DVB / EBU Broadcast Standards Skill

For detailed tables see references/etsi.md and references/ebu.md.

When reviewing FFmpeg args

Interlacing

• -flags +ildct+ilme and -top 1 MUST be present for any interlaced output (PAL, NTSC, HFR-PAL presets).
• They MUST NOT appear for deinterlace/OTT presets (interlaced: false).
• -field_order tt (top-field-first) is correct for PAL/NTSC broadcast.
• EBU R 68: PAL broadcast requires TFF; NTSC is also TFF by convention.

GOP structure

• Fixed GOP is mandatory for CBR broadcast carriage.
• -g <gopSize> sets the maximum GOP length (keyframe interval).
• -keyint_min <gopSize> prevents FFmpeg from inserting early keyframes.
• -sc_threshold 0 disables scene-cut detection (would break the fixed GOP).
• For libx264: also -x264-params nal-hrd=cbr:force-cfr=1:scenecut=0.
• For libx265: also -x265-params hrd=1:nal-hrd=cbr:no-scenecut=1.
• PAL standard: GOP = 25 frames (1 second). NTSC: 30 frames.

Audio

• EBU R 128: loudness target −23 LUFS ±1 LU; true-peak ≤ −1 dBTP.
• Multi-language services: each language must be a separate PES/PID, declared in the PMT with ISO_639_language_descriptor.
• DVB audio PID range: typically 0x101–0x1FF.
• aac in DVB: use audio_type = 0x00 (undefined) in the stream descriptor for stereo; 0x03 (hearing impaired) for HI tracks.

CBR mux rate

• Formula: (videoBitrate + sum(audioBitrates)) × 1.05 (5% TS overhead for null packets, PAT, PMT, PCR).
• -muxrate in FFmpeg mpegts muxer enforces this; without it the muxer runs VBR regardless of video codec settings.
• ETR 290 P1: constant bit-rate streams must not deviate by more than ±100 bps over a 1-second window.

SRT transport

• libsrt stats are emitted to stderr when stats=1&statsintvl=1 are in the URL.
• Key SRT metrics: rttMs (round-trip), pktLoss, pktRetrans, rateMbps.
• SRT latency should be ≥ 3× RTT for reliable delivery.
• Passphrase encryption uses AES-128 (pbkeylen=16) or AES-256 (pbkeylen=32).

DVB SI / PSI tables (EN 300 468)

FFmpeg's mpegts muxer only writes PAT+PMT. NIT, SDT, EIT must be injected externally (e.g. dvblast, OpenCaster) for full DVB compliance.

Common mistakes to flag

1. -muxrate missing on CBR streams — muxer silently goes VBR; ETR 290 P1 alarms will fire on any downstream analyser.
2. -pcr_period not set — FFmpeg default is 20 ms but can drift under CPU load; explicit setting is required.
3. -flags +ildct+ilme on deinterlace path — causes double-interlacing artifact; must be guarded by p.interlaced.
4. Multi-audio keyed by kind instead of sourceIndex — second audio track overwrites first in the parsed stream map.
5. SRT URL built with srt:// prefix already in host field — produces srt://srt://host:port; constructor must strip scheme.
6. 0.0.0.0 bind in API server — violates project rule; must bind to 10.67.18.29.
7. exec() for SNMP traps — shell injection; must use execFile('snmptrap', args).
8. Multicast address outside 239.100.25.0/26 — must be validated before use.

Checking compliance

When asked to audit a set of FFmpeg args for broadcast compliance, work through this checklist:

Video

• Fixed GOP (-g, -keyint_min, -sc_threshold 0) present?
• CBR VBV signalling (-maxrate, -bufsize, HRD params) present?
• Interlace flags match preset (interlaced flag)?
• field_order set to tt for interlaced?
• pixFmt appropriate (yuv420p for SD/HD; yuv420p10le for HDR)?

Audio

• Each audio track mapped by sourceIndex (not overwriting)?
• Language metadata set via -metadata:s:a:N language=xxx?
• Bitrate in kbps (not bare integer)?

Mux / transport

• -muxrate set for CBR streams?
• -pcr_period 20 set?
• -pat_period 0.1 set?
• Service ID, PMT PID, video PID, audio PIDs declared?
• -streamid args match declared PIDs?

SRT / network

• stats=1&statsintvl=1 in SRT URL?
• Latency ≥ 3× expected RTT?
• encodeURIComponent used for passphrase and streamId?

Reference files

• references/etsi.md — ETR 290 priority table, EN 300 468 descriptor list, PIDs, TS limits
• references/ebu.md — EBU R 128 loudness, EBU R 68 interlacing, EBU Tech 3337 AFD, EBU R 48 aspect ratio