Composer Reference Guide R3-2026-2.7.9774.35170-prerelease

SRT Target 16 channel audio

SRT 16-Channel Audio Target properties for Script Engine. Same SRT video transport as the standard SRT Target but supports up to 16 audio channels (8 audio programs) — the additional 4 programs (5–8) are sourced from Audio Channel Strip inputs rather than the scene's main audio bus. Useful for multi-language broadcasts (8+ commentary languages), multi-program audio (clean feed + dirty feed + IFB returns), stadium/event productions with multiple isolated mixes, and distribution to multiple downstream tools that each need their own audio sub-mix. Pick this over the standard SRT Target whenever you need more than four parallel audio programs.

Property Type Access Description
AutoStart bool get/set When On, the SRT target connects automatically when the project loads.
ShowAdvancedOptions bool get/set Reveals advanced/expert properties in the panel. Off by default.
SrtBaseAddress string get/set Base SRT URL in srt://host:port form. Supports @@LocalIP() and @@HostName() macros. Treat as sensitive when targeting private cloud ingest.
SrtOptions string get/set SRT URL query parameters appended after ?. Common keys: mode=caller\|listener, latency=200000 (microseconds — typical 120–500 ms), pkt_size=1316, passphrase=..., streamid=.... Tune latency higher for noisy links, lower for low-glass-to-glass delivery.
SrtStreamKey string get/set Optional SRT stream id (also called streamid). Many cloud ingests require this for routing — receivers identify the publisher by this string. Treat as sensitive.
SimulateLatencyEnabled bool get/set Enable simulated send latency (debug/testing aid). [default=false]. Holds each outgoing frame on the sender thread by Simulated base latency plus a time-varying component, to reproduce variable/congested links for SRT input synchronization tests. Off in production.
SimulatedBaseLatencyMs int get/set Constant added send delay in ms when latency simulation is on. [min=0, max=3000, default=0].
SimulatedJitterMs int get/set Peak-to-peak latency variance in ms around the base when simulation is on. [min=0, max=3000, default=0].
SimulatedLatencyPattern SrtSimulatedLatencyPattern get/set How the simulated latency evolves: Static, RandomWalk, Sine, or StepSchedule.
SimulatedLatencyPeriodMs int get/set Period in ms for the Sine / RandomWalk / StepSchedule patterns. [min=100, max=60000, default=2000].
SrtConnectionString string get The full SRT URL Composer will dial (read-only).
OutputVideoBitrate OutputVideoBitrate get/set Target video bitrate. Match this to the available uplink bandwidth and the receiver's configured input.
H264BFrameDistance H264BframeDistance get/set Number of b-frames used in a GOP
VideoCompressionGopSize VideoCompressionGopSize get/set GOP (Group of pictures) length in frames. Typically this is 2x or 1x the framerate.
H264Profile H264Profile get/set H264 profile
UseAdvanceCbrConfiguration bool get/set Use CBR configuration
MaxVideoRateMultiplier float get/set Max video rate (multiplier)
MinVideoRateMultiplier float get/set Min video rate (multiplier)
BufferSizeMultiplier float get/set Buffer size (multiplier)
H264EncodingQualitySpeed H264EncodingQualitySpeed get/set Quality/Speed control
H264Tune H264Tune get/set Encoder tuning (H264).
H264EncodingThreads H264EncodingThreads get/set Number of CPU threads used for encoding
UseNvenc bool get/set Use NVENC as video encoder (GPU)
UseHevc bool get/set When On, encode with HEVC (H.265) using NVENC instead of H.264. HEVC gives better quality per bit and is required only for SEI timecode carriage (see TimecodeCarriage); the ST 2038 transport embeds timecode with H.264 too. Implies NVENC — HEVC has no software-encoder path here, so this takes precedence over UseNvenc.
NvencAdvancedOptions string get/set Advanced options (json)
EmbedTimecode bool get/set When On, embed an SMPTE timecode into the outgoing stream so a downstream SRT input — or any receiver — can read it back. The carriage is chosen by TimecodeCarriage: video SEI (requires HEVC) or a codec-agnostic SMPTE ST 2038 ancillary stream. With SEI and a non-HEVC codec a warning is logged and no timecode is sent.
TimecodeCarriage TimecodeTransport get/set How the embedded timecode is carried: in-stream video SEI (HEVC only) or a separate SMPTE ST 2038 ancillary-data stream (codec-agnostic — works with H.264 — and readable without software video decoding). Only used when EmbedTimecode is On.
TimecodeStartTime TimecodeStartMode get/set Where the embedded timecode starts counting from when streaming begins (the first written frame): 00:00:00:00, or the wall-clock time of day. Only used when EmbedTimecode is On. How closely Time of day then keeps up with the clock depends on the project frame rate: at 24 / 25 / 30 / 50 / 60 it is exact; at 29.97 / 59.94 it is correct to within about 70 ms, because drop-frame counting corrects in two-frame steps once a minute; at 23.98 it cannot track the clock at all and runs about 0.1% slow (roughly 43 seconds behind by midday, 86 seconds by the end of the day), because timecode labels 24 frames per second of 23.98 material and SMPTE defines no drop-frame scheme for that rate. At 23.98 the value is a running counter, not a clock reading.
SrtAudioChannelOneEncoder SrtAudioEncoder get/set Audio channel one encoder
SrtAudioChannelOneMapping AudioChannelMapping get/set Audio channel one mapping
SrtAudioChannelOneBitRate AacBitRate get/set Audio channel one bitrate
SrtAudioChannelOneLanguage string get/set Audio channel one language description
SrtAudioChannelTwoEncoder SrtAudioEncoder get/set Audio channel two encoder
SrtAudioChannelTwoMapping AudioChannelMapping get/set Audio channel two mapping
SrtAudioChannelTwoBitRate AacBitRate get/set Audio channel two bitrate
SrtAudioChannelTwoLanguage string get/set Audio channel two language description
SrtAudioChannelThreeEncoder SrtAudioEncoder get/set Audio channel three encoder
SrtAudioChannelThreeMapping AudioChannelMapping get/set Audio channel three mapping
SrtAudioChannelThreeBitRate AacBitRate get/set Audio channel three bitrate
SrtAudioChannelThreeLanguage string get/set Audio channel three language description
SrtAudioChannelFourEncoder SrtAudioEncoder get/set Audio channel four encoder
SrtAudioChannelFourMapping AudioChannelMapping get/set Audio channel four mapping
SrtAudioChannelFourBitRate AacBitRate get/set Audio channel four bitrate
SrtAudioChannelFourLanguage string get/set Audio channel four language description
SrtAudioChannelFiveStripSource AudioChannelStripInput.AudioChannelStripInput get/set Audio Channel Strip input that feeds program 5. Set to a scene strip to route an isolated mix (e.g. clean feed, IFB return, alternate-language mic) into this SRT audio program.
SrtAudioChannelFiveEncoder SrtAudioEncoder get/set AAC encoder mode for audio program 5. Set to Unused to skip.
SrtAudioChannelFiveBitRate AacBitRate get/set AAC bitrate for audio program 5.
SrtAudioChannelFiveLanguage string get/set ISO 639 language tag for program 5 (e.g. eng, spa, fra).
SrtAudioChannelSixStripSource AudioChannelStripInput.AudioChannelStripInput get/set Audio Channel Strip input that feeds program 6.
SrtAudioChannelSixEncoder SrtAudioEncoder get/set AAC encoder mode for audio program 6.
SrtAudioChannelSixBitRate AacBitRate get/set AAC bitrate for audio program 6.
SrtAudioChannelSixLanguage string get/set ISO 639 language tag for program 6.
SrtAudioChannelSevenStripSource AudioChannelStripInput.AudioChannelStripInput get/set Audio Channel Strip input that feeds program 7.
SrtAudioChannelSevenEncoder SrtAudioEncoder get/set AAC encoder mode for audio program 7.
SrtAudioChannelSevenBitRate AacBitRate get/set AAC bitrate for audio program 7.
SrtAudioChannelSevenLanguage string get/set ISO 639 language tag for program 7.
SrtAudioChannelEightStripSource AudioChannelStripInput.AudioChannelStripInput get/set Audio Channel Strip input that feeds program 8.
SrtAudioChannelEightEncoder SrtAudioEncoder get/set AAC encoder mode for audio program 8.
SrtAudioChannelEightBitRate AacBitRate get/set AAC bitrate for audio program 8.
SrtAudioChannelEightLanguage string get/set ISO 639 language tag for program 8.
WarnOnLowAverageBitrate bool get/set Warn on low average bitrate (
ReconnectInterval ReconnectInterval get/set Reconnect Interval
MaxOutputQueueSize int get/set Max output queue size (packets)
OutputBufferAllowFrameSkipping bool get/set Allow frame skipping on output queue size warnings.
LogBitrateToDisk bool get/set Log bitrate to disk
UseAlternateConnectionMode bool get/set Use alternate connection mode
ConnectionStatus ConnectionStatus get Current connection status
StartCommand Command get Starts the encoder and the SRT stream
StopCommand Command get Stops the encoder and the SRT stream
ReconnectCommand Command get Forces an immediate reconnect of the live SRT connection without stopping the target. API-only and hidden from the UI; invoke via /api/invokecommand with command ReconnectCommand. Only executable while connected.
ComponentLog ComponentLog get Mini-log messages
UpTimeSinceStart string get Uptime since start
OutgoingBitRate string get Outgoing bitrate
MinilogTime DateTime get SRT message time
AudioChannelUsed string get Audio Channel used
NumAutoReconnectsperformed int get Number of reconnects
CurrentSrtEndPoint string get Current SRT endpoint
ErrorCount int get Error counter
LastErrorDateTime DateTime get Last Error date and time
WarningCount int get Warning counter
LastWarningDateTime DateTime get Last warning date and time

Inherits from: AbstractTarget, NamedModel.

See also: SRT Target 16 channel audio in Targets — user-facing introduction, screenshots, and section summaries.