H.264 GOP structure question

Hi,

We are seeing an unexpected behavior in the Intel Media SDK H.264 encoded bit-stream (hardware version) and looking for further clarification for the same. The details are as below.

We noticed that when GopOptFlag is set to MFX_GOP_STRICT, the GOP pattern generated by H.264 encoder is like this: I_DRBBPBBPBBPBBP…

Here, the ‘B’ frames which are present immediately after the I_DR frame, come before the I_DR frame in the display order. Though, this pattern is technically correct, but we were expecting it to be in the pattern I_DRPBBPBBPBBPBBP……where any frame after the I_DR frame is displayed only after the I_DR frame.

Could you please let us know how can we get the GOP pattern I_DRPBBPBBPBBPBBP… when GopOptFlag is set to MFX_GOP_STRICT?

This behavior is reproducible in the sample application available in the SDK.

Additional details below:

Encoder Configuration

widthxheight: 1920x1080

bitrate: 4300 kbps

targetUsage: MFX_TARGETUSAGE_1

CodecLevel : MFX_LEVEL_AVC_4

CodecProfile: MFX_PROFILE_AVC_HIGH

GopPicSize : 60

GopOptFlag: MFX_GOP_STRICT

IdrInterval : 3

GopRefDist: 3

LookAheadDepth: 60

RateControlMethod: MFX_RATECONTROL_LA

I/O Pattern: MFX_IOPATTERN_IN_SYSTEM_MEMORY

SDK version        : MediaServerStudioEssentials2015R6

OS                       : Centos 7.1

Kernel version   : 3.10.0-229.1.2.39163.MSSr4.el7.centos.x86_64

Processor           : Intel(R) Core(TM) i7-4770R

Regards,

Prashanth Dixit