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Victor
Posts: 23
Posted 11:04 May 12, 2019 |

Hi class.

There's this question in the finals sample questions I don't know how to solve.

Consider a video format with 325 lines/frame, 490 pixels/line, 30 frames/s, color subsampling scheme 4:2:2, image aspect ratio: 4:3. Compute the bit-rate of the system (assuming each luminance and chrominance sample is quantized with 8 bits).

Ans: 76.44 Mbits

What formula is used to get the answer from the question?

kmarlis
Posts: 35
Posted 11:36 May 12, 2019 |

Hi Victor, here is how I got the given answer.

325 lines/frame * 490 pixels/line * 30 frames/s = 4,777,500 pixels/sec

Using the 4:2:2 subsampling scheme:

Y Channel : 4,777,500

Cb Channel : 4,777,500 / 2

Cr Channel : 4,777,500 / 2

total : (4,777,500 + (4,777,500 / 2) * 2 ) * 8 = 76,440,000 bits or 76.44 Mbits

 

Hope this helps!

Victor
Posts: 23
Posted 11:48 May 12, 2019 |

Thank you very much.

Can you tell me how the "interlaced" bit alters this equation?

Last edited by Victor at 11:49 May 12, 2019.
kmarlis
Posts: 35
Posted 11:54 May 12, 2019 |

No problem!

I'm not sure if interlaced vs progressive has an impact on the bit rate. I think those just determine the order in which the rows are processed. I could be wrong though.  

Victor
Posts: 23
Posted 11:57 May 12, 2019 |

Thank you.

I'm very grateful.