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Network-specific definitions• F.731- N-ISDN MM conference services
• F.732- B-ISDN MM conference services
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Terminals
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Multimedia terminals
• H.320: Communications over N-ISDN
• H.310: Communications over B-ISDN
• H.323: Communications over packet networks (mainly IP)
• H.324: Communications using circuit-switched services (fixed and mobile, including
3GPP)
• H.246: Terminal Interworking
Integration of media components from the equipment/protocol point-of-view
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Multimedia terminals (2)
Example: Functional model for H.320 N-ISDN Terminal
NetworkInterface
Video Coding (H.261)
Audio Coding (G.711)
System Control (H.242)
Call Control (Q.931)
MM Mux & Sync
(H.221)
Data Coding (T.120)
UserInterface
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Multimedia terminals (3)
Example: Functional model for H.323 Terminal
NetworkInterface
Audio Coding (e.g. G.711, G.729)
Video Coding (e.g. H.261, H.263)
User Data Coding (T.120)
System Control (H.245)
Call Control (H.225.0, Q.931)
MM Mux & Sync
(H.225.0)
UserInterface
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Multimedia terminals (4)
Example: Functional model for H.324 Terminal
NetworkInterface
Audio Coding (e.g. G.723.1)
Video Coding (e.g. H.261, H.263)
Data Coding (T.120; V.14, LAPM)
System Control (H.245,SRP/LAPM)
Call Control (National standards; V.250)
MM Mux & Sync(Fixed network: H.223;
Mobile: H.223 Annexes A-D)User
Interface
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MM terminals (5): InteroperabilityH.324 H.310
H.320H.323
Audio/Video
User data
User data
User data
User data
Audio/Video
Audio/Video
Audio/Video
Mux
QoS
RTP/Non-QoS
H.223
H.225.0
H.222.0H.222.1
H.221
Call Control (H.245)
Call Control (H.242/H.243)
Call Control (H.245)
Call Control (H.245)
H.223 Anx.A-D
Fixed
Mob
ile
Scope for H.246
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Media components
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Data
• T.120-T.140,T.17x provide definitions for data exchange and control in MM conferencing applications. For example:– T.120 defines data protocols for multipoint
multimedia conferencing (Annex C describes a light version of T.120). E.g. White-board applications.
– T.140 adds text conversation (“chat” e.g. for hearing-impaired people)
– T.17x: MHEG for information retrieval
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Media Coding
Four aspects:
• Audio
• Video
• Still-image
• Other media coding
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Media Coding: Audio
• Three “classic” quality tiers: audio, wideband speech, and telephony speech.
• ITU-T focus on interactive communications, hence mainly produced wideband and telephony speech compression standards (F.700’s A0 and A1 Quality Levels).
• ITU standards:– H.261 Video Codec for N-ISDN– H.262 = MPEG2/Video (“Common text”)– H.263 and Annexes IP, wireless, and N-ISDN– H.26L: successor to H.263 Ongoing
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Media Coding: Still Image
• Still image (B/W & color) is used in facsimile services, in Internet applications, digital photography, etc.
• Standards work performed by a “Collaborative ITU|ISO/IEC Team” working under ISO/IEC SC29 rules and organization
• ITU has “common-text” for JPEG/JBIG (T.80 series); soon-to-be JPEG2000 (T.800 series)
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Other media coding
Currently not performed in ITU-T:• Character coding (ISO/IEC SC2 activity)• Speech synthesis (text-to-speech)• Speech recognition (new developments)
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Conclusion
• Service definitions provide the user perspective for MM communication
• Terminals & protocols integrate different media components for specific applications
• Interoperability adaptations are necessary
• Existing terminals are network-specific, however there is a trend towards more flexible specifications.
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Media Coding Supplemental Slides
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Telephony-band Speech Coding Families
Channel
Formant
Homomorphic
LPC
MBE
Parametric(Vocoding)
WaveformCoding
PCM
DPCM
ADPCM
DM
ADM
CSVD
HybridCoding
APC
RELP
MPLPC
CELP
SELP
SBC
ATC
Sinusoidal
Harmonic
Phase
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Telephony-band Speech Coding Families
1 2 4 8 16 32 64
Vocoding
Waveform Coding
Hybrid Coding
LPC10e
MBE
CELP
APC
MPLPC
ATC
RELP
DPCMADPCM
LogPCM
Quality
Bit rate (kbit/s)
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A2/A3 Non-ITU Standards
• MPEG2/Audio: audio coding > 64 kbit/s (1992)• MPEG4/Audio: audio + speech coding at bit rates
Planned new common texts: • T.800: Part 1, JPEG 2000 Image Coding System: Core
Coding System• T.801: Part 2, JPEG 2000 Image Coding System:
Extensions• T.802: Part 3, Motion JPEG 2000• T.803: Part 4, Conformance Testing• T.804: Part 5, Reference Software• T.805: Part 6, Compound Image File Format• T.806: Part 7, Technical Report: Guideline of minimum
support function of Part-1
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ITU-T Video Coding• H.261: Video Codec for A/V services at p x 64 kbit/s
– The first practical video coding standard (1990)– Used today in (ISDN) video conferencing systems– Bit rates commonly 40 kbit/s to 2 Mbit/s
• H.262: Same as MPEG-2/Video (ISO/IEC 13818-2)– Commonly used for entertainment-quality video applications– The first practical standard for interlaced video– Used in digital cable, digital broadcast, satellite, DVD, etc.– Bit rates commonly 4-20 Mbit/s
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ITU-T Video Coding(continued)
• H.263: Video Coding for Low Bit Rate Communication– Significantly improved video coding compression
performance (especially at very low rates, but also at higher rates as well)
– The first error and packet loss resilient video coding standard– Used in Internet protocol, wireless, and ISDN video
conferencing terminals (H.323, H.324, 3GPP, etc.)– “Baseline” core mode interoperable with MPEG-4/Video– Rich set of features for many applications– Very wide range of bit rates and possible applications
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Non-ITU-T Video Coding• MPEG-1/Video (ISO/IEC 11172-2)
– The first video coding standard using half-pel motion compensation
– Typical bit rates 1-2 Mbits/s
• MPEG-4/Visual (ISO/IEC 14496-2)– The first video coding standard defining arbitrary object shapes– Many creative features for synthetic and synthetic-natural hybrid
content– Contains essentially all features of all prior standard codec
designs– Interoperable with ITU-T H.263 “baseline”– Very wide range of bit rates and possible applications