DirectPlay Voice

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(No Transcript)
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DirectPlay Voice Rod Toll Development
LeadDirectPlay Voice/Lobby Microsoft Corporation
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Overview

• DirectPlay Voice
• Server Implementation Details
• Host Migration Details
• Connection Procedure
• Targeting System Details
• Integrating With Audio Engine
• Common Issues
• Changes For DirectX 8.1 and
• Windows XP

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Peer-To-Peer Session

• Server Implementation Details

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Peer-To-Peer Sessions

• Clients stream audio directly to targets
• Advantages
• Lowest latency (1 hop, 1 queue)
• 3D spatialization supported
• Lowest bandwidth and CPU on host
• Disadvantages
• Highest CPU and bandwidth for clients

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Peer-To-Peer Session
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Mixing Session

• Server Implementation Details

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Mixing Sessions

• Clients stream audio to the server, server mixes
  audio and sends to clients
• Advantages
• Lowest client bandwidth
• Medium bandwidth on server
• Disadvantages
• Highest latency. (2 hops mix)
• High CPU
• No 3D spatialization

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Mixing Session
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Mixing Server Features

• Features
• Per user mixing, per frame
• Adaptive buffering on each incoming stream
  handles jitter
• Handles target specification on a per packet
  accuracy
• Handles up to 64 combinations of players and/or
  groups per packet
• Multiprocessor friendly

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Mixing Server Architecture

• Heavily optimizes mixes
• Does not decompress unless needed
• Reuses mixes when appropriate. (i.e., User A
  Hears User B hears)
• Does not recompress reused mixes
• Locked to clock on server. All clients are sent
  voice content at the same time
• Voice data has timeout of 1.5s to prevent
  infinite backup under load (DirectPlay 8 only)

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Mixing Server Scaling

• Mixer can spawn multiple mixer threads
• of mixer threads of processors
• Provides true concurrent execution on multiple
  processors
• Designed to minimize contention and parallelism
  compression
• Secondary mixer threads only run if primary
  cannot keep up with the workload

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Mixing Server Performance

• Worst case performance is everyone talking to
  everyone else
• Prevents any reuse from occurring as every mix is
  different
• Maximum N compressions N decompressions
• Poorly designed server can cause linear increase
  in CPU usage
• To increase performance minimize the number of
  unique mixes

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Mixing Server Tuning

• To minimize unique mixes
• Limit the number of people any one person can
  speak with
• Break talkers into subgroups to increase
  similarity of mixes
• Use server controlled targeting to enforce
  targeting restrictions

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Forwarding Sessions

• Server Implementation Details

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Forwarding Sessions

• Clients stream audio to the server, server
  forwards audio to targets
• Advantages
• Low CPU on server
• Reduced bandwidth on clients
• Medium latency (2 hops)
• Disadvantages
• Highest bandwidth on server

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Forwarding Session
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Forwarding Server Features

• Features
• Receives streams and forwards them to their
  targets
• Packet reflector and broadcaster
• No buffering on streams
• Handles target specification on a per packet
  accuracy
• Handles up to 64 combinations of players and/or
  groups per packet
• Multiprocessor friendly

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Forwarding Server Tuning

• CPU load is minimal, bandwidth is high
• Worst case bandwidth usage is everyone talking to
  everyone else
• Server is receiving N streams and sending N(N-1)
  streams.
• Can quickly overwhelm a link
• To decrease bandwidth usage minimize the number
  of targets for each client
• Use server controlled targeting to enforce
  restrictions

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Voice Host Migration

• Implementation Details

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Initiating Host Migration

• Host migration is process of electing new host if
  current host becomes unavailable because
• Host node calls StopSession() on host interface
• Host node disconnecting from the session because
  of network error
• Any other situation which makes host unreachable

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Host Migration Properties

• Properties
• Election order follows order voice create player
  was indicated on host
• DirectPlay4 and DirectPlay8 supported
• May complete BEFORE DirectPlay migration
• Limitations on usage
• Peer-to-peer voice sessions only
• Transport must have migration enabled
• Server controlled targeted is not supported

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Disabling Host Migration

• Enabled if enabled for transport.
• Can disable w/ DVSESSION_NOHOSTMIGRATION in
  DVSESSIONDESC
• Can be disabled to shutdown session
• Specify DVFLAGS_NOHOSTMIGRATE to StopSession() in
  the dwFlags parameter

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Host Migration Process

• New host
• Receives a DVMSGID_LOCALHOSTSETUP message which
  allows specification of callback and context for
  new host object
• Receives a DVMSGID_HOSTMIGRATED message which
  contains pointer to new host object
• AddRef() on new host object if needed outside of
  callback
• Clients receive DVMSGID_HOSTMIGRATED with DVID of
  new host

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Connecting

• Connection Procedure

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Connect() Behavior

• Asynchronous behavior (default)
• DVMSGID_CONNECTRESULT when process is complete
• Result of Connect() in message
• Connect() returns DVSUCCESS_PENDING
• Synchronous behavior
• Specify DVFLAGS_SYNC to enable
• Connect does not return until process is complete
• Result of Connect() in return code

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Peer-To-Peer Connects

• Peer-To-Peer sequence
• Connect result is indicated.
• DVMSGID_CREATEVOICEPLAYER for the local player
• DVMSGID_CREATEVOICEPLAYER messages for other
  players
• Voice playback will begin once DVMSGID_CREATEVOICE
  PLAYER for local player has been processed

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Forwarding/Mixing Connects

• Forwarding/mixing sequence
• Connect result is indicated.
• No voice player messages are indicated
• Voice playback will begin as soon as first voice
  traffic arrives

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Connect Procedure

• Voice protocol connect procedure
• Client broadcasts connect message. Will
  retransmit if no response
• Host responds to the message
• Client attempts initialization
• If initialization is unsuccessful connect fails
• If initialization is successful host sends name
  table to the client. (Peer-To-Peer only)

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Targeting

• Targeting System Details

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Targeting

• DirectPlay Voice provides a flexible targeting
  system
• Can specify up to 64 players and/or groups
• Player and group IDs are specified as DVIDs which
  are equivalent to transport IDs (DVID DPID
  DPNID)
• Based on voice nametable NOT transport nametable
• Packet level resolution

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Setting Targets

• SetTransmitTargets is used to set list of
  targets
• Specified as an array of DVIDs
• Cannot contain duplicate IDs
• Can contain a player multiple times (through
  indirection)
• If DVID_ALLPLAYERS is specified it must be the
  only ID

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Client Side Targeting

• Client side targeting implementation
• Changes target list for next packet that is sent
• When list changes DVMSGID_SETTARGETS is indicated
  through callback
• Mixing and Forwarding sessions provide no
  validation for client-side targeting
• Invalid IDs will be ignored on the host
• Can result in audio being sent to no one

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Server Side Targeting

• Server side targeting implementation
• Target list change takes effect on next packet
  after update gets to client
• List changes are indicated through the callback
  on the client with DVMSGID_SETTARGETS
• Full target list validation for all session types

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Target List Maintenance

• If a member of players target list leaves
  session they are automatically removed
• Target list is updated to remove player
• DVMSGID_SETTARGETS message indicated on the
  client
• SetTransmitTarget() replaces previous call
• To add targets, get current list, update and then
  set

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Audio System

• Integrating With Audio Engine

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Sound Engine Integration

• Integrates with existing sound engine by sharing
  DirectSound objects.
• Can share all or any combination
• DirectSound object
• DirectSoundBuffer object
• DirectSoundCapture object
• Can retrieve objects in use by DirectPlay Voice
  through GetSoundDeviceConfig()

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Sharing Objects

• Game creates sound objects
• Specify the DirectSound and DirectSoundBuffer
  objects in DVSOUNDDEVICECONFIG
• DirectPlay Voice creates sound objects
• Specification of flag and priority parameters in
  DVSOUNDDEVICECONFIG
• DirectPlay Voice uses priority mode and creates a
  primary buffer

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Buffer Options

• Main buffer and 3D sound buffers are created with
  following settings
• Flags 3D, Volume, Global, GetCurrent2
• 3D Algorithm Default
• You can control buffer settings by passing
  pre-created buffers to DirectPlay Voice
• Main buffer DVSOUNDDEVICECONFIG
• 3D Buffers Create3DSoundBuffer

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Buffer Formats

• Playback buffer format
• 8khz, 16-bit, mono
• Primary buffer format
• 22khz, 16-bit, stereo
• Recording buffer format varies depending on sound
  configuration

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Audio Stream Access

• Create3DSoundBuffer enables 3D spatialization of
  audio streams
• Developer or DirectPlayVoice provided 3D buffers
• Buffers can be for group or players
• Player can be mixed to multiple buffers
• Peer-To-Peer and forwarding are supported

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Access To Audio Stream

• Voice effects can be placed onto output buffers
  through the use of DirectMedia objects (DMO)
• To apply an effect to a buffer
• Create the buffer with the appropriate settings
• Specify the DMOs to create to SetFX() and check
  for successful initialization
• Pass the buffer to DirectPlay Voice

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Possible Voice Effects

• Possible uses for DMO objects
• Access to audio data through use of DMO that
  forwards data to callback
• Voice morphing
• Lip syncing
• Application of radio static to incoming audio
• Application of ambient noise from transmission
  site

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Common Issues

• Causes and Resolutions

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Sound Quality Issues

• Sound quality is unacceptable
• Causes
• Microphone boost is on and it is not required
• Automatic gain control is disabled and volume is
  too high
• Feedback or echo (see later slides)
• User is breathing into the microphone
• Resolution
• Disable microphone boost
• Enable automatic gain control or lower recording
  volume
• Reposition microphone

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Echoed Speech (Delayed)

• User hears their own voice echoed back to them
  after a delay
• Causes
• Remote users input device is capturing users
  output
• Remote user is configured incorrectly (See Game
  Output Transmitted)
• Resolution
• Switch remote user to headset
• Have remote user reposition their speakers
• Switch to push to talk

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Echoed Speech (Immediate)

• User hears their own voice echoed back to them
  immediately
• Cause Mixer is configured to redirect microphone
  input to the speakers
• Resolution Re-configure playback portion of
  mixer to mute microphone line

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Feedback

• User receives feedback during wizard
• Cause Microphone is picking up output from
  speakers causing a feedback loop
• Resolution Switch to headset or reposition
  speakers

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CD Audio Recorded

• Game or other audio from CD is being transmitted
• Cause Recording mixer is configured to accept
  input from CD line
• Resolution Re-configure recording portion of
  mixer to de-select or mute CD line

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Game Output Transmitted

• Game audio is transmitted to remote users
• Cause
• Recording portion of mixer is configured to
  record all output
• Microphone is picking up speaker output
• Resolution
• Re-configure recording portion of mixer to ensure
  what you hear and wave output lines are
  de-selected or muted
• Reposition speakers

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Configuration Issues

• Symptom Wizard passes but Connect() reports
  DVERR_RUNSETUP
• Cause Running voice wizard on system defaults
  but using voice default for session
• Resolution Ensure device GUIDs passed to
  CheckAudioSetup match those used in Connect()

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Configuration Issues (2)

• User can hear others talking but others cannot
  hear them
• Issue Microphone input not detected because user
  clicks too quickly through wizard. System ends
  up in half duplex mode
• Resolution If half duplex session results have
  user run the wizard again

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Parameter Validation Issues

• Voice API function call failing because of bad
  parameters
• Issue
• Improper parameter usage
• Resolution
• Check ALL return codes
• Install debug bits during development, watch
  debug output for details on reason for failure

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SetTransmitTargets Issue

• Calling SetTransmitTargets fails with invalid
  target
• Issue Valid transport id but not yet valid voice
  id specified in target list
• Resolution Key available list of targets off of
  voice player management messages NOT transport
  messages

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Microphones Issue

• Microphone is plugged in but no voice is being
  recorded. (System with 2 microphones)
• Issue DirectPlay Voice operates on Microphone 0
  on the system
• Resolution Disable automatic mixer configuration
  and have user manually configure volume levels
  and mixer

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Upcoming Changes

• Updates For DirectX 8.1 and Windows XP

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DirectPlay Voice 8.1

• DirectX 8.1 Updates
• Improved AGC algorithm
• Multiprocessor scalable mixing server
• Automated updates to target list when targeted
  client exits
• DirectPlayVoiceCreate no longer supported
• DirectPlay8 used as transport for wizard

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DirectPlay Voice w/XP

• Itanium systems are supported
• 64-bit voice wizard
• 64-bit voice client and server
• DirectPlay8 only (No 64-bit DirectPlay4)
• 32-bit versions are also provided
• Support for all languages supported by Windows XP

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Fast User Switching

• Windows XP provides fast switching between users
• Each users state is preserved and programs
  continue to run
• Voice conferences continue even with user
  switches
• User would be unaware they are transmitting
• DirectPlay Voice automatically mutes playback and
  record when switch occurs

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Further Information

• Where To Go From Here

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DirectX SDK

• SDK documentation
• Updated for DirectX 8.1 with more detail
• Step by step tutorials
• Sample applications
• Peer VoiceConnect, VoicePosition, VoiceGroup
• Mixing/Forwarding Voice client/voice server
• Tutorial applications
• Command-line voice enabled application

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Questions?