AAC Media Types
This topic describes how to specify the format of an Advanced Audio Coding (AAC) stream in Media Foundation.
Two subtypes are defined for AAC audio:
| Subtype | Description | Header |
|---|---|---|
| MFAudioFormat_AAC | Raw AAC or ADTS AAC. | mfapi.h |
| MEDIASUBTYPE_RAW_AAC1 | Raw AAC. | wmcodecdsp.h |
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MFAudioFormat_AAC
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For this subtype, the media type gives the sample rate and number of channels prior to the application of spectral band replication (SBR) and parametric stereo (PS) tools, if present. The effect of the SBR tool is to double the decoded sample rate relative to the core AAC-LC sample rate. The effect of the PS tool is to decode stereo from a mono-channel core AAC-LC stream.
This subtype is equivalent to MEDIASUBTYPE_MPEG_HEAAC, defined in wmcodecdsp.h. See Audio Subtype GUIDs.
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MEDIASUBTYPE_RAW_AAC1
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This subtype is used for AAC contained in an AVI file with the audio format tag equal to WAVE_FORMAT_RAW_AAC1 (0x00FF).
For this subtype, the media type gives the sample rate and number of channels after the SBR and PS tools are applied, if present.
The following media type attributes apply to AAC audio.
| Attribute | Description |
|---|---|
| MF_MT_MAJOR_TYPE | Major type. Must be MFMediaType_Audio. |
| MF_MT_SUBTYPE | Audio subtype. Refer to the previous description for details. |
| MF_MT_AAC_AUDIO_PROFILE_LEVEL_INDICATION | Audio profile and level. The value of this attribute is the audioProfileLevelIndication field, as defined by ISO/IEC 14496-3. If unknown, set to zero or 0xFE ("no audio profile specified"). |
| MF_MT_AUDIO_AVG_BYTES_PER_SECOND | Bit rate of the encoded AAC stream, in bytes per second. |
| MF_MT_AAC_PAYLOAD_TYPE | Payload type. Applies only to MFAudioFormat_AAC. MF_MT_AAC_PAYLOAD_TYPE is optional. If this attribute is not specified, the default value 0 is used, which specifies the stream contains raw_data_block elements only. |
| MF_MT_AUDIO_BITS_PER_SAMPLE | Bit depth of the decoded PCM audio. |
| MF_MT_AUDIO_CHANNEL_MASK | Assignment of audio channels to speaker positions. |
| MF_MT_AUDIO_NUM_CHANNELS | Number of channels, including the low frequency (LFE) channel, if present. The interpretation of this value depends on the media subtype, as described previously. |
| MF_MT_AUDIO_SAMPLES_PER_SECOND | Sample rate, in samples per second. The interpretation of this value depends on the media subtype, as described previously. |
| MF_MT_USER_DATA | The value of this attribute depends on the subtype:
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