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Re: [sdw] Breakout discussion: Video search with location (#1130)

From: Rob Smith via GitHub <sysbot+gh@w3.org>
Date: Thu, 04 Jul 2019 16:19:14 +0000
To: public-sdwig@w3.org
Message-ID: <issue_comment.created-508531749-1562257153-sysbot+gh@w3.org>
Many thanks to all those who participated in the breakout discussion at the [Spatial Data on the Web meeting on 25th June 2019](https://www.w3.org/2017/sdwig/meetings/f2f-4.html) in Leuven. I've now collated the feedback with the goals and [minutes](https://www.w3.org/2019/06/25-sdw-minutes.html#item01).

**Conclusions**

   1. **Captured key missing requirements**

       1. There is a requirement for balance between accuracy and bandwidth, e.g. per frame camera orientation information, in video metadata to avoid overcomplexity.
       1. Three-dimensional location is a requirement for the drone market in particular, as these cameras are airbourne.
       1. Other interpolation algorithms, e.g. cubic splines, may be required in addition to linear interpolation.
       1. Metadata should include dynamic camera attributes, e.g. orientation and zoom, especially for cameras that are not static relative to their mobile platform, e.g. drone cameras can often tilt and pan, and for Augmented Reality (AR) applications.

   1. **Analysed critical gaps in search**

       1. A distributed search use case should be considered, where there is no central server and processing is distributed among several peers with no single control point.
       1. An interval model may be suitable for displaying a (text) subtitle with video, but may not be well-suited to representing location at a particular instant.

   1. **Proposed solutions**

       1. Accuracy versus bandwidth balance is addressed by WebVMT's keyframe and interpolation approach, e.g. to track moving objects with WebVMT paths. Data can be recorded at arbitrary intervals and interpolated to produce interim results with the desired level of accuracy, without imposing a high bandwidth overhead. Consideration should be given to the range of interpolation algorithms available.
       1. Adding an (optional) altitude attribute to WebVMT locations would address the identified 3D location requirement. Omitting altitude would imply a ground-level location.
       1. An interval model for video subtitles, e.g. WebVTT, displays a text phrase for a duration, but also includes the concept of instantaneous position within that interval. Start and end times of a text cue correspond to the start and end of the associated audio content, and the cue advances as individual words are spoken, so instantaneous representation is implicit in the design. The WebVMT path concept takes the same approach, so an object moves from the start to the end location during the cue interval, and its instantaneous location can be calculated in the interim by interpolation.

   1. **Agreed future activities**

       1. Investigate how video metadata search can assist the [OGC Disasters Pilot](http://www.opengeospatial.org/projects/initiatives/dp).
       1. Investigate how video metadata search can assist the [OGC Smart City Interoperability Reference Architecture](http://www.opengeospatial.org/projects/initiatives/scira).
       1. Identify use cases and requirements for non-linear interpolation of video metadata in a separate github issue.
       1. Identify suitable camera attributes and an AR use case in a separate github issue.

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Please view or discuss this issue at https://github.com/w3c/sdw/issues/1130#issuecomment-508531749 using your GitHub account
Received on Thursday, 4 July 2019 16:19:16 UTC

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