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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 CLSIDCLSID_CMPEG2AudDecoderDS (declared in wmcodecdsp.h)
Executablemsmpeg2adec.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:

PropertyRequires
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:

PropertyRequires
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

See also

Audio Subtypes
DirectShow Filters
DVD Media Types

 

 

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