---
title: "SRT Target (8 Channel Audio)"
slug: "srt-target"
updated: 2026-02-26T07:53:39Z
published: 2026-02-26T07:53:39Z
---

> ## Documentation Index
> Fetch the complete documentation index at: https://composer.docs.vindral.com/llms.txt
> Use this file to discover all available pages before exploring further.

# SRT Target (8 Channel Audio)

The **SRT Target** is an output component that sends video and audio from Composer to any SRT (Secure Reliable Transport) receiver. SRT is designed for low-latency, high-quality video transmission over unpredictable networks, making it ideal for live production workflows.

![Image](https://cdn.document360.io/94808959-fd66-406c-ab5e-4691ce952a14/Images/Documentation/image(374).png)---

## When to Use SRT Target

- **Live streaming to SRT receivers**: Send content to media servers, encoders, or CDNs that accept SRT input
- **Contribution feeds**: Deliver high-quality video over the internet with low latency
- **Point-to-point streaming**: Direct streaming between locations with reliable delivery
- **Backup or redundant streams**: Create additional output paths for failover scenarios

Need more audio channels or advanced routing?

If you need more than **4 stereo audio outputs (8 channels total)**, or want to route audio from **Audio Channel Strip components**, use **SRT Target 16 Channel Audio** instead. The standard SRT Target only uses the **main audio bus (channels 1–8)** and supports up to **four stereo encoders**.

---

## Setup

1. **Add SRT Target** to your project outputs
2. **Configure the SRT address**: Enter the destination server address in SRT URL format
3. **Set SRT options**: Configure packet size and latency parameters
4. **Configure video settings**: Set bitrate and encoding options appropriate for your use case
5. **Configure audio channels**: Enable and map audio channels as needed
6. **Start sending**: Use the Start sending command to begin streaming

---

## 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** | Enabled | 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 |
| --- | --- | --- |
| **SRT base server address (srt://ip:port)** | `srt://[ipadress]:[port]` | The destination SRT server address in URL format. Replace with your actual server IP and port |
| **SRT options (packet size, latency etc)** | `pkt_size=1316&latency=200000` | URL query parameters for SRT connection settings. Default configures 1316-byte packets and 200ms latency |
| **SRT stream id (optional, may be required by CDN)** | *(empty)* | Optional stream identifier required by some CDNs or SRT servers for stream routing |
| **SRT connection string** | *(auto-generated)* | Read-only field showing the complete connection string built from the above parameters |

#### Dynamic Placeholders

The **SRT base server address** 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 **SRT options** 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/HEVC 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 |
| **Use HEVC as video codec** | Disabled | Use HEVC/H.265 codec instead of H.264 |
| **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 range from **50 kbit/s** to **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 |
| stillimage | Optimized for static images |
| psnr | Optimized for PSNR metric |
| ssim | Optimized for SSIM metric |
| fastdecode | Optimized for fast decoding |
| zerolatency | Optimized for lowest latency streaming |

#### H264 Threads Options *(Advanced)*

Available values range from **Zero** to **Eight**.

---

### Audio Encoders Configuration

The SRT Target supports up to four independent audio channels, each with its own encoder, channel mapping, bitrate, and language metadata.

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 |
| **Audio channel one bitrate** | 384 kbit/s | Audio bitrate for channel one |
| **Audio channel one language description** | *(empty)* | Language metadata tag for channel one |

#### Audio Channel Two *(Advanced)*

| 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 |
| **Audio channel two bitrate** | 384 kbit/s | Audio bitrate for channel two |
| **Audio channel two language description** | *(empty)* | Language metadata tag for channel two |

#### Audio Channel Three *(Advanced)*

| 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 |
| **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 *(Advanced)*

| 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 |
| **Audio channel four bitrate** | 96 kbit/s | Audio bitrate for channel four |
| **Audio channel four language description** | *(empty)* | Language metadata tag for channel four |

#### 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

| Value | Description |
| --- | --- |
| Channels 1 & 2 | Maps input audio channels 1 and 2 |
| Channels 3 & 4 | Maps input audio channels 3 and 4 |
| Channels 5 & 6 | Maps input audio channels 5 and 6 |
| Channels 7 & 8 | Maps input audio channels 7 and 8 |

#### Audio Bitrate Options

Available bitrates range from **8 kbit/s** to **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 |
| Instant | Reconnect immediately |
| 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 |
| **Stop sending** | Stops the encoder and disconnects from the SRT destination |
| **Reconnect** | Forces a reconnection to the SRT destination |

---

### 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

1. Enter your SRT server address in the format `srt://ip:port`
2. Configure SRT options for your network conditions (default 200ms latency works for most cases)
3. Set video bitrate appropriate for your content and available bandwidth
4. Enable at least one audio channel with appropriate mapping
5. Click **Start sending** to begin streaming

### Low Latency Streaming

1. Keep **Use NVENC as video encoder** enabled for hardware acceleration
2. Use **zerolatency** tune setting (default)
3. Set **H264 B frame distance** to Zero (default)
4. Keep **H264 Gop size** at a low value
5. Reduce SRT latency in options if network conditions allow

### High Quality Streaming

1. Increase **Video bitrate** to match your bandwidth capacity
2. Consider using **high** profile for better compression efficiency
3. Use slower **Quality/Speed control** presets if CPU/GPU resources allow

### Multi-Language Audio

1. Enable multiple audio channels (up to 4)
2. Map each channel to different input channel pairs
3. Set appropriate **language description** for each channel (e.g., "eng", "spa", "fra")
4. Adjust bitrates based on content requirements

### Network Reliability

1. Set **Reconnect Interval** to automatically recover from disconnections
2. Increase SRT latency in options for unreliable networks
3. Enable **Warn on low average bitrate** to monitor stream health
4. Monitor **Error counter** and **Warning counter** for issues

---

## Troubleshooting

**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)"
- Check audio channel mapping matches your input audio configuration
- 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** if needed