Level and Tier Question

[cojj]

When encoding with default preset + crf, I noticed a huge spike in bitrate in rare occasions (e.g. many tiny moving particle scene). It spiked to something like 60,000 kbps.

My network does not have big enough bandwidth so I decided to put some max-bitrate constraint by using vbv.

so I set vbv-bufsize and vbv-maxrate to 16000. Everything went well as expected but I noticed my format profile changed from 4@Main to 4@High.

My questions are:

1) how does this happen when both max-bitrate and average bit-rate went down considerably

2) Is this profile/level/tier important? Will having High tier block my encodings from being played on some devices?

3) Is there alternative way of constraining max bitrate?


Thank you

[sneaker_ger]

1. max bitrate for main tier main/main10 profile is 12000 kbps
https://en.wikipedia.org/wiki/High_Efficiency_Video_Coding#Tiers_and_levels
If you don't use maxrate/bufsize x265 will have to make a guess but may ultimately break the chosen tier and level. Note that a 60000 kbps spike isn't necessarily a breach, though, because vbv doesn't work like that.
2. Yes. The higher the tier/level/profile/bitrate the higher the player demands. But high tier level 4.0 isn't very high in my opinion so I wouldn't worry too much.
3. Alternatively you could use level 4.1 main tier. Would that be more or less compatible? I don't know.

[benwaggoner]

1. max bitrate for main tier main/main10 profile is 12000 kbps
https://en.wikipedia.org/wiki/High_Efficiency_Video_Coding#Tiers_and_levels
If you don't use maxrate/bufsize x265 will have to make a guess but may ultimately break the chosen tier and level. Note that a 60000 kbps spike isn't necessarily a breach, though, because vbv doesn't work like that.
2. Yes. The higher the tier/level/profile/bitrate the higher the player demands. But high tier level 4.0 isn't very high in my opinion so I wouldn't worry too much.
3. Alternatively you could use level 4.1 main tier. Would that be more or less compatible? I don't know.
4.1 Main Tier is definitely more compatible. While lots of devices support High Tier, some don't support ALL of High Tier, and have issues with the maximum vbv-bufsize and vbv-bitrate.

Honestly, with a good offline encode, I've not found cases where Main Tier provided insufficient bits for good distribution quality, using the lowest level compatible with frame size and fps. High Tier is mainly for really high quality at very high speeds (like internal live IP streams), and mezzanine scenarios like IDR-only encoding.

Even the HBO "static" logo holds up quite well with bufsize/maxrate of 12000 for 1080p Main 4.0 using --preset slower.