Dual Encoding

Dual Encoding is designed to ensure that your viewers receive a video which is the appropriate bit rate for the bandwidth of their internet connection.
Faster connections can play high quality video with ease. However, not all connections are made equal, and slower connections frequently struggle with HD video. Instead, they benefit from a lower quality video, which can be played without continuous buffering.

Dual Encoding creates two versions (known as 'renditions') of your video. One at a 'standard' definition (SD) and another at a higher definition (HD). These are delivered according to the bandwidth available.

Dual Encoding settings

When you upload a video, you will see an option to turn on Dual Encoding, towards the bottom of the upload screen. Once dual encoding is enabled, the encoder will produce a standard definition copy of your video. This is produced using the bit rate you’ve set in the standard  encoding settings.
After the encoder has produced an SD copy of your video, it will automatically encode a second, high definition, copy. The quality of this HD encoding can be set within your account’s  encoding settings:

If you set a HD encoding bit rate, which exceeds the bit rate of your video, we’ll encode the HD rendition to match the bit rate of your source (original) file.

What does this mean for my viewers?

The behavior of Dual Encoded videos will vary, according to the  delivery method you’re using.
If you send your videos via RTMPe streams, we will automatically determine the best video quality for the connection speed. This means that, as the video plays, we dynamically alter its bit rate according to the bandwidth available. This should ensure that the video always plays, whilst retaining the best possible quality.
If you send your video via HTTP Progressive Download delivery, the user will be offered a choice between the SD and HD options:

This is because the delivery method is a continuous download, rather than a video stream, so we cannot dynamically select the best encoding.

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