Metadata for Formatting with Multiple Aspect Ratios

Metadata for Formatting with Multiple Aspect Ratios

Graham Jones National Association of Broadcasters Chair – SMPTE S22 Image Formatting AHG HPA Technology Retreat February 24, 2006

Metadata for Image Formatting

Joint initiative by SMPTE, ATSC, and CEA, to produce an end-to-end system solution for image formatting as related to aspect ratio Harmonized standards for format of necessary metadata, metadata carriage, and recommended practices for applications Work in progress – estimated completion mid-2006

Issues

Optimize display of the image for the television viewer Multiple production aspect ratios At least two display aspect ratios Provide guidance for the format conversion process In the receiver and display In post and pre-broadcast Minimize changes to images created by the original program producer Maintain critical image content

Image Aspect Ratios

Displays

Displayed Images

4:3

4:3

16:9

16:9

4:3

Undesirable Results

Broadcast

Viewer Display

16:9 using pillarbox

4:3 using letterbox

“Postage stamp”

Undesirable Results

Other undesirable images – stretched, squashed or vital picture information lost due to cropping

Produce

Broadcast

Viewer Display

16:9

4:3 using letterbox

16:9 using pillarbox

“Postage stamp”

X

Undesirable Results

Produce

Broadcast

Viewer Display

16:9

4:3 using letterbox

16:9 using pillarbox

“Postage stamp”

Image Formatting Metadata

AFD – Active Format Description Bar Data Pan-Scan Information Individual specifications already exist in standards AFD: MPEG, ETSI/DVB, ATSC Bar Data: ATSC Pan-scan: SMPTE, MPEG-2 (also AVC and VC-1) Currently no carriage in HD baseband or MXF Limited guidelines on applications and use

US Network Distribution

ATSC MPEG

CEA

Local Station

HD or SD

ATSC Digital

AFD, Bar Data, and Pan-Scan Carriage in Professional Environment

SMPTE standards in preparation for carriage of AFD, Bar Data, and Pan-Scan in VANC of SDI and HD-DSI for the studio environment These standards also define KLV encoding for carriage in MXF, AAF, etc.

DTV System Block Diagram

Studio/Master Control

Video Subsystem

Service Multiplex &Transport

RF Transmission System

Video

Audio Subsystem

Audio

Ancillary Data

Control Data

Video Source Coding & Compression

Router/MC Switcher

Transport

Channel Coding

Service Multiplex

Audio Source Coding & Compression

Modulation

Active Format Description - AFD

Four-bit code that defines the active image area and protected image areas for various combinations of aspect ratios AFD is independent of image resolution Intended to guide receivers and STBs in how to optimize the displayed image Also applications in the post and pre-broadcast chain Recommended practice for use of AFD and Bar Data now in preparation by CEA

AFD Codes in a 4:3 Coded Frame

AFD Codes in a 16:9 Coded Frame

Format Conversion with AFD

AFD code 1010 Letterbox 16:9 image vertically centered in the frame

Image Aspect Ratio >16:9

AFD code 0100 aspect ratio >16:9

4:3

16:9

Bar Data

Signaled with AFD 0100 (aspect ratio >16:9) to indicate the exact width of the top and bottom bars May also be signaled with AFD 0000 (undefined) to indicate the width of the bars for any other non-standard active image area Bar Data signals one pair of bars only Top/bottom or left/right Not intended to signal a postage stamp - such transmitted images should be discouraged

Bar Data Example

AFD code 0100 (aspect ratio >16:9)

Pan-Scan Information

Used to signal how to extract a different aspect ratio viewport from a source image In broadcast world intended for professional use

Pan-Scan Information

Pan and Scan

© Warner Bros. Screen shot courtesy of Letterbox and Widescreen Advocacy Page www.widescreen.org

US Network Distribution Pan-Scan Application

Local Station

Network Center

HD or SD

US Network Distribution Pan-Scan Application

Local Station

Network Center

HD or SD

ATSC Digital

For MPEG links, Pan-Scan information is carried in display extensions of the video sequence header

US Network Distribution Pan-Scan Application

Local Station

Network Center

HD or SD

ATSC Digital

For MPEG links, Pan-Scan information is carried in display extensions of the video sequence header

Output Documents

CEA – recommended practice for use of AFD and Bar Data by receivers ATSC – minor revisions to A/53 for semantics of AFD and Bar Data for consistency with CEA RP SMPTE standards for carriage of AFD, Bar Data, and Pan-Scan information in VANC of SD and HD video and as KLV data SMPTE – recommended practice for operational use of AFD, Bar Data, and Pan-Scan information Contributions welcome

Related papers at NAB Broadcast Engineering Conference Adam Goldberg:

The Importance of Video Format Metadata Bill Miller: Canceling the Postage Stamp

Thank you gjones@nab

org