Multimedia Software Systems CS4551
Video Compression – Latest Standards
CSULA CS4551 Multimedia Software Systems by Eun-Young Kang
H.26x vs. MPEG
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• SamecompressionprincipleinH.26xandMPEG
• Differenttargetedapplications
– MPEG: in various entertainment applications
• MPEG-1 : Storage of video/audio on CD-ROMS (VCD) • MPEG-2: DVD, digital video broadcasting
• MPEG-4: general interactive multimedia applications
– H.26x: use in various type of network including PSTN, ISDN, LAN, and wireless transmission
• H.261: Video telephony and video conference over ISDN
• H.263: Video application across PSTN and wireless networks (very low bit rate)
• H.264: Targeted at 3G mobile networks and broadcast CSULA CS451 Multimedia Software Systems by Eun-Young Kang
CSULA CS451 Multimedia Software Systems by Eun-Young Kang
Mode selection
H.264 Codec
Control Data
Quant. Transf. coeffs
Reference frame
Motion Data
From Dr. Wiegand’s notes
CSULA CS451 Multimedia Software Systems by Eun-Young Kang
Transform/ Quantizer
Intra/Inter
Deq./Inv. Transform
Motion- Compensated Predictor
Entropy Coding
Motion Estimator
CSULA CS451 Multimedia Software Systems by Eun-Young Kang
H.265 Codec
H.264/265 Distinguished Features (1)
• Variableblock-sizeMotionCompensation • HighlyaccurateMotionCompensation
• MultipleReferenceFrames
• Context-basedAdaptiveCoding
• CodingUnit
– H.264: 16×16 (Macroblock)
– H.265: 64×64 with hierarchical partition
CSULA CS451 Multimedia Software Systems by Eun-Young Kang
H.264/265 Distinguished Features (2)
• Integer-basedtransformandquantization
• Advancedintrapredictionmodes
– H.264 – 9 directional, DC, planar – H.265 – 33 directional
• Efficientinter-predictionmodes – P_SKIP and B_DIRECT
CSULA CS451 Multimedia Software Systems by Eun-Young Kang
Variable Block Size MC – H.264
Partition to variable block sizes down to 4×4 16
CSULA CS451 Multimedia Software Systems by Eun-Young Kang
Variable Block Size MC – H.265
Asymmetric prediction units
CSULA CS451 Multimedia Software Systems by Eun-Young Kang
Sub-pixel Motion Estimation closer matching block→better compression
Integer position pixel 1/8 pixels
1/2 and 1/4 pixels
CSULA CS451 Multimedia Software Systems by Eun-Young Kang
Multiple reference frames
CSULA CS451 Multimedia Software Systems by Eun-Young Kang
Context-based Adaptive Coding
• Disadvantages for entropy coding in MPEG-2/H.263 – Static probability distribution – not resemble the real case – Correlation between symbols are ignored
– Codeword must have integer number of bit
• For the context-based adaptive coding
– Use dynamical probability model
– Exploiting symbol correlations using context
– Fraction of bits is possible using arithmetic coding – H.265 enables parallel encoding
CSULA CS451 Multimedia Software Systems by Eun-Young Kang
Comparison: H.264 vs. MPEG4
CSULA CS451 Multimedia Software Systems by Eun-Young Kang
Comparison: H.264 vs. H.265
CSULA CS451 Multimedia Software Systems by Eun-Young Kang
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