设置AAC解码器输入类型始终失败（UWP）

Question

我正在尝试在clsid_msaacdecmft对象的实例上设置输入类型，但是它总是失败 针对媒体类型指定的数据无效，不一致或不受此对象的支持。

基于Microsoft文档，我在尝试将其设置为输入之前设置了强制性值：

    ComPtr<IUnknown> pUnknown = nullptr;
    HRESULT hResult = CoCreateInstance(CLSID_MSAACDecMFT, nullptr, CLSCTX_INPROC_SERVER, IID_IUnknown, &pUnknown);
    if (S_OK != hResult) {
        LogError("Failed to create AAC decoder");
        return false;
    }

    hResult = pUnknown->QueryInterface(IID_PPV_ARGS(&mAudioDecoder));
    if (hResult != S_OK) {
        LogError("Failed to create AAC decoder");
        return false;
    }

    ComPtr<IMFMediaType> pInputMediaType = nullptr;
    hResult = MFCreateMediaType(&pInputMediaType);
    if (S_OK != hResult) {
        return false;
    }

    pInputMediaType->SetGUID(MF_MT_MAJOR_TYPE, MFMediaType_Audio);
    pInputMediaType->SetGUID(MF_MT_SUBTYPE, MFAudioFormat_AAC);

    pInputMediaType->SetUINT32(MF_MT_AUDIO_BITS_PER_SAMPLE, 16);
    pInputMediaType->SetUINT32(MF_MT_AUDIO_SAMPLES_PER_SECOND, 48000);
    pInputMediaType->SetUINT32(MF_MT_AUDIO_NUM_CHANNELS, 2);

任何人都可以告诉我为什么失败？

非常感谢 彼得

Answer 1

好吧，这很痛苦！误读文档，还有一个其他字段要设置，mf_mt_user_data字段。经过大量的反复错误，我明白了：

    hResult = MFCreateMediaType(&pInputMediaType);
    if (S_OK != hResult) {
        return false;
    }

    pInputMediaType->SetGUID(MF_MT_MAJOR_TYPE, MFMediaType_Audio);
    pInputMediaType->SetGUID(MF_MT_SUBTYPE, MFAudioFormat_AAC);

    std::shared_ptr<AudioMp4Track> audioTrack = mDemuxer->getAudioTrack();

    pInputMediaType->SetUINT32(MF_MT_AAC_PAYLOAD_TYPE, 0);
    pInputMediaType->SetUINT32(MF_MT_AUDIO_SAMPLES_PER_SECOND, audioTrack->getSampleRate());
    pInputMediaType->SetUINT32(MF_MT_AUDIO_NUM_CHANNELS, audioTrack->getChannelCount());

    // This is the desired output bits, why it goes into input, I do not know.
    pInputMediaType->SetUINT32(MF_MT_AUDIO_BITS_PER_SAMPLE, 32);

    // This 14 byte array consists of the HEAACWAVEINFO struct members after WaveFormatEx plus a 2 byte config header
    // Config (from https://wiki.multimedia.cx/index.php/MPEG-4_Audio):
    // Type (5 bits)
    // Sample Rate Index (4 bits)
    // Channel Map Index (4 bits)
    // Reserved and 0 (3 bits)
    // 2 bytes in total
    // 00001 0011 0010 000 0x0990
    uint8_t config[] = { 0x00, 0x00, 0x2a, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x11, 0x90 };

如何设置MF_MF_USER_DATA不太清楚，您无需创建waveformatex object objoct waveformatex这就是您只需要在介质类型上设置斑点，代表波格格式结构以后的相关字段。

人们还可能使用的是如何生成输出类型...文件仅表示有三个强制性字段：数字通道，位和样本率。这对我不起作用，但是我通过可能的输出类型的列表进行了迭代，并且只要有浮点输出类型，将其采用并使用了：

    ComPtr<IMFMediaType> pOutputType = nullptr;
    hResult = MFCreateMediaType(&pOutputType);
    if (S_OK != hResult) {
        return false;
    }

    GUID guidSubType;
    for (int i = 0; i < 10; ++i) {

        ComPtr<IMFMediaType> pTempOutputType = nullptr;
        hResult = MFCreateMediaType(&pTempOutputType);
        if (S_OK != hResult) {
            return false;
        }

        hResult = mAudioDecoder->GetOutputAvailableType(0, i, &pTempOutputType);
        if (hResult == MF_E_NO_MORE_TYPES) {
            break;
        }

        hResult = pTempOutputType->GetGUID(MF_MT_SUBTYPE, &guidSubType);
        if (S_OK != hResult) {
            LogError("oh no");
            continue;
        }

        if (guidSubType == MFAudioFormat_Float) {
            pTempOutputType->CopyAllItems(pOutputType.Get());
            break;
        }
    }

    uint32_t floatOutputBits = 0;
    pOutputType->GetUINT32(MF_MT_AUDIO_BITS_PER_SAMPLE, &floatOutputBits);
    if (floatOutputBits != 32) {
        LogError("No float output type for decoder");
        return false;
    }

    hResult = mAudioDecoder->SetOutputType(0, pOutputType.Get(), 0);
    if (S_OK != hResult) {
        LogError("Couldn't set output type of audio decoder.");
        return false;
    }