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 compression
works?
•Video compression works on square
shaped group of neighboring 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)
36 864
@20 frames/sec
CIF camera (352X288)
72 990
@30 frames/sec
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:
• Spatial characteristics (texture variation
within scene, number and shape of objects,
color etc.)
• Temporal characteristics (object motion,
changes in illumination, movement of the
camera or viewpoint and so on).

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
Factors
• Temporal Sampling
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 Spaces)
• YCbCr
• 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 Spaces)
• YCbCr sampling formats
• 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.

20. Basic object types
• Photos - JPEG, GIF, PNG,
• Video - MPEG-2, DivX, AVI, H.264,QuickTime
• Speech - CELP, HVXC, Text to Speech
• Music - AAC, MP3
• Synthetic music
• Graphics - Java code
• Text
• Animated objects, e.g., talking heads

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 the
standard referred to as conformance testing.

24. Profiles and Levels
Advanced Simple Profile
Quality
Digital cinema
HDTV
MPEG 4
MPEG-2
DVD
Video CD MPEG-1
Mobiles
Simple Profile
Complexity

25. MPEG-4 profiles

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:
• IBBPBBPBBI
• IBBPBBPBBPBBI

27. Distribution System for
MPEG-4

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. H.264(Terminology)
• A field or A frame:
• “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 only.

32. H.264 CODEC
H.264 Encoder

33. H.264 CODEC
H.264 Decoder

34. Profiles and Levels
• The Baseline Profile:
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.

36. Profiles and Levels

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.

38. Comparison of various
compression technique
Text

40. Comparison between
MPEG-4 and H.264

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_compression_for
•MPEG-4 and H.264 video compression (by Iain
E.G.Richardson)