Unexpected MFX_ERR_NOT_ENOUGH_BUFFER

[koby_s_]

Hi

I am trying to encode H264 stream. Sometimes, m_mfxSession->SyncOperation return MFX_ERR_NOT_ENOUGH_BUFFER.
I allocating mfxBitstream buffers according the the value in mfxVideoParam.mfx.BufferSizeInKB * 1000.
Trying to increase the buffer (up to 10MB !) doesn't help and SyncOperation keeps on returning MFX_ERR_NOT_ENOUGH_BUFFER
I attached a code snippet that waits for the bitstream

mfxStatus intel_h264_encoder::PutBS()
{
	mfxStatus	sts				= MFX_ERR_NONE;
	ExtendedBS *pBitstreamEx	= m_BSPool.front();
	
	sts = m_mfxSession.SyncOperation(pBitstreamEx->Syncp, MSDK_WAIT_INTERVAL);

	int i = 0;
	while (sts == MFX_ERR_NOT_ENOUGH_BUFFER)
	{
		LOG << "intel_h264_encoder::PutBS - sync op failed due to NOT ENOUGH BUFFER, extending buffer. #i=" << i++ << " profile=" << m_profile.profile_name;
		mfxStatus allocateBufferSts = AllocateSufficientBuffer(&pBitstreamEx->Bitstream);
		if (allocateBufferSts == MFX_ERR_NONE)
		{
			LOG << "intel_h264_encoder::PutBS - buffer extended, trying to sync again #i=" << i << " profile=" << m_profile.profile_name;
			sts = m_mfxSession.SyncOperation(pBitstreamEx->Syncp, MSDK_WAIT_INTERVAL);
			
			if (sts == MFX_ERR_NONE)
				LOG << "intel_h264_encoder::PutBS - sync op OK after buffer extension" << " profile=" << m_profile.profile_name;
		}
		else if (allocateBufferSts == MFX_ERR_MEMORY_ALLOC)	//
		{
			LOG << "intel_h264_encoder::PutBS - buffer extended to maximum=" << pBitstreamEx->Bitstream.MaxLength << ", GOING TO FAIL #i=" << i << " profile=" << m_profile.profile_name;
			// set original error code
			sts = MFX_ERR_NOT_ENOUGH_BUFFER;
			break;
		}
	}


	if (sts < MFX_ERR_NONE)
	{
		LOG << "intel_h264_encoder::PutBS - sync op failed. sts=" << sts << " profile=" << m_profile.profile_name;
		pBitstreamEx->Bitstream.DataLength = 0;
		pBitstreamEx->Bitstream.DataOffset = 0;

		m_BSPool.pop_front();
		m_pBSStore->Release(pBitstreamEx);

		return sts;
	}

	// don't send samples if draining the encoder
	if (m_run)
	{
		m_encoded_frames++;

		int64_t pts = pBitstreamEx->Bitstream.TimeStamp;
		int64_t dts = pBitstreamEx->Bitstream.DecodeTimeStamp;

		bool b = compressed_frame_ready(pBitstreamEx->Bitstream.Data, pts, dts);
	}

	pBitstreamEx->Bitstream.DataLength = 0;
	pBitstreamEx->Bitstream.DataOffset = 0;

	m_BSPool.pop_front();
	m_pBSStore->Release(pBitstreamEx);

	return sts;
} //

My question are:
why SyncOperation return NOT_ENOUGH_BUFFER error?
Should I increase the allocated buffer size (double it to BufferSizeInKB * 2 * 1000 maybe )  ?
Can I increase the buffer once I got a valid sync point but SyncOperation fail with NOT_ENOUGH_BUFFER (like I do in the above code)
How should I recover from this situation?
If i will not perform SyncOperation on that SyncPoint, all the subsequent calls will fail with MFX_ERR_ABORT
It seems that the only solution is to reset the encoder.
Any help will be appreciated!

Thanks
Koby