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Setting up a low latency HTML5 channel : Walkthrough

This guide is dedicated to the configuration for a low latency HTML5 channel. The low latency HTML5 channel solution is only available starting at the Pro plan and all above plans. More details available here

You will find here: 

-where to find your channel information to enter in your encoder

-all of our tips to reduce the latency to the maximum and to deliver the best quality to your viewers

 

1st Part : Encoder setup for low latency HTML5

This guide focuses solely on the Encoder Setup step. It is broken into three steps to mimic its presentation on the site:

1. Publishing Point

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Publishing Point
Our system auto-detects and optimizes the selection of the publishing point based on the location of your stream.

Stream Quality
Please note that DaCast does not support adaptative live transcoding for now but soon will!
Right now it uses a multi-bitrate method for live video wherein the broadcaster can setup several different qualities to stream at. 

Our player is adaptive and automatically detects your encoder multi-bitrate settings to provide the best quality stream to your viewers based upon their connections.

 

2. Select an Encoder

 

Various encoders are displayed here:

  • OBS Studio: an open broadcaster software that you can use to freely and easily set up your stream. 
    Please be aware that OBS studio does not support multi-bitrate. 
  • Wirecast: a paid software encoder available for Max and Windows (free demo is available but your broadcasts will contain both video and audio watermarks)
  • VMix: a paid encoder for Windows (free 60 days trial)
  • VIDBlaster: a paid encoder for Windows (free demo available but your broadcasts will contain video watermark)
  • Other RTMP Encoders: you are free to use any hardware or software encoders with DaCast as long as they are RTMP-based. 

When choosing the setup in your encoder, make sure your KeyFrame interval is 2 or 3 seconds and nothing else.

 

To have more information on the supported codec and Stream redundancy, Click here. (Part B and C)

3. Start Streaming

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The third step contains the information you will need to enter in your encoder to connect it to your DaCast live channel. 

- Stream URL and Stream names are always needed. If you are having trouble using the Stream URL you might use the Backup URL. 

Example of Stream URL: rtmp://54.193.135.91:1935/live-86671-449175
Example of Back Up URL: rtmp://54.193.135.91:1935/live-86671-449175
Example of Stream name: mystream443175

Some encoders have one URL field only. If this is your case, please go into the "Other RTMP encoders" (step 2) and click on the link below the back up URL to access a full URL. The full URL is a combination of the Stream URL and the stream name. 

Example of a Full URL: rtmp://54.193.135.91:1935/live-86671-443175/mystream449175

- Login and Password are needed when DaCast is not integrated in the dropdown menu of the encoder. 

Example of Login: dacast-449175
Example of Password: 321654

When DaCast is available in the dropdown menu of your encoder you can log in to your account by using your DaCast credentials. 

2nd part : Encoder configuration for the lowest latency and best quality

In this part we will mention all the best settings and configuration in order to have the best quality on your low latency stream. The delay with those settings should remain below 10 seconds (Compared to 30-40 seconds for the normal channel)

You can feel free to change those settings to your liking but it is likely that the latency and the quality will differ.

1. Wirecast (Windows)

wirecast_windows.png

  • Encoder: Intel QuickSync H.264
  • Width and Height: will depend on the quality of the stream you want to send to your viewer. A standard definition is 854x480
  • Frames per second : 30 frames
  • Average bitrate : will depend on your internet connection and resolution (for a standard definition you will want to target 500 Kbps - 2 Mbps for video)
  • Quality : Medium (balanced)
  • Profile : Baseline
  • Keyframe every : 60 frames
  • Timecode every  :30 frames
  • Channel: Stereo
  • Target bitrate : 128kbps
  • Sample rate: 44.100 kHz (however if you notice audio sync issues, try 24.00 kHz)

Latency obtained in-house: 8.63s

 

2. Wirecast (Mac)

wirecast_mac.png

 

 

  • Encoder: Apple H.264
  • Width and Height: will depend on the quality of the stream you want to send to your viewer. A standard definition is 854x480
  • Frames per second : 30 frames
  • Average bitrate : will depend on your internet connection and resolution (for a standard definition you will want to target 500 Kbps - 2 Mbps for video)
  • Profile : High
  • Keyframe every : 60 frames
  • Channel: Stereo
  • Target bitrate : 128 kbps
  • Sample rate: 44.100 kHz (however if you notice audio sync issues, try 24.00 kHz)

Latency obtained in-house: 8.39s

 

3. Vmix

vmix.png

The encoder has been set up for a standard definition: 

  • Video bitrate: 1025 
  • Resolution: 854x480
  • Audio bitrate: 128 
  • Profile : Baseline
  • Level : 1.0
  • Keyframe Frequency : 2 seconds

Latency obtained in-house: 9.23s

 

4. OBS configuration.

obs_ll.png

The encoder has been set up for a standard definition: 

Output - Streaming:

  • Encoder: x264 
  • Output: 854x480
  • Rate control : VBR 
  • Bitrate: 1,500 
  • CFR: 30 
  • Keyframe interval: 2 
  • CPU: ultrafast 
  • Profile: baseline 

    Output - Audio 
  • Bitrate: 128 kbits

Latency obtained in-house: 8.30

 

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For more detailed tutorials on specific encoders, please have a look at the list below. 
Note that these tutorials are based on our standard html5 live channel infrastructure:

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For additional details on the encoder settings, below is a guideline provided by Akamai, our CDN provider: 

Akamai's (our CDN) Encoding Guidelines on :

  • GOP interval (Keyframe interval) (Paragraph D1)    
  • Frame Rate (FPS) (Paragraph D2)
  • Scene Detection (Paragraph D3)
  • Timestamp (Paragraph D4)
  • Interlaced Content (Paragraph D5) 
  • Encoder CPU Load (Paragraph D6) 

 

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