Sphinx 3.4 Development Progress Report in February Arthur Chan, Jahanzeb Sherwani Carnegie Mellon University Mar 1, 2004

This Presentation  S3.4 Development Progress Speed-up Language Model facilities  CALO and S3.5 Development Which features should be there to make CALO better? Schedule for next three months

Review of Last Month Progress  Last month Wrote a speed-up version of s3. Completed some coding of s3.4 speed-up task.  This month Backbone of speed-up functionalities s3.4 completed and tested. Basic LM facilities completed and smoked-tested.

Current Systems Specifications (without Gaussian Selection) Sphinx 3Sphinx 3.3 Speed in P4-1G Tested in Communicator Task ERR 17.2% 11xRT GMM, 3xRT Srch ERR 18.6% 6xRT GMM, 1xRT Srch GMM ComputationsNot optimized (few code optimization) Can applied Sub-VQ-based Gauss. Selection LexiconFlatTree SearchBeam on search, no beam on GMM Beam on Search Beam on GMM.

Speed-up Facilities in s3.3 GMM Computation Seach Frame-Level Senone-Level Gaussian-Level Component-Level Not implemented SVQ-based GMM Selection Sub-vector constrained to 3 SVQ code removed Lexicon Structure Pruning Heuristic Search Speed-up Tree. Standard Not Implemented

Speed-up Facilities in s3.4 GMM Computation Seach Frame-Level Senone-Level Gaussian-Level Component-Level (New) Naïve Down-Sampling (New) Conditional Down-Sampling (New) CI-based GMM Selection (New) VQ-based GMM Selection (New) Unconstrained no. of sub- vectors in SVQ-based GMM Selection (New) SVQ code enabled Lexicon Structure Pruning Heuristic Search Speed-up Tree (New) Improved Word-end Pruning (New) Phoneme- Look-ahead

S3.4 Speed Performance in Communicator Task Sphinx 3.3Sphinx 3.4 Error RateERR: 18.6%ERR: 18.7% Speed (P4-1G)6xRT GMM, 1xRT Search 1.2xRT GMM, 1.5xRT Search Speed (P4-2G)1.6xRT GMM, 0.6xRT Search 0.4xRT GMM 0.9xRT Search Techniques used--CI-based GMM Selection -Word-end pruning

Issues in Speed Optimization  Implementation Issues: Beams applied on GMM causing many techniques hard to be implemented Some facilities were hardwired for specific purpose.  Performance Issues Each techniques reduced computation by % with <5% degradation. However, they didn ’ t add-up ……  Reduction in computation has certain lower bound (usually 75%-80% reduction is max.) Overhead is huge in some techniques  E.g. VQ-based Gaussian Selection take 0.25xRT

Language Model Facilities  S3.3 only accept single LM without class in binary format  So far, S3.4 is able to accept multiple class- based LMs in binary format. One major modification of codes  Affect 6-7 files. Caveats:  Not perfect implementation.  Text format is not yet supported. Backward compatibility is an issue.  Lack of test-cases. Only slightly smoke-tested ~1 more week work

Problems with s3.4 (valid for Feb 29th, 2004)  Only accept DMP file. Txt format reader is very complex in Sphinx 2. Straight conversion is not clean.  LMs are all loaded into memory We can work on this.  Lexical tree are all built at the beginning We tried to avoid the overhead of rebuilding tree in every utterance.

Summary in Sphinx 3.4 Development  Derivative s3.3 With Speed Optimization Better LM facilities  Algorithmic Optimization is 90% completed Still need to improve overhead performance. Tree-based GMM selection is desirable. Improvement for individual technique.  Go-through the major hurdle of multiple LMs and class-based LMs. Need more time to make it more stable.  Expected internal release time : March 8, 2004

Sphinx 3.4 and CALO  Which pieces are missing? Sphinx 3.4 ’ s decoding is still not streamlined => Continuous Listening is not yet enabled. Sphinx ’ s speed may still not be ideal. From s3 to s3.3, ~10% degradation. Sphinx 3.4 doesn ’ t learn from data yet.

Sphinx 3.5. What should we do in next 3 months?  Expected release time (May – June)  Interfaces: Streamlined front-end and decoding (?) Portaudio based audio routine.  Speed/Accuracy Improved lexical tree search Machine optimization of Gaussian computation. Combination of multiple recognizers  Learning Acoustic Model adaptation (?) Language Model adaptation (In Phoenix) Better semantic parsing  Resource Acquisition and Load Balancing

Highlight I: Speed/Accuracy  Improved lexical tree search Current implementation used single lexical tree. May be desirable to create tree copies.  Machine Optimization of Gaussian Computation SIMD (Single Implementation Multiple Data) Require help from assembly language experts. (Jason/Thomas)

Highlight II: Multiple Recognizer Combination and Resource Acquisition  Research by Rong suggests combination of multiple recognizer can improve accuracy  Speed worsen by 100% if we run two recognizers.  An interesting solution: Computation can be shared by other machines in the meeting. Inspired by routing implementation. A very natural solution in meeting scenario because usually only one person will be speaking.  Challenges : Bandwidth and Load Balancing

Highlight III:  Learning Acoustic Model  Maximum Likely Linear Regression (MLLR)  Will be responsible by Jahanzeb (?)Language Model  How?  Cached-based LM? (?)Improved Robust Parsing  Better parsing based on previous command history  Phoenix ’ s source code is not easy to trace  Thomas Harris ’ s implementation may be a good place to start.

Arthur and Jahanzeb ’ s Proposed Schedule ArthurJahanzeb Mar 1 – Mar 15 Windows Port+ Stream-line S3.4 decoding Regression- test + Adaptation Milestone 1 Mar 15- Apr 1 Multiple recognizers Experiments Apr 1 – Apr 15 Preparation for Demo + if (we want) {write-up paper ICSLP}

Cont. ArthurJahanzeb Apr 16 – May 7 Search modification: tree copies implementation Regression- test + Adaptation Milestone 2 May 7 – June 1 Sphinx 3.5 Learning code development + s3.5 release (?)