Live Broadcasting Guidelines

These guidelines help you choose the right broadcasting settings (encoding, bitrate, resolution, framerate, keyframes interval …). In reality, some settings may vary depending on your broadcast soft/hardware, internet speed and type of video content.

Keep in mind that Clevercast does server-side transcoding for adaptive streaming. The video stream you send is used as the highest resolution of the video, but the live stream will also contain other resolutions (= 1080p, 720p, 480p, 360p and 240p, by default). Clevercast player will dynamically switch to the resolution most suitable for the device that you are using (depending on screen size, bandwidth, CPU/GPU).

After you’ve configured your broadcast, you should test if the live stream is stable (preferably in circumstances similar to the live event). Choose a lower resolution and/or bitrate if the stream isn’t stable (due to a lack of outgoing bandwidth or internet connection speed). It’s better to have a stable stream than to push for a higher video quality that results in dropped frames.

Below are our recommended encoder settings for 1080p en 720p resolutions. If you want to stream higher resolutions (2K or 4K) please contact us.

• Resolution: 1920×1080
• Bitrate: 3000 – 6000 kbps
• Rate Control: CBR if you use Translate at Home, otherwise you can also use VBR
• Video Framerate* : 25 fps (preferred) or 30 fps
• Keyframe Interval* : 2 seconds (never 0 or more than 4 seconds)
• (H.264) Profile: Main or High
• Audio Samplerate: 48 kHz (preferred)
• Preset: Quality
• B-frames: 2

* In case of multilingual live streaming we currently stream with a framerate of 25 fps and keyframe interval of 2 seconds, no matter what framerate your broadcast contains. We strongly recommend to also use a framerate of 25 fps and keyframe interval of 2 seconds in your broadcast. Other framerates may cause the floor audio to go shortly out of sync, if not all frames are delivered to Clevercast in time (eg. network connections, insufficient bandwidth at the event location).

The video quality of your live stream depends on a number of elements:

• Resolution & Bitrate : Resolution refers to the size of a video on a screen: use 1080p for Full HD, 720p for HD. Note that Clevercast also delivers lower resolutions for smaller screens through adaptive streaming. Bitrate is the number of bits you are broadcasting per second. Resolution and bitrate go hand in hand: streaming at a higher resolution takes a higher bitrate. Both are limited by your encoding resources and upload bandwidth. Increasing your bitrate can improve video quality, but only up to a point. Having a stable stream is paramount.
• Framerate & Keyframe interval: Framerate refers to the number of image frames that are sent per second. Therefore, a higher framerate takes more encoding power. Keyframes are points in the video where the entire frame is sent instead of just the differences from the previous frame. Having a keyframe interval of 2 means that it takes at most 2 seconds for the viewers to catch up to a point where they can properly display the feed. We recommend a framerate of 25 Frames Per Second (FPS) and a keyframe interval of 2 seconds (or 50 frames). If this isn’t possible, you can also use a framerate of 30 FPS instead. The keyframe interval should never be more than 4 seconds.

For a regular live stream, you should broadcast a single audio track in mono or stereo. This is also the case if you’re using Translate at Home.

The Sample Rate should be set to 48 kHz. An Audio Bitrate of 128 kbps will suffice in most circumstances.

For broadcasts with embedded audio streams, see our guides for multiple audio tracks with SRT and multiple audio channels with RTMP.

Encoding can be taxing on your system. If you can, use GPU encoding (eg NVIDIA NVENC). This will let you broadcast better quality video, without overloading your CPU.

Before you test your broadcast at the event location, you may want to test your connection.

• Run a speed test at the event location to verify your available upload bandwidth. The resolution and bitrate (see below) you can use depends on the available upload bandwidth.
• Make sure that your encoder is cabled and has reserved bandwidth if possible. Only use Wifi (or 4/5G) if necessary. Keep in mind that during the event more people will use the network (and Wifi), so the upload bandwidth may also be lower.
• Also make sure that your broadcast is not blocked by a firewall.
• Note that members of the same company should refrain from watching the live stream via their intranet as much as possible. Otherwise the intranet may get congested, which may also disturb the broadcast.