c++ - 设置 MP3 编码器 mft 输出类型失败

Question

我现在尝试在 Win10 pro Insider 预览版上使用 MP3 编码器 mft，但无法设置输出媒体类型。

下面是我的代码:

// Fill in MPEGLAYER3WAVEFORMAT data   
MPEGLAYER3WAVEFORMAT mp3wfx;
ZeroMemory(&mp3wfx, sizeof(mp3wfx));
mp3wfx.wID = MPEGLAYER3_ID_MPEG;
mp3wfx.fdwFlags = 2; // no padding
mp3wfx.nBlockSize = int16_t(144 * (128000 / 44100)); // bitrate = 128000kbps
mp3wfx.nFramesPerBlock = 1;
mp3wfx.nCodecDelay = 0;
mp3wfx.wfx.wFormatTag = WAVE_FORMAT_MPEGLAYER3;  // MP3 
mp3wfx.wfx.nChannels = 2;
mp3wfx.wfx.nSamplesPerSec = 44100;
mp3wfx.wfx.wBitsPerSample = 16;
mp3wfx.wfx.nBlockAlign = (mp3wfx.wfx.nChannels * mp3wfx.wfx.wBitsPerSample) / 8;
mp3wfx.wfx.nAvgBytesPerSec = mp3wfx.wfx.nSamplesPerSec * mp3wfx.wfx.nBlockAlign;
mp3wfx.wfx.cbSize = sizeof(MPEGLAYER3WAVEFORMAT) - sizeof(WAVEFORMATEX); // 12

LComObject<IMFMediaType> ciOutputType;  // Output media type of the encoder
hr = fpMFCreateMediaType((IMFMediaType**)(ciOutputType.GetAssignablePtrRef()));
WAVEFORMATEX* pWave = (WAVEFORMATEX*)&mp3wfx;
MFInitMediaTypeFromWaveFormatEx(ciOutputType.get(), pWave, sizeof(MPEGLAYER3WAVEFORMAT));
hr = ciEncoder->SetOutputType(0, ciOutputType.get(), 0);

请忽略我对那些 COM 对象/接口(interface)的包装。Mftrace 输出这些

5552,500 05:05:15.03439 CMFPlatExportDetours::MFTEnumEx @ Activate 00 @034CE628, MFT_FRIENDLY_NAME_Attribute=MP3 Encoder ACM Wrapper MFT;MFT_INPUT_TYPES_Attributes=61 75 64 73 00 00 10 00 80 00 00 aa 00 38 9b 71 01 00 00 00 00 00 10 00 80 00 00 aa 00 38 9b 71 ;MFT_TRANSFORM_CLSID_Attribute={11103421-354C-4CCA-A7A3-1AFF9A5B6701};MFT_OUTPUT_TYPES_Attributes=61 75 64 73 00 00 10 00 80 00 00 aa 00 38 9b 71 55 00 00 00 00 00 10 00 80 00 00 aa 00 38 9b 71 ;MF_TRANSFORM_FLAGS_Attribute=1;MF_TRANSFORM_CATEGORY_Attribute=MFT_CATEGORY_AUDIO_ENCODER
5552,500 05:05:15.03616 COle32ExportDetours::CoCreateInstance @ New MFT @03510D20, <NULL>
5552,500 05:05:15.03618 COle32ExportDetours::CoCreateInstance @ Created {11103421-354C-4CCA-A7A3-1AFF9A5B6701} MP3 ACM Wrapper MFT (C:\Windows\System32\mfcore.dll) @03510D20 - traced interfaces: IMFTransform @03510D20, 
5552,500 05:05:15.03681 CMFTransformDetours::SetOutputType @03510D20 Failed MT: MF_MT_AUDIO_AVG_BYTES_PER_SECOND=176400;MF_MT_AUDIO_BLOCK_ALIGNMENT=4;MF_MT_AUDIO_NUM_CHANNELS=2;MF_MT_MAJOR_TYPE=MEDIATYPE_Audio;MF_MT_AUDIO_SAMPLES_PER_SECOND=44100;MF_MT_AUDIO_PREFER_WAVEFORMATEX=1;MF_MT_USER_DATA=01 00 02 00 00 00 20 01 01 00 00 00 ;MF_MT_AUDIO_BITS_PER_SAMPLE=16;MF_MT_SUBTYPE=MFAudioFormat_MP3

感谢帮助

Answer 1

所以它说:

SetOutputType @03510D20 Failed MT: 
MF_MT_MAJOR_TYPE=MEDIATYPE_Audio;
MF_MT_SUBTYPE=MFAudioFormat_MP3; 
MF_MT_AUDIO_PREFER_WAVEFORMATEX=1;
MF_MT_AUDIO_SAMPLES_PER_SECOND=44100;
MF_MT_AUDIO_NUM_CHANNELS=2;
MF_MT_AUDIO_BITS_PER_SAMPLE=16;
MF_MT_AUDIO_AVG_BYTES_PER_SECOND=176400;
MF_MT_AUDIO_BLOCK_ALIGNMENT=4;
MF_MT_USER_DATA=01 00 02 00 00 00 20 01 01 00 00 00 ;

这里有两件重要的事情:

1. MF_MT_AUDIO_AVG_BYTES_PER_SECOND 需要一个正确的值，因为有一个可接受的比特率列表
2. MF_MT_USER_DATA 是媒体类型的附加格式数据；大概是 MPEGLAYER3WAVEFORMAT 值跟在 WAVEFORMATEX 字段之后 - MFT 可能需要某些值，这些值与您提供的值不同。

您采用了要求 MFT 枚举输出媒体类型的正确方法。现在您需要选择最接近的并与您拥有的进行比较，您应该看到使编解码器拒绝您的格式的差异。