As there's no real control over the latency of the hardware decoder in 3.0beta2, I've switched out video conf application to a combination of hardware encoding, software decoding.
This gave rise to a new issue : the MFXVideoDECODE_QueryIOSurf function, called by the decoder (software) to decode the incoming stream (hardware) returns an insufficient number of buffers, causing the application to hang, looking for a free buffer to use.
Namely, it returns 1 buffer, when testing has shown that 9 are required for it to work properly (with much greater latency than with the software encoder, for some reason !)
in short, only this combination of hardware encoder and software decoder seems to have this issue (all settings are for lowest possible latency). Following is the code for the decoder.
Please inform me what else is needed to identify the issue (full source ? a recorded stream ?).
memset (&m_DecodedVideoParameters,0,sizeof (m_DecodedVideoParameters));
Status=MFXVideoDECODE_DecodeHeader (m_DecodingSession, m_InputBitStream,&m_DecodedVideoParameters);
m_DecodedVideoParameters.IOPattern = MFX_IOPATTERN_OUT_SYSTEM_MEMORY;
m_DecodedVideoParameters.mfx.DecodedOrder = 0;
if (CheckError (Status,L"MFXVideoDECODE_Init")) return;
// initialize the frames
if (CheckError (Status,L"MFXVideoDECODE_QueryIOSurf")) return;