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Knowledge Base

TE30, White-Edge Image issue in multi-point conference

Publication Date:  2015-12-30  |   Views:  316  |   Downloads:  0  |   Author:  s00453625  |   Document ID:  EKB1000093374


Issue Description

In a multipoint conference, when users were viewing continuous presence with the TE30 endpoint, images had white edges.



(1)The customer had three TPs, six TE30s, one Service Management Center (SMC), and one VP9630 Multipoint Control Unit (MCU).

(2)Conference parameters: 1 Mbit/s bandwidth and automatically specified audio and video protocols.

(3)The customer's TE30 endpoint had only a 720p@30 fps license, so users could join the conference with 720p as the highest resolution.

Handling Process

(1)    According to the feedback from onsite engineers, the customer had three TPs and six TE30s, but white edges only happened to two TE30s. Engineers suspected that the problem only occurred on specific TE30s. However, after they replaced the TE30s, cables, and displays one by one, the problem still persisted. This result proved that the problem was not caused by the TE30 endpoint.

(2)    Onsite engineers captured media packets on the TE30 endpoint on which white edges appeared. They conducted an analysis on the captured media packets in the lab using the video decoding tool and found that no white edge existed in the video images sent to the MCU from the TE30 endpoint, but the illumination was high. However, the continuous presence sent to the TE30 endpoint by the MCU had obvious white edges. Based on this finding, engineers suspected that the high illumination caused a strong contrast in image edges. Consequently, the endpoint and MCU filtered the images many times, leading to white edges.

Video image sent to the MCU from the TE30 endpoint:

Continuous presence sent to the endpoint from the MCU:

(3)    By analyzing the handling process of images from generation to display, engineers found that images were filtered twice. The first time: The 1080p images from the camera were filtered to 720p by the TE endpoint. The second time: The MCU filtered the 720p images to 720p 1/9 and displayed them in video panes.

(4)    White edges were alleviated after some of the lights were turned off, which proved that the problem was caused by high illumination. During the test, engineers just turned off some lights without strictly adjusting the illumination, so white edges were not completely cleared.

(5)    Onsite engineers conducted a test by joining a conference with the TE30 endpoint in 1080p format, and white edges disappeared. If the TE30 endpoint joined a conference in 1080p format, it sent the 1080p images to the MCU directly, so filtering was decreased once compared with joining a conference in 720p format. Consequently, image quality was apparently improved, which was in line with the preceding analysis.


Root Cause

High illumination caused a strong contrast in white edges, so diffraction of white and black light (white edges) appeared after images were filtered several times by the endpoint and MCU.


(1) Adjust the illumination in the customer's conference room according to the <<Technical Proposal for Lighting Design in the Conference Room Equipped with TE Series Endpoints>>.

(2) Join a conference with TE30 endpoints in 1080p format to decrease filtering times and improve image quality.