Is x265 better than x264 for SD/720p 1-2 Mbit right now?

[frogsy]

I've read posts claiming that x265 is only advantageous at very low bitrates, but I'm unsure as to what qualifies as a very low bitrate. Are we talking 300kbps here, or are 1-2 Mbit still 'low'? Then there are posts saying that x265 is advantageous only at high resolutions (http://forum.doom9.org/showthread.php?p=1740718#post1740718), as in higher than 4K. So is x265's niche -- today -- low bitrate 4K, with x265 better for everything else?

I'm encoding moderate-lowish quality videos, meaning 850x480 or 1280x720, currently at ~2-5 Mbit using x264. I'm wondering whether it'd be smarter today to use libx265 to encode videos of that resolution at ~2 Mbit. I did some tests and to me libx265 is looking just as good at 2/3rds the size, but I'm on a small, low-quality display and don't want to go by that.

[foxyshadis]

Do you have a lot of noise or very fine textures that you must preserve in the source? Then you might be better off sticking to x264, at least until the blocking bothers you more than the blurring. Generally, x265 will start to blur where x264 starts to block.

Although it depends on the source, at 1-2mbps for a traditional film at 720p, I think you're well into the point where you have to make hard trade-offs, and that's where x265 shines. It won't give you the 2x bitrate reduction that it will at 4K, so don't expect comparing a 2mbps x265 to 5mbps x264 to be amazing, but it will degrade more gracefully even at medium preset (similar in speed to x264's veryslow preset). If you don't mind that smoother image, you might be able to push the bitrate to 2x or more below x264's after all.

For clean, noise-free film and animation, x265 can always do better than x264 (lower bitrate, better edges, and/or less banding), with the added benefit that HEVC 10bit decoding hardware is appearing, making its use in future set-top players possible. Commercial AVC 10bit hardware will never exist.

For SD, it's even closer between the two, and that bitrate goes a lot further. It'd be worth testing first.

[benwaggoner]

For low bitrate encoding of noisy content with x265, --nr-inter can be a huge help. It's like an adaptive deadzone just for predicted blocks, so preserves detail in I-frames and intra blocks. So static detail is preserved while random noise is tamped down some.

[kamineko]

For clean, noise-free film and animation, x265 can always do better than x264 (lower bitrate, better edges, and/or less banding), with the added benefit that HEVC 10bit decoding hardware is appearing, making its use in future set-top players possible. Commercial AVC 10bit hardware will never exist.

So does this mean that a hardware decoder with a Main 10 profile will still be unable to decode a Hi10p video?

[sneaker_ger]

Correct, we already have HEVC 10 bit (main10 profile) hardware and it cannot decode AVC 10 bit (Hi10p). Since AVC 10 bit is only used by a very small community of rippers/pirates and not for TV, BluRay or Internet streaming this is probably not going to change. We have HEVC 10 bit hardware because it is used for UltraHD TV/BluRay/Streaming.

[kamineko]

Disappointing, but to be expected. If I look at the 'x265 HEVC Upgrade' solution from x265.com - they say they have an easy convert from mp4 to HEVC. I assume it's not a complete reencode - that wouldn't deserve to be called easy. So, would a 10-bit mp4 run through their solution result in a repackaged, hardware-decodable Main 10 file?

EDIT: Scratch that, I overlooked a page where they show the options. It is a reencode, with the accompanying loss of quality. So the question would be: Is it possible to convert 10-bit AVC to 10-bit HEVC with no or minimal loss of quality, batch-wise (no fine-tuning for each file)?

[Asmodian]

Is it possible to convert 10-bit AVC to 10-bit HEVC with no or minimal loss of quality, batch-wise (no fine-tuning for each file)?

Absolutely not.

[foxyshadis]

You could probably skip the analysis and just reuse all of the x264 decisions, since while HEVC isn't a superset of AVC, they're pretty compatible. They won't be optimal and you won't get any of the benefit of larger block sizes, but it's quick and simple.

But no one's even made a CAVLC/CABAC converter, so don't hold your breath.

[Marsu42]

Generally, x265 will start to blur where x264 starts to block.

True that - and remember the times when video encoding discussions where about "x264 will start to blur where *mpeg4-asp* will start to block". In my (rather limited) experience when re-coding to lower bitrates (like youtube and movies you happen to find 'round the place) x264 seems to have hit a sweet spot after years of tuning.

Btw: What has the world come to? Thread title "Is x264 *better* than (insert whatever else here)"? In the good ol' days, people where executed for less, these new kids don't have no proper education no more :->