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dsound: clamp input buffer size at 62.5 ms #782

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dsound: clamp input buffer size at 62.5 ms #782

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c50fffc
dsound: simplify CalculateBufferSettings()
dechamps Mar 6, 2023
4a658fa
dsound: clamp input buffer size at 62.5 ms
dechamps Mar 6, 2023
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84 changes: 33 additions & 51 deletions src/hostapi/dsound/pa_win_ds.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1725,7 +1725,7 @@ static HRESULT InitOutputBuffer( PaWinDsStream *stream, PaWinDsDeviceInfo *devic

static void CalculateBufferSettings( unsigned long *hostBufferSizeFrames,
unsigned long *pollingPeriodFrames,
int isFullDuplex,
int hasInput, int hasOutput,
unsigned long suggestedInputLatencyFrames,
unsigned long suggestedOutputLatencyFrames,
double sampleRate, unsigned long userFramesPerBuffer )
Expand All @@ -1734,62 +1734,43 @@ static void CalculateBufferSettings( unsigned long *hostBufferSizeFrames,
unsigned long maximumPollingPeriodFrames = (unsigned long)(sampleRate * PA_DS_MAXIMUM_POLLING_PERIOD_SECONDS);
unsigned long pollingJitterFrames = (unsigned long)(sampleRate * PA_DS_POLLING_JITTER_SECONDS);

if( userFramesPerBuffer == paFramesPerBufferUnspecified )
unsigned long adjustedSuggestedOutputLatencyFrames = suggestedOutputLatencyFrames;
if( userFramesPerBuffer != paFramesPerBufferUnspecified && hasInput && hasOutput )
{
unsigned long targetBufferingLatencyFrames = max( suggestedInputLatencyFrames, suggestedOutputLatencyFrames );

*pollingPeriodFrames = targetBufferingLatencyFrames / 4;
if( *pollingPeriodFrames < minimumPollingPeriodFrames )
{
*pollingPeriodFrames = minimumPollingPeriodFrames;
}
else if( *pollingPeriodFrames > maximumPollingPeriodFrames )
{
*pollingPeriodFrames = maximumPollingPeriodFrames;
}

*hostBufferSizeFrames = *pollingPeriodFrames
+ max( *pollingPeriodFrames + pollingJitterFrames, targetBufferingLatencyFrames);
/* In full duplex streams we know that the buffer adapter adds userFramesPerBuffer
extra fixed latency. so we subtract it here as a fixed latency before computing
the buffer size. being careful not to produce an unrepresentable negative result.
*/
adjustedSuggestedOutputLatencyFrames -= min( userFramesPerBuffer, adjustedSuggestedOutputLatencyFrames );
}
else
{
unsigned long targetBufferingLatencyFrames = suggestedInputLatencyFrames;
if( isFullDuplex )
{
/* In full duplex streams we know that the buffer adapter adds userFramesPerBuffer
extra fixed latency. so we subtract it here as a fixed latency before computing
the buffer size. being careful not to produce an unrepresentable negative result.

Note: this only works as expected if output latency is greater than input latency.
Otherwise we use input latency anyway since we do max(in,out).
*/

if( userFramesPerBuffer < suggestedOutputLatencyFrames )
{
unsigned long adjustedSuggestedOutputLatencyFrames =
suggestedOutputLatencyFrames - userFramesPerBuffer;
const unsigned long targetBufferingLatencyFrames = max( suggestedInputLatencyFrames, adjustedSuggestedOutputLatencyFrames );

/* maximum of input and adjusted output suggested latency */
if( adjustedSuggestedOutputLatencyFrames > targetBufferingLatencyFrames )
targetBufferingLatencyFrames = adjustedSuggestedOutputLatencyFrames;
}
}
else
{
/* maximum of input and output suggested latency */
if( suggestedOutputLatencyFrames > suggestedInputLatencyFrames )
targetBufferingLatencyFrames = suggestedOutputLatencyFrames;
}
*pollingPeriodFrames = (userFramesPerBuffer == paFramesPerBufferUnspecified) ?
targetBufferingLatencyFrames / 4 :
max( max( 1, userFramesPerBuffer / 4 ), targetBufferingLatencyFrames / 16 );
*pollingPeriodFrames = min( max( *pollingPeriodFrames, minimumPollingPeriodFrames ), maximumPollingPeriodFrames );

*hostBufferSizeFrames = userFramesPerBuffer
+ max( userFramesPerBuffer + pollingJitterFrames, targetBufferingLatencyFrames);
const unsigned long intendedUserFramesPerBuffer =
(userFramesPerBuffer == paFramesPerBufferUnspecified) ?
*pollingPeriodFrames :
userFramesPerBuffer;
*hostBufferSizeFrames = intendedUserFramesPerBuffer
+ max( intendedUserFramesPerBuffer + pollingJitterFrames, targetBufferingLatencyFrames );

*pollingPeriodFrames = max( max(1, userFramesPerBuffer / 4), targetBufferingLatencyFrames / 16 );
/* In some (most?) systems, DirectSound has an odd limitation where it always uses
a fixed 31.25 ms granularity for the read cursor, regardless of parameters.
This in turn means that if we allocate an input buffer that is less than 31.25 ms,
the read cursor will stay stuck at zero. See https://github.com/PortAudio/portaudio/issues/775
To work around this problem, ensure that the input host buffer is large enough
for at least two 31.25 ms buffer "halves".

if( *pollingPeriodFrames > maximumPollingPeriodFrames )
{
*pollingPeriodFrames = maximumPollingPeriodFrames;
}
On pre-Vista Windows, we don't do this because DirectSound is implemented very
differently, and is therefore unlikely to suffer from the same issue.
*/
if( hasInput && PaWinUtil_GetOsVersion() >= paOsVersionWindowsVistaServer2008 )
{
*hostBufferSizeFrames = max( *hostBufferSizeFrames, 2 * 0.03125 * sampleRate );
}
}

Expand Down Expand Up @@ -2120,7 +2101,8 @@ static PaError OpenStream( struct PaUtilHostApiRepresentation *hostApi,
else
{
CalculateBufferSettings( (unsigned long*)&stream->hostBufferSizeFrames, &pollingPeriodFrames,
/* isFullDuplex = */ (inputParameters && outputParameters),
/* hasInput = */ !!inputParameters,
/* hasOutput = */ !!outputParameters,
suggestedInputLatencyFrames,
suggestedOutputLatencyFrames,
sampleRate, framesPerBuffer );
Expand Down
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