This document discusses motion video encoding techniques. It explains that video frames contain redundant information between frames that compression removes. It describes the MPEG encoding process which converts frames to YUV color space, applies discrete cosine transform, quantization, and variable length coding. It also discusses I-frames, P-frames, and B-frames used in motion estimation and the differences between MPEG-2 and MPEG-4/H.264 standards.

1. CSN08704
Data, Audio, Video and Images
http://asecuritysite.com/comms
Telecommunications
Prof Bill Buchanan
Motion Video

2. Video (basically moving pictures)
Frame rate: Number of images per second
 Lots of redundancy. Very little changes between
frames.
 Eye does not perceive certain things ... such as fast
changes with the image.

3. MPEG Process
RGB to
YUV
DCT Quantisation
Variable
Length
Coding
Image MPEGImage
Pixel blocks (8x8 for U and
V, and 16x16 for Y)
Motion
Detection
Previous pixel block
Full Partial Partial Full

4. Segment into Slices and into Macroblocks
Slices used to
detect movement
(Only luminance
used for motion
detection)
Macroblocks
(16x16)
352x288 pixel
frame (101,376
pixels)
22 macroblocks
18 macroblocks

5. Motion Detection
• Megablocks for (0,0), (0,1) and (0,2) in the
current block are the same as in the
previous blocks. Thus they can be coded
simply with a reference to the previous
image.
• The (0,3) megablock is different to the
previous image, but the (0,3) block is
identical to the (0,2) block of the previous
image, thus a reference to this block is
made.
• This can continue, as most of the blocks in
the image are identical to the previous
image.
• The only other differences in the current
image are at (4,0) and (4,1); these blocks
can be stored in their entirety or specified
with their differences to a previous similar
block
Previous image
Current image
(0,0) (0,15)
(4,0) (4,15)

6. I-Frame, P-Frame and B-frame
• Intra frame (I-frame). A complete image and does not require any extra
information to be added to it to make it complete. No motion estimation
processing. Used as a starting point for other referenced frames, and is usually
the first frame to be sent.
• Predictive frame (P-frame). Uses the preceding I-frame as its reference and has
motion estimation processing. Each macroblock in this frame is supplied as
referenced to an I-frame as either a vector and difference.
• Bidirectional frame (B-frame). The bidirectional frame, or B-frame, is similar to
the P-frame except that it references frames to the nearest preceding or future I-
or P-frame.
I-Frame B-Frame B-Frame I-Frame

7. MPEG-2
Simple ( SP) Main (MP) SNR Spatial High
HIGH (HL) Illegal 1920 1152,
60 fps
Illegal Illegal 1920 1152,
60 fps
960 576,
30 fps
HIGH-1440
(H-14)
Illegal 1920 1152,
60 fps
Illegal 14401152,
60 fps
720 576,
30 fps
1440 1152,
60 fps
720 576,
30 fps
Main (ML) 720 576,
30 fps
720 576,
30 fps
720 576,
30 fps
Illegal 720 576,
30 fps
352288,
30 fps
Low (LL) Illegal 352288,
30 fps
352288,
30 fps
Illegal Illegal
Frame rate 25 frames/sec
Encoded bitstream 150 KB/sec
Maximum P frame motion vectors 32, 32
Maximum B frame motion vectors 16, 16
Number of P frames 3
Number of B frames 2 (between P frames)
Audio stream bitstream 64 Kbps (mono)/128 Kbps (stereo)
MPEG-2 profile Main profile (see Table 11.1)
MPEG-2 level Main level (see Table 11.1)
Format YUV 4:2:2

8. MPEG-4/H264
• H.264 or MPEG-4 Part 10, Advanced Video
Coding (MPEG-4 AVC) defines standard for
video production.
• Has block-oriented motion-compression.
• Developed by ITU-T Video Coding Experts
Group (VCEG) and ISO/IEC JTC1 Moving
Picture Experts Group (MPEG).
• H.264 used with Blu-ray Disc players and
now used by streaming video for Vimeo,
YouTube, and HDTV broadcasts.
• Lossy compression but eye does not see the
losses.
• Covered by patents and licenced by MPEG
LA. Commercial use pays royalties for H.264
MPEG LA.
• Free to end users for streaming.
Previous image
Current image
(0,0) (0,15)
(4,0) (4,15)

9. Sample MP4 file > ffmpeg -i 1mb.mp4
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
creation_time : 1970-01-01 00:00:00
encoder : Lavf53.24.2
Duration: 00:00:05.31, start: 0.000000, bitrate: 1589 kb/s
Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661),
yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 1205 kb/s, 25 fps, 25 tbr,
12800 tbn, 50 tbc (default)
Metadata:
creation_time : 1970-01-01 00:00:00
handler_name : VideoHandler
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000
Hz, 5.1, fltp, 384 kb/s (default)
Metadata:
creation_time : 1970-01-01 00:00:00
handler_name : SoundHandler
At least one output file must be specified
Link

10. MP4 Extract (Frames per second)
ffmpeg -i file.mp4 -r 1/4 filename%03d.jpg
Link

11. CSN08704
Data, Audio, Video and Images
http://asecuritysite.com/comms
Telecommunications
Prof Bill Buchanan
MP4 Magic Number

12. MP4 Magic Number (and other formats)
[00000000] 00 00 00 18 66 74 79 70 6D 70 34 32 00 00 00 01 ....ftypmp42....
[00000016] 6D 70 34 32 6D 70 34 31 00 00 0B E6 6D 6F 6F 76 mp42mp41....moov
[00000032] 00 00 00 6C 6D 76 68 64 00 00 00 00 BF 88 14 86 ...lmvhd........
[00000048] BF 88 14 86 00 00 02 58 00 00 0B A4 00 01 00 00 .......X........
00 00 00 18 66 74 79 70 6D 70 34 32
Link
AVI video file .avi 52 49 46 46 [RIFF]
Flash Shockwave .swf 46 57 53 [FWS]
Flash Video .flv 46 4C 56 [FLV]
Mpeg 4 video file .mp4 00 00 00 ..34 32 [....ftypmp42]
MOV video file .mov 6D 6F 6F 76 [....moov]
Windows Video file .wmv 30 26 B2 75 8E 66 CF
Link

13. CSN08704
Data, Audio, Video and Images
http://asecuritysite.com/comms
Telecommunications
Prof Bill Buchanan
Motion Video