1、 ETSI TR 126 973 V15.0.0 (2018-07) 5G; Update to fixed-point basic operators (3GPP TR 26.973 version 15.0.0 Release 15) TECHNICAL REPORT ETSI ETSI TR 126 973 V15.0.0 (2018-07)13GPP TR 26.973 version 15.0.0 Release 15Reference RTR/TSGS-0426973vf00 Keywords 5G ETSI 650 Route des Lucioles F-06921 Sophi
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13、cts, services or organizations associated with those trademarks. Foreword This Technical Report (TR) has been produced by ETSI 3rd Generation Partnership Project (3GPP). The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or GSM identiti
14、es. These should be interpreted as being references to the corresponding ETSI deliverables. The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under http:/webapp.etsi.org/key/queryform.asp. Modal verbs terminology In the present document “should“, “should not“, “may“, “need
15、 not“, “will“, “will not“, “can“ and “cannot“ are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of provisions). “must“ and “must not“ are NOT allowed in ETSI deliverables except when used in direct citation. ETSI ETSI TR 126 973 V15.0.0 (201
16、8-07)33GPP TR 26.973 version 15.0.0 Release 15Contents Intellectual Property Rights 2g3Foreword . 2g3Modal verbs terminology 2g3Foreword . 4g3Introduction 4g31 Scope 5g32 References 5g33 Abbreviations . 5g34 Extension to the STL2009 Basic Operators . 5g34.1 Analysis of the gap between current basic
17、operators and modern DSP architectures 5g34.2 Test methodology for validating the extended basic operators 6g34.2.0 General 6g34.2.1 Test methodology . 7g34.2.2 Test results for basic operator Mpy_32_16_1 . 8g34.2.3 Test results 12g34.2.4 Test results conclusion 12g35 Alternative EVS Implementation
18、Using the Extended Basic Operators 13g35.1 Merits of an alternative EVS implementation using the extended basic operators. 13g35.2 Example pseudo code to illustrate some of the benefits of modern DSP architectures 15g35.3 Validation of an alternative EVS implementation using updated basic operators
19、17g35.3.1 C-code inspection . 17g35.3.2 Objective performance evaluation of the alternative EVS implementation 17g35.3.3 Subjective performance evaluation of the alternative EVS implementation . 18g36 Conclusions 19g3Annex A: Extended Basic Operators 21g3A.1 Basic operators that use 64 bit registers
20、/accumulators . 21g3A.2 Basic operators which use 32 bit precision multiply 26g3A.3 Basic operators which use complex data types 32g3A.4 Basic operators for control operation . 40g3Annex B: Weights of the STL basic operators 41g3Annex C: Change history 46g3History 47g3ETSI ETSI TR 126 973 V15.0.0 (2
21、018-07)43GPP TR 26.973 version 15.0.0 Release 15Foreword This Technical Report has been produced by the 3rd Generation Partnership Project (3GPP). The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modify th
22、e contents of the present document, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows: Version x.y.z where: x the first digit: 1 presented to TSG for information; 2 presented to TSG for approval; 3 or greater indicates TSG appro
23、ved document under change control. y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc. z the third digit is incremented when editorial only changes have been incorporated in the document. Introduction The last major update to the IT
24、U-T Basic Operators 6 was in 2005, with a follow on update in 2009. These basic operators serve as a foundation for reference software of codecs specified by 3GPP. During the last several years, processors with wide accumulators, and support for single-instruction-multiple-data (SIMD), and very long
25、 instruction word (VLIW) features have become prevalent. The basic operators of 2009 now need to be extended to leverage these capabilities of modern processors so that implementations with lower mega-cycles-per-second (MCPS) and lower-power may be realized. Enhanced Voice Services (EVS) is one of t
26、he recent codecs defined by 3GPP that can leverage these features of modern processors. The existing EVS reference software would have to be appropriately modified to leverage these extended basic operators without changing the underlying algorithm. This is referred to as an alternative EVS implemen
27、tation using the extended basic operators. This alternative EVS implementation would have to be evaluated to ensure that inter-operability is maintained in addition to ensuring that voice quality is not impacted. ETSI ETSI TR 126 973 V15.0.0 (2018-07)53GPP TR 26.973 version 15.0.0 Release 151 Scope
28、The present document covers the following topics: 1) Assessment of the gaps between modern processors and the existing set of basic operators (STL2009) 6. 2) Proposal of an extended set of operators addressing modern DSP architectures as an extension to STL2009. 3) Assessment of merits of an alterna
29、tive EVS implementation using extended STL2009 Basic Operators. 4) Proposal for validation of an alternative EVS implementation using extended STL2009 Basic Operators. 2 References The following documents contain provisions which, through reference in this text, constitute provisions of the present
30、document. - References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific. - For a specific reference, subsequent revisions do not apply. - For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP docume
31、nt (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document. 1 3GPP TR 21.905: “Vocabulary for 3GPP Specifications“. 2 3GPP TS 26.442: “Codec for Enhanced Voice Services (EVS); ANSI C code (fixed-point)“
32、. 3 Recommendation ITU-T P.800 (08/1996): “Methods for subjective determination of transmission quality“. 4 Recommendation ITU-T P.863 (09/2014): “Perceptual objective listening quality assessment“. 5 3GPP TS 26.443: “Codec for Enhanced Voice Services (EVS); ANSI C code (floating-point)“. 6 Recommen
33、dation ITU-T G.191 (03/10): “Software tools for speech and audio coding standardization“. 7 3GPP TR 26.952: “Codec for Enhanced Voice Services (EVS); Performance Characterization (Release 14)“. 3 Abbreviations For the purposes of the present document, the abbreviations given in 3GPP TR 21.905 1 and
34、the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in 3GPP TR 21.905 1. SIMD Single Instruction Multiple Data STL Software tools for speech and audio coding standardization VLIW Very Long Instruction Word. 4 Ext
35、ension to the STL2009 Basic Operators 4.1 Analysis of the gap between current basic operators and modern DSP architectures State-of-the-art processor architectures, such as the recent ones from Intel, ARM, QUALCOMM, Texas Instruments etc., support wide accumulators, SIMD and VLIW capabilities. The l
36、ast major update to the ITU-T Basic Operators was ETSI ETSI TR 126 973 V15.0.0 (2018-07)63GPP TR 26.973 version 15.0.0 Release 15in 2005, with a follow on update in 2009 6. It appears that these earlier versions of the Basic Operators (2009 and earlier) were influenced by older DSP architectures suc
37、h as the Texas Instruments TMS320C5x and TMS320C54x processors where the accumulator was 40 bits wide. However, a survey of the state-of-the-art processor architectures shows that most of them support the following capabilities: - Wider (64 bit) accumulators and registers. - Wider accumulators enabl
38、e additional guard bits which eliminate the need for checking for saturation after every basic operation. - SIMD (Single Instruction Multiple Data) instructions which can process vector data. For example, a single instruction can process two 32-bit data elements or four 16-bit elements in parallel.
39、- VLIW (Very Long Instruction Word) enables several operations to be executed in parallel in a single cycle. Basic operators that are friendlier to compilers, and enable SIMD and VLIW features to be leveraged, can significantly reduce implementation time. Improved compiler technology and software de
40、velopment tools interpret data types and associated basic operators to map them to a processor architecture for better Out-of-box (OOB) performance. Without this computer assisted optimization, an engineer would have to hand-optimize the code which would result in increased engineering effort and lo
41、nger time to market. Many recent audio/hybrid codecs make extensive use of 16bit x 32bit MAC (multiply and accumulate) and 32bit x 32bit MAC operations which are realized quite differently between VLIW and SIMD architectures and the current Basic Operators: - Current STL2009 Basic operators require
42、saturation and truncation after every multiply-accumulate (MAC) operation to maintain bit-exactness. - The current Basic operator saturation checks prevent use of SIMD parallelism. - To maintain bit-exactness, cycles are wasted resulting in higher MCPS and power on VLIW and SIMD capable devices. - H
43、igher precision variables, such as 64bit operands, are partitioned into smaller width operands, processed and then put back to the original width. This results in an overhead and processor cycles are wasted. Considering the capabilities of modern processor architectures, as well as the characteristi
44、cs of the latest speech and audio codecs, there is a need for extending STL2009 with additional basic operators basic operators need to be mapped to processor instructions. A standard reference C code written with these aspects in mind will result in an implementation that leverages SIMD and VLIW (V
45、ery Long Instruction Word) features of the processor better and results in an out-of-the-box (OOB) performance that is quite close to the final desired performance. The compiler can optimize the code across all the files and functions thereby significantly reducing manual optimization effort. Implem
46、enters can go to market faster. Figure 6 shows the benefits of creating an alternate reference C code for EVS using the updated basic operator: 1) Reduced hand-optimization efforts lead to reduced total engineering effort, and hence improved time to market. 2) Improved MCPS numbers in OOB and final
47、hand-optimized code. 3) Reduced code size. Reduced MCPS and memory reduces overall power used. This should facilitate extended battery life. Figure 6: Benefits of proposed alternate reference C for EVS Using the existing standard EVS Reference code version 14.0.0 as a starting point, an alternative
48、C code that leverages the proposed basic operators has been created. During this creation process, step by step, several key parameters have been monitored such as the engineering effort spent expressed as time (days, weeks, months), and corresponding reduction in MCPS. Figure 7 shows the optimizati
49、on level achieved versus engineering effort measured in units of time. As the figure shows, the OOB performance of the existing reference C is at 269 MCPS, while the OOB performance of the proposed alternative EVS reference C code is at 162 MCPS. This is a gain of 1.66x achieved in matter of a few days of engineering effort. Next, time is spent restructuring the code and hand optimizing. The final hand-optimized version is at 61.9 MCPS compared to 77.5 MCPS for the existing EVS reference implementation. This is a gain of 1.25x. ETSI ETSI TR 126 973 V15
