What device allocates data bit rates according to scene requirements for multiplexed digital television channels?

The statistical multiplexer is the correct choice because it efficiently allocates data bit rates based on real-time scene requirements, especially in the context of multiplexed digital television channels. This device dynamically adjusts the bandwidth of each channel depending on the complexity of the video content being transmitted. For example, scenes with high motion may require a higher bit rate to maintain quality, while simpler scenes can use less bandwidth.

This adaptability makes statistical multiplexers crucial for maximizing the use of available bandwidth and ensuring that viewers receive the best possible quality without waste. They achieve this through a process called statistical multiplexing, where they analyze incoming video streams and allocate the resources accordingly, enhancing overall system efficiency and quality for broadcasting.

Other devices listed, such as digital video recorders, MPEG-2 decoders, and signal processors, serve different specific roles within the digital television ecosystem. While they are essential for recording, decoding, or processing video data, they do not focus on the allocation of data bit rates in the way that a statistical multiplexer does.