Week 12 : 30 April 2014
In class I've learned what is Video Digital
Video : Digital video has supplanted analog video as the method of choice for making video for multimedia use. Video in multimedia are used to portray real time moving pictures in a multimedia project.
Input: Analog Video is usually captured by a video camera and then digitised.
There are a variety of video (analog and digital) formats
Raw video can be regarded as being a series of single images.
There are typically 25, 30 or 50 frames per second.
E.g. A 512 512 size monochrome video images take 25
0:25 = 6.25MB for a second to store uncompressed.
Typical PAL digital video (720 576 pixels per colour frame)
1:24 25 = 31MB for a second to store uncompressed.
High Definition video on Blu-ray (up to 19201080 = 2 Megapixels per frame) 6:225 = 155MB for a second to store uncompressed.
(There are higher possible frame rates!)
Digital video clearly needs to be compressed for most times.
In class I've learned reason for video compression
Over the past decades, video compression technologies have become an integral part of the way we create, communicate and consume visual information. Digital video communication can be found today in many applications such as broadcast services over satellite and terrestrial channels, digital video storage, wires and wireless conversational services and etc.
The data quantity is very large for the digital video and the memory of the storage devices and the bandwidth of the transmission channel are not infinite, so reducing the amount of data needed to reproduce video saves storage space, increases access speed and is the only way to achieve motion video on digital computers.
For instance, we have a 720 x 480 pixels per frame, 30 frames per second, total 90 minutes full color video, then the full data quantity of this video is about 167.96 G bytes. This raw video contains an immense amount of data, and communication and
storage capabilities are limited and expensive. Thus, several video compression algorithms had been developed to reduce the data quantity and provide the acceptable quality as possible as they can. There are two international standards in compressing video, known as MPEG-1 and MPEG-2.
Compression basically removes redundancy in the data
Example: 10101010101010101010101010101010101010
Coding: 19 times ”10”
Compression find as short a representation as possible by removing correlation in the data
Temporal – correlation in Audio and video Spatial
– correlation between neighbouring pixels in images and video
Spectral – correlation between colour or luminescence components
”Perceptual – correlation” by exploiting human perceptual properties
Information is measured in number of bits
Redundancy of a representation is: Bits in representation – bits in shortest representation
Compression ratio is: Ratio between original file and compressed file
In class I've learned why can video be compressed?
The reason is that video contains much spatial and temporal redundancy.
Spatial redundancy
In a single frame, nearby pixels are often correlated with each other. This is called spatial redundancy, or the intraframe correlation.
Temporal redundancy
Another one is temporal redundancy, which means adjacent frames are highly correlated, or called the interframe correlation. Therefore, our goal is to efficiently reduce spatial and temporal redundancy to achieve video compression.
In class I've learned the difference between Spatial compression and Temporal Compression
Spatial (intra-frame) compression
– Compress each frame in isolation, treating it as a bitmapped image
• Image compression applied to each frame
• Can be either lossless or lossy
• Motion JPEG
– Purely spatial compression
– Apply JPEG to each frame
– Used by most analogue capture cards
– No standard but MJPEG No standard, but MJPEG-A format widely A format widely supported
Temporal(inter-frame) compression
– Compress sequences of frames by only storing differences between them
A video consists of a time-ordered sequence of frames
• Contents do not change rapidly between Contents do not change rapidly between frames
• A solution to video compression would be predictive predictive codingbasedon previous previousframes
Video : Digital video has supplanted analog video as the method of choice for making video for multimedia use. Video in multimedia are used to portray real time moving pictures in a multimedia project.
Input: Analog Video is usually captured by a video camera and then digitised.
There are a variety of video (analog and digital) formats
Raw video can be regarded as being a series of single images.
There are typically 25, 30 or 50 frames per second.
E.g. A 512 512 size monochrome video images take 25
0:25 = 6.25MB for a second to store uncompressed.
Typical PAL digital video (720 576 pixels per colour frame)
1:24 25 = 31MB for a second to store uncompressed.
High Definition video on Blu-ray (up to 19201080 = 2 Megapixels per frame) 6:225 = 155MB for a second to store uncompressed.
(There are higher possible frame rates!)
Digital video clearly needs to be compressed for most times.
In class I've learned reason for video compression
Over the past decades, video compression technologies have become an integral part of the way we create, communicate and consume visual information. Digital video communication can be found today in many applications such as broadcast services over satellite and terrestrial channels, digital video storage, wires and wireless conversational services and etc.
The data quantity is very large for the digital video and the memory of the storage devices and the bandwidth of the transmission channel are not infinite, so reducing the amount of data needed to reproduce video saves storage space, increases access speed and is the only way to achieve motion video on digital computers.
For instance, we have a 720 x 480 pixels per frame, 30 frames per second, total 90 minutes full color video, then the full data quantity of this video is about 167.96 G bytes. This raw video contains an immense amount of data, and communication and
storage capabilities are limited and expensive. Thus, several video compression algorithms had been developed to reduce the data quantity and provide the acceptable quality as possible as they can. There are two international standards in compressing video, known as MPEG-1 and MPEG-2.
Compression basically removes redundancy in the data
Example: 10101010101010101010101010101010101010
Coding: 19 times ”10”
Compression find as short a representation as possible by removing correlation in the data
Temporal – correlation in Audio and video Spatial
– correlation between neighbouring pixels in images and video
Spectral – correlation between colour or luminescence components
”Perceptual – correlation” by exploiting human perceptual properties
Information is measured in number of bits
Redundancy of a representation is: Bits in representation – bits in shortest representation
Compression ratio is: Ratio between original file and compressed file
In class I've learned why can video be compressed?
The reason is that video contains much spatial and temporal redundancy.
Spatial redundancy
In a single frame, nearby pixels are often correlated with each other. This is called spatial redundancy, or the intraframe correlation.
Temporal redundancy
Another one is temporal redundancy, which means adjacent frames are highly correlated, or called the interframe correlation. Therefore, our goal is to efficiently reduce spatial and temporal redundancy to achieve video compression.
In class I've learned the difference between Spatial compression and Temporal Compression
Spatial (intra-frame) compression
– Compress each frame in isolation, treating it as a bitmapped image
• Image compression applied to each frame
• Can be either lossless or lossy
• Motion JPEG
– Purely spatial compression
– Apply JPEG to each frame
– Used by most analogue capture cards
– No standard but MJPEG No standard, but MJPEG-A format widely A format widely supported
Temporal(inter-frame) compression
– Compress sequences of frames by only storing differences between them
A video consists of a time-ordered sequence of frames
• Contents do not change rapidly between Contents do not change rapidly between frames
• A solution to video compression would be predictive predictive codingbasedon previous previousframes
In class I've learned the many types of video file format
In class I've learned video editing software
Adobe Premiere and Media Shop Pro are two good examples of these tools.
Adobe Premiere is a powerful tool for professional digital video editing. It is primarily used to produce broadcast quality movies. It has excellent editing tools that enable you to work with complete flexibility. This software first digitizes the sound and video and then allows you to edit them to preserve picture quality. It can edit video and multimedia movies in AVI as well as MPEG format. It can create titles and graphics and then add them to your multimedia project. It uses digital filtering for incorporating special effects. This software has applications in film editing and movie making.
Media Studio Pro also gives you the most complete set of advanced video editing tools. It can capture the video from VCR, TV or camcorders. It is capable of capturing a batch of scenes. It brings all the components of a multimedia project like video,
sound, animation and titles together. One can add effects and transitions and finally save the video in the desired format. It can retouch videos by painting directly over any frame in a video sequence. It has an audio editor, which can remove background noise and add another sound to your video.
Other video editing is as below:
Adobe Premiere and Media Shop Pro are two good examples of these tools.
Adobe Premiere is a powerful tool for professional digital video editing. It is primarily used to produce broadcast quality movies. It has excellent editing tools that enable you to work with complete flexibility. This software first digitizes the sound and video and then allows you to edit them to preserve picture quality. It can edit video and multimedia movies in AVI as well as MPEG format. It can create titles and graphics and then add them to your multimedia project. It uses digital filtering for incorporating special effects. This software has applications in film editing and movie making.
Media Studio Pro also gives you the most complete set of advanced video editing tools. It can capture the video from VCR, TV or camcorders. It is capable of capturing a batch of scenes. It brings all the components of a multimedia project like video,
sound, animation and titles together. One can add effects and transitions and finally save the video in the desired format. It can retouch videos by painting directly over any frame in a video sequence. It has an audio editor, which can remove background noise and add another sound to your video.
Other video editing is as below:
In class I've learned the formula to calculate video file size