videobitrate

How to calculate bitrate of PAL format?

I have to calculate the bitrate of PAL format (576∗720). I have the following data:

  1. 25 frames per second
  2. Interlaced
  3. Interior representation is: 4:2:0
  4. 8 bpp

I have tried the following formula but I am really not sure at all if it is correct because I have not clearly understood the difference between interlaced and non-interlaced video and how this difference changes the calculation fo the bitrate.

This is what I tried:

(576∗720)∗(1+1/4+1/4)∗8∗25

This part: (1+1/4+1/4) is due to the specific representation 4:2:0

Solution

  • Your formula is correct.

    Interlace video with 50 fields per second has the same bitrate as progressive video with 25 frames per second.

    Interlace video is transmitted in fields.
    Each field contains 1/2 of the video lines of the frame.
    PAL frame is 576 video lines, so PAL field is 288 video lines.

    According to ProVideo Coalition, the order of the field in PAL is "upper field first".
    Size of two interlace fields equals the size of one frame:
    Interlace
    Remark: It's possible that the two fields are captured in separated times, and the two fields do not belong to the same frame (in 4:2:0 separate times it is unlikely).

    In 4:2:0 format, the resolution of the Y component is the resolution of the frame.
    The U and V components are down-sampled by a factor of 2 in each axis.
    Assuming 8 bits per component, there are 12 bit per pixel in average.

    Interlace or not, your formula is correct.

    bitrate = (576∗720)∗(1+1/4+1/4)∗8∗25 [bits per second].