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Transcoding key to sharing multimedia

Posted: 02 Aug 2004 ?? ?Print Version ?Bookmark and Share

Keywords:transcode? multimedia? video? audio? dvd?

Consumers are witnessing a dramatic transformation in their ability to create and share multimedia content across devices. They can take a video clip on their digital camera, save it to a memory card that also fits in their PDA and watch it as they ride the train. At home, they can insert the card in their DVD player and watch the clip in their living room.

Gadgets abound for audio and video as well as images, yet each has its own storage needs and multimedia format requirements. Given the bevy of data storage formats and encoding/decoding standards in existence today, it becomes a real challenge for system designers to figure out a way to make sure their devices can "talk" to other devices.

The problem with today's multimedia market is that designers have too many options to choose from when it comes to media storage and retrieval. First, they must ascertain which types of storage are most appropriate for their end market. Second, they must consider when, in the usage pattern of the device, this storage interface is needed. Furthermore, designers need to consider all possible uses of a storage interface; for instance, many ports can double as I/O interfaces that connect to 802.11 or Ethernet transceivers. Finally, they must allow for the fact that consumers want to reuse their media across devices, using the same memory card for their camera as they do for their portable audio player.

For portable markets, NAND flash memories constitute, by far, the most popular storage interfaces. They have no moving parts (unlike classical and miniaturized hard drives), basically consume power only during reading/writing and also allow for dense storage in rugged form factors. Since NAND flash is meant to be accessed sequentially (in blocks), rather than randomly (as in NOR flash), it is well-suited for audio, image and video applications. This is why compact flash, secure digital and memory stick are widely used in digital cameras today.

But because these various memory formats do not talk seamlessly with one another, it is important for multimedia devices to have a unifying interface that serves as a data transport channel from one platform to another. This role is increasingly being served by peer-to-peer-enabled USB 2.0, IEEE 1394 (Firewire) and 802.11a/b/g (Wi-Fi) connections.

Moving content

Interfacing to a PC remains essential for most portable multimedia devices, because the PC constitutes a source of constant Internet connectivity and near-infinite storage. To facilitate interaction with a PC, a high-speed port is mandatory, given the substantial file sizes of multimedia data. Conveniently, the same transport channel that allows portable devices to converse in a peer-to-peer fashion also lets them dock with the "mother ship" as a slave device.

Now, getting the relevant multimedia content to a target device is only half the story. The other half revolves around how the target figures out what to do with the content it receives.

Consumers demand a seamless pathway through which to share, transfer and experience media. Today, transcoding of multimedia content is helping remove barriers between different encoding/decoding platforms. Transcoding allows data to move transparently between and within wired and wireless networks. It allows compression of a data stream to meet a target storage size or a specific transmission path. For example, MPEG-2 content from a source device might be transcoded into MPEG-4 before transmission across a wireless network. The result would be a significant bit stream reduction that translates into dollars saved. On the target device, the data could then be transcoded into the native format of the platform before being played.

The availability of embedded media processors has greatly increased a product developer's design options where transcoding is concerned. The high performance (clock rates exceeding 600MHz) of these processors enables completely programmable coding across different media formats, while their low-power dissipation and small size make them ideal for portable applications. Increased integration of ubiquitous interfaces like USB and Wi-Fi allows for streamlined sharing of files between media nodes.

Moreover, improvements in storage technology continue to drive denser storage into smaller form factors. These trends are all merging, ultimately making the process of creating and sharing media a seamless endeavor for the consumer.

- David Katz and Richard Gentile

Blackfin Applications Group

Analog Devices Inc.

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