TIA TIA-718-E-1

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-exact implementation, 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) speechcodec, the EVRC-WB is the Service Option 70 (SO 70) speechcodec, the EVRC-NW is the Service Option 73 (SO 73) speechcodec, and the EVRC-NW2K is the Service Option 77 (SO 77) speechcodec all described in [1]. The procedures specified in thisdocument for the SO 3 speech codec are fully consistent withthose contained in [3]. The SO 3 speech codec is used to digitallyencode the speech signal for transmission at a variable datarate of 8550 bps, 4000 bps, or 800 bps. The SO 68 speech codecis used to digitally encode the speech signal for transmission at avariable data rate of 8550 bps, 4000 bps, 2000 bps, or 800bps. The SO 70 speech codec is used to digitally encode the speechsignal for transmission at a variable data rate of 8550 bps, 4000bps, or 800 bps. The SO 73 speech codec is used to digitallyencode the speech signal for transmission at a variable data rateof 8550 bps, 4000 bps, 2000 bps, or 800 bps. The SO 77 is sameas SO 73 except it includes a maximum  rate 2 kbps mode speechcodec.

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 proceduresset forth in Sections 2.1.1 and 38 2.1.2, or Sections 2.2.1 and2.2.2, or Sections 2.3.1 and 2.3.2, or Section 2.4.1 and 2.4.2 3(SO 73), or Section 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 9 encoder and decoder butalso that this level of performance is maintained with operationbetween any 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 wheninteroperating with all other manufacturers’ equipment meetingthe standard. This standard provides a means for measuringperformance levels while trying to ensure proper interoperationwith 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 tosupply equipment, this becomes a prohibitive task; therefore,the objective and subjective tests rely upon the use of a”master codec”. The master codec is defined as the floating-pointimplementation of specific EVRC written in the C programminglanguage. The master codec software 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 Section 21 3.5.3 (SO 77) is used as partof the interoperability testing.

Edition:

E

Published:

12/01/2013

Number of Pages:

222

File Size:

1 file , 2.2 MB