Playback, remux, and seeking

Every playback request goes through a local HTTP proxy that NZB-DAV runs as a background service. Kodi talks only to this proxy on 127.0.0.1, never directly to your WebDAV server. This design avoids a Kodi bug where scanning the parent directory over WebDAV throws an Open - Unhandled exception, and it lets NZB-DAV add seeking, format handling, and recovery on top of the raw stream.

What the proxy does for you

• Preserves seeking through HTTP range requests.
• Fixes tail-moov MP4s so 4 GB+ MP4 remuxes play on 32-bit Kodi, using a pure-Python rewriter (no ffmpeg needed).
• Recovers from missing articles mid-stream by probing forward and filling the gap, so a few bad blocks don't kill playback.
• Offers optional remux tiers for very large or awkward files.
• Enables mid-playback source switching via fallback streams.

How a file is served

NZB-DAV picks a serving path based on the container, the file size, and your settings:

flowchart TD
    A[Stream request] --> B{Container?}
    B -->|MP4 already faststart| C[Direct pass-through proxy<br/>full range seeking]
    B -->|MP4 moov at tail| D[Virtual faststart<br/>pure-Python rewrite]
    B -->|MKV / other| E{Large non-MP4 stream mode<br/>+ size vs threshold}
    E -->|Pass-through default| F[Byte pass-through<br/>native seeking + gap recovery]
    E -->|Matroska remux| G[ffmpeg -c copy pipe<br/>approximate seek]
    E -->|fMP4 HLS| H[HLS VOD, full random seek<br/>DV-gated]
    D -->|parse fails| G

• MP4, already faststart — proxied directly with full range seeking.
• MP4 with moov at the tail — rewritten in pure Python into a virtual faststart file so it plays immediately; if parsing fails, it falls back to an ffmpeg remux.
• MKV and other containers — by default, streamed as a byte pass-through with native seeking and gap recovery.

Settings that control playback

These live on the Advanced tab. Defaults are safe; change them only with a reason.

Setting	Default	What it does
Large non-MP4 stream mode	Direct pass-through	Chooses how large non-MP4 files are served: Direct pass-through (default, no ffmpeg), fMP4 HLS (experimental, full random seek), or Matroska remux (compatibility).
Force ffmpeg remux above (MB)	15000 (~15 GB)	The size at which the two remux modes kick in. 0 disables remux entirely, so everything streams pass-through regardless of size.
Convert MP4 subtitles to SRT	On	Converts MP4 mov_text subtitles to SRT during remux so embedded subs survive.

Pass-through is the default for a reason

On 32-bit devices such as many CoreELEC boxes, direct pass-through gives the best compatibility. The remux tiers exist for specific hard cases (very large Dolby Vision or lossless-audio remuxes) and require ffmpeg. If ffmpeg isn't installed, NZB-DAV automatically falls back to pass-through.

Full seeking on large files

Direct pass-through supports full seeking only if Kodi's in-memory cache is turned off. Setting <cache><memorysize>0</memorysize></cache> in advancedsettings.xml enables this. Without it, seeking on large files is limited on 32-bit Kodi: the default mode stays pass-through and does not switch to remux on its own. For bounded-seek remux instead, set Large non-MP4 stream mode to a remux tier. NZB-DAV prompts you about the cache setting the first time a remux tier handles a large file. See advancedsettings.xml and seeking.

Dolby Vision handling

When you enable the fMP4 HLS mode, NZB-DAV probes each source for its Dolby Vision profile and routes accordingly, because not every DV variant is safe over HLS on Amlogic devices:

Source	Route
Dolby Vision Profile 7 FEL (dual-layer)	Matroska remux (HLS can't carry it)
Dolby Vision Profile 7 MEL	fMP4 HLS (metadata-only, experimental)
Dolby Vision Profile 5 / 8 / other	Matroska remux (safest on Amlogic)
Non-DV	fMP4 HLS
Unknown	Matroska remux (fail-safe)

Resilience knobs

The Advanced tab also exposes recovery controls — a strict upstream contract mode, a density breaker, a zero-fill budget, a retry ladder, a stall-wait budget, and a read-ahead buffer. Each is documented in the Settings reference and explained in How it works → Stream proxy.