H.264 320x240 encode produces a duplicate frame

[edwarddavidbaker]

Hi all, Recently I've been investigating an issue on GLK where H.264 encode at 320x240 produces a duplicate frame. Specifically VAProfileH264ConstrainedBaseline VAEntrypointEncSlice CBR with the quality level set to 7 and a target bitrate of 400,000 bps.

/usr/local/libexec/chrome-binary-tests/video_encode_accelerator_tests \
    --codec=h264 \
    --bitrate=400000 \
    --output_bitstream  \
    --gtest_filter=*FlushAtEndOfStream football_320x240.yv12.yuv

The issue is that all of the macroblocks for the 3rd picture are skip, which results in a duplicate picture 2. If I set the quality level to the default (4), the issue is not present. I searched for all variables which the quality level indexes into. I then trimmed the possibilities to every list where the values in 4 and 7 do not match. Then for each variable I set the value at preset 7 to the value in preset 4. The result from each test is in the "Fix?" column.

                                                  Fix?  Col 0  Col 1  Col 2  Col 3  Col 4  Col 5   Col 6   Col 7
gen9_avc_all_fractional[PRESET_NUM]                 No      0      3      3      3      3      3       3       0
gen9_avc_b_me_method[PRESET_NUM]                    No      0      4      4      6      6      6       6       4
gen9_avc_b_search_x[PRESET_NUM]                     No      0     32     32     32     32      32      32     24
gen9_avc_b_search_y[PRESET_NUM]                     No      0     32     32     32     32      32      32     24
gen9_avc_enable_adaptive_search[PRESET_NUM]         No      0      1      1      1      1      1       0       0
gen9_avc_enable_adaptive_tx_decision[PRESET_NUM]    No      0      1      1      1      1      1       1       0
gen9_avc_kernel_mode[PRESET_NUM]                    No      1      0      0      1      1      1       1       2
gen9_avc_max_b_ref_id0[PRESET_NUM]                  No      0      3      3      1      1      1       0       0
gen9_avc_max_ftq_based_skip[PRESET_NUM]             No      0      3      3      3      3      3       3       0
gen9_avc_max_len_sp[PRESET_NUM]                     No      0     57     57     25     25     25      16       9
gen9_avc_max_ref_id0_progressive_4k[PRESET_NUM]     No      0      3      3      2      2      2       0       0
gen9_avc_max_ref_id0[PRESET_NUM]                    No      0      7      5      2      2      2       0       0
gen9_avc_max_ref_id1[PRESET_NUM]                    No      0      1      1      1      1      1       0       0
gen9_avc_p_me_method[PRESET_NUM]                    No      0      4      4      6      6      6       6       4
gen9_avc_search_x[PRESET_NUM]                      Yes      0     48     48     48     48     48      48      28
gen9_avc_search_y[PRESET_NUM]                      Yes      0     40     40     40     40     40      40      28
gen9_avc_super_combine_dist[PRESET_NUM]             No      0      1      1      5      5      5       9       9
gen9_avc_ultra_hme[PRESET_NUM]                      No      0      1      1      1      1      1       1       0

Forcing gen9_avc_search x and y for preset 7 to the values in preset 4 seems to fix this issue.

diff --git a/src/i965_avc_const_def.c b/src/i965_avc_const_def.c
index 34d0335..f68d6d6 100644
--- a/src/i965_avc_const_def.c
+++ b/src/i965_avc_const_def.c
@@ -1022,10 +1022,10 @@ const unsigned int gen9_avc_hme_combine_len[PRESET_NUM] = {
 };
 
 const unsigned int gen9_avc_search_x[PRESET_NUM] = {
-    0, 48, 48, 48, 48, 48, 48, 28
+    0, 48, 48, 48, 48, 48, 48, 48
 };
 const unsigned int gen9_avc_search_y[PRESET_NUM] = {
-    0, 40, 40, 40, 40, 40, 40, 28
+    0, 40, 40, 40, 40, 40, 40, 40
 };

[edwarddavidbaker]

I'm not sure if the above change is reasonable though. iHD uses the same list of values for SearchX and SearchY.

• https://github.com/intel/media-driver/blob/master/media_driver/agnostic/gen9_bxt/codec/hal/codechal_encode_avc_g9_bxt.cpp#L2352
• https://github.com/intel/media-driver/blob/master/media_driver/agnostic/common/codec/hal/codechal_encode_avc.cpp#L70