IMediaObject::GetInputMaxLatency method (mediaobj.h)

Статья
4/26/2023

[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The GetInputMaxLatency method retrieves the maximum latency on a specified input stream.

Syntax

HRESULT GetInputMaxLatency(
        DWORD          dwInputStreamIndex,
  [out] REFERENCE_TIME *prtMaxLatency
);

Parameters

dwInputStreamIndex

Zero-based index of an input stream on the DMO.

[out] prtMaxLatency

Pointer to a variable that receives the maximum latency.

Return value

Returns an HRESULT value. Possible values include those in the following table.

Return code	Description
DMO_E_INVALIDSTREAMINDEX	Invalid stream index.
E_FAIL	Failure.
E_NOTIMPL	Not implemented. Assume zero latency.
S_OK	Success.

Remarks

The latency is the difference between a time stamp on the input stream and the corresponding time stamp on the output stream. The maximum latency is the largest possible difference in the time stamps. For a DMO, determine the maximum latency as follows:

Process input buffers until the DMO can produce output.
Process as many output buffers as possible.
The maximum latency is the largest delta between input time stamps and output time stamps (taken as an absolute value).

Under this definition, latency does not include the time that it takes to process samples. Nor does it include any latency introduced by the size of the input buffer.

For the special case where a DMO processes exactly one sample at a time, the maximum latency is simply the difference in time stamps.

Latency is defined only when samples have time stamps, and the time stamps increase or decrease monotonically. Maximum latency might depend on the media types for the input and output streams.

Requirements

Requirement	Value
Target Platform	Windows
Header	mediaobj.h (include Dmo.h)
Library	Dmoguids.lib

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