CODEWITHSUNDEEP
c++winapiencodingms-media-foundation
Ove
Ove

Reputation: 6317

Get encoder name from SinkWriter or ICodecAPI or IMFTransform

I'm using the SinkWriter in order to encode video using media foundation.

After I initialize the SinkWriter, I would like to get the underlying encoder it uses, and print out its name, so I can see what encoder it uses. (In my case, the encoder is most probably the H.264 Video Encoder included in MF).

I can get references to the encoder's ICodecAPI and IMFTransform interface (using pSinkWriter->GetServiceForStream), but I don't know how to get the encoder's friendly name using those interfaces.

Does anyone know how to get the encoder's friendly name from the sinkwriter? Or from its ICodecAPI or IMFTransform interface?

Upvotes: 2

Views: 1716

Answers (2)

Rudolfs Bundulis
Rudolfs Bundulis

Reputation: 11934

This is by far an effective solution and i am not 100% sure it works, but what could be done is:

1) At start-up enumerate all the codecs that could be used (as i understand in this case H264 encoders) and subscribe to setting change event

MFT_REGISTER_TYPE_INFO TransformationOutput = { MFMediaType_Video, MFVideoFormat_H264 };
DWORD nFlags = MFT_ENUM_FLAG_ALL;
UINT32 nCount = 0;
CLSID* pClsids;
MFTEnum( MFT_CATEGORY_VIDEO_ENCODER, nFlags, NULL, &TransformationOutput, NULL, &pClsids, &nCount);
// Ok here we assume nCount is 1 and we got the MS encoder
ICodecAPI *pMsEncoder;
hr = CoCreateInstance(pClsids[0], NULL, CLSCTX_INPROC_SERVER, __uuidof(ICodecAPI), (void**)&pMsEncoder);
// nCodecIds is supposed to be an array of identifiers to distinguish the sender
hr = pMsEncoder->RegisterForEvent(CODECAPI_AVEncVideoOutputFrameRate, (LONG_PTR)&nCodecIds[0]);

2) Not 100% sure if the frame rate setting is also set when the input media type for the stream is set, but anyhow you can try to set the same property on the ICodecAPI you retrieved from the SinkWriter. Then after getting the event you should be able to identify the codec by comparing lParam1 to the value passed. But still this is very poor since it relies on the fact that all the encoders support the event notification and requires unneeded parameter changing if my hypothesis about the event being generated on stream construction is wrong.

Upvotes: 1

Roman Ryltsov
Roman Ryltsov

Reputation: 69632

Having IMFTransform you don't have a friendly name of the encoder.

One of the options you have is to check transform output type and compare to well known GUIDs to identify the encoder, in particular you are going to have a subtype of MFVideoFormat_H264 with H264 Encoder MFT.

Another option is to reach CLSID of the encoder (IMFTransform does not get you it, but you might have it otherwise such as via IMFActivate or querying MFT_TRANSFORM_CLSID_Attribute attribute, or via IPersist* interfaces). Then you could look registry up for a friendly name or enumerate transforms and look your one in that list by comparing CLSID.

Upvotes: 0

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