This document compares video compression standards MPEG-4 and H.264. It provides an overview of both standards, including their development histories and profiles. MPEG-4 was the first standard to support object-based video coding and compression of different media types. H.264 provides significantly better compression than prior standards like MPEG-2 at the cost of higher computational complexity. Both standards are widely used today for applications ranging from mobile and internet video to television broadcasting and digital cinema.
1. MPEG-4 vs.
H.264
09BCE009 – Utsav Dholakia
Guided By- Prof. Purvi
Kansara
2. Introduction
What is video compression?
Quality factors for video
compression
Intro of MPEG-4 and overview
Profiling and coding of MPEG-
4
Intro of H.264 and overview
Profiles and levels
Future scopes and Usage
References
3. Introduction
•What is the format of video file
and how does it affect the video
quality?
•What is .mp4, .mov file extension?
•Is video recorded in the same
format that we see?
4. Video Compression
•Why video compression is needed?
•Memory and bandwidth is very
expensive.
•So video compression is useful as
it decreases file size and
maintains almost same quality.
•Video compression is of 2 types:
•Lossless compression
•Lossy compression
5. Video Compression
•Video compression is the combination of spatial
image compression and temporal motion
compression.
•It effectively reduces video size for
transmitting it via either :
• Terrestrial broadcast
• Satellite TV
• Cable TV
•In HDTV data rate is 1.5Gb/s so to transmit it
over normal channel ~80:1 compression rate is
required.
6. How video
•Video compression works on square
shaped compression group of neighboring works?
pixels
called macroblocks.
•The group of pixels in different
frames are compared and only
difference between them is sent so
redundancy is reduced and size is
also reduced.
•So if there is much more motion in
the movie then compression doesn’t
work efficiently and size is not
much reduced. Ex: Fire scenes,
explosions
7. Size of uncompressed
video and bandwidth of
carriers
Video Source Output data rate[Kbits/sec]
Quarter VGA (320X240)
@20 frames/sec 36 864
CIF camera (352X288)
@30 frames/sec 72 990
VGA (640X480) @30 frames/sec 221 184
Transmission Medium Data Rate [Kbits/sec]
Wireline modem 56
GPRS (estimated average rate) 30
3G/WCDMA (theoretical maximum) 384
8. Terminology
•Video
• Transmission or storage formats for
moving pictures
•Video compression format
• Specification for digitally
representing a video as a file or a
bitstream
• Example: MPEG-2 part2 ,MPEG-4
part2 ,H.264
9. Terminology
•Video codec
• A specific software or hardware
implementation of video compression and/or
decompression using a specific video
compression format is called a video codec
• Example: QuickTime, x264, FFmpeg
•Video container
• A video container is a meta file format
whose specification describes how meta data
and different data elements coexist in a
computer file.
• Example: flv , avi , mp4 , mkv , wav , AIFF
, 3gp
10. Video Compression
Factors
• Digital video is a representation of
natural scene sampled temporally and
spatially.
• Characteristics of a typical natural
video scene that are relevant for video
processing and compression include:
1.Spatial characteristics (texture
variation within scene, number and
shape of objects, color etc.)
2.Temporal characteristics (object
motion, changes in illumination,
movement of the camera or viewpoint
11. Video Compression
Factors
• Spatial Sampling:
Sampling occurs at each of the
intersection points on the grid
and the sampled image may be
reconstructed by representing
each sample as a square picture
element (pixel). The visual
quality of the image is
influenced by the number of
sampling points.
12. Video Compression
• Temporal SaFmaplcintgors
A moving video image is captured by
taking a rectangular snapshot of
the signal at periodic time
intervals. Playing back the
series of frames produces the
appearance of motion. A higher
temporal sampling rate (frame
rate) gives apparently smoother
motion in the video scene but
requires more samples to be
captured and stored.
13. Video Compression
Factors
• Frames & Fields
A video signal may be sampled as a series
of complete frames ( progressive
sampling) or as a sequence of interlaced
fields (interlaced sampling). In an
interlaced video sequence, half of the
data in a frame (one field) is sampled
at each temporal sampling interval.
14. Video Compression
Factors
• Color Spaces
• Most digital video applications rely on the
display of color video and so need a mechanism
to capture and represent color information.
• The method chosen to represent brightness
(luminance or luma) and color is described as a
color space.
• The two color spaces are explained in following
slides.
15. Video Compression
Factors(Color
Spaces)
• RGB
• In the RGB color space, a color image sample is
represented with three numbers that indicate the
relative proportions of Red, Green and Blue
• The RGB color space is well-suited to capture and
display of color images. Capturing an RGB image
involves filtering out the red, green and blue
components of the scene and capturing each with a
separate sensor array.
16. Video Compression
Factors(Color
• YCbCr Spaces)
• The human visual system (HVS) is less sensitive to
color than to luminance (brightness).
• It is possible to represent a color image more
efficiently by separating the luminance from the
color information and representing luma with a
higher resolution than color.
• Luma component Y =KyR+KgG+KbB
where K are weighting factors.
• Cb, Cr, Cg are chroma components. Each chroma
component is the difference between R,G,B and Y.
17. Video Compression
Factors(Color
• YCbCr sampliSngp faorcmeatss)
• 4:4:4 sampling means that the three components
(Y, Cb and Cr) have the same resolution and hence
a sample of each component exists at every pixel
position.
• 4:2:2 in this sampling (sometimes referred to as
YUY2), the chrominance components have the same
vertical resolution as the luma but half the
horizontal resolution.
• 4:2:0 in this popular 4:2:0 sampling format
(YV12), Cb and Cr each have half the horizontal
and vertical resolution of Y.
18. MPEG-4
•MPEG-4 (Moving Pictures Experts Group) is an
ISO/IEC 14496 standard for a coded
representation of audio and video data for
transmission.
•Does not give implementation.
•First version: October 1998
•MPEG-4 (coding of audio-visual objects) is the
latest standard that deals specifically with
audio-visual coding.
19. MPEG-4
•Object based system: using natural and/or
synthetic objects.
•Makes use of local processing power to recreate
sounds and images
•This makes it one of the most efficient
compression systems.
21. Method of object
based compression
•The selected objects are put together in a 2D or
3D scenes.
•In 3D the viewer can change the shape of the
image and view it from other positions in the 3D
space.
•Each object is compressed using the best and
optimum method for that type of data.
22. MPEG-4(Profiles and
levels)
•Features are left on to individual developers
for deciding whether to implement them.
•So there are no complete implementation of
MPEG4 set of standards.
•Thus came the concept of “Profiles” & “Levels”
•This gave the opportunity to implement specific
set of properties necessary for application.
23. Profiles & Levels •Subsets of MPEG-4 tools are provided for
specific application implementation.
•This subsets are “profiles” which decrease size
of the tool set a decoder is required to
implement.
•In order to reduce computational complexity ,
one or more levels are set for each profiles.
The combination of both levels & profiles
allows:
• A codec builder to implement only a subset of
standard needed for maintaining
internetworking with other MPEG-4 devices
that implement same combination.
• Checking whether MPEG-4 devices comply with
24. Profiles and Levels
Quality
Complexity
Digital cinema
DVD
Video CD
Mobiles
MPEG-1
MPEG-2
HDTV
Advanced Simple Profile
Simple Profile
MPEG 4
26. Temporal Redundancy
Reduction
• For temporal redundancy reduction the compression
frames are group of pictures(GOP). It consists of
series of I,B,P frames.
• I frames are independently encoded.
• P frames are based on previous I,P frames.
• B frames are based on previous and following
I,P frames.
• The typical series of encoding frames are:
1.I B B P B B P B B I
2.I B B P B B P B B P B B I
28. Uses of MPEG-4
•3G mobile phones
•Portable devices, PDAs, iPod
videos
•Interactive television / IPTV
•New interactive multimedia formats
•Web pages
•Interactive music format
•Security systems
29. H.264
•H.264/ MPEG-4 Part 10 or AVC(Advanced Video
Coding) is currently one of the most used
format for recording , compression and
distribution of HD videos.
•Final drafting of the version was completed
on May,2003.
•H.264/MPEG-4 AVC is a block-oriented,
motion-compensation-based codec standard
developed by the ITU-T ,Video Coding Experts
Group (VCEG) together with the International
Organization for
Standardization(ISO)/International Electro
technical Commission(IEC) MPEG.
30. H.264
•The intent of the H.264/AVC project was
to create a standard capable of providing
good video quality at lower bit rates
than previous standards (like MPEG-2,
H.263, or MPEG-4 Part 2), but not
increasing the complexity of design so
much that it would be impractical or
excessively expensive to implement.
•With the use of H.264 50% of bit rate
saving is reported.
31. • A fHie.l2d 6or4 A( Tfreamrem: inology)
• “A field” (of interlaced video) or a “frame”
(of progressive or interlaced video) is encoded
to produce a coded picture.
• Macroblocks:
• A coded picture consists of a number of
”macroblocks”, each containing 16 16 luma
samples and associated chroma samples (8 8 Cb
and 8 8 Cr samples in the current standard).
• Within each picture, macroblocks are arranged
in slices, where a slice is a set of
macroblocks in raster scan order.
• I,P,B slices are coded as per MPEG-4 standard
34. • TheP Brasoefliinel Persof ilaen: d Levels
It supports intra and inter-coding (using I-slices and P-slices)
and entropy coding with context-adaptive
variable-length codes (CAVLC).
Potential applications of the Baseline Profile include
videotelephony, videoconferencing and wireless
communications.
• The Mainline Profile:
It includes support for interlaced video, inter-coding
using B-slices, inter coding us- ing weighted prediction
and entropy coding using context-based arithmetic coding
(CABAC).
Potential applications of the Main Profile include
television broadcasting and video storage.
35. Profiles and Levels
• The Extended Profile:
It does not support interlaced video or CABAC but adds
modes to enable efficient switching between coded
bitstreams (SP- and SI-slices) and improved error
resilience (Data Partition- ing).
Potential application of extended Profile may be
particularly useful for streaming me- dia applications.
37. Uses of H.264
•Very broad application range from low bit
rate internet streaming to HDTV broadcast
and digital cinema broadcasting.
•Blu-ray Disc
•AVCHD a HD recording format designed by
Sony & Panasonic uses H.264.
•Common DSLRs use QuickTime .mov as a
native recording.
41. Future options
•MPEG-4 is still being developed and all new
parts will work with the old formats.
•Studio quality versions for HDTVs
•Digital cinema 45-240 Mbit/s H.264
•Home video cameras with MPEG-4 output straight
to the web form the hard drive.
•Integrated Service Digital Broadcast(ISDB)
•Newspaper + TV + data
•Integration with MPRG7 databases
•Games with 3D texture mapping
42. References
•http://en.wikipedia.org/wiki/Video_compression#
Video
•http://en.wikipedia.org/wiki/H.264/MPEG-
4_AVC
•http://en.wikipedia.org/wiki/MPEG-4
•http://en.wikipedia.org/wiki/Video_compre
ssion_format
•MPEG-4 and H.264 video compression (by
Iain E.G.Richardson)
