Feb 06, 2016
High Definition Video: Acquisition to Broadcast
Overview
• Defining the term “High Definition”• Pixel, frame and video formats• Image acquisition• Storage media• Compression• Post production• Transmission and the digital
switchover• Reception and “HD Ready”• Home entertainment HD
What is HD?
• Anything providing more resolution than current standard definition (SD) video.
• It is a generic term for “better”• It doesn’t specify how much better.
Standard definition
• For the UK, a system known as PAL• Broadcast systems comprising 625
lines• 25 frames per second• After signalling and data removed, a
frame resolution of 768x576 pixels• Frame aspect of 4:3 (768:576
simplified to it’s lowest common factor)
Standard definition
SD, 4:3
4
3
768
576
Standard definition
• 768x576 assumes a square pixel• Pixels don’t have to be square and in
SD video, they usually aren’t!• 4:3 PAL uses a pixel aspect of
1.066666:1• Your TV “stretches” the frame
horizontally• Anything that increases the size of a
pixel reduces resolution
Standard definitionStandard definition
4
3
Widescreen
• A further extension of this kludge• Very un-square pixels• 16:9 broadcasts take the 720x576
frame and stretch it even more horizontally
Standard definitionWidescreen standard definition
4
3
16
9
Standard definition
• Uses anamorphic pixels• 4:3 – 1.0666:1• 16:9 – 1.4222:1• Results in resolution being lost due
to the stretching process
High Definition
• Two common formats– 720p– 1080i
• SD frame: 720 x 576• 720p frame: 1280 x 720 (2.2 x SD)• 1080i frame: 1920 x 1080 (5 x SD)
High Definition
1920x1080i, 16:9
1280x720p, 16:9
SD 720x576, 4:3
High Definition(or “what all the fuss is about”)
• 1080i provides almost five times the resolution of Standard Definition
• Unencumbered by legacy technology• Native 16:9 aspect ratio• True 720p and 1080i are square pixel
formats – no resolution-killing scaling when displayed
Image Acquisition
• Professional: anything with mechanical manual focus
• “Prosumer” – Servo-operated focus / fixed lenses that provide similar functionality to pro cameras
• Consumer - point-and-shoot cameras that do all of the hard work for you!
Professional camerasUnlimited budget
ARRI 320D•Can shoot film resolutions•CCD is the same size as a 35mm frame•Needs a huge amount of peripherals•Camera alone starts at £200,000•Lenses £20,000 upwards
Professional cameras
Professional cameras
•Native 1080p•Variable frame rates (1 to 60fps)•Still needs lots of peripherals•Camera alone starts at £80,000
Top-end
HDC-1500L444
Professional camerasMainstream HD
HDW-F900R
•Native 1080i•Integral HDCAM recorder•More realistic price: £40,000
Professional cameras
Optical storage
PDW-F350
•Native 1080i•Integral ProDisc recorder•£10,000
Professional cameras
Budget professional
JVC GY-HD251E
•Native 1080i•Integral 720p HDV recorder•Still uses “proper” lenses•£5000
“Prosumer” cameras
Canon XHA1
•Native 1080i•Integral 1080i HDV recorder•Internal focus lens•£2200
“Prosumer” cameras
Sony HVR-V1E•Native 1080i•Integral 1080i HDV recorder•Internal focus lens•£1500
Consumer camerasSony HDR-HC7E
•Native 1080i•Integral 1080i HDV recorder•Internal focus lens•£800
Consumer camerasCanon HV20
•Native 1080i•Integral 1080i HDV recorder•Internal focus lens•£650
Consumer cameras
SanyoDMX-HD1000
•Native 1080i•Uses standard SD flash storage•4.2 megapixel stills•£450
Consumer cameras
Image Acquisition
• For home use, size and convenience are generally more important than features
• “More expensive” doesn’t necessarily mean “better” or “more suited”
• The manual functions on pro cameras just get in the way when you’re simply trying to shoot something
Image Acquisition
Lens
Image sensor
Processing electronics
Storage
Image Acquisition
Video storage
• Tape• Optical disc• Hard drives• Flash memory
Video Tape Recorders
Video Tape Recorders
Video Tape Recorders
Video Tape Recorders
Principal HD tape formats
Tape: pros
• Relatively cheap• Universally accepted for interchange• Long shelf life when stored correctly• Long recording durations
Tape: cons
• Linear by nature• Limited record / playback cycles• No warning during recording of drop-
out• Easily damaged if handled carelessly• Easily damaged by deck malfunction• Easily damaged by incorrect storage• Decks can be very expensive to
maintain
Tape: cons
Deck malfunction Incorrect storage
Tape: cons
• Linear by nature• Limited record / playback cycles• No warning during recording of drop-
out• Easily damaged if handled carelessly• Easily damaged by deck malfunction• Easily damaged by incorrect storage• Decks can be very expensive to
maintain
Tape: cons
Video storage: TapeQ:Who won the VHS vs. Beta format war?A: Sony’s Beta!
•Betacam SP•Betacam SX•MPEG IMX•Digital Betacam•HDCAM•HDCAM SR
Video storage: Tape
Video storage: optical disc
Optical disc: pros
• Robust• High number of read/write cycles• Non-linear: near instant access• Easy ingest to editing systems• Improved workflow• Supports multiple formats (SD & HD)
Optical disc: cons
• Read/write cycles not as high as expected
• Harsh conditions can upset recording• Limited shelf-life – data degrades with
time
Video storage: hard discs
Hard drives: pros
• Fast – capable of recording uncompressed
• Non-linear – instant access• Capacity – multi-terrabyte• Unlimited read/write cycles• Immediate ingest
Hard drives: cons
• Not portable• Camera-to-drive interfaces can be
costly• Failures often catastrophic• Not practical for long-term storage• Can be noisy
Video storage: hard discs
Video storage: flash
Video storage: flash
Video storage: flash
Flash: pros• Fast – capable of recording
uncompressed• Non-linear – instant access• Portable, compact, light• Incredibly robust• High number of read/write cycles• Immediate ingest• Hot-swap of cards• Can be stored practically indefinitely• Cheap for consumer flash
Flash: cons
• Limited capacity• Often used in conjunction with HDD• Very expensive for pro grade flash• Not cost-effective for long-term
storage
Video compression
• Video is big!
Data rates for common formats
SD 720/25P 1080/25P 2K 4K0
100
200
300
400
500
600
700
800
900
1000
14.8343.95
98.88
216
864
MB/sec
Exponential (MB/sec)
Video compression
• Video is very big• Most storage media can not handle
this
How to reduce data rates?
• Lower image resolution• Remove image information• Encode image information more
efficiently
The compression compromise Low compression
High data rateHigh quality
Short runtime
High compressionLow data rateLow qualityLong runtime
HDV compression
1920x10801:1PA16BPP1:1CR25FPS= 99MB/sec
1440x10801.333:1PA16BPP1:1CR25FPS= 74MB/sec
140x10801.333:1PA12BPP1:1CR25FPS= 55MB/sec
1440x10801.333:1PA12BPP17:125FPS= 3MB/sec
Downsample
Requantise
Compress
Final output is only 3% of original!
Post Production
Edit suites
• HD presents a big challenge for computers
• 5 x the resolution means 5 x the time• Heavy compression causes quality
problems
Problems with compression
• Editing can not be performed on compressed frames
• Each frame must be uncompressed• The frame is modified• The resulting frame is recompressed• All intermediate stages should remain
uncompressed to maintain quality• Very similar to analogue video
generation loss during duplication
Uncompressed editing?
• Essential for top-end production• Often unrealistic for mid- to low-budget
productions and home use• Storage demands can be staggering
– A real-time fade needs 200 MB/sec!
• Not a realistic prospect with easily accessible / affordable equipment
• All UK mainland terrestrial analogue TV transmissions will cease by the end of 2012
• Central switchover in 2011• Three to six digital TV channels in place
of one analogue channel• Not guaranteed that spectrum freed by
analogue switch-off will be used for TV• Digital does not mean high definition!
3 ways of receiving digital HD
Is it real HD?• Very nearly • SkyHD digibox outputs a 1920x1080i
signal• It receives a 1440x1080i transmission• Anamorphic pixels, so we’re loosing
resolution again• Highly compressed• Far better than SD and appreciably
better than 720p• All channels are equal, but some
channels are more equal than others…
And the quality?
• Surprisingly good!• MPEG-4• 46 megabit/sec transponders• Up to 15 megabit/sec per channel• Subjectively similar to HD-DVD or
BluRay
• Does not mean it actually displays true HD
• Simply means it can accept an HD signal
• Only the specifications will reveal what the TV is natively capable of
TV Specifications• Check the panel’s native resolution• This is the actual number of pixels
contained in the display• Values below your intended format
means the you’re throwing resolution away
• Differences – above or below – mean scaling
Image scaling
• The display is generating a new image to fit its display size
• Professional equipment to do the same job costs tens of thousands of pounds
• Your TV probably costs less than £2000
TV Specifications
• Aim for a TV that has a native resolution of 1920 x 1080 – this will handle all frame sizes
• TVs with a lower resolution are not necessarily bad, just remember you’re not seeing as much as you could
Home entertainment HD
HD Interconnects
• HD isn’t necessarily digital!• Three popular formats
HD Interconnects
Analogue component
HDMI
DVI
HD Interconnects• They don’t need to be expensive• Most high-street stores charge
astronomical prices for HD interconnects
• For short runs, you do not need nitrogen-filled, gold plated, double-helix, oxygen-free-copper-cored cables.
• eBay is your friend!
HD Interconnects
HD Interconnects
Home entertainment HD
HDCP• High-bandwidth Digital Content Protection• Designed by Intel
HDCP negotiation
HD Content
Downsampled SD
HDCP• Vast majority of HD-ready TVs and
most computer panels support HDCP• Worth checking if you…
– Are running Windows Vista or MacOS X– Have a BluRay or HD-DVD drive installed– Intend to watch HD movies on your PC or
Mac
• Can be present on HDMI and DVI• Only a problem if your source wants to
negotiate an HDCP-protected session
HDCP and home entertainment• HD-DVD, BluRay, HD set top boxes,
XBox360 and PlayStation 3 all require an HDCP-compliant target
• Every device in the chain must support HDCP encryption– Switchers– AV amplifiers– Distribution boxes– TVs and monitors
Any questions?