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A backward compatible, efficient use of broadcast bandwidth, when simulcasting a Digital Television channel in two related resolutions, by use of Hierarchical Modulation and common Chroma components.

IP.com Disclosure Number: IPCOM000238101D
Publication Date: 2014-Aug-01
Document File: 3 page(s) / 37K

Publishing Venue

The IP.com Prior Art Database

Abstract

Television Broadcast Organizations have to support a viewing audience that have viewing equipment that supports different Television standards and different resolutions. At the moment, to be able to reach the largest possible audience, broadcasters must use multiple channel spaces in the broadcast frequency bands to show the same programme or channel at different resolutions, known as Simulcasting. This wastes the available broadcast frequency bands which are already constrained. This idea reduces the broadcast bandwidth required when broadcasting the same programme at different resolutions with a 4:1 resolution relationship, by only broadcasting one copy of part of the image information. This single copy of information is then shared between the two broadcast channels, therefore reducing the total bandwidth required.

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A backward compatible, efficient use of broadcast bandwidth, when simulcasting a Digital Television channel in two related resolutions, by use of Hierarchical Modulation and common Chroma components.

Disclosed is a system for simulcasting a Digital Television channel in two related resolutions, that can be backwards compatible with existing Digital Television reception equipment. This system employs a novel reuse of existing Digital Television standards, to allow the two simulcast versions to share data. This removes redundancy and reduces broadcast bandwidth needs, compared to simulcasting the two channels separately, making more efficient use of scarce radio frequency resources.

This idea is a novel reuse of two technologies.

    The first is a feature of the signal modulation method called Quadrature Amplitude Modulation (QAM) [1]. Data is modulated into patterns called "symbols" that represent multiple bits of data at once. QAM has the ability to encode two data channels that are broadcast in parallel on the same frequency, as the most significant bits and least significant bits of the multi bit number represented by the symbol. A consequence of this is the two channels stay synchronised when broadcast.

    The second is Chroma subsampling http://en.wikipedia.org/wiki/Chroma_subsampling . This is where the colour information in each frame of video is stored and broadcast at one quarter the resolution of the brightness information (the "black and white" image). Therefore there is a 4:1 relationship between the resolution of the Luma and Chroma subchannels. The viewer's perceived reduction in picture quality is much less than the actual reduction in bandwidth use.

    This 4:1 resolution relationship between the brightness and colour information can be exploited when one wishes to broadcast the same video stream in two different resolutions with this same 4:1 resolution relationship, such as when Simulcasting. One video stream is broadcast with full information, with no colour subsampling, and the other video stream is broadcast only with the brightness information and reuses the colour information from the other video stream. The colour information is broadcast only once, reducing the bandwidth requirements.


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Key to diagram:
1. Single channel in the Broadcast Television frequency bands.

2. QAM Demodulator
3. Data channel for lower resolution video stream.

4. Data channel for higher resolution video stream.

5. Luma subchannel of current lower resolution frame.

6. Chroma subchannels of current lower resolution frame.

7. Luma subchannel of current higher resolution frame.

8. Chroma subchannels from current lower resolution frame, reused as Chroma subchannels of current higher resolution frame.

9. Recombined final lower resolution image on display screen.

10. Recombined final higher resolution image on display screen.

This idea relies on two technologies:

    The first is the signal modulation method called Quadrature Amplitude Modulati...