Browse Prior Art Database

ROTATION FLAG IN VIDEO STREAMS

IP.com Disclosure Number: IPCOM000237810D
Publication Date: 2014-Jul-14
Document File: 9 page(s) / 232K

Publishing Venue

The IP.com Prior Art Database

Related People

Sijia Chen: AUTHOR [+3]

Abstract

Techniques are presented herein to solve the problem of necessarily inserting intra-predicted frames into a video stream when resolution changes due to rotation on mobile devices. Rotation flags and related syntax are added in a video bit stream, so as to make it possible for the frames at rotation to not necessarily bring in an intra-predicted frame, and thus to avoid undesired impact, such as bursts in real-time video transmissions.

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ROTATION FLAG IN VIDEO STREAMS

AUTHORS:

 Sijia Chen Xiaolin Shen Rui Zhang

CISCO SYSTEMS, INC.

ABSTRACT

    Techniques are presented herein to solve the problem of necessarily inserting intra-predicted frames into a video stream when resolution changes due to rotation on mobile devices. Rotation flags and related syntax are added in a video bit stream, so as to make it possible for the frames at rotation to not necessarily bring in an intra-predicted frame, and thus to avoid undesired impact, such as bursts in real-time video transmissions.

DETAILED DESCRIPTION

    With the fast-growing popularity of mobile devices, video coding schemes need to adapt to the special requirements for video on mobile devices. Cameras on video devices have two orientations of output, for example 1280x720 or 720x1280, based on a gravity detector (accelerometer) and a motion detector.

    It is very common for the user to rotate the mobile device when recording or during real-time communication, especially when the user is walking or moving when capturing video. The camera on mobile devices will keep the ratio of video as the same as that at the beginning of recording, and the objects in video can become rotated, as shown in FIG. 1 below.

Copyright 2014 Cisco Systems, Inc.

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FIG. 1

    However, the desired content to be viewed should be in the same direction of the actual scene, as shown in FIG. 2 below.

FIG. 2

    For video compression using a standard format, in order to keep the video content with the same direction of the actual scene before and after rotation, one approach is to rotate the content of video. Another approach is to encode two video streams with difference intra-predicted frames since the video coding standards do not allow resolution change at non-IDR frames.

    Screen captured video from mobile devices will have the same problem, particularly because many applications on mobile devices have different but similar user

Copyright 2014 Cisco Systems, Inc.

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interface (UI) layouts between landscape mode and portrait mode. When remote screen sharing on a mobile device, it is possible that the presenter wants to show different content from a different UI of the in-use application on the mobile device.

    This innovation proposes to add rotation flags in a video bit stream, making it possible for the frames at rotation to not necessarily bring in an intra-predicted frame.

Two flags are suggested in the syntax of bit stream to support such a function:

1. Enabling the rotation flag at sequence level.

2. Indicating the rotation flag at slice or frame level.

Usage of the flags:

Step 1. Enabling the rotation flag at sequence level. Reference is made to FIG.

3 below.

    At the beginning of the stream, a flag is used to indicate the possibility of applying the rotation flag in the current stream. If the rotation is possible, it is needed to buffer a reference picture to use a larger size than the current picture. More specifically, if the frame size...