Top HTML5 Video Interview Questions and Answers

HTML5 video has revolutionized web development by making it easy to embed and stream video without third-party plugins. As video continues to grow as a fundamental medium of online communication, understanding HTML5 video has become an essential skill for any web developer or engineer.

In this article, we’ll explore some of the most common and important HTML5 video interview questions that employers may ask related to

• Key features of HTML5 video
• Implementation and syntax
• Browser support
• Performance optimization
• Comparison to Flash and other plugins

Whether you’re prepping for an upcoming HTML5 interview, or just want to brush up on your video skills, read on for the top HTML5 video interview questions and answers.

HTML5 Video Interview Questions

Here are some of the most frequently asked HTML5 video interview questions

Q1. Give a simple implementation of the <video> tag to embed a video stored at http://www.example.com/amazing_video.mp4.

<video width="320" height="240" controls>  <source src="http://www.example.com/amazing_video.mp4" type="video/mp4"></video>

To embed a video the <video> tag is used. The src attribute points to the video source file. type specifies the video format. width and height set the player dimensions. controls displays the browser’s default video controls.

Q2. How does the HTML5 <video> tag differ from the <embed> tag?

The <video> tag is new in HTML5 and provides a standard way to embed video that is supported across modern browsers. <embed> is an older generic embed tag that often required third-party plugins like Flash. The <video> tag has better accessibility, performance, and semantic meaning.

Q3. What are some supported video formats for the HTML5 <video> element?

HTML5 <video> supports MP4, WebM, and Ogg video. MP4 has the widest browser support. WebM and Ogg provide free open source formats. To support multiple browsers provide MP4 and WebM or Ogg sources.

Q4. How can you embed a YouTube or Vimeo video in HTML5?

Use the iframe embed code provided by YouTube and Vimeo directly into your HTML. Make sure to include width, height, frameborder, allowfullscreen, and other attributes for proper display and permissions.

Here’s an example of embedding a YouTube video:

<iframe width="560" height="315" src="https://www.youtube.com/embed/12345abc" frameborder="0" allowfullscreen></iframe>

Q5. What are some benefits of using the HTML5 <video> tag over Flash or other plugins?

Some key benefits include:

• Better performance – HTML5 video runs natively in the browser without plugins.

• Wider device support – Works on mobile devices that don’t support plugins.

• More semantic meaning – <video> clearly defines video content.

• Accessibility – HTML5 video integrates better with assistive technologies.

• Easier styling/scripting – using CSS and JavaScript.

Q6. How can you control video playback programmatically using JavaScript?

Use the HTMLMediaElement API to control video playback:

// Get video element var video = document.querySelector("video");// Functions like:video.play(); // playvideo.pause(); // pausevideo.volume = 0.5; // set volume

Q7. What are some important <video> attributes that can be set?

Some commonly used attributes include:

• src – The video URL
• controls – Show browser controls
• autoplay – Auto-start playback
• loop – Loop when finished
• muted – Mute audio by default
• poster – Image shown before playing
• preload – Preload data on page load

Q8. What are some use cases where HTML5 video provides the best solution?

Some ideal use cases include:

• Streaming hosted video content
• Embedding videos natively without plugins
• Building customized video players with JavaScript
• Displaying videos on mobile and tablet devices
• Websites focused on video content like screencasts or courses

Q9. How can you ensure older browsers support HTML5 video?

The <video> tag is not supported in older IE versions. To support IE 8/9 provide a Flash fallback using SWFObject. Modernizr library also helps detect support. Also set reasonable min-width and min-height on <video> for graceful degradation.

Q10. What are some tools that can be used to convert video formats?

Some commonly used command line tools include:

• FFmpeg – Cross-platform converter
• Handbrake – Great for optimizing MP4s
• Miro – Nice GUI converter

There are also many online converter tools like Zamzar, CloudConvert, Convertio, etc.

Q11. What are some tips to ensure HTML5 video works well across browsers?

Some tips:

• Offer both MP4 and WebM sources
• Use a Jpeg poster image for the first frame
• Handle unsupported browsers gracefully
• Set correct MIME types on sources
• Compress videos without losing too much quality
• Use a CSS wrapper div to constrain proportions
• Preload metadata to improve performance

Q12. What are some factors to consider regarding performance when serving HTML5 video?

Some performance considerations include:

• File size/compression – optimize with FFmpeg or Handbrake
• Hosting/delivery – use a CDN like CloudFlare or Azure
• Image resolution – provide SD, HD, and Ultra HD options
• Page load impact – lazy load offscreen videos
• Video length – avoid very long videos when possible
• Buffering configuration – find optimal buffer size
• Analytics – monitor playback errors and statistics

Q13. What are Media Fragments and how can they be used with HTML5 video?

Media Fragments allow extracting a portion of a video by adding #t=START,END to the end of a URL. This can be used to play slices of videos without editing the source.

For example:

<source src="video.mp4#t=30,60">

Plays the video from second 30 to 60. Very useful for creating previews!

Q14. How can you check if a browser supports a particular video format?

Check for support using the canPlayType method:

var mp4 = document.createElement("video").canPlayType("video/mp4"); if (mp4 == "") {  // MP4 not supported} else if (mp4 == "probably") {   // MP4 supported}

Q15. What are some differences between streaming video vs progressive downloads?

Some key differences:

• Streaming video loads chunks of content continuously from server. Progressive downloads the entire file first.

• Streaming allows seeking through the video. Progressive downloads must download to certain point before allowing seek.

• Streaming adapts to changing network conditions by adjusting quality. Progressive downloads can easily fail or stall on slower networks.

• Streaming protocols include HLS, MPEG-DASH, RTMP. Progressive uses HTTP.

Q16. What is MPEG-DASH and how does it help with HTML5 video delivery?

MPEG-DASH is an adaptive streaming protocol that breaks video into small HTTP-based chunks allowing switching between quality levels as network conditions change. This provides a reliable streaming experience. Integrates well with HTML5 video capabilities.

Q17. How can you protect or DRM encrypt HTML5 video content?

Some options to encrypt HTML5 video streams include:

• Microsoft PlayReady
• Google Widevine
• Apple FairPlay Streaming
• HTML5 Premium Extensions
• Media Source Extensions + Encryption

This prevents unauthorized download/distribution of video assets.

Q18. What is AV1 and how does it compare to other HTML5 video codecs?

AV1 is a new open source royalty-free video codec. It offers better compression efficiency than older codecs like H.264 and VP9. Enables high quality 4K and HD video at lower bitrates. Supported by many major browsers and platforms. Expected to become a popular HTML5 video codec.

Summary

In this guide we explored 18 HTML5 video interview questions covering everything from basic syntax, performance, adaptive streaming, security, codecs, and more. HTML5 video skills allow building rich media experiences on the web.

Knowing these fundamentals will help you be prepared to discuss HTML5 video during any technical interview. The open web offers immense possibilities for delivering immersive video content to billions of users worldwide. Leveraging HTML5 video is key knowledge for any aspiring web developer or engineer.