Electronic Design

High-Resolution Television Coming To A Cell-Phone Near You

So you think people aren’t going to watch TV and video clips on their cell phones? Just as critics laughed at cell phones with cameras and subsequently were proven grossly wrong, many people will find it hard to believe that consumers will watch video on their phone.

Yet portable media players (PMPs) such as Apple’s iPod and Microsoft’s Zune, as well as most high-end cell phones, already can play back low-resolution video clips. Also, new phones on the market from Samsung, LG, and other companies can even receive and play back terrestrial broadcast TV.

Many broadcasters now make TV shows available for download on their Web sites (for a price) almost immediately after they’re broadcast. And, content providers such as MobiTV report millions of new customers every year. Standup comedy bits and sports highlights are the most popular types of clips.

Technically, though, two hurdles must be leaped to achieve success: resolution and quality. Most devices available today can play back CIF (352 by 240) or VGA (640 by 480) resolution video encoded in the low-quality MPEG-4 Simple Profile or H.264 Baseline profile video encoding standards. The video is grainy at best, and you can’t store too big a video stream.

In response, the portable-device market will move to H.264 Main Profile as the video coding standard to encode video streams for portable devices. This profile was designed for high compression and high quality of video—two very important prerequisites for the small screen size and limited storage available on cell phones and portable media players.

Furthermore, LCDs in cell phones and PMPs are becoming large enough to support D1 or standard definition (SD) resolution video. In fact, Sony’s PlayStation Portable already uses a variant of the H.264 Main Profile for video content distributed on its UMD and memory-stick flash storage cards.

The Main Profile of H.264 achieves higher compression (and, therefore, requires less storage memory on the storage-limited cell phones and PMPs) over the Baseline Profile while providing higher quality due to three primary techniques: a more advanced entropy encoding method called CABAC (Context-Adaptive Binary Arithmetic Coding); interlaced coding (PicAFF and MBAFF); and inclusion of B-slices in the encoded video.

The CABAC entropy encoding method alone achieves between 5% and 15% higher compression than the CAVLC (Context-Adaptive Variable Length Coding) method used in the Baseline Profile. The PicAFF and MBAFF interlaced coding techniques and use of B-slices lead to even further improvements in compression when using Main Profile.

Better compression becomes particularly important at higher resolutions (D1 and above). That’s because the video file becomes too large to be encoded in Baseline Profile for a storage-limited device like a cell phone or a PMP. Main Profile can encode these large-resolution videos at a much higher quality, at higher bit rates, and with much higher compression, creating a smaller file.

In addition, the H.264 Baseline Profile is only defined in the H.264 standard up to D1 resolution (since it’s only defined up to Level 3), whereas Main Profile is defined all the way up to high-definition (HD) resolution. Lastly, consumers also are likely to prefer cell phones that take less time to download and upload clips (and thus use fewer bytes on their data plan).

Another important aspect in using a portable device as a video player is the display size. As a result, cell phones and PMPs are beginning to include a “TV Out.” Besides using the LCD display to view videos, this feature lets customers hook up the device to any LCD display (computer or television) to view their videos or TV broadcast.

Just as cameras have become standard on cell phones, camcorders will be standard in next-generation phones. Consumers will use the video-capture capability to create home videos and share them with their friends and family. The software challenge will be for the YouTubes, Yahoos, and MySpaces of the world to provide a seamless and integrated application to upload, share, and view user-generated video content.

But the quality of the video from these devices is likely to be poor, and consumers usually will capture and share short clips. So, the encoders on these portable devices typically will use the computationally less expensive (and thus more silicon- and power-efficient) MPEG-4 ASP (Advanced Simple Profile) or SP (Simple Profile) video-encoding standard.

For the fabless semiconductor companies, it isn’t as cut and dried as creating a multimedia chip that can decode H.264 Main Profile streams and encode using MPEG-4 ASP. In fact, video content on the Internet comes encoded in many different video standards, including H.264, MPEG-4, VC1/WMV9, MPEG-2, Real, and even MPEG-1.

The multimedia systems-on-a-chip (SoCs) will have to incorporate a programmable multistandard video decoder/encoder block. Programmability in these video codec blocks is important because there are always new standards that become available, and become popular, among consumers. For example, China recently announced an H.264-like, royalty-free video codec called AVS. At the end of the day, though, the content creators and providers will decide the popularity of a video standard.

The implication of all these technology and product innovations is that the same youngsters who drove cameras on cell phones will now drive TV and camcorders on cell phones, too. So don’t laugh the next time someone tells you that TV is coming to a cell phone near you! It could be as soon as next year.

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