Left-only/Right-only – a stereo audio format that contains only the left and right channels without any matrix-encoded surround information, used as a basic stereo deliverable for platforms that don't support or require surround decoding capabilities.
What is LoRo?
LoRo (Left-only/Right-only) is a simple stereo audio format that contains only the left and right channels without matrix-encoded surround information. It is the basic form of a stereo downmix for platforms without surround decoding.
Basic Principle
| Aspect | Description |
|---|---|
| Meaning | Left-only/Right-only |
| Channels | 2 (L + R) |
| Surround Info | None |
| Decoding | Not required |
LoRo vs. LtRt
| Aspect | LoRo | LtRt |
|---|---|---|
| Channels | 2 | 2 |
| Surround Info | None | Matrix-encoded |
| Decoding | No | Yes (Pro Logic) |
| Complexity | Simple | Complex |
Channel Content
| Channel | Content |
|---|---|
| Left | Left side only |
| Right | Right side only |
| Center | Distributed in the mix |
| Surround | Not included |
Typical Downmix Formula
| Source | Target L | Target R |
|---|---|---|
| L | 1.0 | 0 |
| R | 0 | 1.0 |
| C | 0.707 | 0.707 |
| Ls | 0.707 | 0 |
| Rs | 0 | 0.707 |
Application Areas
| Platform | Usage |
|---|---|
| Simple Players | Without decoder |
| Web Streaming | Basic audio |
| Mobile Devices | Without surround |
| Archiving | Simple stereo |
Creation
| Method | Description |
|---|---|
| DAW Downmix | Automatic |
| Console Folddown | Hardware |
| Manual Mix | Separate stereo version |
| Encoder | At delivery |
Advantages
| Advantage | Description |
|---|---|
| Compatibility | Playable everywhere |
| Simplicity | No decoding |
| Consistency | Always the same |
| File Size | Smaller than surround |
Disadvantages
| Disadvantage | Description |
|---|---|
| No Surround | Loss of dimensionality |
| Phase Loss | In 5.1 downmix |
| Less Immersive | Flatter listening experience |
| Center Distribution | Dialogue less focused |
Quality Control
| Check | Criterion |
|---|---|
| Level | Correct loudness |
| Balance | L/R balanced |
| Phase | No cancellations |
| Dialogue | Understandable |
Delivery Requirements
| Platform | Specification |
|---|---|
| Netflix | LoRo as an option |
| Amazon | LoRo required |
| Broadcast | Often LoRo standard |
| DVD/BD | As an alternative |
Technical Specifications
| Parameter | Typical Value |
|---|---|
| Sample Rate | 48kHz |
| Bit Depth | 24-bit |
| Loudness | -24 LKFS (TV) |
| True Peak | -2 dBTP |
Difference to Mono
| Aspect | LoRo | Mono |
|---|---|---|
| Channels | 2 | 1 |
| Stereo Image | Yes | No |
| File Size | 2x | 1x |
| Compatibility | Standard | Universal |
Post-Production Workflow
| Phase | Activity |
|---|---|
| 5.1 Mix | Surround version |
| LtRt | Matrix downmix |
| LoRo | Simple downmix |
| QC | Check all versions |
Avoiding Phase Issues
| Measure | Description |
|---|---|
| Correlation | Check |
| Mono Check | Turn off? |
| Dialogue | Center handling |
| Music | Stereo balance |
Software Tools
| Tool | Function |
|---|---|
| Pro Tools | Downmix options |
| Nuendo | MixConvert |
| DaVinci Resolve | Fairlight |
| Plugins | Dedicated Downmixer |
Best Practices
| Practice | Reason |
|---|---|
| Separate QC | Compare LoRo vs. LtRt |
| Dialogue Check | Understandability |
| Loudness | Adhere to standards |
| Documentation | What is what? |
Today
LoRo remains an important component of professional audio deliveries. Although surround sound is standard on many platforms, simpler playback devices and certain streaming services still require a clean LoRo stereo. The correct creation and quality control of both stereo formats (LoRo and LtRt) is part of the standard audio post-production workflow.