What is a good HEVC CRF rate to balance Size with Quality?

[theaviguy]

I'm working with varying sources of media from DVD, standard BluRay, downloaded video, some already encoded in other formats & sizes but none with resolutions greater than 1080p. Most are either in h.264 or Xvid format. I resize everything to either 640x480 for SD sources or 640x360 for HD sources. My goal is to find a good HEVC CRF for all sources to give a reasonably small file size with a quality close to HD broadcast television. Any suggestions would be greatly appreciated. Thanks!

[El Heggunte]

QUESTION: ¿What is a good HEVC CRF rate to balance Size with Quality?

ANSWER: It depends.

1) Each case will be a case, because the compressibility of the video sources is not a constant or fixed value.
When I re-encode with x265, I choose a CRF-value between 22 and 20, because my target is not only a much-smaller filesize, but also a "watchable" quality. But sometimes those CRF-values cannot produce a significant filesize reduction, and then I simply discard the HEVC reencodes.

2) By the way...

¿Why resize "everything" to 640x480 or 640x360?
FWIW: we are not in the golden days of DivX/Xvid anymore
I mean, those low resolutions made sense when "everybody" had only an analog (CRT) TV set, and fitting a 2-hour movie on a 700 MB CD-R was considered acceptable (or desirable). Unless your goal is to watch your HEVC reencodes on a smartphone

[Selur]

640x480 or 640x360 even with quant/crf 0 that is nowhere near HD broadcast television.

[krykmoon]

I'm working with varying sources of media from DVD, standard BluRay, downloaded video, some already encoded in other formats & sizes but none with resolutions greater than 1080p. Most are either in h.264 or Xvid format. I resize everything to either 640x480 for SD sources or 640x360 for HD sources.

Simply resizing a full HD 1080p source to 640x360 it's losing 1/3 of the original information.. so it' s quite purposeless to talk about finding an efficient quality/compression ratio..

I don't know if you have a specific reason to resize a 1080p source to 360p (standard HD for broadcast starts from a minimum of 720p).. but it's a very destructive process, quality wise.. and once it's done finding a good quality/compression ratio becomes quite irrelevant.. since most of the "quality" is already lost.

[Cornucopia]

@krykmoon, it's more like losing 90% of the original information (1080p60 HD is 2 Mpixels, 640x360 is 0.23 Mpixels, and that's not counting the possible change in framerate from 60p).



Scott

[krykmoon]

@krykmoon, it's more like losing 90% of the original information (1080p60 HD is 2 Mpixels, 640x360 is 0.23 Mpixels, and that's not counting the possible change in framerate from 60p).



Scott

You're absolutely right, I meant resolution..
As Mpixel (and so as information) you lose much more (because 1920x1080 -> 640x360 it's 3 times the width and 3 times the height.. not counting any framerate change)

[theaviguy]

It's really a matter or storage space. I'm looking for compression to reduce filesize so I can fit more on my drives withouth losing too much quality. Forget the HD TV standard "bit". I just want a "watchable" show or movie with a smaller filesize. Yeah, I know the dimensions are outdated for today's standards but it's just what I do. Anything I reduce to that size it quite watchable on a HD TV. I just went with the lowest 4:3 & 16:9 dimensions.