Comparing H.265 (HEVC) and H265 video file size • Hacker News Board

Re: Comparing H.265 (HEVC) and H265 video file size

#11

Post by azernik » Thu, Mar 25, 2021, 1:44 AM UTC

boomboomsubban wrote: post #8

mrtnmcc wrote: post #3

This is compressing video recordings of a computer desktop. The frames don't change much so this isn't surprising.

Can you clarify this please? Does h.265 have some better deduplication compression or does reencoding apply something that the original recording could not, meaning h.264 would have the same benefit.

A compression algorithm allows multiple different encodings of the same underlying data - spend more CPU time finding redundancies in the data, and you can make the file smaller.

I strongly suspect that the difference here is between real-time compression that runs while capturing the screen recording, and less time-constrained offline compression during transcoding.

Re: Comparing H.265 (HEVC) and H265 video file size

#12

Post by viraptor » Thu, Mar 25, 2021, 1:44 AM UTC

LeoPanthera wrote: post #7

miles wrote: post #2

> Some more Ducking made me aware that using '-tag:v hvc1' in FFmpeg creates files that QuickTime can eat. Can you please share the full ffmpeg syntax used for converting the H.264 files to H.265?

If your videos are already h.264, you probably should not convert them to h.265. You'll lose some quality to generation loss and the difference in size is not huge.

You're responding in context of an article which says:

> "what if I convert my screen recordings from H.264 to H.265?" Well, two things happend: My files shrink to 6% (not a type)

Sounds like the difference can be huge.

Re: Comparing H.265 (HEVC) and H265 video file size

#13

Post by minimaxir » Thu, Mar 25, 2021, 1:45 AM UTC

As of macOS Big Sur, you can Export videos from QuickTime (i.e. the screen recording) in H.265, and it's faster than converting it via ffmpeg as it can leverage the GPU via VideoToolbox.

...but you still have to record-and-save it in H.264 first then reload into QuickTime, and for some reason the H.265 quality isn't great. This is still the case even when using GPU VideoToolbox via ffmpeg/Handbrake, and it's something I've never figured out why.

As an aside, for more serious recordings (and if you don't want to use paid software), I recommend using OBS instead, as it gives you a lot more recording flexibility that the native macOS screen recorder lacks.

Re: Comparing H.265 (HEVC) and H265 video file size

#14

Post by userbinator » Thu, Mar 25, 2021, 1:45 AM UTC

boomboomsubban wrote: post #8

mrtnmcc wrote: post #3

This is compressing video recordings of a computer desktop. The frames don't change much so this isn't surprising.

Can you clarify this please? Does h.265 have some better deduplication compression or does reencoding apply something that the original recording could not, meaning h.264 would have the same benefit.

Although I have not worked with '265 or any of the other newer codecs past '263, I suspect it's the latter --- encoders running in realtime tend to aim for a constant bitrate rather than maximum compression.

Re: Comparing H.265 (HEVC) and H265 video file size

#15

Post by dsiegel2275 » Thu, Mar 25, 2021, 1:47 AM UTC

Without reading the details, to see a compression improvement of that magnitude I can only suspect that it is a "middle out" compression algorithm...

Re: Comparing H.265 (HEVC) and H265 video file size

#16

Post by dylan604 » Thu, Mar 25, 2021, 1:47 AM UTC

boomboomsubban wrote: post #8

mrtnmcc wrote: post #3

This is compressing video recordings of a computer desktop. The frames don't change much so this isn't surprising.

Can you clarify this please? Does h.265 have some better deduplication compression or does reencoding apply something that the original recording could not, meaning h.264 would have the same benefit.

h.265 makes files smaller than h.264 for a given bit rate. So an h.265 I-frame will be smaller than an h.264 I-frame. If it's a mostly static computer screen, then you can get even better encoding effeciency by using a longer GOP structure so the I-frames are spread out even futher. Of course, the trade of is seeking gets worse, but works out great for push play and watch type of deliverables. h.264 can do this as well, but it still goes back to the purpose of h.265 is to be better than h.264

Re: Comparing H.265 (HEVC) and H265 video file size

#17

Post by mirthflat83 » Thu, Mar 25, 2021, 1:49 AM UTC

viraptor wrote: post #12

LeoPanthera wrote: post #7

Earlier quoted context omitted.

If your videos are already h.264, you probably should not convert them to h.265. You'll lose some quality to generation loss and the difference in size is not huge.

You're responding in context of an article which says: > "what if I convert my screen recordings from H.264 to H.265?" Well, two things happend: My files shrink to 6% (not a type) Sounds like the difference can be huge.

Yeah so if he re-encoded his video in H.264 I bet he would have seen a similar level of compression.

Re: Comparing H.265 (HEVC) and H265 video file size

#18

Post by kayson » Thu, Mar 25, 2021, 1:52 AM UTC

The title is a bit of an exaggeration... Maybe I'm missing something but there's actually nothing in the article about the FFMPEG setting used, most importantly the encoding bitrate or quality. There's also no quantitative comparison between the old video and the new. It's relatively straightforward to measure the noise added during the encoding process.

That being said, H265 definitely does improve filesizes.

Re: Comparing H.265 (HEVC) and H265 video file size

#19

Post by KMnO4 » Thu, Mar 25, 2021, 1:53 AM UTC

Mostly static a screen recordings are pretty much the ideal content to show off H.265. The screen would be broken down into blocks, and ones that don’t contain much motion or complexity would use nearly no bandwidth. This image should demonstrate that:

https://postimg.cc/D8MZyzHd

Also, I’m not criticizing the authors English (which is much better than my Dutch), but some of those mistakes were almost poetic:

> Some more Ducking made me aware that using '-tag:v hvc1' in FFmpeg creates files that QuickTime can eat.

Re: Comparing H.265 (HEVC) and H265 video file size

#20

Post by bawolff » Thu, Mar 25, 2021, 1:56 AM UTC

Sounds likely that the initial recording was a live screen recording so mac probably uses lowest compression settings so to be able to transcode in real time well at the same time not monopolizing the cpu.

Maybe i'm wrong, but the comparision is stupid without having ffmpeg re-encode the video with the same codec. Otherwise its just apples to oranges.