HEIF(HEVC image)検証#2

下記投稿からの続きです。
HEIF(HEVC image)検証#1 - 記憶は人なり
　

入力画像1の場合

入力画像

解像度

640x13026

画像フォーマット

PNG

内容

スクリーンショット(無地背景に大量のテキスト)

※掲載用画像は縮小しています　
　

検証結果

▶実測値(上記グラフの元データ)を展開

Condition	Mean of Diff	Max of Diff	File Size [bytes]
Original(PNG)	0	0	1,764,638
x265 CRF0	28.5111	37522	1,657,706
x265 CRF1	30.312	37779	1,611,287
x265 CRF2	32.4614	37265	1,564,822
x265 CRF3	34.583	37008	1,516,208
x265 CRF4	36.8105	37008	1,466,835
x265 CRF5	39.2383	37522	1,416,284
x265 CRF6	42.0062	37522	1,366,523
x265 CRF7	44.6273	37779	1,316,402
x265 CRF8	47.8972	38550	1,266,638
x265 CRF9	51.5439	39064	1,220,970
x265 CRF10	55.7566	38550	1,175,902
x265 CRF11	60.4521	37522	1,133,361
x265 CRF12	65.608	37265	1,088,314
x265 CRF13	71.5051	37779	1,034,851
x265 CRF14	77.7895	37779	994,934
x265 CRF15	84.4838	38807	956,914
x265 CRF16	91.6288	38807	919,712
x265 CRF17	98.8311	43176	883,080
x265 CRF18	106.472	42148	846,477
x265 CRF19	116.178	42148	811,474
x265 CRF20	127.305	43433	776,840
x265 CRF21	139.337	39321	743,430
x265 CRF22	151.181	42405	710,246
x265 CRF23	166.98	50886	677,156
x265 CRF24	183.785	52942	645,331
x265 CRF25	202.066	50886	613,536
x265 CRF26	220.967	57054	582,174
x265 CRF27	246.395	57825	551,892
x265 CRF28	275.902	48059	522,023
x265 CRF29	311.738	52428	492,669
x265 CRF30	350.259	59110	464,264
x265 CRF31	384.335	52171	435,752
x265 CRF32	436.35	51400	408,653
x265 CRF33	481.022	56026	382,148
x265 CRF34	540.264	59367	357,015
x265 CRF35	598.445	63222	332,205
x265 CRF36	668.376	65535	309,036
x265 CRF37	758.536	65535	286,473
x265 CRF38	855.405	65535	265,029
x265 CRF39	945.428	65535	244,879
x265 CRF40	1057	65535	225,410
x265 CRF41	1189.95	65535	207,728
x265 CRF42	1293.19	65535	190,809
x265 CRF43	1440.97	65535	175,364
x265 CRF44	1579.07	65535	161,411
x265 CRF45	1757.48	65535	149,145
x265 CRF46	1896.11	65535	139,476
x265 CRF47	2023.92	65535	131,317
x265 CRF48	2174.44	65535	123,875
x265 CRF49	2277.56	65535	117,236
x265 CRF50	2442.08	65535	111,858
x265 CRF51	2533.28	65535	108,081
JPEG Quality1	1725	65535	214,927
JPEG Quality2	1723.81	65535	215,171
JPEG Quality3	1667.85	65535	231,044
JPEG Quality4	1906.39	65021	259,034
JPEG Quality5	2693.97	62965	287,394
JPEG Quality6	1385.95	62194	320,788
JPEG Quality7	1284.31	61423	345,487
JPEG Quality8	1571.04	61166	368,519
JPEG Quality9	2048.19	61166	390,917
JPEG Quality10	1132.21	61166	413,727
JPEG Quality11	1082.74	61423	433,921
JPEG Quality12	1214.14	61423	452,020
JPEG Quality13	1011.97	61166	471,950
JPEG Quality14	975.123	61423	488,288
JPEG Quality15	1117.88	61423	505,540
JPEG Quality16	1263.88	61166	522,091
JPEG Quality17	896.956	61166	539,865
JPEG Quality18	1033.75	61166	555,351
JPEG Quality19	1012.24	61166	568,887
JPEG Quality20	1165.96	59624	582,030
JPEG Quality21	800.373	58853	598,479
JPEG Quality22	951.121	58082	611,033
JPEG Quality23	762.708	60652	624,869
JPEG Quality24	747.904	61166	638,492
JPEG Quality25	733.436	54227	650,774
JPEG Quality26	717.498	57054	663,303
JPEG Quality27	703.831	54227	675,704
JPEG Quality28	860.647	56026	687,626
JPEG Quality29	848.666	55769	698,104
JPEG Quality30	666.51	57568	711,201
JPEG Quality31	654.925	53713	720,895
JPEG Quality32	645.039	55255	732,895
JPEG Quality33	804.493	55769	743,461
JPEG Quality34	795.233	54741	752,022
JPEG Quality35	784.107	53456	765,348
JPEG Quality36	774.363	50629	776,530
JPEG Quality37	767.47	61166	783,449
JPEG Quality38	755.736	61166	795,690
JPEG Quality39	577.111	61166	805,420
JPEG Quality40	570.287	61166	811,597
JPEG Quality41	732.503	61166	824,787
JPEG Quality42	728.057	61166	831,055
JPEG Quality43	720.203	61166	839,641
JPEG Quality44	709.522	60395	851,689
JPEG Quality45	704.523	53456	858,282
JPEG Quality46	524.592	51400	870,697
JPEG Quality47	519.148	52428	876,750
JPEG Quality48	513.852	52171	885,274
JPEG Quality49	508.702	47545	897,164
JPEG Quality50	503.482	47288	901,826
JPEG Quality51	498.173	45746	906,727
JPEG Quality52	490.49	48059	917,889
JPEG Quality53	484.56	49601	927,621
JPEG Quality54	478.48	51400	934,627
JPEG Quality55	472.665	50629	943,561
JPEG Quality56	466.026	48573	953,837
JPEG Quality57	459.296	48316	965,395
JPEG Quality58	452.409	47802	976,192
JPEG Quality59	446.03	48059	985,233
JPEG Quality60	439.774	48316	994,306
JPEG Quality61	432.667	48059	1,008,618
JPEG Quality62	425.969	47545	1,018,821
JPEG Quality63	418.052	46517	1,033,513
JPEG Quality64	411.452	46260	1,043,004
JPEG Quality65	575.509	45232	1,056,591
JPEG Quality66	567.668	44461	1,068,609
JPEG Quality67	559.797	42919	1,079,294
JPEG Quality68	379.968	43433	1,096,941
JPEG Quality69	372.134	44204	1,110,166
JPEG Quality70	363.226	45232	1,127,882
JPEG Quality71	353.658	45232	1,143,528
JPEG Quality72	345.822	46517	1,156,963
JPEG Quality73	337.438	45489	1,174,547
JPEG Quality74	328.156	46260	1,197,077
JPEG Quality75	321.014	46260	1,206,326
JPEG Quality76	310.263	45746	1,226,671
JPEG Quality77	300.21	39835	1,253,138
JPEG Quality78	290.664	39321	1,275,874
JPEG Quality79	281.512	39835	1,293,918
JPEG Quality80	270.557	41120	1,318,141
JPEG Quality81	259.522	43176	1,347,527
JPEG Quality82	248.947	42662	1,372,201
JPEG Quality83	238.044	42405	1,405,580
JPEG Quality84	226.879	42405	1,433,615
JPEG Quality85	215.555	43176	1,461,757
JPEG Quality86	203.515	40606	1,504,191
JPEG Quality87	191.983	40863	1,533,587
JPEG Quality88	179.436	40606	1,582,069
JPEG Quality89	167.486	40606	1,621,352
JPEG Quality90	143.387	11051	1,741,594
JPEG Quality91	130.921	11822	1,789,982
JPEG Quality92	116.851	8995	1,844,442
JPEG Quality93	103.34	8224	1,925,840
JPEG Quality94	88.7652	6939	2,020,627
JPEG Quality95	74.7486	5140	2,118,407
JPEG Quality96	59.5254	4883	2,233,278
JPEG Quality97	44.7648	3598	2,364,728
JPEG Quality98	28.7318	2827	2,506,576
JPEG Quality99	11.6195	1285	2,709,243
JPEG Quality100	4.48096	1028	2,814,001

▶HEVC CRF値毎に、同じようなファイルサイズとなるJPEG Quality及び同じような差分となるJPEG Qualityを整理した表を展開

パターン	ファイルサイズが近いJPEG	差分の平均が近いJPEG
x265 CRF0	JPEG Quality89	JPEG Quality99
x265 CRF1	JPEG Quality88	JPEG Quality98
x265 CRF2	JPEG Quality87	JPEG Quality98
x265 CRF3	JPEG Quality86	JPEG Quality98
x265 CRF4	JPEG Quality85	JPEG Quality98
x265 CRF5	JPEG Quality83	JPEG Quality98
x265 CRF6	JPEG Quality81	JPEG Quality98
x265 CRF7	JPEG Quality79	JPEG Quality98
x265 CRF8	JPEG Quality77	JPEG Quality97
x265 CRF9	JPEG Quality75	JPEG Quality97
x265 CRF10	JPEG Quality73	JPEG Quality97
x265 CRF11	JPEG Quality70	JPEG Quality96
x265 CRF12	JPEG Quality67	JPEG Quality96
x265 CRF13	JPEG Quality63	JPEG Quality96
x265 CRF14	JPEG Quality60	JPEG Quality95
x265 CRF15	JPEG Quality56	JPEG Quality95
x265 CRF16	JPEG Quality52	JPEG Quality94
x265 CRF17	JPEG Quality47	JPEG Quality94
x265 CRF18	JPEG Quality43	JPEG Quality93
x265 CRF19	JPEG Quality39	JPEG Quality93
x265 CRF20	JPEG Quality36	JPEG Quality92
x265 CRF21	JPEG Quality32	JPEG Quality91
x265 CRF22	JPEG Quality29	JPEG Quality90
x265 CRF23	JPEG Quality27	JPEG Quality90
x265 CRF24	JPEG Quality24	JPEG Quality88
x265 CRF25	JPEG Quality22	JPEG Quality87
x265 CRF26	JPEG Quality20	JPEG Quality85
x265 CRF27	JPEG Quality17	JPEG Quality83
x265 CRF28	JPEG Quality15	JPEG Quality80
x265 CRF29	JPEG Quality14	JPEG Quality76
x265 CRF30	JPEG Quality12	JPEG Quality72
x265 CRF31	JPEG Quality11	JPEG Quality68
x265 CRF32	JPEG Quality9	JPEG Quality61
x265 CRF33	JPEG Quality8	JPEG Quality54
x265 CRF34	JPEG Quality7	JPEG Quality46
x265 CRF35	JPEG Quality6	JPEG Quality39
x265 CRF36	JPEG Quality5	JPEG Quality30
x265 CRF37	JPEG Quality4	JPEG Quality38
x265 CRF38	JPEG Quality4	JPEG Quality29
x265 CRF39	JPEG Quality3	JPEG Quality17
x265 CRF40	JPEG Quality2	JPEG Quality18
x265 CRF41	#N/A	JPEG Quality20
x265 CRF42	#N/A	JPEG Quality7
x265 CRF43	#N/A	JPEG Quality6
x265 CRF44	#N/A	JPEG Quality8
x265 CRF45	#N/A	JPEG Quality1
x265 CRF46	#N/A	JPEG Quality1
x265 CRF47	#N/A	JPEG Quality4
x265 CRF48	#N/A	JPEG Quality9
x265 CRF49	#N/A	JPEG Quality9
x265 CRF50	#N/A	JPEG Quality9
x265 CRF51	#N/A	JPEG Quality9

　

考察

• 順当にHEVCはCRF、JPEGはQualityパラメータに依存して差分の大小が現れるのが確認できる
  • 但し、差分の平均についてはCRF及びQualityパラメータに依存しているが、差分の最大については規則性というか傾向がはっきりしない
• HEVC CRF0の時点でJPEGのQuality89と同程度のファイルサイズでありながら、差分の平均はJPEGのQuality99と同程度の高画質を達成しており、画質・ファイルサイズ共に優れた結果と判断できる
  • 一方で、HEVCはCRF0でもJPEGのQuality100以上に大きい差分が現れている点には留意すべきかもしれない
• 参考までにHEVC CRF0(最高画質・最大ファイルサイズ)/CRF51(最低画質・最小ファイルサイズ)及びJPEG Quality1(最低画質・最小ファイルサイズ)/Quality100(最高画質・最大ファイルサイズ)でエンコードされた画像をピクセル等倍でクロップした画像は以下の通り
  
  
  
  
• 参考までに差分画像を正規化*1し、上記と同条件でクロップした画像は以下の通り。
  
  
  
  

続きます…。
HEIF(HEVC image)検証#3 - 記憶は人なり

*1:正規化しないと一見して真っ黒な画像にしか見えないため、どこに差分が発生しているのか可視化しやすくするために正規化を行なった。