Digital Multimedia Broadcasting (DMB) is a technology that extends the Digital Audio Broadcasting (DAB) system to transmit not only audio but also video, text, and other data services. It is designed to deliver a wide range of content, including music, videos, and text, to handheld devices such as mobile phones and PDAs. DMB is particularly well-suited for providing mobile TV and other services on compact devices.
DMB can be implemented in two main versions:
- Terrestrial DMB (T-DMB): This version of DMB operates over terrestrial networks and provides a data capacity of approximately 1.5 Mbps per radio channel with a 1.5 MHz bandwidth. Various compression techniques can be applied, including the original DAB compression standard (MP2: MPEG 1/2 Layer II) for audio, as well as more modern standards like AAC for audio and MPEG-4 for video.
- Satellite DMB (S-DMB): S-DMB, on the other hand, utilizes satellite technology for broadcasting. It offers a means of distributing content over a wider geographic area, making it suitable for regions with limited terrestrial infrastructure.
The DMB standard specifies a video service that relies on MPEG-4 (AVS/H.264) video compression in combination with HE-AAC audio compression. Both streams are combined into an MPEG-2 Transport Stream. To enhance reliability, an additional error correction mechanism is employed, as video data is more susceptible to errors than audio data. This error correction reduces the available data capacity by approximately 7.8%.
DMB initially faced challenges with adoption in Germany but gained more success in South Korea, where it saw a more successful introduction. South Korea deployed DMB using both satellite and terrestrial broadcasting stations, making it a viable platform for mobile multimedia services.