Another important development in digital signal processing was data compression. Linear predictive coding (LPC) was first developed by Fumitada Itakura of Nagoya University and Shuzo Saito of Nippon Telegraph and Telephone (NTT) in 1966, and then further developed by Bishnu S. Atal and Manfred R. Schroeder at Bell Labs during the early-to-mid-1970s, becoming a basis for the first speech synthesizer DSP chips in the late 1970s. The discrete cosine transform (DCT) was first proposed by Nasir Ahmed in the early 1970s, and has since been widely implemented in DSP chips, with many companies developing DSP chips based on DCT technology. DCTs are widely used for encoding, decoding, video coding, audio coding, multiplexing, control signals, signaling, analog-to-digital conversion, formatting luminance and color differences, and color formats such as YUV444 and YUV411. DCTs are also used for encoding operations such as motion estimation, motion compensation, inter-frame prediction, quantization, perceptual weighting, entropy encoding, variable encoding, and motion vectors, and decoding operations such as the inverse operation between different color formats (YIQ, YUV and RGB) for display purposes. DCTs are also commonly used for high-definition television (HDTV) encoder/decoder chips.