YouTube Engineering and Developers Blog: video

Smoother <video> in Chrome

Tuesday, November 10, 2015

Video quality matters, and when an HD or HFR playback isn’t smooth, we notice. Chrome noticed. YouTube noticed. So we got together to make YouTube video playback smoother in Chrome, and we call it Project Butter.
For some context, our brains fill in the motion in between frames if each frame is onscreen the same amount of time - this is called motion interpolation. In other words, a 30 frames per second video won’t appear smooth unless each frame is spaced evenly each 1/30th of a second. Smoothness is more complicated than just this - you can read more about it in this article by Michael Abrash at Valve.
Frame rates, display refresh rates and cadenceYour device’s screen redraws itself at a certain frame rate. Videos present frames at a certain rate. These rates are often not the same. At YouTube we commonly see videos authored at 24, 25, 29.97, 30, 48, 50, 59.94, and 60 frames per second (fps) and these videos are viewed on displays with different refresh rates - the most common being 50Hz (Europe) and 60Hz (USA).
For a video to be smooth we need to figure out the best, most regular way to display the frames - the best cadence. The ideal cadence is calculated as the ratio of the display rate to frame rate. For example, if we have a 60Hz display (a 1/60 second display interval) and a 30 fps clip, 60 / 30 == 2 which means each video frame should be displayed for two display intervals of total duration 2 * 1/60 second.
We played videos a bunch of different ways and scored them on smoothness.
Smoothness scoreUsing off the shelf HDMI capture hardware and some special video clips we computed a percentage score based on the number of times each video frame was displayed relative to a calculated optimal display count. The higher the score, the more frames aligned with the optimal display frequency. Below is a figure showing how Chrome 43 performed when playing a 30fps clip back on a 60Hz display:

Smoothness: 68.49%, ~Dropped: 5 / 900 (0.555556%)
The y-axis is the number of times each frame was displayed, while the x-axis is the frame number. As mentioned previously the calculated ideal display count for a 30fps clip on a 60Hz display is 2. So, in an ideal situation, the graph should be a flat horizontal line at 2, yet Chrome dropped many frames and displayed certain frames for as many as 4 display cycles! The smoothness score reflects this - only 68.49 percent of frames were displayed correctly. How could we track down what was going on?
Using some of the performance tracing tools built into Chrome, we identified timing issues inherent to the existing design for video rendering as the culprit. These issues resulted in both missed and irregular video frames on a regular basis.

There were two main problems in the interactions between Chrome’s compositor (responsible for drawing frames) and its media pipeline (responsible for generating frames) --

The compositor didn’t have a timely way of knowing when a video frame needed display. Video frames were selected on the media pipeline thread while the compositor would occasionally come along looking for them on the compositor thread, but if the compositor thread was busy it wouldn’t get the notification on time.

Chrome’s media pipeline didn’t know when the compositor would be ready to draw its next new frame. This led to the media pipeline sometimes picking a frame that was too old by the time the compositor displayed it.

In Chrome 44, we re-architected the media and compositor pipelines to communicate carefully about the intent to generate and display. Additionally, we also improved which video frames to pick by using the optimal display count information. With these changes, Chrome 44 significantly improved on smoothness scores across all video frame rates and display refresh rates:

Smoothness: 99.33%, ~Dropped: 0 / 900 (0.000000%)
Smooth like butter. Read more in public design document, if you’re interested in further details.
Dale Curtis, Software Engineer, recently watched WARNING: SCARIEST GAME IN YEARS | Five Nights at Freddy's - Part 1Richard Leider, Engineering Manager, recently watched Late Art Tutorial.Renganathan Ramamoorthy, Product Manager, recently watched Video Game High School

YouTube Channels: Get with the Program!

Monday, September 24, 2012

It's never been easier to create compelling videos and build a social presence on YouTube. At this year's Google I/O, YouTube product managers and channel gurus Dror and A.J. presented tips and tricks for making great content centered around raising brand awareness, raising money, and obtaining feedback about your products and services.

Don't worry if you missed their talk, we recorded it! So, sit back, grab some popcorn, and get ready to learn how to showcase your brand in front of YouTube's 800 million unique visitors per month!

Click here to view the slides from the video above.

Not sold yet? Well, have a sneak peek at some of the great material they cover below, and remember Dror and A.J.’s number one recommendation: make content, not commercials!

Sneak Peek

Tips and Tricks

Hook the user in the first 15 seconds (or they'll leave)
Brand your channel!
Make the most of your budget

Review YouTube’s Trends for ideas
Camera shy? Consider animation. (It might actually be cheaper than video.)
Several successful channels focus on curating videos from their community
Enhance your videos without fancy software/hardware using the YouTube Editor or other integrated web editors

Many, many more...

What's your goal?

Raising awareness

Master your PR via video (include all your features and make bloggers’ lives easier)
Provide product/service demo videos to promote your company
Tell backstories about clients using your products/services

Raising money

Add video to your crowdfunding pitch to increase funds raised by 114% (source: Indiegogo)

Researching and supporting users

Record tutorials to promote and educate (see which features are the most popular using YouTube’s Analytics... you might be surprised)
Use Google Hangouts for scalable office hours and virtual focus groups
Figure out what features customers like/dislike via the world’s largest focus group

Resources to learn more

Creator Hub
Creator Playbook (what you wish you knew about YouTube)
Trends Dashboard
YouTube for Developers (that’s us)

Wow, you made it this far without watching the video? Did we tell you they fill the presentation with awesome videos that showcase their points (including Chuck Testa)? Nope!? Well, now you know, and you will definitely want to watch the whole thing!

-Jeremy Walker, YouTube API Team

Build awesome YouTube experiences with new APIs and tools

Wednesday, June 27, 2012

When we introduced the first YouTube API in 2005, we knew that it would be developers who would help us grow YouTube as a platform for connecting the world through video. At this year’s Google I/O, we’re continuing on with that mission through an entire track dedicated to YouTube, where we’re announcing new APIs and developer tools, as
well as a showcase of some of the most innovative apps built with YouTube.

Make mobile video shine
With mobile video now making up as much as half of all mobile traffic, your mobile experience needs video that’s high quality, fast and sleek. We want to give you the best tools to build these experiences, so we’re previewing the new YouTube Android Player API for high-quality and fluid video playback.

Engage with your communities through video
The next generation of YouTube Direct allows you to engage with your community by having them submit videos which you can then feature in playlists. YouTube Direct Lite is implemented in client-side JavaScript using CORS, and does not require any server-side deployments—adding it to your site is as simple as adding an

MMMmmm...data!Retrieving analytics data for your videos used to mean downloading an archive of CSV files that you then had to process. Now, you can use our new YouTube Analytics API to build custom tools for your data. It's a RESTful web service that gives you the freedom to request customized reports containing only the data you care about. We’re also giving the YouTube Data API a facelift with new features like universal search and updated client libraries in 8 different languages.

Play, watch and learn from developers like you at Google I/O

We’ll be talking about these new features and other developer tools at Google I/O this week, so check out our sessions and codelabs, download the official Google I/O app, and follow online at developers.google.com/io. At I/O you can also visit with Developer Sandbox companies like Flipboard, Dude Perfect and SONY PlayStation @ Home who are building awesome experiences with YouTube APIs. We’ll also share our sessions on the Google Developers YouTube Channel, and you can always find us on Google+ and our developer forum.

Cheers,
—Amanda Surya, YouTube API Team

YouTube APIs: Search Explained

Tuesday, May 5, 2009

Engineering and Developers Blog

Smoother <video> in Chrome

YouTube Channels: Get with the Program!

Build awesome YouTube experiences with new APIs and tools

YouTube APIs: Search Explained

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