in settings/output, up your bitrate to 3000 and check mark "Enable Advanced Encoder Settings" and "Use Constant Bitrate." Also, set "Encoder Preset" to the slowest your pc can handle without dropping any frames.
the higher the bitrate and the slower the encoder preset, the less pixelation you will see. but if you set the encoder preset too low, your stream will be very choppy and unwatchable.
