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# Satellite Communications/How to calculate video bit rate not total bit rate?

Question
DEAR SIR,
MY QUESTION IS I WANT TO CALCULATE VIDEO BITRATE not total bit rate BY FORMULLA? WHAT WILL BE THE FORMULA OF CALCULATION OF VIDEO BITRATE AND TOTAL BIT RATE FOR QPSK, 8PSK, AND FOR OTHER MODULATION TECHNIQUES? IT IS VERY MUCH IMPORTANT FOR ME SO, PLEASE ANSWER THIS IN DETAIL AND ASAP. IFYOU TELL ME THE FOLLOWING FORMULAS THEN I LL BE VERY THANKFUL TO U.
VIDEO BITRATE
TOTAL BIT RATE
BANDWIDTH
SYMBOL RTAE

REGARDS,
ABDULRAB

Bit Rate Calculations
26 February 2015
Dear AbdulRab:

Bits

There are three principal frame rate standards in the TV and digital cinema business: 24p, 25p, and 30p. However, there are many variations of these as well as newer emerging standards.
   The number refers to frames per second (FPS) and the p indicates that it is a progressive format, as opposed to an interlaced format. Thus, 24p is a progressive format with 24 FPS.
Television pictures have differing amounts of definition (rendering of fine detail) according to how many individual picture elements (pixels) are provided to reconstruct the picture. This definition is expressed as the number of horizontal lines and picture elements (pixels) in each line that are used for different formats. Thus when we say a format is 640 Χ 480p we mean there are 640 elements in each of 480 horizontal lines (scanned progressively) for a total of 307,200 pixels and an aspect ratio of 640χ480 or 4:3 (4 units wide by 3 units high) or Standard Definition TV (SDTV).
Pixel Rate

The pixel rate of a video signal is the frame rate (FPS) times pixels per frame.
   SDTV (standard-definition TV) in the 30p format has 30 FPS X 307,200 pixels per frame = 9,216,000 pixels per second.
   HDTV (high-definition TV) in the 30p format has 1920 X 1080p (2,073,600 pixels per frame) X 30 FPS = 62.2 megapixels per second.
   4K UHDTV (2160p) (ultra-high-definition TV) is 3840 pixels wide by 2160 pixels tall (8.3 megapixels per frame)  249 megapixels per second for 30p format.
   8K UHDTC is 7,680 pixels wide by 4320 pixels tall (33.2 megapixels per frame)  996 megapixels per second for 30p format.

Data Rate

The data rate from a video sensor is the product of the pixel rate times the number of bits per pixel (bpp). 30 bpp is not uncommon for high-quality color, so using 30 bpp for the four examples above gives:
   SDTV data rate is 9.2 megapixels per second X 30 bpp = 276 Mbps
   HDTV data rate is 62.2 megapixels per second X 30 bpp = 1,866 Mbps
   4K UHDTV data rate is 249 megapixels per second X 30 bpp = 7,470 Mbps
   8K UHDTV data rate is 996 megapixels per second X 30 bpp = 29,880 Mbps
It is clear that even SDTV transmission requires data compression.

Data Compression

MPEG-2 and MPEG-4 are two standards for compressing video data. MPEG-2 dates from 1995. MPEG-4 dates from 1998it uses further coding tools with additional complexity to achieve higher compression ratios than MPEG-2.

A MPEG-4 codec (coder/decoder) can reduce video bps by factors of 20 to 200. (In decibels, this would be data rate reductions of 13 dB to 23 dB.) Using the same examples as above, an MPEG-4 codec could reduce TV output data rates by:
   SDTV: 276 Mbps  between 13.8 Mbps and 1.38 Mbps (20X and 200X compression, respectively)
   HDTV: 1,866 Mbps  between 93.3 Mbps and 9.33 Mbps (20X and 200 X compression, respectively)
   etc.

I am not an expert in MPEG, so I can only approximate. As noted above, MPEG-4 provides more compression that MPEG-2. Assuming that MPEG-2 is half as effective as MPEG-4, and MPEG-2 codec could reduce data rates by a factor of 10 to 100 (10 dB to 20 dB). Using same examples as for MPEG-4 MPEG-2 would provide:
   SDTV: 276 Mbps  between 27.6 Mbps and 2.76 Mbps (20X and 200X compression, respectively)
   HDTV: 1,866 Mbps  between 186.6 Mbps and 18.66 Mbps (20X and 200 X compression, respectively)
   etc.

The data rate coming out of an MPEG-2 codec at the source is higher than the data rate coming out of an MPEG-4 at the source. Since the satellite link does not affect the data rate, the data rate into an MPEG-2 codec and the receiver is higher than it would be for an MPEG-4 compression scheme.
These are the data rates out of the TV subsystem that includes the sensor and the codec. This is the data rate input to the satellite link and is the data rate used in link budget calculations.

Symbols

Thus far, we have discussed only bits and bits per second (bps).Modulators input bits and output symbols. Symbol rate (symbols per second (Sps)) is synonymous with baud rate. The term baud originates from the French engineer Emile Baudot, who invented the 5-bit teletype code. Baud rate refers to the number of signal or symbol changes that occur per second. A symbol is one of several voltage, frequency, or phase changes created by the uplink modulator. There is a corresponding demodulator at the ground receiver.

The following are relationships between bit rates and symbol rates for some of the more common modulation schemes.
   BPSK: 1 bit per symbol
   QPSK: 2 bits per symbol
   8PSK: 3 bits per symbol
   16PSK: 4 bits per symbol
   etc.

Extending out earlier examples of MPEG-4 coded to various modulation schemes
   SDTV: 276 Mbps  between 13.8 Mbps and 1.38 Mbps (20X and 200X compression, respectively)
o   BPSK symbol rate = 13.8 MSps to 1.38 MSps
o   QPSK symbol rate = 6.9 MSps to 0.69 MSps
o   8PSK symbol rate = 4.6 MSps to 0.46 MSps
o   16PSK symbol rate = 3.45 MSps to 0.35 MSps
   etc.
   etc.

The system design of a system that relays TV data from ground source through a satellite to a ground is complex. It involves a number of complex factors:
   TV resolution (SDTV, HSTV, UHDTV, )
   Data compression scheme and implementation (MPEG-2, MPEG-4, )
   Type of modulation (BPSK, QPSK, 8PSK, 16PSK, )

For each of the factors, implementation becomes more complex and more costly to implement as you move from left to right (e.g., SDTV  HDTC  UHDTV).

One must make cost / performance tradeoffs within each factor and then make inter-factor tradeoffs and optimization.

Reference Material

If I need information, I generally start with a Google search. If the search results include a Wikipedia entry, I go there next. If further information is needed, I then start going through the other search results.

For the response to your questions, I used Wikipedia for the following terms: link budget, MPEG, digital TV, bit rate, codec, etc.

I also used a PowerPoint presentation entitled Satellite Communication: Lecture 3Satellite Links, Multiple Access Methods, and Frequency Bands.

I hope that my answers have adequately addressed your questions. If not, please advise me. If you are satisfied with my work, I would truly appreciate it if you would take a few minutes to provide an evaluation.

Sincerely,

Thomas Burke, PhD, PMP

Questioner's Rating
 Rating(1-10) Knowledgeability = 10 Clarity of Response = 10 Politeness = 10 Comment Writer is very kind and have deep knowledge. I am fully satisfied with the answer. Thanx fv the answer. Regards Abdulrab

Satellite Communications

Volunteer

#### Thomas E. Burke

##### Expertise

No restrictions on questions.

##### Experience

Forty years of experience with satellite communications. Have held roles as system engineer on JPL Mariner 9 program and a program manager for a number of classified communication satellite programs. Served as head of TRW / Defense Communications Division / Engineering Development Operation, a 1,400-person organization responsible for all aspects of classified communication satellite design and development.

Education/Credentials
Ph.D. Chemistry, California Institute of Technology (1969) B.A. magna cum laude Chemistry, University of Minnesota (1962)