Optimizing audio & video for the web


Working with audio in dominKnow | ONE is super simple, and it is all about the MP3 format which has become a universal audio format. Most audio recording software exports to MP3 and there are many paid and free MP3 compressors to help optimize your file size. 


MP3 Sample Rate and Resolution 

The factors that impact MP3 file size and quality are sampling rate and sampling resolution. The sampling rate, measured in kilohertz (KHz), is set when sound is digitized.  It affects the audio range by defining the highs and lows of the digitized sound.  Higher sampling rates generate better quality sound and larger audio files.  Some types of sound, such as narration, do not depend on high and low ranges for better quality and can withstand lower sampling rates. The typical sample rates are 22.050 kHz, 44.1 kHz, and 48 kHz and the typical resolutions are 8-bit stereo, 16-bit mono, and 16-bit stereo. 

Smaller File Size - To - Larger File Size

22.050 kHz  

44.1 kHz 

48 kHz 
8-bit stereo16-bit mono16-bit stereo

How do I determine MP3 File Size? 

To help make it easier, you can use this online audio file calculator.  

To determine the file size of an audio file, multiply the bit rate of the audio by its duration in seconds. You can find Stereo and Mono sizes per second, minute, and hour according to bitrate at this Audio File Size resource.

View the calculations and formulas.  




    A standard CD quality is 44.1 KHz at 16-bit stereo resolution. If you reduce 44.1 KHz sampling rate in half to 22.05 kHz it will cut the file size in half. Changing the resolution from stereo to mono also cuts the file size in half. Often, with narration you will not hear a difference between stereo and mono. You should be able to balance acceptable MP3 audio quality and reduction in file size. Some audio tools may have dithering. Dithering adds noise as it reduces the file size. Dithering works best on files with rich full music, so the listener does not notice the noise. For this reason, you should avoid dithering for narration or files that have pauses and silence as it will add some unwanted noise.    


    Some commonly used Audio compression tools 


    Audio “How to” in the dominKnow | ONE Community 


    There are 2 ways to use video in dominKnow | ONE: 

    1. upload the video (MP4) to dominKnow | ONE and insert the video on a page
    2. load the video on a streaming server (youtube, vimeo, etc.) and embed or display the video via a link on a page 

    Understanding all of the different information about video formats, codecs, and containers is helpful but not essential to be productive. 


    Why/when should I upload my video to dominKnow | ONE?

    You can use dominKnow | ONE to store your large production/work files but there are limits to the sizes of the videos you can upload and include while authoring and publishing courses with dominKnow | ONE. A key reason you would upload your video is to take advantage of the interactive video features or xAPI reporting. With dominKnow | ONE, you can set actions and triggers based on the video timeline and overlay/hide/show things based on the video and trigger video playback pause etc. If you are going to take advantage of these advanced interactive features, you will need to get your video ready for the web and optimize the video before uploading to dominKnow | ONE.


    “I’ve made my video; how do I get it ready for the web?” 

    You can start by using this simple video compression guide for the web. 


    What Video format does dominKnow | ONE Recommend?  

    We recommend that the .mp4 format be used for best compatibility across all platforms.


    What Video Codecs/Compression formats should I use? 

    dominKnow | ONE supports the H.264/MPEG-4 or AVC (Advanced Video Coding) video compression codec. This provides the best compression rate without compromising quality and is ideal for online and mobile delivery.  For all media, you should experiment for what works best for your application. Generally, the size of your video should match the maximum size (height and width) that you expect it to be viewed by your learners. Video compression tools have a default use "for web" and we recommend that you start with the "for web" export settings. For more information, refer to dominKnow blog Best Practices for Video Compression.



      How do I make interactive Videos?


      Using Streaming Services to Host and Deliver Your Video

      Streaming video services allow you to embed your video into your eLearning content. The video from streaming services appears in dominKnow just as if you had uploaded it. The difference is that it is using the player and controls from that service rather than the dominKnow | ONE controls. You may want to use a service if your videos are large and over the dominKnow | ONE file size limits. You may also choose a streaming service if you do not need any interactivity around them or if they are already being hosted and delivered from the services.

      Streaming services are being used more and more to support eLearning because they provide the proper infrastructure to deliver your video media across all the devices your learners might have and they support larger video files with a longer run-time. There are pros and cons to the available streaming services, some of which are free and some paid. This article 10 Best Video Hosting Solutions to Consider in 2021 (Free vs Paid) provides good information, including the Video Upload Guidelines and Specifications of each.


      YouTube - Video Upload Guidelines and Specifications

      • Minimum dimension: 240p (426 x 240).
      • Maximum dimension:  4K (3840 x 2160).
      • Aspect ratio: 16:9 (automatically adds black frame for 4:3 videos).
      • Max file size: 128 GB.
      • Max video length: 12 hours.
      • Total file storage: Unlimited.
      • Accepted video formats: .MOV, .MPEG4, MP4, .AVI, .WMV, .MPEGPS, .FLV, 3GPP, and WebM.


      Vimeo - Video Upload Guidelines and Specifications

      • Minimum dimension: 240p (426 x 240).
      • Maximum dimension:  8K (8192 × 4320.
      • Aspect ratio: 16:9 (automatically adds black frame for 4:3 videos).
      • Max file size: 500 MB for free users (up to 256 GB for pro users).
      • Max video length: restricted by file size.
      • Total file storage: 500 MB/week for free users (20 GB/week for pro users).
      • Accepted video formats: .MOV, .MPEG4, MP4, .AVI, .WMV, .FLV, .MKV, 3GPP, etc.


      dominKnow | ONE Custom Playlist Widget

      We have developed a custom widget that you can use to display playlists from streaming services in dominKnow | ONE, see Sample - Playlist Widgets for Youtube and Vimeo videos.


      Commonly Used Video Compression Tools


      Video “How to” in the dominKnow | ONE Community 

      Collection: Web Media Optimization Recommended Practice 

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