Fallback streams¶
Usenet retention is imperfect. A release can lose articles at any time, and a source that starts fine can fail partway through. Fallback streams protect your playback against this. If the source you're watching goes bad mid-stream, NeNeTeePee-Stream-Kodi switches to a verified alternate upload of the same file. An exact length check and SHA-256 fingerprints of sampled byte ranges must match first. Playback then continues from the same byte position, without stopping or rewinding.
Fallback streams are on by default. They apply to the nzbdav backend. The NZBGet backend uses the same settings to drive NZBGet's Smart Duplicates failover instead.
How it behaves¶
- Backups aren't free. Once playback has run for a short delay (120 seconds by default), NeNeTeePee-Stream-Kodi submits standby backups to nzbdav in the background. Even healthy playback therefore uses some backend and Usenet capacity.
- NeNeTeePee-Stream-Kodi prepares backups only after playback has actually started, so they don't compete with the fragile stream startup.
- NeNeTeePee-Stream-Kodi switches only after it verifies that the alternate matches what you were watching: the length must match exactly, and sampled SHA-256 fingerprints must match too. If it can't verify a backup, it won't switch.
- Mid-stream switching happens on the byte pass-through path, which is the default for MKV and other non-MP4 files. NeNeTeePee-Stream-Kodi doesn't switch streams served through the MP4 faststart rewrite or an ffmpeg remux tier mid-stream. See Playback, remux, and seeking.
- When a switch happens, a brief notification tells you which backup it switched to ("fall back to candidate #N successful"). Playback doesn't pause or jump.
Settings¶
These settings are in the Fallback Streams group on the Advanced tab:
| Setting | Default | What it does |
|---|---|---|
| Enable fallback streams | On | Turns the whole feature on or off. |
| Maximum standby fallback streams | 5 | How many backups NeNeTeePee-Stream-Kodi keeps ready per title. On the nzbdav backend, values are clamped to 0–5. 0 turns off backup discovery. |
| Seconds into playback before submitting fallback backups | 120 | How long playback must run before backups are submitted. 0 submits them as soon as playback starts. |
Why the delay before submitting backups
Submitting backups opens extra connections to your backend. In the first seconds of playback, the stream's own cache is still filling. Extra connections then can starve the live stream and stall video on some devices. NeNeTeePee-Stream-Kodi therefore waits until playback is well established (120 seconds by default) before it prepares backups.
Beta feature
The Seconds into playback before submitting fallback backups setting was added in 2.0.0-beta.1 and is available on the Beta channel.
How a backup is chosen¶
Candidates come from the search results you picked from. On NZBHydra2, NeNeTeePee-Stream-Kodi can also find same-release uploads that Hydra collapsed into one row. Before NeNeTeePee-Stream-Kodi reads any NZB, it prefetches only candidates whose indexer size is within 25% of your pick.
NeNeTeePee-Stream-Kodi admits a candidate only when it's a plausible copy of the same file:
- It's the same content: the same title, year, season and episodes, part number, edition, and PROPER/REPACK status.
- It's from the same release group at the same resolution. Both must be parsed and equal. If either is unknown, NeNeTeePee-Stream-Kodi rejects the candidate.
- Its codec, container, quality, HDR format, audio, and channels are compatible.
- It's a different upload. Its NZB link and article set must differ from your pick's.
- The video payload in its NZB is within about 10% of your pick's size.
NeNeTeePee-Stream-Kodi then ranks the admitted candidates:
- Exact same video filename first.
- Then by similarity tier. Every candidate already has the same release
group and resolution, and a known codec mismatch is rejected, so the tiers
are:
- Tier 0: same codec, with a size within 3%.
- Tier 1: same codec, larger size difference.
- Tier 2: codec not recognized on one side.
- Then by smallest size difference.
NeNeTeePee-Stream-Kodi treats uploads posted within an hour of each other as the same upload and collapses them to the single best-ranked copy. It drops candidates posted within an hour of your pick, because they're the same upload as the one you're watching.
Beta feature
Tiered ranking, post-date collapsing, and same-release discovery through Hydra were added in 2.0.0-beta.1 and are available on the Beta channel.
How the switch is verified¶
Switching sources mid-stream only works if the bytes line up exactly. NeNeTeePee-Stream-Kodi runs a two-stage, sampled check before any switch:
- Length check: the alternate's total size must exactly equal the current source's size.
- Fingerprint sweep: NeNeTeePee-Stream-Kodi compares SHA-256 hashes of matching 4 KiB ranges sampled across both files: 20 samples for files under 1 GiB and 100 for larger files. Every sampled range must match.
These checks sample the file rather than compare every byte, so they give strong evidence that the files match, not proof. In practice a different encode or a corrupted upload almost always fails the length check or one of the samples.
NeNeTeePee-Stream-Kodi checks backups in the background as soon as they're ready, so a switch can happen instantly when it's needed. It discards a candidate that fails the check and never uses it.
When the source can't be saved¶
Upstream read errors, recoverable short reads, or a stretch where the source stops delivering new data trigger a switch. If a backup is attached but none has been verified yet, the current source first gets another pass through its retry ladder. If no verified backup can resume from the exact byte position and the retries are used up, NeNeTeePee-Stream-Kodi closes the stream cleanly. It doesn't skip bytes or show corruption. You get a clear failure instead of a broken picture.
For the full switch sequence, see How it works → Fallback cutover. It covers how the byte offset is preserved, how the dead source is demoted, and the tri-state match logic.