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Comparing compression in AV1, x264, and x265

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.

30
30 comments

  • You might want to use a code block instead of bullet points for your table, the way you presented it is unreadable but I found the info on your blog page.

    One of my criteria for video formats is the portability. Like sometimes I might watch something through a web browser which natively supports x264. Yeah x265 provides better compression, and AV1 certainly looks interesting, but they both require the addition of codecs on most of my viewing devices and in some cases that's not possible.

    For most cases I've found that CRF25 with x264 works reasonably well. I tend to download 720p videos to watch on our 1080p TV and don't notice the difference except in very minor situations like rapid motion on a solid-color background (usually only seen on movie studio logo screens). Any sort of animated shows can go even lower without noticeable degradation.

    • I did try to format the table here better. I used code blocks the first time, and it ended up being even uglier. After about four edit attempts i kinda just gave up. Tables don't seem to exist as far as I can tell either.

      Your experience with x264 just about matches up with mine. As long as I don't pixel peep, crf 24 does a pretty great job of conveying the information. It also does a pretty great job of working with just about everything compatibility-wise. I don't expect it to go away any time soon specifically because of that.

      AV1 is super neat in that we can buy hardware accelerated encoding for it for really cheap using the Intel Arc video cards, and can be decoded by their latest CPU generation. It makes for a great choice for something like security camera footage where playback compatibility is good enough (you can play it in a modern pc), hardware encoding works with a 200$ card, and you save a lot of money using the video card instead of buying extra storage space.

      • Tables do exist ! 
        | Tables | do | exist | ! |
|--------|----|-------|---|

      • with a 200$ card, and you save a lot of money using the video card instead of buying extra storage space.

        With $200, you could buy ~12TB worth of HDD(s) instead. You'd need >36TB of video for that to make financial sense and you'd always lose quality.

        Additionally, you'd have to factor in the power it needs to transcode but, with HW accel, it's not quite as much as with CPUs.

  • Feels like certain information is missing. You get very different results both in encoding time and file size depending what preset you use.

    CRF value also can't be translated 1:1 between codecs so comparing e.g. h265 CRF 21 to h264 CRF 21 doesn't mean much.

    • I consider the 'good enough' level to be, if I didn't pixel peep, I couldn't tell the difference. The visually lossless levels were the first crf levels where I couldn't tell a quality difference even when pixel peeping with imgsli. I also included VAMF results, which say that the quality loss levels are all the same at a pixel level.

      I know that av1, x264, and x265 all have different ways of compressing video. Obviously, the whole point of this was to get a better idea of what that actually looked like. Everything on the visually lossless section is completely indistinguishable to my eyes, and everything on the good enough section has very minor bits of compression only noticed when i'm looking for it in a still image. This does not require the same codec to compare and contrast with.

      Frankly, for anything other than real-time encoding, I don't actually consider encoding time to be a huge deal. None of my encodes were slower than 3fps on my 5800x3d, which is plenty for running on my media server as overnight job. For real-time encoding, I would just grab a Intel Arc card, and redo the whole thing since the bitrates will be different anyways.

      • Frankly, for anything other than real-time encoding, I don't actually consider encoding time to be a huge deal. None of my encodes were slower than 3fps on my 5800x3d, which is plenty for running on my media server as overnight job. For real-time encoding, I would just grab a Intel Arc card, and redo the whole thing since the bitrates will be different anyways.

        Encoding speed heavily depends on your preset. Veryslow will give you better compression than medium or fast, but at a heavy expense of encoding speed. You're not gonna re-encode a movie overnight on slow preset. GPU encoding will also give you worse result than CPU encode so that's something one would have to take into consideration. It's not a big deal when you're streaming, but if it's for video files, I'd much prefer using the CPU.

        I consider the 'good enough' level to be, if I didn't pixel peep, I couldn't tell the difference. The visually lossless levels were the first crf levels where I couldn't tell a quality difference even when pixel peeping with imgsli. I also included VAMF results, which say that the quality loss levels are all the same at a pixel level.

        I was mostly talking about how you organised your table by using CRF values as the rows. It implies that one should compare the results in each row, however that wouldn't be a comparison that makes much sense. E.g. looking at row "24" one might think that av1 is less effective than h264/5 due to greater file size, but the video quality is vastly different. A more "informative" way to present the data might have been to organise each row by their vmaf score.

        Hopefully I don't come across as too cross or argumentative, just want to give some feedback on how to present the data in clearer way for people who aren't familiar with how encoding works.

  • I would like to have seen more data on that table. The time it took to run each video compression.. the final bitrate of each stream. Besides that, very interesting results.

  • The "av1" numbers, which codec is that? There are many av1 encoders and even for Intel HW accel, there are at least two.

  • Thanks for posting. I'm still new to this and had no idea what settings I should be using.

  • Can you explain what you mean by "visually lossless"? Is this a purely subjective classification, or is there a specific definition or benchmark you used?

  • I've also gone down that rabbit hole and found Vivictpp pretty good. It allows you to play two videos so you can swipe between them like imgsli you mentioned.

    There's a whole range measurements trying to approximate quality differences between a video source and encode. PSNR, SSIM, VMAF, MS-SSIM
    All of them with some strong areas and tricks you can use to cheat them.

  • Just buy bigger disks 🫢

30 comments