1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 . TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-!).4%.!.#%G0G0/&G0G0).4%2.!4)/.!,3/5.$G0 G002/2!-%G0G0!.$G0G04%,%6)3)/.42!.3-)33)/.G0G0#)2#5)4315!,)49G0G0!.$G0G0)-0!)2-%.4G0G0!33%33-%.4)45G134G0G02ECOMMENDATIONG0G0. (Extract from the “LUEG0“OOK)NOTES1 ITU
2、-T Recommendation N.64 was published in Fascicle IV.3 of the Blue Book. This file is an extract from theBlue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identical to the Blue Book version and copyright condit
3、ions remain unchanged (see below).2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this publication may be reproduced or utilized in an
4、y form or by any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle IV.3 - Rec. N.64 1Recommendation N.64Fascicle IV.3 - Rec. N.64QUALITY AND IMPAIRMENT ASSESSMENT1 5-grade scale for quality and impairment assessmentThe 5-grade s
5、cale, applicable to both quality and impairment assessments in Table 1/N.64 should be used.TABLE 1/N.64Although the scale is intended, in connection with television, to apply to overall picture assessment, it shouldbe noted that the same scale could be used for a critical assessment of particular pi
6、cture characteristics. Moreover, thenumber of the grade can be taken as either a quality assessment or an impairment assessment. Depending on the context,for example, a Grade 3 picture is of fair quality, having slightly annoying impairments. The same scale can be used inthe case of types of transmi
7、ssion other than television.Note 1 It is implicit that before a circuit is handed over to a broadcasting organization all reasonable stepswill have been taken to ensure that the circuit quality from the point of view of transmission is the best that can beachieved at the beginning of the preparatory
8、 period.Note 2 Grade 1 should be applied only to a transmission considered to be unusable by the broadcastingorganization concerned. If, under exceptional circumstances, the broadcasting organization decides to use a transmissionso graded, because of the interest in the information to be transmitted
9、, this should not constitute a precedent for changingthe grade or for changing the significance of Grade 1.Note 3 This Recommendation does not apply to the assessment of speech transmission quality in telephony.Grade Quality Impairment5 Excellent Imperceptible4 Good Perceptible but not annoying3 Fair Slightly annoying2 Poor Annoying1 Bad Very annoying
