Understanding QAM 256 and 128 difference

[thickglass14]

Hi guys, I set HDMI Modulator recently, but here is one question - it has QAM 16/32/64/128/256. What is the practical difference between 128 and 256 for example if I keep resolution and bitrate the same?

 

[tech99]

Hi guys, I set HDMI Modulator recently, but here is one question - it has QAM 16/32/64/128/256. What is the practical difference between 128 and 256 for example if I keep resolution and bitrate the same?

Going from 128 to 256 QAM and keeping the bandwidth constant will provide a small increase in data rate but will require a higher Carrier to Noise Ratio.