IBM(R) WebSphere(R) Voice Server for Multiplatform(R) Version 6.1.1.0 Software Interim Fix - APAR LI74673 README CONTENTS 1.0 ABOUT THIS README FILE 2.0 WHAT IS NEW IN THIS Interim Fix 3.0 INSTALLATION 4.0 UNINSTALLATION 5.0 NOTICES 6.0 TRADEMARKS 1.0 ABOUT THIS README FILE This README provides information about the patch available in this Interim Fix. This fix can be installed on IBM WebSphere Voice Server OEM 6.1.1.0 Linux only. 2.0 WHAT IS NEW IN THIS Interim Fix This iFix addresses a problem of stutter or cut-off audio in TTS synthesized audio with WVS and WebSphere Voice Response. The problem occurs when the synthesized audio is sent to WVR and is caused by delays in sending RTP packets. By default, WVS sends RTP packets in real-time - 160 byte packets in 20 ms intervals. Although WVS is scheduled to send the packets at a fixed rate, some packets may be delayed because of short CPU spikes that may happen even under moderate load. Such delays do not normally cause any problem because the jitter buffer of WVR allows WVR to play the audio out of its buffer until the delayed RTP packets arrive. However, if there are longer delays, or multiple delays occur during the time a long audio is transmitted to WVR, the jitter buffer of WVR is emptied, resulting in stutter or cut-off audio. To handle this problem, this iFix adds an optional mechanism for compensating for RTP packet delay. With this option, WVS can be configured to send the first several packets at a faster rate (faster than real time), so that WVR has a larger buffer when it starts playing the audio. After that, WVS monitors the actual rate packets are sent, and if a delay is identified it sends one or more packets faster to compensate to compensate for the delay, and to keep the buffer of WVR large enough. Installing this iFix does not change the default method of sending RTP packets in real-time. If you do encounter TTS stutter or cut-off audio, you can use the new configuration parameters added by this iFix to apply the delay compensation mechanism. The two new configuration parameters are: com.ibm.voice.server.mc.rtp-num-fast-packets - the number of packets that WVS sends faster than real-time at the beginning of the audio transmission com.ibm.voice.server.mc.rtp-fast-rate-ms - the rate in milliseconds used for sending these first packets These new configuration parameters are used in conjunction with the two existing configuration parameters that define the packet size and the rate for normal RTP packets sending (real-time). These parameters and their default values are: com.ibm.voice.server.mc.rtp-send-size=160 com.ibm.voice.server.mc.rtp-send-threshold-ms=19 With these default values, WVS sends 160 bytes packets every 20 ms (threshold + 1). When applying the delay compensation option described above, it is recommended to change the default packet sending parameters so that WVS sends larger packets at a lower rate. Refer to the example below of the parameter values that can be used to apply the delay compensation mechanism: com.ibm.voice.server.mc.rtp-num-fast-packets=8 com.ibm.voice.server.mc.rtp-fast-rate-ms=20 com.ibm.voice.server.mc.rtp-send-size=1600 com.ibm.voice.server.mc.rtp-send-threshold-ms=199 In this example, the packet size is increased from 160 to 1600 bytes, and the normal (real-time) rate is increased accordingly from 20 to 200 (199 + 1) ms. With these settings, WVS first sends 8 packets of 1600 bytes at a rate of 20 ms. The following packets are sent at a 200 ms rate, as long as there are no delays in sending RTP packets. If WVS identifies that a delay in sending has occurred, it will send one or more packets iat the faster rate (20 ms) to compensate for the delay. To use the two new configuration parameters you need to add them to the configuration file cwv.properties, located in the $WVS_ROOT/config directory. After adding the parameters to the file, you can update their values using a configuration script such as the putParam sample script. Note that the two other parameters, rtp-send-size and rtp-send-threshold already exist in WVS and you should not add them to the file. You can use the putParam script to update the values of these parameters. To disable the delay compensation mode and switch back to the default behavior, either remove the two new parameters from the cwv.properties file or set the value of num-fast-packets to 0. 3.0 INSTALLATION 3.1 Prerequisites o You must have root access to update the IBM WebSphere Voice Server software. o It is assumed the IBM WebSphere Voice Server software is already installed. 3.2 Installation Procedure This fix is delivered in these files: wvsapp.ear, libmibmgram.so are packaged in the ifix_LI74673.tar file. 1. Login to the WVS server system as the root userid. 2. Create an ifix directory to contain the ifix_LI74673.tar file. (e.g. /download/WVSifixLI74673 ) 3. cd to this ifix directory. (e.g. cd /download/WVSifixLI74673 ) 4. Untar the ifix_LI74673.tar file. (e.g. tar -xvf ifix_LI74673.tar) 5. The WebSphere Application Server setupCmdLine.sh is required to be sourced before starting the installation. This is done via the command syntax: source /opt/IBM/WebSphere/AppServer/bin/setupCmdLine.sh ** assuming the WAS install location is /opt/IBM/WebSphere/AppServer 6. The WAS server will be started/stopped as required by the ifix script. Begin the ifix installation script using the command syntax: ./ifix_LI74673.sh -install 7. The ifix install script will provide status messages and directions. 8. Once the install completes without error, reboot the system. 9. Once the system is restarted, verify the WVS installation verification test passes (available from the firststeps application). 10. Ifix is now applied 11. The temporary ifix directory is not required for uninstallation 4.0 UNINSTALLATION 1. Login to the WebSphere VoiceServer system as the root userid. 2. cd $WVS_ROOT/ifix directory. 3. Begin the uninstall of ifix_LI74673 by invoking the ifix_LI74673.sh script with the syntax: ./ifix_LI74673.sh -uninstall 4. The ifix script will provide status messages and directions. 5. Once the uninstall completes without error, reboot the system. 6. Once the system is restarted, verify the WVS installation verification test passes (available from the firststeps application). 7. Given the WVS ivt has passed, now remove the $WVS_ROOT/ifix/LI74673 directory via the command: rm -rf $WVS_ROOT/ifix/LI74673 8. Ifix is now removed. 5.0 NOTICES This information was developed for products and services offered in the United States. IBM may not offer the products, services, or features discussed in this document in other countries. Consult your local IBM representative for information on the products and services currently available in your area. Any reference to an IBM product, program, or service is not intended to state or imply that only IBM product, program, or service may be used. Any functionally equivalent product, program, or service that does not infringe any IBM intellectual property right may be used instead. However, it is the user's responsibility to evaluate and verify the operation of any non-IBM product, program, or service. IBM may have patents or pending patent applications covering subject matter described in this document. The furnishing of this document does not give you any license to these patents. 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This information could include technical inaccuracies or typographical errors. Changes are periodically made to the information herein; these changes will be incorporated in new editions of the publication. IBM may make improvements and/or changes in the product(s) and/or the program(s) described in this publication at any time without notice. The licensed program described in this information and all licensed material available for it are provided by IBM under terms of the IBM Customer Agreement, IBM International Program License Agreement, or any equivalent agreement between us. 6.0 TRADEMARKS IBM, AIX and WebSphere are registered trademarks of International Business Machines Corporation in the United States, other countries, or both. (C)Copyright IBM Corporation 2000, 2008. All Rights Reserved. Note to U.S. Government Users Restricted Rights - Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp.