decoder/RtspSession.java[656-683]
- android/app/src/main/java/com/openipc/decoder/RtspClient.java[119-137]
## Recommended Fix
Track whether single-view video frames are actually decoded while RTP arrives over Auto UDP. After a bounded no-frame interval, report the UDP stream as broken and reconnect over TCP, while avoiding a fallback during ordinary key-frame startup.

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

---

2. New slots lose audio when UDP audio fails ✓ Resolved

Description

RtspSession.connect() disables audio when its UDP audio SETUP fails or selects an unusable
transport, without marking Auto's UDP attempt as failed. On a camera that accepts UDP video but
needs TCP for audio, a newly defaulted slot continues playing video over UDP without audio rather
than reconnecting over TCP for both tracks.

Code

android/app/src/main/java/com/openipc/decoder/Decoder.java[519]

+            mTransports[i] = Transport.Mode.stored(pref.getString("transport_" + i, null));

Evidence

The new default reaches the UDP branch in connect(). Both the single-view client and multi-view
cells request audio, but a failed UDP audio SETUP or unusable audio transport merely sets `audio =
false`, and the session proceeds to PLAY over UDP; the video-only fallback cannot respond to this
failure.

android/app/src/main/java/com/openipc/decoder/Decoder.java[515-519]
android/app/src/main/java/com/openipc/decoder/RtspClient.java[65-68]
android/app/src/main/java/com/openipc/decoder/QuadCell.java[199-203]
android/app/src/main/java/com/openipc/decoder/RtspSession.java[317-345]
android/app/src/main/java/com/openipc/decoder/RtspSession.java[375-407]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
Auto can accept UDP video but silently omit audio when the camera rejects or changes the UDP audio transport.
## Fix Focus Areas
- android/app/src/main/java/com/openipc/decoder/Decoder.java[518-519]
- android/app/src/main/java/com/openipc/decoder/RtspSession.java[375-407]
## Recommended Fix
For Auto sessions with an advertised audio track, treat a transport-specific UDP audio setup failure as a reason to close the UDP attempt, record the failure, and retry the session over TCP instead of silently disabling audio.

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

---

3. New slots cannot play when UDP ports fail ✓ Resolved

Description

RtspSession.connect() calls UdpReceiver.addTrack() for Auto before reaching its fallback branch,
which handles only a rejected video SETUP response. If a local UDP port pair cannot be bound, the
exception reaches networkLoop() and subsequent attempts try UDP again instead of TCP, now
affecting slots with no stored transport.

Code

android/app/src/main/java/com/openipc/decoder/Decoder.java[519]

+            mTransports[i] = Transport.Mode.stored(pref.getString("transport_" + i, null));

Evidence

Unset preferences now select Auto. That mode binds a UDP video port before issuing SETUP;
addTrack() throws if its attempts fail, while the fallback branch requires a returned RTSP
response. The outer network loop catches the exception and retries without marking UDP unavailable.

android/app/src/main/java/com/openipc/decoder/Decoder.java[515-519]
android/app/src/main/java/com/openipc/decoder/UdpReceiver.java[82-116]
android/app/src/main/java/com/openipc/decoder/RtspSession.java[317-345]
android/app/src/main/java/com/openipc/decoder/RtspSession.java[204-239]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
An Auto slot repeatedly retries UDP when local receiver allocation fails, although TCP remains available.
## Fix Focus Areas
- android/app/src/main/java/com/openipc/decoder/Decoder.java[518-519]
- android/app/src/main/java/com/openipc/decoder/RtspSession.java[317-345]
- android/app/src/main/java/com/openipc/decoder/UdpReceiver.java[82-116]
## Recommended Fix
Catch receiver creation and port-binding failures in Auto mode, clean up any allocated receiver, mark UDP unavailable, and retry the connection using TCP. Preserve explicit UDP mode's failure behavior.

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

---

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[compot-dev]

Qodo review — all three accepted and fixed (they matter now that new slots use Auto):

1. New single-view slots can stay black — the single view gets the same check as the cells (fix: Auto falls back to TCP when UDP delivers packets but no frame decodes (#113) #125): over UDP, with bytes arriving and no decoded frame for 8 s, it reports the stream broken and Auto reconnects over TCP (RtspClient.playsOverUdp() / reportUdpBroken(), checked once a second while resumed).
2. New slots lose audio when UDP audio fails — with Auto, a failed or unusable UDP audio SETUP marks UDP failed and reconnects over TCP for both tracks instead of dropping the sound; explicit UDP keeps the old behaviour (video without audio).
3. New slots cannot play when UDP ports fail — a failed local port binding marks UDP failed for Auto/Multicast, so the next attempt uses TCP; explicit UDP keeps retrying UDP.

[qodo-free-for-open-source-projects]

Qodo review — all three accepted and fixed (they matter now that new slots use Auto):

1. New single-view slots can stay black — the single view gets the same check as the cells (fix: Auto falls back to TCP when UDP delivers packets but no frame decodes (#113) #125): over UDP, with bytes arriving and no decoded frame for 8 s, it reports the stream broken and Auto reconnects over TCP (RtspClient.playsOverUdp() / reportUdpBroken(), checked once a second while resumed).
2. New slots lose audio when UDP audio fails — with Auto, a failed or unusable UDP audio SETUP marks UDP failed and reconnects over TCP for both tracks instead of dropping the sound; explicit UDP keeps the old behaviour (video without audio).
3. New slots cannot play when UDP ports fail — a failed local port binding marks UDP failed for Auto/Multicast, so the next attempt uses TCP; explicit UDP keeps retrying UDP.

Confirmed from the diff: all three findings appear addressed:

• finding 1: Single-view UDP stall detection now triggers TCP fallback after 8 seconds without decoded frames.
• finding 2: Auto treats UDP audio setup or transport mismatches as a session failure and retries over TCP; explicit UDP behavior is preserved.
• finding 3: Auto/Multicast now marks UDP unavailable when local port allocation fails, allowing a TCP retry.

The changes align with the reported fixes.

[compot-dev]

Device check (Aceline-1, 37c83ea): stored TCP slots unchanged (TCP/TCP); slot 3 on Auto plays over UDP in the grid and in single view (transport UDP, transport_mode AUTO, video + Opus audio over UDP), no false fallback in 20 s; the U cell UDP push. A brand-new slot's default (Auto) is covered by the unit test — a fresh install would wipe the bench's slots.