Improved chroma prediction
draft-midtskogen-netvc-chromapred-02

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Network Working Group                                      S. Midtskogen
Internet-Draft                                                     Cisco
Intended status: Standards Track                        October 31, 2016
Expires: May 4, 2017

                       Improved chroma prediction
                  draft-midtskogen-netvc-chromapred-02

Abstract

   This document describes the technique used to improve the chroma
   prediction in the Thor video codec.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on May 4, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   3.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   2
   4.  Computing the improved prediction . . . . . . . . . . . . . .   3
   5.  Performance . . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Modern video coding standards such as Thor [I-D.fuldseth-netvc-thor]
   form predictions for the luma channel (Y) and chroma channels (U and
   V) which are encoded separately (in that order).  The prediction for
   each channel has spatial or temporal dependencies only in its own
   channel.  Most of the perceived information of a video is to be found
   in the luma channel, but there still remain correlations between the
   luma and chroma channels.  For instance, the same shape of an object
   can often be seen in all three channels, and if this correlation is
   not exploited, some structural information will be transmitted three
   times.  Thor will attempt to improve the chroma prediction by finding
   linear relationships between the each of the initial chroma
   predictions and the luma prediction, and if certain criteria are
   satisfied, use that relationship to form a new prediction based on
   the reconstructed luma samples.

2.  Definitions

2.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

3.  Background

   The improved predictions are derived from the reconstructed luma
   samples using a mapping.  The underlying assumption is that the
   colours can be identified by their luminosities.  Informally we can
   say that a new chroma prediction is formed from the reconstructed
   luma block painted with the colours of the initial chroma prediction.

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