![]() ![]() The default settings are reflected in the media types returned by the encoder's IMFTransform::GetOutputAvailableType method. The default encoding bit rate is set at 256 kbps for stereo and 192 kbps for mono. The following table shows the relation between encoding bit rate and MF_MT_AUDIO_AVG_BYTES_PER_SECOND. To specify the encoding bit rate, set the MF_MT_AUDIO_AVG_BYTES_PER_SECOND attribute in the output type. The size of each output buffer depends on the bit rate and the sample rate. The duration is equivalent to the duration of 1536 PCM samples at the current sampling rate (32 msec) at 48 kHz sample rate, 34.83 msec at 44.1 kHz, and 48 msec at 32 kHz). The encoder caches input samples until it has enough for 1536 audio samples per channel at which point the encoder outputs one AC-3 frame.Įach output buffer contains one raw AC-3 frame. The size of each input buffer must be a multiple of the block alignment. ![]() However, each input buffer to the encoder may contain any number of PCM samples. RemarksĮach Dolby AC-3 audio frame contains 1536 audio samples per channel. The encoder does not support sample-rate conversion or stereo/mono conversion. If set, the value must be identical to MF_MT_AUDIO_BITS_PER_SAMPLE. Number of valid bits of audio data in each audio sample. If set, the value must match the output type. Must equal block alignment × samples per second. MFAudioFormat_Float: Number of channels × 4.īit rate of the encoded AC3 stream, in bytes per second.MFAudioFormat_PCM: Number of channels × 2.The value must be 16 if the subtype is MFAudioFormat_PCM, or 32 if the subtype is MFAudioFormat_Float. Must be MFAudioFormat_PCM or MFAudioFormat_Float. The following table lists the required and optional attributes for the input media type. If the optional attributes are not set, the encoder adds them to the media type after the type is set. If this attribute is not set, the encoder uses a default bit rate, as described in Remarks. If set, the value must be 0x3 for stereo (front left and right channels) or 0x4 for mono (front center channel).īit rate of the encoded AC-3 stream, in bytes per second. Specifies the assignment of audio channels to speaker positions. The following table lists the required and optional attributes for the output media type. The output type must be set first, before the input type. ![]() The class identifier (CLSID) of the Dolby audio encoder is CLSID_CMSDolbyDigitalEncMFT, defined in the header file wmcodecdsp.h. For versions of Windows prior to Windows 8, the Microsoft implementation of the Dolby Digital technology is restricted under terms of the Dolby Digital licensing program to use by Microsoft applications.įor more information about Dolby Digital audio, refer to Advanced Television Systems Committee (ATSC) document Digital Audio Compression Standard (AC-3, E-AC-3) Revision B. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |