TIA TIA-718-E

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This document specifies the procedures to test implementationsof EVRC-A, EVRC-B, EVRC-WB, EVRC-NW or EVRC-NW2K compatiblevariable-rate speech codecs either by meeting the bit-exactimplementation, or meeting recommended minimum performancerequirements. The EVRC-A is the Service Option 3 (SO 3) speechcodec, the EVRC-B is the Service Option 68 (SO 68) speech codec,the EVRC-WB is the Service Option 70 (SO 70) speech codec, theEVRC-NW is the Service Option 73 (SO 73) speech codec, and theEVRC-NW2K is the Service Option 77 (SO 77) speech codec alldescribed in [1]. The procedures specified in this document for theSO 3 speech codec are fully consistent with those contained in [3].The SO 3 speech codec is used to digitally encode the speech signalfor transmission at a variable data rate of 8550 bps, 4000 bps, or800 bps. The SO 68 speech codec is used to digitally encode thespeech signal for transmission at a variable data rate of 8550 bps,4000 bps, 2000 bps, or 800 bps. The SO 70 speech codec is used todigitally encode the speech signal for transmission at a variabledata rate of 8550 bps, 4000 bps, or 800 bps. The SO 73 speech codecis used to digitally encode the speech signal for transmission at avariable data rate of 8550 bps, 4000 bps, 2000 bps, or 800 bps. TheSO 77 is same as SO 73 except it includes a maximum rate 2 kbpsmode speech codec.

Like some other speech coding standards, this standard providesa bit-exact method of verifying the test codec for minimumperformance. In this optional procedure, a given set of testvectors are input to the test codec and the output vectors from thetest codec must be bit-exact with the output vectors given in thesoftware distribution which is associated with this standard. Ifthey are bit-exact, the test codec passes the minimum performancerequirement and no further testing is required. The bit-exact modeof testing, however, is only applicable to codecs whose designconforms in all respects to the algorithmic description of thespecific EVRC service option, including the noise suppression, ratedetermination and post-filter components.

Should the candidate EVRC differ in any of these components, thetest codec shall be tested using the objective and subjective testsprescribed by this standard. That is, EVRC-compliance of a “testcodec” can be achieved by either:

• Complying with Sections 2.1.1 and 2.1.2 (SO 3), or Sections2.2.1 and 2.2.2 (SO 68), or Sections 2.3.1 and 2.3.2 (SO 70), orSection 2.4.1 and 2.4.2 (SO 73), or Section 2.5.1 and 2.5.2 (SO 77)and demonstrating bit-exactness according to the proceduredescribed in Section 3.1.4 (SO 3), or Section 3.2.4 (SO 68), orSection 3.3.4 (SO 70), or Section 3.4.4 (SO 73), or Section 3.5.4(SO 77) respectively.

• Following the objective and subjective testing procedures setforth in Sections 2.1.1 and 2.1.2, or Sections 2.2.1 and 2.2.2, orSections 2.3.1 and 2.3.2, or Section 2.4.1 and 2.4.2 (SO 73), orSection 2.5.1 and 2.5.2 (SO 77) of this standard.

With the exception of Sections 3.1.4, 3.2.4, 3.3.4, 3.4.4, and3.5.4, the remaining text applies only to implementations that donot satisfy the requirement for bit-exactness.

Testing the codec is based on two classes of procedures:objective tests and subjective tests. In the event that the testcodec fails any of the objective or subjective tests, the testcodec fails the compliance test. Objective tests are based uponactual measurements from the speech codec function. Subjectivetests are based on listening tests to judge overall speech quality.The minimum subjective requirement for the test codec is based uponthe ability of the test codec to demonstrate performance equivalentto or better than that of the specific EVRC floating-pointbit-exact codec within a fixed allowable statistical error.

The purpose of the testing is not only to ensure adequateperformance between one manufacturer’s encoder and decoder but alsothat this level of performance is maintained with operation betweenany pairing of manufacturers’ encoders and decoders. Thisinteroperability issue is a serious one. Any variation inimplementing the exact standard must be avoided if it cannot beensured that minimum performance levels are met when interoperatingwith all other manufacturers’ equipment meeting the standard. Thisstandard provides a means for measuring performance levels whiletrying to ensure proper interoperation with other manufacturers’equipment.

The issue of interoperation can only be definitively answered bytesting all combinations of encoder/decoder pairings. With thenumber of equipment manufacturers expected to supply equipment,this becomes a prohibitive task; therefore, the objective andsubjective tests rely upon the use of a ―master codec‖. The mastercodec is defined as the floating-point implementation of specificEVRC written in the C programming language. The master codecsoftware which is described in Section 3.1.3 (SO 3), Section 3.2.3(SO 68), Section 3.3.3 (SO 70), Section 3.4.3 (SO 73), or Section3.5.3 (SO 77) is used as part of the interoperability testing.

Edition:

E

Published:

02/01/2012

Number of Pages:

224

File Size:

1 file , 5.7 MB