by Tom Nguyen
by Maxim Levkov
23 August 2011
Installed today on over one billion computers, smartphones, and tablets, Adobe Flash Player allows more people to watch high-quality video on the web than any other technology. Because it makes it easy to reach more viewers with seamless, smooth, beautiful video, it is the de facto standard for online video playback.
The quality and reach of a video also depends on how it is encoded, which may entail complex technical decisions and tradeoffs. On the web, varying codec and encoding support means that a video watchable on one platform may not be viewable on others. However, Flash Player helps overcome these challenges by delivering consistent codec support across devices and browsers.
This article describes simple encoding guidelines that allow developers, designers, and content providers not well-versed in video encoding to maximize the reach of their video content with minimal cost and effort using Flash Player. These recommendations account for varying hardware decoding capabilities found across the range of relevant smartphones and tablets that support Flash Player in the browser. They also apply to installed apps delivered with Adobe AIR on these devices. Beyond phones and tablets, these encoding recommendations also ensure your videos can be viewed seamlessly across browsers on virtually all desktop and notebook computers.
These mobile video encoding recommendations have been designed to do the following:
- Provide a good playback experience over a broad range of smartphones and tablets with Flash Player, including Android phones and tablets and the BlackBerry PlayBook tablet (along with connected TVs and 99% of connected computers)
- Provide smooth video playback without stutter or choppiness
- Minimize fragmentation and multiple encoding requirements for developers
- Maximize device battery life, taking advantage of efficient hardware acceleration
The simplified recommendations here complement more comprehensive encoding information that Adobe provides for advanced developers and publishers interested in further optimizing their video encoding for specific content types and devices.
By using the encoding recommendations in Table 1—as few as two encodings if you do not need to target older 2G-connected devices—you can maximize the reach of your video across millions of devices.
Table 1. Simple encoding recommendations for most devices
|H.264 profile||H.264 level,
|2G (e.g., Edge)||Baseline||2.1||250 kbps||144p||30fps||AAC, mono, 32 kHz, up to 64 kbps||Disable weighted prediction and CABAC. Non-interlaced. Square pixel aspect ratio.|
|3G||Baseline||3.1||800 kbps||480p||30fps||AAC, stereo, 44.1 kHz, up to 64 kbps||Disable weighted prediction and CABAC. Non-interlaced. Square pixel aspect ratio.|
|4G and Wi-Fi||Baseline**||3.2||1.2 Mbps||480p (smart-phone) 720p (tablet †)||30fps||AAC, stereo, 44.1 kHz, up to 128 kbps||Disable weighted prediction and CABAC. Non-interlaced. Square pixel aspect ratio.|
* Following are sample recommended encoding resolutions for common aspect ratios, following the guidelines in Table 1.
|144p||192 × 144||256 ×144|
|288p||384 × 288||512 × 288|
|480p||640 × 480||640 × 360|
|720p||960 × 720||1280 × 720|
** Although some tablets may also support H.264 Main profile, use H.264 Baseline profile for maximum reach.
† Some dual core–class smartphones also support 720p resolution but provide a 480p encoding for broad reach across those devices.
When encoding content intended for mobile devices, you should also do the following:
- Keep the video frame dimensions (both width and height) divisible by 16
- Maintain the original picture aspect ratio
- Create video encodings that are targeted for specific frame sizes rather than relying on scaling of higher resolution videos to fit smaller frame sizes
For a more detailed explanation of how to prepare your content to deliver the highest-quality playback experience, refer to the Video Encoding Cookbook and Profile Guidelines for the Adobe Flash Platform and the comprehensive mobile encoding addendum. You can also learn more about optimizing ActionScript in your video player application for optimal performance, or leverage an existing media player such as Flash Media Playback or the Open Source Media Framework to play your videos.
Beyond its core video playback capabilities, Flash Player enables the delivery of consistent, rich, interactive experiences on the web. Some of its other benefits for video playback include full pipeline hardware acceleration, advanced streaming controls for smoother, high-quality playback, DVR-like playback control, adaptive bitrate management, content protection, analytics, and sophisticated interactivity. To learn more about how to take advantage of these features, visit the Video Technology Center on the Adobe Developer Connection.
This work is licensed under a Creative Commons Attribution-Noncommercial 3.0 Unported License.