What's in a capture — tutti.dunn.dev

A capture is a directory. manifest.json at the root is the index every consumer reads first; everything else is referenced from it by relative path. This page walks the shape end to end: what tutti writes per device, how the manifest stitches it together, and the controlled vocabularies a renderer or downstream tool can rely on.

The wire-level theory behind these artifacts (SSDP, mDNS, descriptor parse, AVTransport drive) lives in protocols. The failure modes that motivated each capture surface live in why it goes wrong. This document is about what tutti hands you.

Three phases, one directory. Discover is passive listening plus M-SEARCH bursts. Analyse is library-decision reimplementation against each fetched descriptor. Drive is opt-in: tutti only sends real AVTransport actions when you pass –drive. Everything is written to disk before the binary exits — you can review the bundle, edit notes.md, and decide whether to submit.

What tutti captures, per source

Per device on your LAN, a capture records:

SSDP: the M-SEARCH inputs (target, MX, ST list), every response (USN, ST, LOCATION, SERVER, BOOTID, CONFIGID, source IP:port), and per-USN grouping. Raw wire dump and parsed JSON sit side by side.
mDNS / DNS-SD: every audio-renderer service type announced (_airplay._tcp, _googlecast._tcp, _raop._tcp, _spotify-connect._tcp, _sonos._tcp, and a handful of vendor-specific types), with full TXT records.
Device descriptor: raw XML as fetched, and a parsed canonical form (deviceType, friendlyName, manufacturer, modelName, UDN, X_DLNADOC, icons, services list with SCPD/control/event URLs).
Library decisions: for each Go UPnP control-point library tutti knows about (go-upnpcast, huin/goupnp), the accept/reject result with a machine-parseable reason_code. v0 ships reimplementations of each library’s parser (see internal/decisions), keyed as <lib>@reimpl-of-<version>. Real library invocation lands later; the schema field decision.method distinguishes reimplementation (today) from library_call (future).
GetProtocolInfo: the device’s Sink list (every MIME type it claims to accept), with derived counts per format class (DSD, MQA, FLAC, etc.). Drives discovery of the kind of bug that hides behind a device that plays a format but doesn’t announce it.
Drive test (opt-in via --drive): a real SetAVTransportURI + Play against test tones, with polled GetTransportInfo / GetPositionInfo capture. Format matrix is intersected with the device’s protocol_info Sink list, so tutti only attempts formats the device claims to accept (PCM 44.1/48/96/192 kHz, FLAC at common rates, MP3, AAC, Opus). Tones are math-generated 5-second sine waves built by scripts/gen-tones.sh, embedded in the binary, served from a transient local HTTP server tutti spins up on a random port.
Metadata on two surfaces (per drive run):
- DIDL-Lite envelope that tutti sends with SetAVTransportURI: title "tutti probe: <format>@<rate>", artist tutti.dunn.dev, album Audio Renderer Probes. v0 omits <upnp:albumArtURI> (no cover art site yet); when tutti.dunn.dev/audio/covers/ exists, each scenario will reference a 300×300 PNG with PROBE and the format/rate overlaid.
- Embedded tags inside each test file (ID3v2 for MP3, Vorbis comments for FLAC/Ogg, MP4 atoms for AAC/ALAC): title "tutti embed: <format>@<rate>", artist tutti.dunn.dev, album Audio Renderer Probes (embedded). Embedded artwork is a v1+ addition.

The two surfaces use deliberately different title prefixes (probe vs embed) so tutti can read GetPositionInfo’s TrackMetaData and derive which surface the device honored: didl-lite, embedded, mixed, or none. When cover art lands, devices that render it will show whichever card the device preferred on their display, adding a visible confirmation channel.

Directory layout

capture-2026-05-09T143022Z-andrewdunndev/
├── manifest.json                 # schema-versioned index, the renderer reads this
├── ssdp.json                     # parsed SSDP responses
├── ssdp-raw.txt                  # original wire dump
├── mdns.json                     # parsed mDNS records, all audio service types
├── devices/
│   └── eversolo-dmp-a6/          # one dir per device
│       ├── descriptor.xml        # raw, fetched
│       ├── descriptor.json       # parsed, canonical fields
│       ├── decisions.json        # per-library accept/reject + reason
│       ├── protocol-info.json    # parsed Sink list with derived counts
│       ├── protocol-info.txt     # raw GetProtocolInfo response
│       └── drive/                # only if --drive
│           ├── run-1-opus.log
│           ├── run-2-dsd64.log
│           └── run-3-dsd256.log
└── notes.md                      # writable by you, prose context

The slug under devices/ is canonical and stable: <vendor>-<model> lowercased, hyphenated. It’s what evidence/ uses, what the device page URL is keyed on, and what manifest.json references.

manifest.json (schema v1, illustrative)

{
  "schema_version": 1,
  "tutti_version": "0.1.0",
  "capture_id": "01HX7Z2FJK4Q3P9V8R5N6M2W3T",
  "captured_at": "2026-05-09T14:30:22Z",
  "contributor": "github:andrewdunndev",
  "host": { "os": "darwin", "arch": "arm64", "interfaces": ["en0"] },

  "scaninfo": {
    "ssdp_st_list": ["ssdp:all", "upnp:rootdevice",
                     "urn:schemas-upnp-org:device:MediaRenderer:1"],
    "ssdp_mx": 3,
    "mdns_service_types": ["_airplay._tcp", "_googlecast._tcp",
                           "_raop._tcp", "_spotify-connect._tcp"]
  },

  "runstats": {
    "elapsed_seconds": 12.4,
    "ssdp_responses": 9,
    "ssdp_unique_usns": 6,
    "mdns_records": 14,
    "exit": "success"
  },

  "redactions": ["client-ip", "device-ip", "auth-tokens",
                 "salt", "username", "lan-topology"],

  "devices": [
    {
      "slug": "eversolo-dmp-a6",
      "vendor": "EVERSOLO",
      "model": "DMP-A6 Master Gen 2",
      "firmware": "5.6.46-100",
      "udn": "uuid:800a805eef11-dmr",
      "tags": ["dlna", "discovery-ok", "drive-ok"],

      "discovery": {
        "ssdp_usns": ["uuid:800a805eef11-dmr",
                      "uuid:800a805eef11-dmr::upnp:rootdevice"],
        "mdns_services": []
      },

      "decisions": {
        "go-upnpcast@reimpl-of-v0.1.0": {
          "result": "accepted",
          "reason_code": "mediarenderer_v1_avtransport_found",
          "reason_text": "deviceType matched MediaRenderer:1; AVTransport, RenderingControl, ConnectionManager all parsed",
          "method": "library_call",
          "confidence": "high"
        },
        "huin/goupnp@reimpl-of-v1.3.0": {
          "result": "accepted",
          "reason_code": "device_with_av_transport",
          "reason_text": "...",
          "method": "library_call",
          "confidence": "high"
        }
      },

      "protocol_info": {
        "sink_count": 392,
        "audio_sink_count": 107,
        "format_matches": { "dsd": 0, "flac": 4, "mqa": null }
      },

      "drive_test": {
        "performed": true,
        "runs": [
          {
            "scenario": "flac-96k-24",
            "mime": "audio/flac",
            "rate_hz": 96000,
            "bits": 24,
            "metadata_didl_lite_sent": {
              "title": "tutti probe: FLAC 96k/24",
              "artist": "tutti.dunn.dev",
              "album": "Audio Renderer Probes",
              "art_url": "https://tutti.dunn.dev/audio/covers/probe-flac-96000-24.png"
            },
            "metadata_embedded": {
              "title": "tutti embed: FLAC 96k/24",
              "artist": "tutti.dunn.dev",
              "album": "Audio Renderer Probes (embedded)",
              "art_card": "embed-flac-96000-24.png"
            },
            "metadata_echoed": {
              "title": "tutti probe: FLAC 96k/24",
              "art_url": "https://tutti.dunn.dev/audio/covers/probe-flac-96000-24.png"
            },
            "metadata_source": "didl-lite",
            "metadata_round_trip": "matched",
            "art_fetch_observed": true,
            "result": "playing",
            "transitions": ["TRANSITIONING", "PLAYING"],
            "transcript_file": "devices/eversolo-dmp-a6/drive/run-1-flac-96k-24.log"
          }
        ]
      }
    }
  ]
}

Field notes

reason_code is a controlled vocabulary; the renderer filters and colors on it. reason_text is for humans reading the bug report. capture_id is a ULID; cite it in upstream issues so the maintainer can find the source-of-truth bundle.

A device entry must always have discovery (the SSDP/mDNS announcements that surfaced it). Everything else (decisions, protocol_info, drive_test, descriptor) is optional but at least one must be present. This lets tutti record evidence for devices that announce only on mDNS (AirPlay-only, Spotify-Connect-only) or whose descriptor URL is unreachable, without dropping them from the manifest.

The full JSON Schema lives at schema/manifest.v1.json in the source tree. That file is the source of truth. Everything downstream is derived from it: tutti’s Go validator, this site’s TypeScript types, and the CI gate on contribution MRs.