Dolby TrueHD Bitrate Question

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Some scenes may not require the bit bitrate to be higher than 1200kbps.

With PCM 16-bit 48kHz all channels runs at a constant bit-rate of 768kb, which gives you a total of 4608kbps.

But imagine a scene with dialog only, no other speaker than the center channel has to play. Then you can cut down the bitrate for the other channels.