low ssim value when decoding hhi_burst_long.bits. 
random issue(test 5 times, this issue only arise 1 time), the ssim is:
e.g.
filename  Y SSIM extreme Y SSIM average U SSIM extreme U SSIM average V SSIM extreme V SSIM
hhi_burst_long.bits 0.239132 0.368341 0.720362 0.813650 0.785594 0.86527

1. Testing Env:
========================================================================
Libva:                  (staging)35e70cb9b9c77dfb99fb370e319ed501f0c31b17
Libva_intel_driver:     (staging)fbbe401aa28a0b3859d587ef08f0df15a2f7c8f2
Gstreamer10:            (1.0)4e880d4d1e151ea64f83c28b5c3e1bbc06c57903
Gst_plugins_base10:     (1.0)2dd3f028c1e6dea799d7496639f53220818b20b1
Gst_plugins_good10:     (1.0)643d425f51f81b56deec16c01162637546708ee5
Gst_plugins_bad10:      (1.0)0587ab41b4f9979e9cfc11011ed5c970569ee3d3
Gst_plugins_ugly10:     (1.0)c7c911b8320576429e4a4234a1e29ec7436e6814
Gst_plugins_vaapi10:    (master)f0d3d9cd3c2fa852e71198184336b31259762a25
Gstreamer010:           (0.10)76fc67b18c38e7f6c9cfacc4e4d0ed11d3b2c548
Gst_plugins_base010:    (0.10)1e1e6eaf3f0dd11f6618154d9739cbe3e007d206
Gst_plugins_good010:    (0.10)5af6f5bfb6c3619a9ccc3b1681579aeb90e8b89a
Gst_plugins_bad010:     (0.10)cef47d85294a0dca38631f938b81a3f0dd6891bd
Gst_plugins_ugly010:    (0.10)5ddd97ff27ffeb03298be3a02ed18e8c2674d365
Gst_plugins_vaapi010:   (0.4)90713fdc442f27b4ea449b92660a294f7796f83e

2. Testing Steps:
========================================================================
    1.run command "gst-launch-1.0 filesrc location=/root/media_tools/decoder/bitstreams/hhi_burst_long.bits '!' mpegvideoparse '!' vaapidecode '!' vaapisink sync=false"
	2.run command "/root/media_tools/decoder/video/decoder/mpeg2decode -b hhi_burst_long.bits -f -r -o0 hhi_burst_long.bits%d"
	3.judge the YUV file that create by above command to get ssim value.
	
3. Bisect Information:
it's intel driver's issue, git bisect information is:
fbbe401aa28a0b3859d587ef08f0df15a2f7c8f2 is the first bad commit
commit fbbe401aa28a0b3859d587ef08f0df15a2f7c8f2
Author: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
Date:   Wed May 28 15:02:41 2014 -0600

    Fix the segfault while encoding multiple slice per frame.
    Zero initialize the packed raw data index array and
    packed slice header index array during each preallocation.
    Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
    Reviewed-by: Zhao, Yakui <yakui.zhao@intel.com>

3. Frequency of Occurence:
========================================================================
20%