Media file formats for broadcasters

Media File Formats for the Broadcaster

Unraveling the mystery

Tom Beckers Matthias De Geyter
Wim Ermens Luk Overmeire

VRT Medialab - 16/10/2008

Agenda

Part One - Luk Overmeire & Matthias De Geyter
Introduction
Image and advanced compression formats for HD
File formats for HD production: MXF and AAF
--- pause ---
Part Two - Tom Beckers & Wim Ermens
Visual and technical quality control for HD
Demos

2 VRT-medialab: onderzoek en innovatie

VRT Medialab
4 research domains
broadcaster customer
Information management Information front-end
Research Archiving User generated
Personalization
content

Product
Development

Manufacturing Distribution User interaction Social platforms
Engineering Automation

information
essence
Production infrastructure Distribution
Editing Mastering
Wireless and
Internet
wired networks
Media
Ingest Asset Mgnt Playout

Mobile Satellite

Infrastructure
(storage and network)


VRT Medialab
4 research domains

Information management Information front-end
Research Archiving User generated
Personalization
content

Product
Development

Manufacturing Distribution User interaction Social platforms
Engineering Automation

Production infrastructure Distribution
Editing Mastering
Wireless and
Internet
wired networks
Media
Ingest Asset Mgnt Playout

Mobile Satellite

Infrastructure
(storage and network)


Context: tape-based media
production


Context: file-based media
production with central warehouse

information
information

essence
essence


File-based media production
Concurrent
engineering
Browse Clients Processing
during
ingest/transfer

Draft POST Craft
editors
Processing Production
Media
Analysis
Asset Mgmt Subtitling

INGEST IP network PLAY-OUT

Central storage
Annotation Central Archiving
Storage
Post- Follow-up
sonorisation continuity Editor-in-Chief


Media production formats
information

essence =
image formats
! resolution, frame rate, raster
essence
compression formats
! high & low resolution

+
file/wrapper formats information


Typical broadcast chain

post P
File-based camera I production
N L
G A Web

contribution Y
E
central O
distribution linear
S Blu-ray DVD
T warehous U
Studio acquisition e T

production

archive


Formats for Standard Definition
576 lines, interlaced
25 frames/sec

DV25
MXF MXF/AAF post P
I production
File-based camera
L H.263/VC-1
N IMX-30
G A Web
MPEG-2 MPEG-2
contribution Y
long GOP
E IMX-50
central O
distribution
long GOP linear
S 4:2:0
4:2:2 warehous U DVD
T MXF OP1a 8-10 Mbps
10-25 Mpbs
Studio acquisition e T MPEG-2
MPEG-1
VC-1
production

DV25

archive IMX-30
long GOP IMX-50

Formats for High Definition
720p50, 1080i25,
1080p25, 1080p50

MXF/AAF,
Quicktime postXDCAM HD,
MXF
File-based camera I AVC-Intra, P
production H.264/VC-1
N DNxHD, L
G ProRes, A H.264 4:2:0
Web
MPEG-2 ->H.264
contribution JPEG2000 Y
4:2:0, 4:2:2
E
O
distribution
bit rate ? linear
SMXF OP1acentral Blu-ray DVD
bit rate ? T warehous U
Studio acquisition e T H.264/VC-1
H.264 (1),
production (2),
H.264
…

uncompressed, XDCAM HD,
lossless compressed ? AVC-Intra,
archive DNxHD,
ProRes,
long GOP JPEG2000

Proliferation of media formats

HD image formats
! 720p50,1080i25, 1080p25
=> 1080p50

HD compression formats
! legacy versus new formats
! contribution, camera, production, archive, distribution

proxy formats (low resolution)
wrapper formats
! MXF flavors, Quicktime


The HDTV format jungle

HDTV increases
variety of formats
Abtastformat
Abtastformat
Lossy Abtastformat
Kompressionsformat HDTV increases
conversions Abtastformat
Sampling formats
Kompressionsformat variety of options
(1080i/25, 720p/50, 1920/1440 pixels,
Kompressionsformat
IT-basiert: File Format
4:2:0, 4:4:4, ... )
Kompressionsformat HDTV increases need
Compression formats Format
IT-basiert: File
for efficient wrapping
(MPEG-2,IT-basiert: File Format
H.264, JPEG2000, ..) Transport
Physikalischer
IT-basiert: File Format
Physikalischer Transport
File Formats Further formats (e.g. consumer)
Presentation (Displays)
(MXF, QT, ..) Transport
Physikalischer
Physikalischer Transport
Physical Transport
Contribution („live“ and/or „File “)
Distribution
(HD-SDI, IP, Tape, ..)
Production
(more granular variants for news, features, etc.)
„A format“


Production areas

high-end production
! landmarks, drama

mainstream production
! soap series, documentaries, shows

Mainstream HDTV platform
quot; single or multiple scanning formats ?
News and sports quot; single or multiple compression formats ?
quot; 720p/50 a/o 1080i/25
video journalism quot; 4:2:2 a/o further
subsampling
! consumer cameras quot; 10 Bit a/o 8 Bit
quot; I-frame only a/o long GOP
quot; Headroom a/o low data rate
quot;… a/o …


Image formats for HD
(and beyond)

Today’s and future image formats
Super Hi-Vision (U-HDTV)
resolution 7680 x 4320 24 Gbit/s
Far future 60 frames/sec, progressive
audio: 22.2 channels
?
System 4 – 1080p50 3 Gbit/s
Future resolution 1920 x 1080
50 frames/sec
progressive

Today 1,5 Gbit/s
System 1 – 720p50
resolution 1280 x 720
50 frames/sec
progressive

EBU
System 2 – 1080p25 System 3 – 1080i25
resolution 1920 x 1080
Tech 3299 resolution 1920 x 1080
25 frames/sec HDTV System 1-4 50 fields/sec
progressive interlaced


EBU – Tech 3299

HDTV
Horizontal Active Frame Sub-sampling / Net image Bit Interface Bit
Systems samples lines rate Quantisation [Bit] Rate [Gbit/s] Rate [Gbit/s]
EBU 3299

System 1
1280 720 50 4:2:2 10 0,9216 1,5
720p/50

System 2
1920 1080 25 4:2:2 10 1,0368 1,5
1080i/25

System 3
1920 1080 25 4:2:2 10 1,0368 1,5
1080p/25

System 4
1920 1080 50 4:2:2 10 2,0736 3,0
1080p/50

SDTV 25 0,27
720 576 4:2:2 10 0,207
576i/25


The resolution revolution
now
+ 5y
Maximal viewing distance:

SD: d < 5.h
HD: d < 3.h
U-HDTV: d < 0.75.h

d = viewing distance
h = display height

+ 15y?


Good HDTV – More than a
numbers game

1080 (i) > 720 (p) => “More is better” ?


How can smaller be better ? (1)

interlace factor
! interlaced scanning: 50 fields/sec (1 field = ! frame)

! 540 lines < dynamic vertical resolution < 1080 lines
Studies (Bell Laboratories, NHK): interlace factor ! 0.6 => 648 lines < 720 lines



interlace factor
interlace artefacts (motion rendition)
! e.g. serrated edges



interlace factor
interlace artefacts
resolution capacity of human eye (quot; 1 arc minute)
Required horizontal sampling for different screen sizes, viewed at 2.7m

720x576


How can smaller be better?
interlace factor
interlace artefacts
resolution capacity of human eye
compression artefacts
! better compression performance for progressive
! compression of interlaced media generally involves de-
interlacing


Progressive versus interlaced

far better suited for moving pictures (e.g.
Pro
legacy format
sports)
! as of today, generally better
easier to encode supported throughout the workflow
plasma, LCD are progressive displays – camera, set-top-box, post
=> end-to-end progressive workflow is possible production, central MAM, …
same resolution visibility from “viewing ! existing program material
distance” ! current offering is predominantly
rescaling is easier than deinterlacing 1080i25 content
the future is progressive => evolution to
1080p50 is more straightforward
compatible with 1080p25 through 1080psf

Contra
full support in end-to-end workflows to be higher complexity
carefully tested
! down conversion requires de- and re-
! camera (quality), central MAM, post interlacing
production, Dolby E surround sound ! de-interlacing is very hard to do well
! time labeling ! (editing) legacy format - “wet van de remmende voorsprong”
! distribution (Telenet, Belgacom, …) less suited for slow motion and chroma keying
! contribution (productiehuizen)


Different scenarios for image
formats
Production Distribution
Acquisition format format
Distribution Full HD
Production
Display
1080i
Scenario 1 1080i 1080i 1080i 1080i to 1080p
Best supported
1080p

1080i 720p
Scenario 2 720p 1080p
1080i 1080i 1080i to to
720p 1080pWhat is effect
of conversion
1080i 720p 720p on quality?
720p 720p 1080p
Scenario 3 1080i to to
720p 1080p

720p
Scenario 4 720p 720p 720p 720p 1080p
to Best quality
1080p

Deinterlacing Rescaling
converter converter


Broadcast production chain –
Points of attention for 720p50 workflows
Motion compensation algorithm
Today’s content is mostly 1080i
EICTA label - HDTV
2 9
1 Set-top-box
Cross-convertor Cross-convertor

EBU Joint Taskforce on
8 Timing & Synchronisation
Real-time infrastructure

p50 timing

Post production
Studio camera Support (legacy systems)
Surround sound

5 7 Dolby E compatibility with p50

MXF 6 TC support (legacy formats)

3 4 Full tested support (essence, TC, …)
Light sensitivity, S/N ratio File-based production environment
Central MAM

End-to-end workflow should be carefully designed !


EBU/SMPTE Joint Taskforce on
Time Labelling and Synchronization

twofold goal
! new time labelling method allowing higher frame rates (50 fps
and higher)
! new synchronization mechanism
! current standards (SMPTE 12M, colour black) are 30 years old
=> workable but limited

status
! Request For Technology (RFT) – February 2008
– responses from Sony, Harris, TGV, …
! draft Request For Standardisation (RFS)
– time-related labeling


Scenarios for 1080p25
psf = progressive with segmented frames
! frames are segmented into two interlaced fields with equal time
index => compatible with 1080i distribution
! easy deinterlacer (simple “weave”)

Acquisition Distribution Full HD
Production
Display

1080p25 1080psf 1080psf
Scenario 1 1080p25 1080p25 1080p25 to 1080p
to (1080i)
1080psf 1080p

1080p25 720p
Scenario 2 720p 1080p
1080p25 1080p25 1080p25 to to
720p 1080p

Rescaling Rescaling Simple
converter converter reordening
with loss of
resolution


What about 1080p50?

no one already broadcasts in 1080p50
! but some have plans …

1080p50 in production
! not around the corner, but plausible within 3-5 years
! very good master for both 720p50 and 1080i25
! better quality (less artifacts due to smaller block sizes and
higher coding efficiency)

1080p50 in distribution
! commercial factors will likely be the driving factor


Basics of video coding

What is video compression?
! Video compression is a technique that reduces the bit rate to
represent video images by exploiting signal redundancies while
preserving the original quality as much as possible

basic types of redundancies
! statistical redundancies
– spatial and temporal interpixel redundancies
– coding redundancy
! psycho-visual redundancies
– human visual system is less sensitive to higher frequencies
and color


Common techniques for video
compression
rate control
CBR/VBR

lossless
vs lossy

input source re- entropy compressed
video encoder quantization encoding video

subsampling prediction transform

horizontal Intra-frame DCT
subsampling
color Interframe wavelet
subsampling


Color subsampling
rate control
CBR/VBR

lossless
vs lossy

input source entropy compressed
video quantization video
encoder encoding

subsampling prediction transform

horizontal Intra-frame DCT
subsampling
color
Interframe wavelet
color
subsampling
subsampling


Typical compression ratios

Reference = HD-SDI 720p50/1080i25 (10 bit)

Coding technique Factor Video bit rate

HD-SDI (4:2:2 subsampling) 1 1,5 Gbps
(net quot; 1 Gbps)
Lossless encoding 1/2 500 Mbps

Intra-frame compression vs 1/5-1/20 50-200 Mbps
Interframe compression 1/20-1/30 35-50 Mbps
horizontal subsampling 3/4

color subsampling 4:2:0 3/4

Quantization = 8 bits 4/5


Mainstream HD production
platform – codec dilemmas

horizontal subsampling?
color subsampling: 4:2:2 or 4:2:0?
8 or 10 bit quantization?
intra-frame or interframe coding?
scalable or single-layer compression?
single or multiple compression formats?
required bit rate?

720p or 1080i?


Legacy HD production formats
Compression Bit rate (Mbps) Subsampling Intra/interframe
algorithm coding
Quantization

HDCAM SR 440 4:2:2 or 4:4:4 Intra
10 bit

HDCAM 140 (*) 4:2:2; 8 bit Intra
Horizontal
subsampling
DVCProHD 100 4:2:2; 8 bit Intra
Horizontal
subsampling
XDCAM HD 35 35 4:2:0; 8 bit Inter
Horizontal
subsampling
HDV 20/25 4:2:0; 8 bit Inter
Horizontal
subsampling

(*): net video rate = 117Mbps


Advanced HD compression formats for
Camera formats (optimized for storage and power
consumption)

MPEG-2 Long-GOP
4:2:2, 8 Bit, data rate 50 Mbps, VBR
XDCAM HD

AVC Intra
4:2:2/4:2:0, 10/8 Bit, data rate 100 / 50 Mbps, CBR
P2 HD

DNxHD
4:2:2, 8 Bit, Data rate 120 Mbit/s (185 Mbps), CBR
EditcamHD

JPEG2000
4:2:2, 10 Bit, Data rate 100 / 75 / 50
Infinity Mbit/s


Advanced HD compression formats for
post-production formats (optimized for editing)

DNxHD quot; ProRes

Standard SMPTE VC-3 Standard ---

Quantisation [Bit] 8 / 10 Bit Quantisation [Bit] 8 / 10 Bit

Colour sub-sampling 4:2:2 Colour sub-sampling 4:2:2

Net video data rate 185 / 120 Net video data rate 185 / 120
[Mbit/s] [Mbit/s]

“intermediate codecs”

MPEG-2 long GOP

aka XDCAM HD422
advantages
! proven and optimized codec
! same bit rate as for Standard Definition (50Mbps)
! in general: good quality for first generation
! early support for end-to-end broadcast chain
disadvantages
! interframe is less suited for editing purposes
– smart rendering techniques necessary
– fade-to-black, dissolve effects
– artefacts affect multiple frames
! quality loss in multi-generation scenarios
successor = H.264 long GOP?


H.264 - AVC Intra

H.264 = MPEG-4 AVC = MPEG-4 Part 10
! joint project of ITU and MPEG
addition of High Profiles for HD resolution
! FRExt (Fidelity Range Extension)
– higher bit depths (10), 4:2:2/4:4:4 colour formats
! High 10 Intra (50 Mbps) and High 4:2:2 Intra (100 Mbps)
advanced compression tools
! Intra prediction: use of correlation between adjacent pixels
! entropy encoding improvement
– CABAC: Context Adaptive Binary Arithmetic Code
point of attention
! higher computational complexity


JPEG 2000

available bit rates: 50/75/100 Mbps
advantages
! scalable codec: no need for proxy transcoding
! wavelet-based coding: no blocking artefacts
! industry standard for Digital Cinema
! low latency
! license free

disadvantages
! not widely supported in end-to-end broadcast chain at this
moment


Dirac codec family

developed by BBC R&D (2000-now)
! license-free, open source/well documented
wavelet-based codec
wide range of applications
! Dirac (long GOP): low bit rate distribution (mobile, Web)
! Dirac Pro (intra-frame): low latency, high-quality production
(HD, DC, Super Hi-Vision)
– SMPTE VC-2
– transport mapping to SDI (720p50/1080i25) and HD-SDI
(1080p50)
! high flexibility: lossy/lossless, variable bit depths and colour
sample schemes, …
not yet supported, less mature than other HD codecs


Scalable video coding (SVC)

extension of H.264
! recently standardized (2007)
! base layer (H.264) + enhancement layers

scalability options
! spatial, temporal, SNR/quality, combined

possible applications
! alternative for simulcast: SD/HD
! HD TV distribution for 720p@50fps or 1080i@25fps with
1080p@50fps enhancement
! broadcast production for different resolutions

targeted profiles for broadcasting


Choice of HD compression
format

key parameters
! quality (desired, floor level)
! storage and bandwidth requirements
! workflow
– recording medium
– editing requirements: layers, editing easiness, …
– support by different systems in HD production architecture
– end-to-end performance (transcoding, rendering, …)
! when?


Mainstream HD production
platform – codec dilemmas

horizontal subsampling? no

color subsampling: 4:2:2 or 4:2:0? 4:2:2

8 or 10 bit quantization? 8/10

intra-frame or interframe coding?
scalable or single-layer compression?
single or multiple compression formats?
required bit rate? 50/100 Mbps

720p or 1080i?


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