Generation of a stream of data bits 0s and 1s at a certain bit or data rate This is a very basic question ,but basics important, : How is a stream of data bits (zeros and ones that express a certain information) and at a certain rate being generated? what is involved in terms of processing and possibly hardware?  a clock? a quantizer? a sampler? or what exactly?  I really would like to get a brief idea
Multimedia signals such as video,picture, music, speech have bandwidths associated with their baseband analog source nature. 

For digital processing this bandlimited analog source is passed through a analog to digital converter (into a sequence of samples), which operates at a clock-frequency determined by the signal sampling rate, $F_s$, which is also limited by the source bandwidth due to Nyquist-Shannon sampling theorem. 

Furthermore for each sample, a number of bits are used to quantize (numerically resolve) it. The number of bits is dictated by the signal amplitude accuracy requirement. For digital video, it's mostly 8-bits per RGB channel. Or for audio it can be 16-bits per stereo L/R channel. 

Hence, the multiplication of samlping rate $F_s$ and bit-per-sample gives you the raw source bit rate $R_b$. You may prefer to apply some statistical or perceptual data compression to reduce $R_b$ to a minimum. 

Then you choose a digital modulation scheme such as FSK,PSK,GMSK,OFDM... and transmit those bits through your favorite medium. Before doing this, you may increse $R_b$ (by adding redundancies) for channel transmission error correction purposes. The result is your bit-stream (not necessarily logic signal levels of 0s and 1s though) that's traveling accross the universe...

I hope I clarified it.