The SRT Target 16 Channel Audio is an output component that sends video and audio from Composer to any SRT (Secure Reliable Transport) receiver. This variant supports up to 16 audio channels (8 stereo pairs), making it ideal for multi-language broadcasts and complex audio workflows. SRT is designed for low-latency, high-quality video transmission over unpredictable networks.
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When to Use SRT Target 16 Channel Audio
- Multi-language broadcasts: Deliver content with multiple language audio tracks simultaneously
- Live streaming to SRT receivers: Send content to media servers, encoders, or CDNs that accept SRT input
- Contribution feeds: Deliver high-quality video with multiple audio channels over the internet
- Complex audio workflows: Combine main audio channels with Audio Channel Strip sources for flexible routing
- Point-to-point streaming: Direct streaming between locations with reliable delivery and multiple audio options
Looking for a simpler setup?
If you only need up to 4 stereo audio outputs (8 channels total) from the main audio bus, the standard SRT Target is usually sufficient.
The 16 Channel Audio variant is intended for workflows that require up to 16 audio channels using a combination of the main audio bus and Audio Channel Strip components.
Setup
- Add SRT Target 16 Channel Audio to your project outputs
- Configure the SRT address: Enter the destination server address in SRT URL format
- Set SRT options: Configure packet size and latency parameters
- Configure video settings: Set bitrate and encoding options appropriate for your use case
- Configure audio channels 1-4: Enable and map audio channels from the main audio bus
- Configure audio channels 5-8: Select Audio Channel Strip sources for additional audio channels
- Start sending: Use the Start sending command to begin streaming
Important: Audio channels must be configured continuously. You cannot skip channels (e.g., enable channel 1 and 3 but disable channel 2).
Parameters
Options marked (Advanced) are only visible in the UI when Show advanced options is set to Yes.
General Settings
| Parameter | Default | Description |
|---|---|---|
| Autostart when application starts | Disabled | When enabled, the SRT stream will automatically start when the Composer project is started |
| Show advanced options | No | Toggle to reveal advanced configuration options for video encoding, additional audio channels, and output buffer settings |
Addresses
| Parameter | Default | Description |
|---|---|---|
| Server address (srt://ip:port) | srt://[ipadress]:[port] |
The destination SRT server address in URL format. Replace with your actual server IP and port |
| Options (latency etc) | pkt_size=1316&latency=200000 |
URL query parameters for SRT connection settings. Default configures 1316-byte packets and 200ms latency |
| Stream id (optional) | (empty) | Optional stream identifier required by some CDNs or SRT servers for stream routing |
| Connection string | (auto-generated) | Read-only field showing the complete connection string built from the above parameters |
Dynamic Placeholders
The Server address (srt://ip:port) field supports dynamic placeholders that are resolved at connection time:
| Placeholder | Description |
|---|---|
@@HostName() |
Replaced with the local machine's hostname |
SRT Connection Modes
You can add mode=caller or mode=listener to the Options (latency etc) field to control the connection behavior:
| Mode | Description |
|---|---|
mode=caller |
Composer connects to a remote SRT server (default behavior) |
mode=listener |
Composer listens for incoming SRT connections on the specified port |
If no mode is specified in the SRT options field, Composer automatically uses mode=caller.
Example: To set Composer as a listener with 200ms latency, enter: pkt_size=1316&latency=200000&mode=listener
Video Encoder Configuration
| Parameter | Default | Description |
|---|---|---|
| Video bitrate | 3.00 Mbit/s | Target video bitrate for the H.264 encoder |
| H264 B frame distance (Advanced) | Zero | Number of B-frames between reference frames. Zero disables B-frames for lowest latency |
| H264 Gop size (Advanced) | Same as double processing framerate | GOP (Group of Pictures) length. Controls keyframe interval |
| H264 profile (Advanced) | baseline | H.264 encoding profile. Baseline offers widest compatibility |
| Use CBR configuration (Advanced) | Enabled | Enable Constant Bit Rate mode for consistent bandwidth usage |
| Max video rate (multiplier) (Advanced) | 1.000 | Maximum bitrate multiplier relative to target bitrate |
| Min video rate (multiplier) (Advanced) | 1.000 | Minimum bitrate multiplier relative to target bitrate |
| Buffer size (multiplier) (Advanced) | 1.000 | Encoder buffer size multiplier relative to target bitrate |
| Quality/Speed control (Advanced) | veryfast | Encoder preset balancing quality vs. encoding speed |
| Tune (Advanced) | zerolatency | Encoder tuning optimized for specific content types or latency requirements |
| H264 threads (Advanced) | Two | Number of CPU threads for software encoding (only used when NVENC is disabled) |
| Use NVENC as video encoder | Enabled | Use NVIDIA hardware encoder for better performance |
| Advanced options (json) (Advanced) | {"no-scenecut": "1","zerolatency": "1","strict_gop": "0","gpu": "any","preset": "p4","delay": "0","rc-lookahead": "0","surfaces": "1", "rc": "cbr"} |
JSON configuration for advanced NVENC encoder options |
Video Bitrate Options
Available bitrates: 50 kbit/s, 100 kbit/s, 150 kbit/s, 200 kbit/s, 250 kbit/s, 300 kbit/s, 350 kbit/s, 400 kbit/s, 450 kbit/s, 500 kbit/s, 600 kbit/s, 700 kbit/s, 750 kbit/s, 800 kbit/s, 850 kbit/s, 900 kbit/s, 1.00 Mbit/s, 1.10 Mbit/s, 1.20 Mbit/s, 1.30 Mbit/s, 1.40 Mbit/s, 1.50 Mbit/s, 1.75 Mbit/s, 2.00 Mbit/s, 2.10 Mbit/s, 2.20 Mbit/s, 2.30 Mbit/s, 2.40 Mbit/s, 2.50 Mbit/s, 2.75 Mbit/s, 3.00 Mbit/s, 3.50 Mbit/s, 4.00 Mbit/s, 5.00 Mbit/s, 6.00 Mbit/s, 8.00 Mbit/s, 10.00 Mbit/s, 12.00 Mbit/s, 18.00 Mbit/s, 24.00 Mbit/s, 25.00 Mbit/s, 30.00 Mbit/s
H264 B Frame Distance Options (Advanced)
| Value | Description |
|---|---|
| Zero | No B-frames (lowest latency) |
| One | One B-frame between reference frames |
| Two | Two B-frames between reference frames |
H264 Gop Size Options (Advanced)
| Value |
|---|
| Same as processing framerate |
| Same as double processing framerate |
| 25 frames |
| 30 frames |
| 50 frames |
| 60 frames |
| 90 frames |
| 100 frames |
| 120 frames |
| 150 frames |
| 180 frames |
| 200 frames |
| 250 frames |
H264 Profile Options (Advanced)
| Value | Description |
|---|---|
| baseline | Basic profile with widest device compatibility |
| main | Main profile with improved compression |
| high | High profile for best quality at given bitrate |
| high10 | High 10-bit profile |
| high422 | High 4:2:2 chroma profile |
| high444 | High 4:4:4 chroma profile |
Quality/Speed Control Options (Advanced)
| Value | Description |
|---|---|
| ultrafast | Fastest encoding, lowest quality |
| superfast | Very fast encoding |
| veryfast | Fast encoding with reasonable quality |
| faster | Faster than default |
| fast | Fast encoding |
| medium | Balanced speed and quality |
| slow | Slower encoding, better quality |
| slower | Much slower encoding |
| veryslow | Very slow encoding, high quality |
| placebo | Maximum quality, extremely slow |
Tune Options (Advanced)
| Value | Description |
|---|---|
| film | Optimized for film content |
| Animation | Optimized for animated content |
| Grain | Preserves film grain |
| Still image | Optimized for static images |
| psnr | Optimized for PSNR metric |
| ssim | Optimized for SSIM metric |
| Fast decode | Optimized for fast decoding |
| Zero latency | Optimized for lowest latency streaming |
H264 Threads Options (Advanced)
| Value |
|---|
| Zero |
| One |
| Two |
| Three |
| Four |
| Five |
| Six |
| Seven |
| Eight |
Audio Encoders Configuration
The SRT Target 16 Channel Audio supports up to eight independent audio encoder outputs. Audio channels 1-4 take input from the main audio bus using channel mapping. Audio channels 5-8 take input from Audio Channel Strip components.
ImportantImportantImportant
Important: You cannot skip channels
Audio channels must be enabled sequentially without gaps. For example, to use Audio Channel Three, you must also enable Audio Channel One and Two. You cannot skip channels.
Audio Channel One
| Parameter | Default | Description |
|---|---|---|
| Audio channel one encoder | AAC Stereo (L/R) | Audio encoder for channel one |
| Audio channel one mapping | Channels 1 & 2 | Source audio channels to encode from the main audio bus |
| Audio channel one bitrate | 128 kbit/s | Audio bitrate for channel one |
| Audio channel one language description | (empty) | Language metadata tag for channel one |
Audio Channel Two
| Parameter | Default | Description |
|---|---|---|
| Audio channel two encoder | None (disabled) | Audio encoder for channel two |
| Audio channel two mapping | Channels 3 & 4 | Source audio channels to encode from the main audio bus |
| Audio channel two bitrate | 128 kbit/s | Audio bitrate for channel two |
| Audio channel two language description | (empty) | Language metadata tag for channel two |
Audio Channel Three
| Parameter | Default | Description |
|---|---|---|
| Audio channel three encoder | None (disabled) | Audio encoder for channel three |
| Audio channel three mapping | Channels 5 & 6 | Source audio channels to encode from the main audio bus |
| Audio channel three bitrate | 128 kbit/s | Audio bitrate for channel three |
| Audio channel three language description | (empty) | Language metadata tag for channel three |
Audio Channel Four
| Parameter | Default | Description |
|---|---|---|
| Audio channel four encoder | None (disabled) | Audio encoder for channel four |
| Audio channel four mapping | Channels 7 & 8 | Source audio channels to encode from the main audio bus |
| Audio channel four bitrate | 128 kbit/s | Audio bitrate for channel four |
| Audio channel four language description | (empty) | Language metadata tag for channel four |
Additional Audio Encoders Configuration
Audio channels 5-8 use Audio Channel Strip components as their input source instead of the main audio bus channel mapping. This allows for flexible audio routing from auxiliary buses.
Audio Channel Five
| Parameter | Default | Description |
|---|---|---|
| Audio channel five strip source | (none) | Select an Audio Channel Strip component as the audio source |
| Audio channel five encoder | AAC Stereo (L/R) | Audio encoder for channel five |
| Audio channel five bitrate | 128 kbit/s | Audio bitrate for channel five |
| Audio channel five language description | (empty) | Language metadata tag for channel five |
Audio Channel Six
| Parameter | Default | Description |
|---|---|---|
| Audio channel six strip source | (none) | Select an Audio Channel Strip component as the audio source |
| Audio channel six encoder | AAC Stereo (L/R) | Audio encoder for channel six |
| Audio channel six bitrate | 128 kbit/s | Audio bitrate for channel six |
| Audio channel six language description | (empty) | Language metadata tag for channel six |
Audio Channel Seven
| Parameter | Default | Description |
|---|---|---|
| Audio channel seven strip source | (none) | Select an Audio Channel Strip component as the audio source |
| Audio channel seven encoder | AAC Stereo (L/R) | Audio encoder for channel seven |
| Audio channel seven bitrate | 128 kbit/s | Audio bitrate for channel seven |
| Audio channel seven language description | (empty) | Language metadata tag for channel seven |
Audio Channel Eight
| Parameter | Default | Description |
|---|---|---|
| Audio channel eight strip source | (none) | Select an Audio Channel Strip component as the audio source |
| Audio channel eight encoder | AAC Stereo (L/R) | Audio encoder for channel eight |
| Audio channel eight bitrate | 128 kbit/s | Audio bitrate for channel eight |
| Audio channel eight language description | (empty) | Language metadata tag for channel eight |
Audio Encoder Options
These options apply to all audio channels.
| Value | Description |
|---|---|
| None (disabled) | Audio channel is disabled |
| AAC Stereo (L/R) | Stereo AAC encoding with left/right channels |
| AAC Mono downmix (L+R) | Mono AAC encoding with left+right downmix |
Audio Channel Mapping Options
These options apply to audio channels 1-4 only.
| Value | Description |
|---|---|
| Channels 1 & 2 | Maps input audio channels 1 and 2 from the main audio bus |
| Channels 3 & 4 | Maps input audio channels 3 and 4 from the main audio bus |
| Channels 5 & 6 | Maps input audio channels 5 and 6 from the main audio bus |
| Channels 7 & 8 | Maps input audio channels 7 and 8 from the main audio bus |
Audio Bitrate Options
Available bitrates: 8 kbit/s, 16 kbit/s, 24 kbit/s, 32 kbit/s, 40 kbit/s, 48 kbit/s, 56 kbit/s, 64 kbit/s, 80 kbit/s, 96 kbit/s, 128 kbit/s, 160 kbit/s, 192 kbit/s, 224 kbit/s, 256 kbit/s, 320 kbit/s, 384 kbit/s
Options (Advanced)
| Parameter | Default | Description |
|---|---|---|
| Warn on low average bitrate (<10%) | Enabled | Display warnings when average bitrate falls below 10% of target |
| Reconnect Interval | 5 seconds | Time to wait before attempting automatic reconnection after disconnection |
| Max output queue size (packets) | 150 | Maximum number of packets to buffer before dropping. Range: 150-500 |
| Allow frame skipping | Disabled | When enabled, allows dropping frames if output queue warnings occur |
Reconnect Interval Options (Advanced)
| Value | Description |
|---|---|
| (Never) | Automatic reconnection disabled |
| 1 second | Wait 1 second before reconnecting |
| 3 seconds | Wait 3 seconds before reconnecting |
| 5 seconds | Wait 5 seconds before reconnecting |
| 10 seconds | Wait 10 seconds before reconnecting |
| 15 seconds | Wait 15 seconds before reconnecting |
| 20 seconds | Wait 20 seconds before reconnecting |
| 30 seconds | Wait 30 seconds before reconnecting |
Commands
| Command | Description |
|---|---|
| Start sending | Starts the video encoder and begins streaming to the SRT destination (changes to "Start listening" in listener mode) |
| Stop sending | Stops the encoder and disconnects from the SRT destination (changes to "Stop listening" in listener mode) |
Status Information
These fields display real-time information about the SRT stream and are read-only.
| Field | Description |
|---|---|
| Log | Recent log messages from the SRT Target |
| Uptime since start | Duration since the stream was started |
| Outgoing bitrate | Current measured outgoing bitrate |
| SRT message time | Timestamp of the last SRT status message |
| Number of audio channels used | Count and description of active audio channels |
Performance and Properties
These fields display connection statistics and diagnostics and are read-only.
| Field | Description |
|---|---|
| Number of reconnects | Count of automatic reconnections performed |
| Current SRT endpoint | The currently connected SRT server address |
| Error counter | Total number of errors encountered |
| Last Error DateTime | Timestamp of the most recent error |
| Warning counter | Total number of warnings encountered |
| Last Warning DateTime | Timestamp of the most recent warning |
Workflow Tips
Basic Setup
- Enter your SRT server address in the format
srt://ip:port - Configure SRT options for your network conditions (default 200ms latency works for most cases)
- Set video bitrate appropriate for your content and available bandwidth
- Enable at least one audio channel with appropriate mapping
- Click Start sending to begin streaming
Multi-Language Audio Setup
- Configure audio channels 1-4 for your main language tracks using channel mapping from the main audio bus
- For additional languages, create Audio Channel Strip components in your project
- Route your additional language sources to the Audio Channel Strips
- Configure audio channels 5-8 to use those Audio Channel Strips as sources
- Set appropriate language description metadata for each channel (e.g., "eng", "spa", "fra", "deu")
- Remember: Audio channels must be continuous - no gaps allowed
Using Audio Channel Strips
Audio Channel Strips act as auxiliary audio buses. To use them with channels 5-8:
- Add Audio Channel Strip components to your project
- Route audio sources to the strips using send controls
- In the SRT Target 16 Channel Audio, select the appropriate strip for each channel 5-8
- Configure encoder and bitrate settings for each channel
Low Latency Streaming
- Keep Use NVENC as video encoder enabled for hardware acceleration
- Use Zero latency tune setting (default)
- Set H264 B frame distance to Zero (default)
- Keep H264 Gop size at a low value
- Reduce SRT latency in options if network conditions allow
High Quality Streaming
- Increase Video bitrate to match your bandwidth capacity
- Consider using high profile for better compression efficiency
- Use slower Quality/Speed control presets if CPU/GPU resources allow
Network Reliability
- Set Reconnect Interval to automatically recover from disconnections
- Increase SRT latency in options for unreliable networks
- Enable Warn on low average bitrate (<10%) to monitor stream health
- Monitor Error counter and Warning counter for issues
Troubleshooting
Audio channels configuration error:
- Ensure audio channels are configured continuously without gaps
- You cannot enable channel 3 if channel 2 is disabled
Stream fails to connect:
- Verify the SRT server address is correct and reachable
- Check that the destination port is open and the SRT server is running
- Ensure SRT stream id is provided if required by the destination
High latency or buffering:
- Reduce video bitrate if bandwidth is limited
- Increase SRT latency parameter for unstable networks
- Check Outgoing bitrate matches your target bitrate
Video quality issues:
- Increase video bitrate
- Try a slower Quality/Speed control preset
Audio not working:
- Verify at least one audio encoder is not set to "None (disabled)"
- For channels 1-4: Check audio channel mapping matches your input audio configuration
- For channels 5-8: Ensure the selected Audio Channel Strip has audio routed to it
- Ensure source audio is present in Composer
Frequent disconnections:
- Increase SRT latency for network instability
- Check network connectivity and bandwidth
- Set appropriate Reconnect Interval for automatic recovery
- Review error and warning counters for patterns
NVENC encoder not available:
- Verify NVIDIA GPU is installed and drivers are up to date
- Disable Use NVENC as video encoder to fall back to software encoding
- Check GPU is not overloaded by other applications
Output queue warnings:
- Reduce video bitrate
- Enable Allow frame skipping as temporary measure
- Check CPU/GPU load and network bandwidth
- Increase Max output queue size (packets) if needed