I recently got it into my head to compare the various popular video codecs in an effort to better understand how av1 works and looks compared to x264 and x265. I also had ideas of using a intel video card to compress a home video security setup, and what levels of compression I would need to get good results.

The Setup
I used the 4k 6.3gb blender project, tears of steel as a source. I downscaled the video to 1080p using all three codecs, and then attempted to compare the results using various crf levels.

To compare results I used imgsli, FFMetrics, and my own picture viewer to try and see what the differences are.

The Results

crf	av1 KB	x265 KB	x264 KB
18	419,261	632,079	685,217 – x246 visually lossless
21	352,337	390,358 – x265 visually lossless	411,439
24	301,517 – av1 VAMF visually lossless	250,426	263,524 – x264 good enough
27	245,685	165,079 – x265 good enough	176,919
30	205,008	110,062	122,458
33	168,192	73,528	86,899
36	139,379 – av1 My visually lossless	48,516	63,214
39	116,096	31,670	47,161
42	97,365 – av1 my good enough	20,636	35,801
45	81,805	13,598	27,484
48	69,044	9,726	20,823
51	58,316	8,586 – worst possible	16,120 – worst possible
54	48,681	-	-
57	39,113	-	-
60	29,062	-	-
63	16,533 – worst possible	-	-

Here is av1 rcf 36 vs crf 24.

I go into more detail with the hows and whys of my choices, in my journal-style blog post, as well as how i came to these conclusions, But in essence, if you want to lose practically no visual information, crf24 through 36 for av1, crf 21 for x265, and crf 18 for x264 will do the job.

If you are low on space, using my ‘good enough’ choices will get you practically the same visual results while using less space, depending on the codec.