Microsoft Media Foundation - 解码 h264 样本

Question

我使用 Microsoft Media Foundation 示例（即 MFCaptureToFile）从网络摄像头捕获 H264 帧并将其写入文件。

我正在尝试使用 IMFTransform 解码捕获的帧并获取下划线图像（YUV、BMP 等）。

但是，ProcessInput 方法永远不会返回 MF_E_NOTACCEPTING，而 ProcessOutput 方法始终返回 MF_E_TRANSFORM_NEED_MORE_INPUT。

我基本上读取每一帧并对其调用 ProcessInput。

有什么想法吗？有人可以修改 MFCaptureToFile 示例以向我展示它是如何完成的吗？我在 CCapture::OnReadSample 下进行所有处理。

任何帮助将不胜感激！

伊多

Answer 1

我已经能够成功使用 MF H264 解码器 MFT 将 .mp4 文件中存储的帧解码为原始 YUV。完整的代码示例可在此处获得。

关键部分是创建 H264 解码器 MFT，然后为其提供示例。我已经包含了下面这两位的代码片段。

// Create H.264 decoder.
CHECK_HR(CoCreateInstance(CLSID_CMSH264DecoderMFT, NULL, CLSCTX_INPROC_SERVER,
    IID_IUnknown, (void**)&spDecTransformUnk), "Failed to create H264 decoder MFT.\n");

CHECK_HR(spDecTransformUnk->QueryInterface(IID_PPV_ARGS(&pDecoderTransform)), "Failed to get IMFTransform interface from H264 decoder MFT object.\n");

MFCreateMediaType(&pDecInputMediaType);
CHECK_HR(pFileVideoMediaType->CopyAllItems(pDecInputMediaType), "Error copying media type attributes to decoder input media type.\n");
CHECK_HR(pDecoderTransform->SetInputType(0, pDecInputMediaType, 0), "Failed to set input media type on H.264 decoder MFT.\n");

MFCreateMediaType(&pDecOutputMediaType);
pDecOutputMediaType->SetGUID(MF_MT_MAJOR_TYPE, MFMediaType_Video);
pDecOutputMediaType->SetGUID(MF_MT_SUBTYPE, MFVideoFormat_IYUV);
CHECK_HR(MFSetAttributeSize(pDecOutputMediaType, MF_MT_FRAME_SIZE, VIDEO_SAMPLE_WIDTH, VIDEO_SAMPLE_HEIGHT), "Failed to set frame size on H264 MFT out type.\n");
CHECK_HR(MFSetAttributeRatio(pDecOutputMediaType, MF_MT_FRAME_RATE, 30, 1), "Failed to set frame rate on H264 MFT out type.\n");
CHECK_HR(MFSetAttributeRatio(pDecOutputMediaType, MF_MT_PIXEL_ASPECT_RATIO, 1, 1), "Failed to set aspect ratio on H264 MFT out type.\n");
pDecOutputMediaType->SetUINT32(MF_MT_INTERLACE_MODE, 2);

CHECK_HR(pDecoderTransform->SetOutputType(0, pDecOutputMediaType, 0), "Failed to set output media type on H.264 decoder MFT.\n");

CHECK_HR(pDecoderTransform->GetInputStatus(0, &mftStatus), "Failed to get input status from H.264 decoder MFT.\n");
if (MFT_INPUT_STATUS_ACCEPT_DATA != mftStatus) {
    printf("H.264 decoder MFT is not accepting data.\n");
    goto done;
}

CHECK_HR(pDecoderTransform->ProcessMessage(MFT_MESSAGE_COMMAND_FLUSH, NULL), "Failed to process FLUSH command on H.264 decoder MFT.\n");
CHECK_HR(pDecoderTransform->ProcessMessage(MFT_MESSAGE_NOTIFY_BEGIN_STREAMING, NULL), "Failed to process BEGIN_STREAMING command on H.264 decoder MFT.\n");
CHECK_HR(pDecoderTransform->ProcessMessage(MFT_MESSAGE_NOTIFY_START_OF_STREAM, NULL), "Failed to process START_OF_STREAM command on H.264 decoder MFT.\n")

创建解码器后，您将从某处获取编码的 H264 帧，您需要将它们传递到上面创建的 MFT。

    MFCreateSample(&reConstructedVideoSample);
CHECK_HR(MFCreateMemoryBuffer(srcBufLength, &reConstructedBuffer), "Failed to create memory buffer.\n");
CHECK_HR(reConstructedVideoSample->AddBuffer(reConstructedBuffer), "Failed to add buffer to re-constructed sample.\n");
CHECK_HR(reConstructedVideoSample->SetSampleTime(llVideoTimeStamp), "Error setting the recon video sample time.\n");
CHECK_HR(reConstructedVideoSample->SetSampleDuration(llSampleDuration), "Error setting recon video sample duration.\n");

byte *reconByteBuffer;
DWORD reconBuffCurrLen = 0;
DWORD reconBuffMaxLen = 0;
CHECK_HR(reConstructedBuffer->Lock(&reconByteBuffer, &reconBuffMaxLen, &reconBuffCurrLen), "Error locking recon buffer.\n");
memcpy(reconByteBuffer, srcByteBuffer, srcBuffCurrLen);
CHECK_HR(reConstructedBuffer->Unlock(), "Error unlocking recon buffer.\n");
reConstructedBuffer->SetCurrentLength(srcBuffCurrLen);

CHECK_HR(srcBuf->Unlock(), "Error unlocking source buffer.\n");

CHECK_HR(pDecoderTransform->ProcessInput(0, reConstructedVideoSample, 0), "The H264 decoder ProcessInput call failed.\n");

CHECK_HR(pDecoderTransform->GetOutputStatus(&mftOutFlags), "H264 MFT GetOutputStatus failed.\n");

//if (mftOutFlags == MFT_OUTPUT_STATUS_SAMPLE_READY)
//{
    CHECK_HR(pDecoderTransform->GetOutputStreamInfo(0, &StreamInfo), "Failed to get output stream info from H264 MFT.\n");

    while (true)
    {
        CHECK_HR(MFCreateSample(&mftOutSample), "Failed to create MF sample.\n");
        CHECK_HR(MFCreateMemoryBuffer(StreamInfo.cbSize, &pBuffer), "Failed to create memory buffer.\n");
        CHECK_HR(mftOutSample->AddBuffer(pBuffer), "Failed to add sample to buffer.\n");
        outputDataBuffer.dwStreamID = 0;
        outputDataBuffer.dwStatus = 0;
        outputDataBuffer.pEvents = NULL;
        outputDataBuffer.pSample = mftOutSample;

        mftProcessOutput = pDecoderTransform->ProcessOutput(0, 1, &outputDataBuffer, &processOutputStatus);

        if (mftProcessOutput != MF_E_TRANSFORM_NEED_MORE_INPUT)
        {
            // ToDo: These two lines are not right. Need to work out where to get timestamp and duration from the H264 decoder MFT.
            CHECK_HR(outputDataBuffer.pSample->SetSampleTime(llVideoTimeStamp), "Error getting YUV sample time.\n");
            CHECK_HR(outputDataBuffer.pSample->SetSampleDuration(llSampleDuration), "Error getting YUV sample duration.\n");

            IMFMediaBuffer *buf = NULL;
            DWORD bufLength;
            CHECK_HR(mftOutSample->ConvertToContiguousBuffer(&buf), "ConvertToContiguousBuffer failed.\n");
            CHECK_HR(buf->GetCurrentLength(&bufLength), "Get buffer length failed.\n");

            printf("Writing sample %i, sample time %I64d, sample duration %I64d, sample size %i.\n", sampleCount, yuvVideoTimeStamp, yuvSampleDuration, bufLength);

            byte *byteBuffer;
            DWORD buffCurrLen = 0;
            DWORD buffMaxLen = 0;
            buf->Lock(&byteBuffer, &buffMaxLen, &buffCurrLen);
            outputBuffer.write((char *)byteBuffer, bufLength);
            outputBuffer.flush();
        }
        else {
            break;
        }

        mftOutSample->Release();
   }
    

Answer 2

Microsoft H264 Decoder MFT 有点特殊。它内部缓冲大量样本。 （这就是为什么它不能用于实时场景的原因，因为由于内部缓冲，它总是会引入大约一秒的延迟）。 我想你至少必须向它提供完整的 GOP 才能接收一些输出样本。 尝试一下