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Microsoft MPEG-1/DD/AAC Audio Decoder

This filter decodes the following audio formats:

MPEG-1 audio layers I and II.
Backward-compatible MPEG-2 audio, layers I and II (ISO/IEC 13818-3), mono and stereo only.
Advanced Audio Coding (AAC) Low Complexity (LC) profile.
High-Efficiency AAC (HE-AAC) version 1 and version 2.
Pass-through Digital Theater Systems (DTS) for digital output.
LPCM, mono and stereo only, with or without PES headers.
Dolby Digital.
Dolby Digital Plus, including conversion from Dolby Digital Plus to Dolby Digital for digital output.

Note The Microsoft implementation of the Dolby Digital technology is restricted under terms of the Dolby Digital licensing program to use by Microsoft applications.

Note This filter is not supported on IA-64-based platforms.

Decoding of Dolby Digital Plus, AAC, and HE-AAC formats requires Windows 7. Decoding of Dolby Digital or Dolby Digital Plus is not supported on Windows 7 Home Basic or Windows 7 Starter.

In the registry, the friendly name of this filter is "Microsoft DTV-DVD Audio Decoder".

Filter Information
Filter Interfaces	IBaseFilter ICodecAPI
Input Pin Media Types	In Windows Vista and later, the filter supports the following input types: MEDIATYPE_Audio, MEDIASUBTYPE_DOLBY_AC3 (See Note 1.) MEDIATYPE_Audio, MEDIASUBTYPE_MPEG1Audio MEDIATYPE_Audio, MEDIASUBTYPE_MPEG1Payload MEDIATYPE_Audio, MEDIASUBTYPE_MPEG2_AUDIO MEDIATYPE_DVD_ENCRYPTED_PACK, MEDIASUBTYPE_DOLBY_AC3 (See Note 1.) MEDIATYPE_DVD_ENCRYPTED_PACK, MEDIASUBTYPE_DTS (See Note 2.) MEDIATYPE_DVD_ENCRYPTED_PACK, MEDIASUBTYPE_DVD_LPCM_AUDIO MEDIATYPE_DVD_ENCRYPTED_PACK, MEDIASUBTYPE_MPEG2_AUDIO MEDIATYPE_MPEG2_PES, MEDIASUBTYPE_DOLBY_AC3 (See Note 1.) MEDIATYPE_MPEG2_PES, MEDIASUBTYPE_DTS (See Note 2.) MEDIATYPE_MPEG2_PES, MEDIASUBTYPE_DVD_LPCM_AUDIO MEDIATYPE_MPEG2_PES, MEDIASUBTYPE_MPEG2_AUDIO MEDIATYPE_Stream, MEDIASUBTYPE_DOLBY_AC3 (See Note 1.) MEDIATYPE_Stream, MEDIASUBTYPE_MPEG1Audio MEDIATYPE_Stream, MEDIASUBTYPE_MPEG2_AUDIO Starting in Windows 7, the filter also supports the following input types: MEDIATYPE_Audio, MEDIASUBTYPE_DOLBY_DDPLUS (See Note 1.) MEDIATYPE_Audio, MEDIASUBTYPE_DTS2 (See Note 2.) MEDIATYPE_Audio, MEDIASUBTYPE_DVD_LPCM_AUDIO MEDIATYPE_Audio, MEDIASUBTYPE_DVM (See Note 1.) MEDIATYPE_Audio, MEDIASUBTYPE_MPEG_ADTS_AAC MEDIATYPE_Audio, MEDIASUBTYPE_MPEG_LOAS MEDIATYPE_Audio, MEDIASUBTYPE_MPEG1AudioPayload MEDIATYPE_Audio, MEDIASUBTYPE_RAW_AAC1 MEDIATYPE_Stream, MEDIASUBTYPE_DOLBY_DDPLUS (See Note 1.) MEDIATYPE_Stream, MEDIASUBTYPE_MPEG_ADTS_AAC MEDIATYPE_Stream, MEDIASUBTYPE_MPEG_LOAS The input type can change dynamically during streaming. For more information about these media types, see Audio Subtypes. Note 1. The Microsoft implementation of the Dolby Digital technology is restricted under terms of the Dolby Digital licensing program to use by Microsoft applications. Note 2. For Digital Theater Systems (DTS) input, only S/PDIF output is supported (DTS over S/PDIF). Audio decoding is not supported.
Input Pin Interfaces	ICodecAPI IKsPropertySet IMemInputPin IPin IQualityControl
Output Pin Media Types	In Windows Vista and later, the filter supports the following output types: MEDIATYPE_Audio, MEDIASUBTYPE_DOLBY_AC3_SPDIF (same as KSDATAFORMAT_SUBTYPE_IEC61937_DOLBY_DIGITAL) MEDIATYPE_Audio, MEDIASUBTYPE_PCM Starting in Windows 7, the filter also supports the following output types: MEDIATYPE_Audio, KSDATAFORMAT_SUBTYPE_IEC61937_DTS MEDIATYPE_Audio, MEDIASUBTYPE_IEEE_FLOAT
Output Pin Interfaces	IMediaSeeking IPin IQualityControl
Filter CLSID	CLSID_CMPEG2AudDecoderDS (declared in wmcodecdsp.h)
Executable	msmpeg2adec.dll
Merit	MERIT_NORMAL - 1
Filter Category	CLSID_LegacyAmFilterCategory

Note An earlier version of the documentation stated that this filter can decode "MPEG-2 audio." The filter decodes only backward-compatible MPEG-2 audio.

Remarks

Mono streams are always decoded to stereo.

For streams with a channel configuration of two or more speakers, the decoder does one of the following:

Up-mixes to six channels, using the common 5.1 speaker configuration.
Downmixes to stereo.

To select between these two options, use the ICodecAPI interface to set the AVDecCommonOutputFormat property, before connecting the pins. Alternatively, when the application builds the filter graph, it can set the desired media type on the output pin.

AAC Decoding

For AAC, the decoder has certain format constraints on the compressed AAC input. These format constraints are the same as the Media Foundation AAC Decoder, and are documented in the section "Format Constraints".

The DirectShow decoder also accepts different input types than the Media Foundation decoder. The DirectShow decoder supports the following AAC input types:

MEDIASUBTYPE_RAW_AAC1: Raw AAC, typically found in AVI or Matroska (.MKV) files.
MEDIASUBTYPE_MPEG_ADTS_AAC: AAC in an Audio Data Transport Stream (ADTS) for streaming.
MEDIASUBTYPE_MPEG_LOAS: Transport stream with a synchronization layer (LOAS) and a multiplex layer (LATM).

The Media Foundation decoder supports the following AAC input types:

MFAudioFormat_AAC (same as MEDIASUBTYPE_MPEG_HEAAC) for MP4 file playback.
MEDIASUBTYPE_RAW_AAC1.

Property Sets

The decoder's input pin supports the following property sets through IKsPropertySet:

Note Starting in Windows 7, the decoder supports trick mode through the rate-change property set. It supports playback rates in the range [0.501 – 2.0], where 1.0 is normal playback rate, and 2.0 is twice the normal rate.

Codec Properties

The decoder's input pin supports the following properties through ICodecAPI:

Property	Requires
AVAudioChannelConfig	Windows Vista
AVAudioChannelCount	Windows Vista
AVAudioSampleRate	Windows Vista
AVDDSurroundMode	Windows Vista only; not supported in Windows 7 or later.
AVDecAudioDualMono	Windows Vista
AVDecCommonInputFormat	Windows Vista
AVDecCommonMeanBitRate	Windows 7

The filter supports the following properties through ICodecAPI:

Property	Requires
AVDecAACDownmixMode	Windows 7
AVDecAudioDualMonoReproMode	Windows Vista
AVDecCommonOutputFormat (See Note 3.)	Windows Vista
AVDecDDDynamicRangeScaleHigh	Windows Vista
AVDecDDDynamicRangeScaleLow	Windows Vista
AVDecDDOperationalMode	Windows Vista
AVDecMmcssClass	Windows Vista
AVDSPLoudnessEqualization	Windows 7
AVDSPSpeakerFill	Windows 7

Note 3. The AVDecCommonOutputFormat property must be set before the decoder's output pin is connected. Otherwise, the change has no effect.

Requirements

Minimum supported client	Windows Vista Home Premium, Windows Vista Ultimate, Windows 7 [desktop apps only]
Minimum supported server	None supported
Header	Wmcodecdsp.h

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