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Aspect ratios and H.264

This is a simple overview and a list of different aspect ratios that are 16:9, and some notes on encoding them with H.264.

H.264

The best results for H.264 encoding comes from using 16×16 blocks. This should allow the encoder to do a much better task at encoding. However, you don’t need to. Since you are starting out with a 16:9 resolution (likely 1920×1080 or 1280×720 (ie: 1080p and 720p)), there are not many which provide a width which is divisible by 16.

For my tests, I didn’t actually take this into account, and simply used my original HDV resolution (1440×1080 really, but I wanted to convert it to square pixels) .

In addition, I’ve found very few good encoders for H.264 which are, to me, easy to use. The one I have been using is StaxRip, since it has an excellent walkthrough from start to finish, although contains some issues; it can’t do anamorphic video, which HDV uses. Instead, square pixels are the name of the game. Also, when creating a queue (as internet video is prone to be in at least low and high quality) it sometimes goes odd. The audio encoding part of it also seems a bit unwieldy with very little information being available to change the AAC audio encoding. But it works fine still!

Recommended resolutions

If you are not cropping a 1920×1080 image, then the maximum resolution you’d really want to put on the internet is around 50% of the original, being 960×540. For medium (and very acceptable) size, I chose to half it again to 480×270. Then, for a tiny size, half again is 256×144.

Out of these, only 256×144 is able to make full use of H.264’s 16×16 encoding, but this didn’t worry me. To get the best encoding however, choosing a suitable scale from the tables below with both height and width in italics would be a good idea – then using around half, and around a quarter sizes of this initial resolution to produce lower quality versions.

For a better quality “High” – perhaps for release onto TV sets – scaling down 1920×1080 to 1280×720 (which is 66.67% of the size) is a good idea, and is also able to take advantage of 16×16 encoding. This is 720p scale.

For other resolutions then 16:9, try the aspect ratio calculator to find them.

1920×1080 resolutions

To find a perfect lower resolution here is a list of them. The bolded entries are ones in roughly 10% steps of the original size (so 90%, 80% etc. of the original size). The Italic numbers are divisible by 16, which of course means all the heights are.

Width Height % of original
16 9 0.83
32 18 1.67
48 27 2.5
64 36 3.33
80 45 4.17
96 54 5
112 63 5.83
128 72 6.67
144 81 7.5
160 90 8.33
176 99 9.17
192 108 10
208 117 10.83
224 126 11.67
240 135 12.5
256 144 13.33
272 153 14.17
288 162 15
304 171 15.83
320 180 16.67
336 189 17.5
352 198 18.33
368 207 19.17
384 216 20
400 225 20.83
416 234 21.67
432 243 22.5
448 252 23.33
464 261 24.17
480 270 25
496 279 25.83
512 288 26.67
528 297 27.5
544 306 28.33
560 315 29.17
576 324 30
592 333 30.83
608 342 31.67
624 351 32.5
640 360 33.33
656 369 34.17
672 378 35
688 387 35.83
704 396 36.67
720 405 37.5
736 414 38.33
752 423 39.17
768 432 40
784 441 40.83
800 450 41.67
816 459 42.5
832 468 43.33
848 477 44.17
864 486 45
880 495 45.83
896 504 46.67
912 513 47.5
928 522 48.33
944 531 49.17
960 540 50
976 549 50.83
992 558 51.67
1008 567 52.5
1024 576 53.33
1040 585 54.17
1056 594 55
1072 603 55.83
1088 612 56.67
1104 621 57.5
1120 630 58.33
1136 639 59.17
1152 648 60
1168 657 60.83
1184 666 61.67
1200 675 62.5
1216 684 63.33
1232 693 64.17
1248 702 65
1264 711 65.83
1280 720 66.67
1296 729 67.5
1312 738 68.33
1328 747 69.17
1344 756 70
1360 765 70.83
1376 774 71.67
1392 783 72.5
1408 792 73.33
1424 801 74.17
1440 810 75
1456 819 75.83
1472 828 76.67
1488 837 77.5
1504 846 78.33
1520 855 79.17
1536 864 80
1552 873 80.83
1568 882 81.67
1584 891 82.5
1600 900 83.33
1616 909 84.17
1632 918 85
1648 927 85.83
1664 936 86.67
1680 945 87.5
1696 954 88.33
1712 963 89.17
1728 972 90
1744 981 90.83
1760 990 91.67
1776 999 92.5
1792 1008 93.33
1808 1017 94.17
1824 1026 95
1840 1035 95.83
1856 1044 96.67
1872 1053 97.5
1888 1062 98.33
1904 1071 99.17
1920 1080 100

1280×720 resolutions

And here is 1280×720 resolutions, with the same key:

Width Height % of original
16 9 1.25
32 18 2.5
48 27 3.75
64 36 5
80 45 6.25
96 54 7.5
112 63 8.75
128 72 10
144 81 11.25
160 90 12.5
176 99 13.75
192 108 15
208 117 16.25
224 126 17.5
240 135 18.75
256 144 20
272 153 21.25
288 162 22.5
304 171 23.75
320 180 25
336 189 26.25
352 198 27.5
368 207 28.75
384 216 30
400 225 31.25
416 234 32.5
432 243 33.75
448 252 35
464 261 36.25
480 270 37.5
496 279 38.75
512 288 40
528 297 41.25
544 306 42.5
560 315 43.75
576 324 45
592 333 46.25
608 342 47.5
624 351 48.75
640 360 50
656 369 51.25
672 378 52.5
688 387 53.75
704 396 55
720 405 56.25
736 414 57.5
752 423 58.75
768 432 60
784 441 61.25
800 450 62.5
816 459 63.75
832 468 65
848 477 66.25
864 486 67.5
880 495 68.75
896 504 70
912 513 71.25
928 522 72.5
944 531 73.75
960 540 75
976 549 76.25
992 558 77.5
1008 567 78.75
1024 576 80
1040 585 81.25
1056 594 82.5
1072 603 83.75
1088 612 85
1104 621 86.25
1120 630 87.5
1136 639 88.75
1152 648 90
1168 657 91.25
1184 666 92.5
1200 675 93.75
1216 684 95
1232 693 96.25
1248 702 97.5
1264 711 98.75
1280 720 100

Other resolutions

You can calculate whatever resolutions you like on my aspect ratio calculator.

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