1.2 Multimedia – Graphics & Sound
AS Level · 23 questions found
What this topic covers
Section titled “What this topic covers”- Bitmap images: pixel, file header, image/screen resolution, colour/bit depth
- Calculate bitmap file size; effects of changing resolution or colour depth on quality and size
- Vector graphics: drawing object, property, drawing list
- Justify bitmap vs vector for a given task
- Sound: sampling, sampling rate, sampling resolution, analogue vs digital
- Impact of changing sampling rate/resolution on file size and accuracy
Past paper questions
Section titled “Past paper questions”(a) A sound file is compressed by reducing the sampling rate. 1 mark
State whether this is lossless or lossy compression. Justify your choice.
Type of compression
Justification
(b) The following table shows some words and corresponding denary values. 1 mark
| Word | Denary value |
|---|---|
| Computing | 55 |
| Science | 56 |
| Computers | 57 |
| are | 58 |
| Brilliant! | 59 |
| is | 60 |
| Fun! | 61 |
| Amazing! | 62 |
The following table shows three bytes of data that have been received.
Use the table to find the corresponding words from the binary values received.
| Binary value | 00111000 | 00111100 | 00111110 |
|---|---|---|---|
| Word |
Working
(c) A computer system uses even parity. The least significant (rightmost) bit of each byte is the parity bit.
(i) Complete the byte by writing the missing parity bit: 1 mark
parity bit
(ii) The computer also uses parity block check. The parity block check uses even parity.
Computer A transmits four bytes of data to computer B, followed by a parity byte. Computer B receives the following sequence of bytes.
parity bit
| 1 | 0 | 1 | 1 | 0 | 1 | 1 | 1 |
|---|---|---|---|---|---|---|---|
| 0 | 1 | 1 | 1 | 0 | 0 | 0 | 0 |
| 0 | 0 | 0 | 1 | 1 | 0 | 1 | 1 |
| 0 | 1 | 1 | 1 | 0 | 1 | 0 | 0 |
| 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 |
Following transmission, one of the four bytes of data has an error in one of the bits.
Circle the bit that has been altered during the data transfer. [1]
(d) A bitmap image has a resolution of 1000 pixels wide by 2000 pixels high. The colour depth is 16 bits. 2 marks
Calculate an estimate of the file size in megabytes.
Show your working.
File size ______ megabytes
Show mark scheme
6(a) [1 mark]
1 mark for correct answer Type of compression: lossy Justification: There will be fewer samples per second, so data will be permanently lost // There will be fewer samples per second, so the original sound cannot be re- created
6(b) [1 mark]
1 mark for correct words in the correct order Binary Value 0011 1000 0011 1100 0011 1110 Word Science is Amazing!
6(c)(i) [1 mark]
1 mark for correct answer parity bit ↓ 0 1 0 1 1 1 0 0
6(c)(ii) [1 mark]
1 mark for correct answer parity bit ↓ 1 0 1 1 0 1 1 1 0 0 1 1 1 0 0 0 0 0 0 1 1 0 1 1 0 1 1 1 0 1 0 0 parity byte→ 1 0 1 0 0 0 0 0 [1]
6(d) [2 marks]
1 mark for the working 1 mark for the correct answer Working: (1000 * 2000 * 16) / (8 * 1000 * 1000) // (1000 * 2000 * 2 / (1000 * 1000) Answer: 4 megabytes
(a) A student creates sound recordings. 3 marks
Making changes to a sound recording may impact the accuracy of the resulting sound file or the size of the file.
Draw two lines from each change to the impacts it has on the sound file.
Change
increase the duration of the recording
increase the sampling rate
decrease the sampling resolution
Impact
the file size gets bigger
no change in the file size
the file size gets smaller
the accuracy of the sound file improves
no change to the accuracy of the sound file
the accuracy of the sound file worsens
(b) The file names of the sound recordings are stored using the ASCII character set. 2 marks
Explain how text is represented by the ASCII character set.
(c) Give two differences between the ASCII and UNICODE character sets. 2 marks
1
2
Show mark scheme
1(a) [3 marks]
1 mark for each correctly connected change box, max 3 marks the file size gets bigger increase the duration of the recording no change in the file size the file size gets smaller increase the sampling rate the accuracy of the sound file improves no change to the accuracy of the sound file decrease the sampling resolution the accuracy of the sound file worsens
1(b) [2 marks]
1 mark per bullet point, max 2 marks • Each character has a unique code • Each character in the text is replaced sequentially / in order by its code
1(c) [2 marks]
1 mark per bullet point, max 2 marks • ASCII uses 7 / 8 bits Unicode can use many more / up to 32 bits • Unicode can represent a wider range of characters including different languages
A digital video camera records students in a classroom. The data is transferred from the digital video camera over the internet to a server. Artificial Intelligence (AI) is used to analyse the video on the server to identify when students are interacting with the lesson and the teacher.
(a) Describe one ethical impact of this use of AI in the classroom. 2 marks
(b) A video is made of many bitmap images called frames. 30 frames are recorded every second. 2 marks
Each frame is 4000 pixels wide by 3000 pixels high. The video records using 16‑bit colour depth.
Calculate an estimate for the file size for one second of the video in gigabytes.
Show your working.
File size ______ gigabytes
(c) Identify and describe one method of data verification that can be used when transferring data from the digital video camera to the server. 3 marks
Method
Description
(d) Describe two reasons why the server that stores the videos uses magnetic hard disks instead of solid state (flash) memory. 4 marks
1
2
(e) The table contains three algorithms that perform data validation. The third algorithm uses the functions MID and LENGTH. 3 marks
The functions MID and LENGTH are defined as follows:
MID(ThisString : STRING, x : INTEGER, y : INTEGER) RETURNS STRING returns a string of length y starting at position x from ThisString
LENGTH(ThisString : STRING) RETURNS INTEGER returns the integer value representing the length of ThisString
Complete the table to identify the method of data validation for each algorithm. Each method of data validation must be different.
| Algorithm | Method of data validation |
|---|---|
| INPUT x IF x < 1 or x > 26 THEN OUTPUT "Invalid" ENDIF |
|
| INPUT x IF x <> 'R' AND x <> 'G' AND x <> 'B' THEN OUTPUT "Invalid" ENDIF |
|
| INPUT x FLAG FALSE FOR INDEX 1 TO LENGTH(x) IF MID(x, INDEX, 1) = "@" THEN FLAG TRUE ENDIF NEXT INDEX IF NOT FLAG THEN OUTPUT "Invalid" ENDIF |
Show mark scheme
7(a) [2 marks]
1 mark per point, max 2 marks e.g. • The learning experience could be improved • … by identifying students who are struggling • …. and employing more personalised learning • There could be early Intervention • … to determine which students require extra support • • Teachers and students could understand the challenges better • …and identify optimal times for learning • There could be privacy concerns • …. students / teachers could be uncomfortable with constant surveillance • ... students might not want their data / actions passed to third parties • There could be Mental Health concerns • …. due to constant monitoring and pressure • …. contributing to student stress and anxiety
7(b) [2 marks]
1 mark for the working 1 mark for the correct answer Working: (400030003016) / (8100010001000) //(40003000302) / (10001000*1000) Answer: 0.72 gigabytes
7(c) [3 marks]
1 mark for the name 2 marks for the matching description, max 3 marks • Parity Byte Check • a parity bit is added to each byte to make the number of 1s match the parity, odd or even • each byte can be checked on receipt and request to be resent if the byte does not match parity • Parity Block Check • a bit is added to each byte, but a parity byte is also set for each block • the location of an error can be found using vertical and horizontal parity • Checksum • A calculation is made from the data and transmitted with the data • The receiver performs the same calculation and compares with received checksum to see if they match
7(d) [4 marks]
1 mark per reason, 1 mark for corresponding justification x2 max 4 marks • Lower cost per unit of storage • ... so the high capacity of storage required for large number of video files will be less costly • A large number of read/write operations are being performed continuously • ... and magnetic storage is likely to have a longer life span compared with solid state
7(e) [3 marks]
1 mark for each validation check correctly identified, max 3 marks Range Check Existence Check Format Check
A computer stores images and text files.
Show mark scheme
3(a) [3 marks]
1 mark for each correct answer Statement The term for the smallest element that pixel makes up an image. 8 The largest number of different colours that 256 // 2 can be represented with a bit depth of 8 bits. The term for the dots per inch (dpi) when an Screen resolution image is displayed.
3(b)(i) [2 marks]
1 mark each to max 2 • A wider range of characters can be represented • so characters from more languages can be represented • and symbols such as emojis can be used
3(b)(ii) [1 mark]
1 mark for: 10,094
3(b)(iii) [1 mark]
1 mark for: 8,512
(a) A student paints a picture in an art class.
Show mark scheme
1(a)(i) [2 marks]
1 mark for correct working: e.g. 2000000 * 16 / (8 * 1000 * 1000) 1 mark for answer: 4MB
1(a)(ii) [4 marks]
1 mark each Image: • There will be fewer shades of colour available • so the image does not match the original as detail is lost Image file: • Fewer bits are used to store each pixel • so less data is stored, therefore the file size is reduced
1(b) [3 marks]
1 mark for each correct term: Description Sound term the number of times the amplitude is measured Sampling rate per time interval the number of bits used to store each Sampling resolution amplitude measurement the type of sound wave before it is recorded by Analogue a computer
1(c)(i) [2 marks]
1 mark each to max 2 • 8 / 16 / 32 / bits per character • 8 16 Represents 2 / 2 / etc. characters • Represents every language and other characters such as emojis
1(c)(ii) [3 marks]
1 mark for each correctly completed space Character Denary 8–bit Binary Hexadecimal ! 33 0010 0001 21 L 76 0100 1100 4C ü 252 1111 1100 FC
A student takes a photograph of a science experiment.
(a) The photograph is saved as a bitmapped image.
(i) Define the following bitmap terms. 2 marks
Colour depth
File header
(ii) Explain why changing the image resolution will affect the image quality and file size. 2 marks
Image quality
File size
(iii) Identify one lossless method of compressing an image. 1 mark
(b) The student draws a picture on paper that is scanned into the computer and saved as a vector graphic. 2 marks
Define the vector graphic terms property and drawing list.
Property
Drawing list
Show mark scheme
7(a)(i) [2 marks]
1 mark for each correct definition Colour depth: • the number of bits used to represent a colour // the number of colours that can be represented in an image File header: • stores data about the image file / metadata
7(a)(ii) [2 marks]
1 mark for each correct explanation Image quality: • Decreasing resolution means details within the image are lost because there are fewer pixels // Increasing resolution means the image is more detailed because there are more pixels File size: • Decreasing the resolution will decrease the file size because there are fewer pixels therefore less data // Increasing the resolution will increase the file size because there are more pixels therefore more data
7(a)(iii) [1 mark]
1 mark for correct method For example: • Run-Length Encoding
7(b) [2 marks]
1 mark for each correct definition Property: • an attribute of a drawing object // data about a shape // defines one aspect of the appearance of a drawing object Drawing list: • all the drawing objects/shapes in an image // stores the commands/descriptions / mathematical equations required to draw each object
A computer system stores text, images and sound.
(a) A character set is used to represent characters in a computer. 2 marks
Identify and describe one character set.
Character set
Description
(b) The colour of each pixel in a bitmapped image is represented by 8 bits.
(i) State the largest number of different colours that can be represented by 8 bits. 1 mark
(ii) State one drawback of increasing the number of bits that represents each pixel in the bitmap image. 1 mark
(iii) A bitmap image can be compressed using lossy compression. 2 marks
Explain the reasons why lossy compression is often suitable for a bitmap image.
(c) (i) Explain how an analogue sound wave is converted into digital data. 2 marks
(ii) Describe one method of compressing a sound file using lossy compression. 2 marks
Show mark scheme
6(a) [2 marks]
1 mark for identification 1 mark for matching description e.g. • ASCII • 7/8 bits per character // represents 128/256 characters // represents all characters from Latin alphabet • UNICODE • 8/16/32 bits per character // represents 256/65536+ characters // represents all characters in all languages
6(b)(i) [1 mark]
1 mark for: 256 // 2 8
6(b)(ii) [1 mark]
1 mark for: Increased file size
6(b)(iii) [2 marks]
1 mark for each bullet point ( max 2 ) e.g. • The change may not be noticeable // Data removed is usually not noticed by the human eye • … for example, changes in shade/detail • It produces a larger decrease in file size compared to lossless // Lossy decreases file size considerably
6(c)(i) [2 marks]
1 mark for each bullet point ( max 2 ) • Value magnitude/size of the analogue sound wave is measured a set / number of times each second/time / at set intervals • Each sample/reading/measurement is given the binary number and stored in sequence
6(c)(ii) [2 marks]
1 mark for each correct point and 1 mark for matching expansion e.g. • Decrease sample rate • … fewer samples/readings/measurements stored per second // fewer bits per second stored • Decrease sample resolution • … fewer bits per sample/reading/measurement // each sample has fewer bits • Sound outside of set/human hearing range is removed • … fewer measurements are stored / decreases the number of possible binary values so fewer bits are stored
A photograph is stored as a bitmap image.
Show mark scheme
2(a) [2 marks]
1 mark for working: 4000 * 3000 * 4 1 mark for correct answer: 48MB
2(b)(i) [2 marks]
1 mark each to max 3 : The file takes less storage space on the web server than if lossless compression was used The file is faster to upload/download to/from the server than if lossless compression was used The file uses less bandwidth to transmit than if lossless compression was used The file consumes less data allowance than if lossless compression was used
2(b)(ii) [2 marks]
1 mark each: Identifies consecutive repeating pixels of the same colour Stores the colour /pattern and the number of times it repeats
2(c)
1 mark each to max 2 : Colour/bit depth Image resolution
(a) Draw one line from each vector graphic term to its most appropriate description. 2 marks
Term
drawing list
Description
a component created using a formula
defines one characteristic drawing object of a component
data required to create all property components in the graphic
(b) State what is meant by the bit depth of a bitmap image and explain how changing the bit depth affects the image. 3 marks
Definition
Explanation
(c) Explain why a bitmap image is often compressed before it is attached to an email. 2 marks
Show mark scheme
1(a) [2 marks]
2 marks for all 3 lines correct 1 mark for 1 line correct Description Term a component created drawing list using a formula defines one characteristic drawing object of a component data required to create all property components in the graphic
1(b) [3 marks]
1 mark for the definition • The number of bits used to represent each colour 1 mark for each bullet point for the explanation • Increase in bit depth means the image has a greater range of colours // Decrease in bit depth means the image has a smaller range of colours • Increase in bit depth makes the image closer to the original / more realistic // Decrease in bit depth makes the image less like the original / less realistic
1(c) [2 marks]
1 mark for each bullet point ( max 2 ) • Reduced bandwidth usage when transmitting the message • Reduced transmission time from email client to email server • Reduced storage space on the email • Email accounts often have a maximum size for an attachment
(a) A real-time video of a music concert needs to be streamed to subscribers. 3 marks
| Tick (✓) one b | box to identify |
|---|---|
| Lossy | Lossless |
Justification
(b) Explain the impact of changing the sampling resolution on the accuracy of a sound recording. 3 marks
(c) A bitmap image has a resolution of 2048 pixels wide and 1024 pixels high. 2 marks
The image has a bit depth of 10 bits per pixel.
Estimate the file size of the bitmap image in mebibytes. Show your working.
Working
Estimated file size in mebibytes
Show mark scheme
6(a) [3 marks]
1 mark for each bullet point ( max 3 ) Lossy compression (ticked) • Loss of quality will not be noticed • Needs to be viewed in real time so less bandwidth needed if file size smaller • Smaller file sizes will reduce buffering so the video will play more smoothly • Viewers may watch on different devices, so may not need high quality resolution Lossless compression (ticked) • Original recording may not have been made in high resolution • Could be streaming to high bandwidth devices • The reduction in the file size is sufficient for the receiving device • Viewers do not want any loss of quality
6(b) [3 marks]
1 mark for each bullet point ( max 3 ) Increase sampling resolution • … the number of bits used for each sample is increased • … there will be more values available to represent each sample // more amplitudes can be represented • ... each binary amplitude/note in the digital recording is closer to the analogue amplitude/note • … quantisation errors are reduced • … the digital soundwave is closer to the original analogue soundwave Decrease sampling resolution • … the number of bits used for each sample is decreased • … there will be fewer values available to represent each sample // fewer amplitudes can be stored • ... each binary amplitude/note in the digital recording is further from the analogue amplitude/note • … quantisation errors are increased • … the digital soundwave is less like the original analogue soundwave
6(c) [2 marks]
1 mark for answer, 1 mark for working Answer: 2.5 mebibytes Working: (2048 1024 10) / (8 1024 1024)
(a) State what is meant by analogue data . 1 mark
(b) Draw one line from each term to its most appropriate description. 2 marks
Term Description
sampling
sampling rate
sampling resolution
the number of samples taken per second
taking measurements at regular intervals and storing the values
the number of bits used to store each sample
Show mark scheme
1(a) [1 mark]
1 mark for: • data values that are continuously changing // variable // any value
1(b) [2 marks]
1 mark for 1 correct line 2 marks for 3 correct lines Description Term the number of samples sampling taken per second taking measurements at sampling rate regular intervals and storing the values the number of bits used to sampling resolution store each sample
(a) Describe the impact of increasing the image resolution on the quality of a bitmap graphic. 2 marks
(b) Calculate the file size of a bitmap image using the following information: 2 marks
image resolution of 2048 pixels wide and 1024 pixels high
bit depth of 16 bits.
Give your answer in kibibytes. Show your working.
Working
Answer in kibibytes
Show mark scheme
2(a) [2 marks]
1 mark for each bullet point: • more pixels can be stored / are available • the image is sharper / less pixelated
2(b) [2 marks]
1 mark for answer. 1 mark for working Answer: 4096 kibibytes Working: File size = (2048 1024 16) / (8 1024)
Images are being created to advertise holidays.
Some of the images are bitmap images and some are vector graphics.
| (a) Complete the | e table by defining the image terms. |
|---|---|
| Term | Definition |
| Drawing list | ______ |
| Pixel | ______ |
| Colour depth | ______ |
| 3 marks |
(b) The bitmap images are photographs of the holiday locations.
(i) Colour depth and image resolution are both included in the file header of a bitmap image. 2 marks
Identify two other items that could be included in the file header of each photograph.
1
2
Show mark scheme
1(a) [2 marks]
1 mark for each correct definition Term Definition Drawing list All the drawing objects in an image // a list that stores the commands required to draw each object Pixel The smallest part of the image // one square / dot of one colour Colour depth The number of bits per pixel // determines the number of colours that can be represented in the image
1(b)(i) [2 marks]
1 mark each Examples: Confirmation that it is a bitmap // file type Compression type Location/offset of data within the file Dimensions e.g.100 100 pixels
1(b)(ii)
1 mark for working; 1 mark for answer Working: (1500 * 3000 * 8) / 1000 / 1000 Answer: 36 MB
1(c)(i) [3 marks]
1 mark each Examples: The customers will be able to download the photographs in less time …and they will take less of the customer's bandwidth The photographs will take up less space on the customer's storage medium …therefore the customers can store more images …and will have more space for other files
1(c)(ii) [2 marks]
1 mark each to max 2 for explanation; 1 mark for an image related example RLE stores a colour and the number of times it occurs consecutively An image may not have many sequences of the same colour It would need to store each colour and then the count/number 1 which adds data Example: Red-Green-Blue would become Red 1 Green 1 Blue 1
A mobile telephone is used to record a video.
(a) The mobile telephone has a touchscreen. There are different types of touchscreen. 5 marks
Complete the description of the principal operation of touchscreens.
A ______ touchscreen has two layers. When the user touches
the screen, the layers touch and a ______ is completed.
A ______ touchscreen has several layers. When the top layer
is touched, there is a ______ in the electric current.
A microprocessor identifies the ______ of the touch.
(b) The mobile telephone uses a built-in digital camera to record the video. 3 marks
The digital camera automatically focuses on the faces of people.
Explain how Artificial Intelligence (AI) is used by the camera to automatically focus on the faces of people.
(c) The video includes a sound recording.
(i) Describe how sound is represented in a computer. 3 marks
Show mark scheme
3(a) [3 marks]
1 mark for each term Resistive Circuit Capacitive Change Coordinates A resistive touchscreen has two layers. When the user touches the screen, the layers touch and a circuit is completed. A capacitive touchscreen has several layers. When the top layer is touched there is a change/increase/decrease in the electric current. A microprocessor identifies the coordinates of the touch.
3(b)
1 mark each to max 3 Examples: Scans the scene in real time Identifies if there are faces in the image Uses facial recognition ... uses image recognition ... takes each frame individually ... analyses the pixels ... stores pattern for a face ... looks for patterns that match/come close to the pattern for a face Camera focuses on the pattern identified
3(c)(i) [4 marks]
1 mark each The amplitude is recorded a set number of times a second Each (instance of an) amplitude is given a corresponding binary number The binary number (of each amplitude) is saved in sequence
3(c)(ii) [4 marks]
1 mark each; max 2 for rate and max 2 for resolution Sampling rate There are smaller 'gaps' in the sound wave // sound is recorded more often Digital waveform is closer to the analogue waveform The quantisation errors are smaller Sampling resolution There are more bits per sample // a wider range of amplitudes can be stored Each binary amplitude /note (in the digital recording) is closer to the analogue amplitude /note Digital waveform is closer to the analogue waveform The quantisation errors are smaller
Draw one line from each security feature to its most appropriate description.
Security feature Description
converts data to an alternative form
firewall
redirects a user to a fake website
pharming
verifies the authenticity of data
anti-virus software
scans files on the hard drive for malicious software
encryption
accepts or rejects incoming and outgoing packets based on criteria 4 marks
Show mark scheme
2 [4 marks]
1 mark for each correct line. Description Security feature converts data to an alternative form firewall redirects a user to a false website pharming verifies the authenticity of data anti-virus software scans files on the hard drive for malicious software encryption accepts or rejects incoming and outgoing packets based on criteria
A Local Area Network (LAN) consists of four computers, one server and a switch.
The LAN uses a star topology.
(a) Complete the following diagram to show how the hardware is connected. 1 mark
Computer Computer Server Computer Computer
(b) A router is attached to one of the devices on the LAN shown in part (a) to connect the LAN to the internet.
(i) Identify the device. Give a reason for your choice. 2 marks
Device
Reason
(ii) Describe the role and function of the router in the network. 3 marks
Show mark scheme
10(a) [1 mark]
all four computers directly connected to the switch and no other connections.
10(b)(i) [2 marks]
1 mark for the device. 1 mark for corresponding reason. • Device: Server • Reason: Server processes the requests and authorises traffic // firewall software on the server authorises traffic // server acts as the proxy • Device: Switch • Reason: Switch is connected to all the computers // to share access to the router on the network
10(b)(ii) [3 marks]
1 mark for each bullet point (max 3) : • receive packets from devices / internet • find destination of packets using the IP address • forward packets to the destination • assign private IP addresses to devices on LAN • store/update/maintain a routing table • find most efficient path to destination • maintain table of MAC and IP addresses • provides the LAN with a public IP address • acts as a gateway • performs protocol conversion • acts as a firewall
Show mark scheme
10(a) [3 marks]
1 mark for each bullet point: • to ensure the system operates with the given criteria • ... by enabling system output to affect subsequent system input • ... thus allowing conditions to be automatically adjusted
10(b)(i) [2 marks]
1 mark for identification of a suitable sensor 1 mark for corresponding justification Example: • sound sensor • if a sound occurs inside the car the alarm is activated • infra-red sensor • senses the heat of person in the car / infra-red beams are broken • pressure sensor • an intruder sits in the driver’s seat
10(b)(ii) [3 marks]
1 mark for each bullet point ( max 3 ): • the embedded system is built into / integrated (into the car alarm) • combination of hardware and software designed for a specific function • must have a processor, memory and input / output • The system is not easily changed /updated by the car owner
(a) Draw one line from each image representation term to its correct definition. 3 marks
Term Definition
Pixel
Bit depth
Image resolution
File header
The number of pixels wide by the number of pixels high
The smallest identifiable component of an image
Stores data about the image file, e.g. file format, number of bits per pixel, file size
The number of bits used to represent each colour
(b) The following section of a bitmap image is 10 pixels wide and 5 pixels high. In this example, each colour is represented by a letter, e.g. B is blue.
| B | B | B | B | B | B | B | B | B | B |
|---|---|---|---|---|---|---|---|---|---|
| Y | Y | P | Y | Y | Y | P | Y | Y | Y |
| R | R | M | R | P | K | T | T | R | R |
| B | O | P | Y | Y | Y | P | G | P | P |
| R | O | R | P | P | P | R | R | R | R |
The complete image can have up to 256 colours.
(i) Identify the smallest number of bits that can be used to represent each colour in the complete bitmap image. 1 mark
Show mark scheme
1(a) [3 marks]
1 mark for 1 correct line 2 marks for 2 or 3 correct lines 3 marks for all 4 correct lines Term Definition The number of pixels wide by the number of Pixel pixels high The smallest identifiable Bit depth component of an image Stores data about the image file, e.g. file Image resolution format, number of bits per pixel, file size The number of bits used File header to represent each colour
1(b)(i) [1 mark]
8
1(b)(ii) [2 marks]
1 mark for working 10 * 5 * 8 (bits) / 8 // = 50 (pixels) * 8 (bits) / 8 1 mark for answer 50 (bytes)
1(c) [2 marks]
1 mark per point Increasing the colour depth results in increased file size // Decreasing the colour depth results in smaller file size Increasing the colour depth means more bits per pixel and hence more data stored // Decreasing the colour depth means fewer bits per pixel and hence less data stored
1(d) [2 marks]
1 mark per point Use run-length encoding // RLE Record the colour Blue, and the number of times it occurs 10
Bobby is recording a sound file for his school project.
(a) He repeats the recording of the sound several times, with a different sample rate each time.
(i) Describe the reasons why the sound is closer to the original when a higher sample rate is used. 2 marks
(ii) Describe the reasons why the sound file size increases when a higher sample rate is used. 2 marks
(b) Bobby wants to email the sound file to his school email address. He compresses the file before sending the email.
(i) Explain the reasons why Bobby compresses the sound file. 2 marks
(ii) Bobby uses lossless compression. 2 marks
Describe how lossless compression can compress the sound file.
Show mark scheme
7(a)(i) [2 marks]
1 mark per bullet point Smaller time gaps between the samples • Makes the digital sound wave more accurate • Smaller quantisation errors •
7(a)(ii)
1 mark per bullet point More samples/data are taken/recorded • … so more bits are stored altogether •
7(b)(i) [2 marks]
1 mark per bullet point Reduces the file size • Faster to transmit/download • Original file is too large for email storage/attachment •
7(b)(ii) [2 marks]
1 mark per bullet point to max 2 e.g. Reduce amplitude to only the range used • … limited amplitudes mean fewer bits per sample • Run-length-encoding • … Where consecutive sounds are the same record the binary value of the • sound and number of times it repeats Record the changes instead of the actual sounds •
Riya has created the following logo as a vector graphic.
| R | ||
(a) Complete the table by writing a description of each vector graphic term and give an example for this logo. 4 marks
| Term | Description | Example from logo |
|---|---|---|
| Property | ||
| Drawing list |
(b) Riya takes a photograph using a digital camera. The photograph is stored as a bitmap image.
(i) Describe two differences between a vector graphic and a bitmap image. 4 marks
1
2
(ii) Riya needs to email the photograph. She compresses the photograph before sending it using an email. 4 marks
Describe two lossy methods that Riya can use to compress the image.
Method 1
Method 2
Show mark scheme
5(a) [4 marks]
1 mark for each description, 1 mark for each valid example Term Description Example from logo e.g. data about the shapes black line // white fill // black fill // defines one aspect of the Property //solid (line) // font of letter // appearance of the drawing colour of triangle object e.g. the list of shapes involved in triangle // capital letter R // an image Drawing rectangle // line // a list that stores the list command/description required to draw each object
5(b)(i) [4 marks]
1 mark for each bullet point to max 2 for each difference Bitmap made up of pixels // bitmap is made of colours stored for • individual pixels Vector graphic store a set of instructions about how to draw the shape • When bitmap is enlarged the pixels get bigger and it pixelates • When vector is enlarged it is recalculated and does not pixelate • Bitmap files are usually bigger than vector graphics files because of the • need to store data about each pixel Vector graphics have smaller file size because they contain just the • instructions to create the shapes Bitmap images can be compressed with significant reduction in file size • Vector graphic images do not compress well because of little redundant • data
5(b)(ii) [4 marks]
1 mark for each bullet point to max 2 for each method Reduce bit depth • ... reduces the number of bits per colour / pixel which means each pixel • has fewer bits Reduce colour palette // reduce number of colours • ... fewer colours mean fewer bits needed to store each colour • Reduce image resolution • ... fewer pixels per unit measurement means less binary to store •
Bobby is recording a sound file for his school project.
(a) He repeats the recording of the sound several times, with a different sample rate each time.
(i) Describe the reasons why the sound is closer to the original when a higher sample rate is used. 2 marks
(ii) Describe the reasons why the sound file size increases when a higher sample rate is used. 2 marks
(b) Bobby wants to email the sound file to his school email address. He compresses the file before sending the email.
(i) Explain the reasons why Bobby compresses the sound file. 2 marks
(ii) Bobby uses lossless compression. 2 marks
Describe how lossless compression can compress the sound file.
Show mark scheme
7(a)(i) [2 marks]
1 mark per bullet point Smaller time gaps between the samples • Makes the digital sound wave more accurate • Smaller quantisation errors •
7(a)(ii)
1 mark per bullet point More samples/data are taken/recorded • … so more bits are stored altogether •
7(b)(i) [2 marks]
1 mark per bullet point Reduces the file size • Faster to transmit/download • Original file is too large for email storage/attachment •
7(b)(ii) [2 marks]
1 mark per bullet point to max 2 e.g. Reduce amplitude to only the range used • … limited amplitudes mean fewer bits per sample • Run-length-encoding • … Where consecutive sounds are the same record the binary value of the • sound and number of times it repeats Record the changes instead of the actual sounds •
Anya scans an image into her computer for a school project.
(a) The scanned image is a bitmapped image. 2 marks
| (i) Com | mplete the following table to describe the two terms about graphics. |
|---|---|
| Term | Description |
| Pixel | ______ |
| File header | ______ |
(ii) The image is scanned with an image resolution of 1024 × 512 pixels, and a colour depth of 8 bits per pixel. 3 marks
Calculate an estimate for the file size, giving your answer in mebibytes. Show your working.
Working
Answer ______ mebibytes
(b) The image is compressed using lossless compression. 3 marks
Identify one method of lossless compression that can be used to compress the image and describe how the method will reduce the file size.
Lossless compression method
Description
Show mark scheme
1(a)(i) [3 marks]
1 mark for each description Pixel: A single square of one colour • The smallest addressable element in an image • File header: Data about the bitmap image (e.g. number of colours) •
1(a)(ii) [3 marks]
1 mark per bullet point for working, 1 mark for answer Working: 1024 512 = 524 288 pixels/bytes • × 524288 / 1024 / 1024 • Answer: 0.50 mebibytes
1(b)
1 mark for naming method, 1 mark per description to max 2 Run-length encoding • Replace sequences of the same colour pixel • … with colour code and number of identical pixels •
1(c)(i) [1 mark]
252
1(c)(ii) [3 marks]
1 mark per bullet point Converting 15 to binary • 0000 1111 Method for addition • Final answer • 0010 0011
- 0000 1111 0011 0010 1 111
1(c)(iii) [3 marks]
1 mark per bullet point Converting −10 to two's complement binary • 1111 0110 Adding values • Final answer • 0001 1001 10 = 0000 1010 –10 = 1111 0110 0010 0011
- 1111 0110 0001 1001 11 11
1(d) [2 marks]
1 mark per bullet point to max 2 The formal and legal rights to ownership // intellectual property rights • Protects against unauthorised reproduction of work • Provides for legal right of redress •
Anya scans an image into her computer for a school project.
(a) The scanned image is a bitmapped image. 2 marks
| (i) Com | mplete the following table to describe the two terms about graphics. |
|---|---|
| Term | Description |
| Pixel | ______ |
| File header | ______ |
(ii) The image is scanned with an image resolution of 1024 × 512 pixels, and a colour depth of 8 bits per pixel. 3 marks
Calculate an estimate for the file size, giving your answer in mebibytes. Show your working.
Working
Answer ______ mebibytes
(b) The image is compressed using lossless compression. 3 marks
Identify one method of lossless compression that can be used to compress the image and describe how the method will reduce the file size.
Lossless compression method
Description
Show mark scheme
1(a)(i) [3 marks]
1 mark for each description Pixel: A single square of one colour • The smallest addressable element in an image • File header: Data about the bitmap image (e.g. number of colours) •
1(a)(ii) [3 marks]
1 mark per bullet point for working, 1 mark for answer Working: 1024 512 = 524 288 pixels/bytes • × 524288 / 1024 / 1024 • Answer: 0.50 mebibytes
1(b)
1 mark for naming method, 1 mark per description to max 2 Run-length encoding • Replace sequences of the same colour pixel • … with colour code and number of identical pixels •
1(c)(i) [1 mark]
252
1(c)(ii) [3 marks]
1 mark per bullet point Converting 15 to binary • 0000 1111 Method for addition • Final answer • 0010 0011
- 0000 1111 0011 0010 1 111
1(c)(iii) [3 marks]
1 mark per bullet point Converting −10 to two's complement binary • 1111 0110 Adding values • Final answer • 0001 1001 10 = 0000 1010 –10 = 1111 0110 0010 0011
- 1111 0110 0001 1001 11 11
1(d) [2 marks]
1 mark per bullet point to max 2 The formal and legal rights to ownership // intellectual property rights • Protects against unauthorised reproduction of work • Provides for legal right of redress •