# Using FFmpeg with OptiView Live

**FFmpeg** is a free open-source command-line tool for handling video, audio, and other multimedia. It is commonly used in production workflows to broadcast a media file using RTMP to OptiView Live.

> **Tip**
>
> See the official [ffmpeg.org](https://ffmpeg.org/) documentation for installation instructions and additional support.

## Streaming a file

```shell
ffmpeg -re -stream_loop -1 -i /path/to/file.mp4 \
  -c:v copy -c:a copy -f flv \
  -rtmp_playpath "your-stream-key" \
  -rtmp_live live "rtmps://rtmp.<region>.theo.live/live"
```

| Parameter        | Description                                                   |
| ---------------- | ------------------------------------------------------------- |
| -re              | Read input at native frame rate (for file-based sources only) |
| -stream\_loop -1 | Loop the video indefinitely                                   |
| -c:v copy        | Copy the video codec from the input                           |
| -c:a copy        | Copy the audio codec from the input                           |
| -f flv           | Package flash video                                           |

> **-re flag**
>
> Do not use the `-re` flag when the input is an actual capture device or a live stream as it may cause packet loss and higher latency.

> **Upload bandwidth**
>
> Make sure that your encoder has a stable connection and enough upload bandwidth. This will ensure all data is correctly sent to the OptiView Live channel.

## Low Latency Encoding Settings

The following settings are recommended to achieve the lowest possible latency when re-encoding when streaming to OptiView Live. These prioritize encoding speed and reduced buffering at the cost of some video quality.

| Parameter         | Description                                                 |
| ----------------- | ----------------------------------------------------------- |
| -vb 4500k         | Video Bitrate setting of 4.5 Mbps                           |
| -vprofile main    | H264 video profile                                          |
| -g 60             | Group of pictures (GOP) size                                |
| -preset veryfast  | Faster encoding speed at the cost of compression efficiency |
| -tune zerolatency | Disables internal buffering for low-latency streaming       |
| -bf 0             | Disable B-frames to reduce encoding delay                   |

```shell
ffmpeg -f decklink -i "DeckLink Mini Recorder" \
  -vcodec libx264 -vb 4500k -vprofile main -g 60 \
  -preset veryfast -tune zerolatency -bf 0 \
  -c:a aac -ab 128k -f flv \
  -rtmp_playpath "your-stream-key" \
  -rtmp_live live "rtmps://rtmp.<region>.theo.live/live"
```