The ffmpeg wiki page for H.264 states that:

Consider 18 (CRF) to be visually lossless or nearly so: it should look the same or nearly the same as the input but it isn't technically lossless.

Although, while I understand that H.265 is a relatively new codec, are there any general recommended settings to achieve a "visually lossless" encoding using X264 with ffmpeg?

The H.265 wiki page does state:

The CRF of 28 should visually correspond to libx264 video at CRF 23, but result in about half the file size.

But from what I've picked up, this scale of equivalents is not the same.

Edit regarding the duplicated question I am aware of the linked question, however 'visually lossless' strikes me as more of quite a specific thing - i.e. the point where specifying higher quality does not change the final image.

The linked question is asking about equivalent CRF levels to achieve equivalent quality. Although as I've just said, visually lossless would appear to me to be something much more specific than asking 'the equivalent of CRF 18'...

  • 1
    See this question.
    – Gyan
    Jan 1, 2016 at 19:02
  • The point here is even if the CRF scale of H265 is "different" from the H264 one, H265 developers state that the visually lossless one is again the CRF 18. Considering that the final visual resulting quality of a h265 transcode with same crf of a h264 one is generally greater, if is true that CRF 18 in h264 is visually lossless, the same should go for h265. Said this and if you want go over a descriptional comparison, if you want have mathematical compare the goodness of the various settings you can make your own check with SSIM and PSNR. Jan 29, 2016 at 16:39
  • They are standard indexes for compare quality rendering of different encodings, useful when you reach levels of quality so close that are impossible to tell visually and they are inside a reply into my original question. Jan 29, 2016 at 16:41
  • If you are in the mood of testing, you could prepare a big amount of different video types and encode them first in h264 with crf 18, then in h265 with cfr 18 or higher in steps and compare the 2 indexes said above until you find something similar between your 18crf h264 and the h265 files.. but it's something very time consuming and probably someone else already did it ;) Jan 29, 2016 at 17:04


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