Issues with encoding level restriction for Roku device playback

[copperheadclgp]

I have a large library of videos which I am trying to convert to hevc for playback on a Roku Ultra. Per Roku's official streaming specifications (https://developer.roku.com/docs/specs/media/streaming-specifications.md#supported-video-codecs) the maximum level that it can support is 5.1. I have tested this and while higher levels do work, there are playback issues like tearing and hanging, so I need to stick with the 5.1 level. I am using FFmpeg to perform the conversions.

Here's my issue; I have been playing with both software (libx265) and hardware (hevc_nvenc) to do the conversions. However, I keep running into issues where the conversion will fail because the set level (5.1) isn't sufficient for the bit rate. For example, if I run the following:

-c:v libx265 -vf scale=3840:2160 -preset veryslow -crf 23 -profile:v main -x265-params "level-idc=5.1" -c:a copy

I get the error:

x265 [error]: frame rate is out of range for specific level

If I run:

-c:v hevc_nvenc -vf scale=3840:2160 -preset:v 18 -tune:v 1 -profile:v 0 -level:v 153 -tier:v 1 -rc:v 1 -cq:v 23  -c:a copy

I get:

InitializeEncoder faile: invalid param (8): Invalid Level

The maddening thing is that if i remove the Level 5.1 arguments, let the encode complete (which results in a Level 6 / 5.2 / etc.), then re-encode it again with the Level 5.1 argument, it works fine because the bitrate has dropped to a level which is supported by Level 5.1. Obviously, this isn't a good option because the loss levels go through the roof by re-encoding twice.

My question is two-fold; first, is there anything I could be doing differently to get this to function in one pass, second, is it possible to set the level on an existing file without re-encoding? This would let me convert everything to whatever level the encoder determines is needed, drop the bitrate to an appropriate level, then manually set the level to 5.1.

[ProWo]

You can try to change level only, without reencoding, with clever Ffmpeg-GUI, main section.

[copperheadclgp]

You can try to change level only, without reencoding, with clever Ffmpeg-GUI, main section.

Thank you, this does appear to work! The question I have now is whether you or anyone else knows the raw commands to do this natively. I am using FFmpeg Batch to run these conversions in bulk and would like to create a preset to do this following conversion. I did not see any option in Clever FFmpeg-GUI to create a log file showing the commands being passed nor did I see anything in Windows Event Log...

EDIT: I figured it out. Basically, what you need to do is run the stream through the bitstream filter like so:

-c:v copy -bsf:v hevc_metadata=level=153 -c:a copy