Visually lossless bitrate with 1-pass encoding

[codemaster]

When choosing software encoding over hardware encoding, using the x264 encoder, I know how to make the output visually lossless. I use CRF mode, with the value 15. Or I use 2-pass mode, with the maximum bitrate that CRF 15 allocates (which is 17 Mb/s for 1080p 30 fps).

The problem is that when I export a video from a NLE, I have to use hardware encoding, because software encoding is too slow. It's not just 2x slower, it can be up to 10x slower. So to export at a reasonable speed, I have to choose Intel QSV instead of 2-pass software encoding. If I choose 2-pass software encoding, and set the bitrate to 17 Mb/s for a 1080p project, I know the output file will be visually lossless. But if I choose Intel QSV and set the bitrate to 17 Mb/s, i know the output will not be visually lossless because encoding is done with only 1-pass.

So 1-pass and 17 Mb/s is lower visual quality than 2-pass and 17 Mb/s. Which means I have to set the bitrate higher than 17 Mb/s for 1-pass, to compensate. So my question is: if 1-pass and 17 Mb/s is not equivalent to 2-pass and 17 Mb/s, then how can I find out what bitrate is equivalent?

The easiest solution is to just set 17 Mb/s for 1-pass, but I was hoping there was a way to find out the visually lossless bitrate for 1-pass, just as there is a way to find it for 2-pass.

[davexnet]

Too many half truths and false assumptions

[codemaster]

The problem I have is I don't know what bitrate to choose when exporting a 1080p 30 fps video, with Movavi Video Editor.

One solution I found is to use the same bitrate that x264 CRF 15 uses, which is 17 Mb/s. Another solution I found is to use the same bitrate that my camera uses, which is 17 Mb/s. But what I can't find is how to make sure the output file will be visually lossless when encoding with Intel QSV or AMD VCN.

[davexnet]

Just use CRF, don't use a specific bitrate.
Different videos, depending on their complexity (smooth/textured
soft/sharp, mostly action/mostly still, etc - have varied
Bitrate needs to achieve a certain quality.
Just use CRF and allow the encoder to find the right rate
to fit the needs of the particular video

[codemaster]

In Kdenlive it's very simple because I can select CRF 15 from a slider when exporting, and I don't have to know what bitrate to set in order to make sure the output file will be visually lossless. But because Kdenlive doesn't have the features I need, I have to use Movavi Video Editor. And with Movavi I have to set a bitrate, because it doesn't have CRF mode.

[jagabo]

The problem I have is I don't know what bitrate to choose when exporting a 1080p 30 fps video

Nobody knows what bitrate to use. Different videos require different bitrates. Action, noise, flickering lights, smoke, fog, smooth gradients all require more bitrates. If you encode everything at at the same bitrate some videos will get more than they need, other less. If you encode two different videos at crf 15 one might turn out 17 Mb/s, another 25 Mb/s, and another 5 Mb/s, all depending on the properties of the different videos.

And "visually lossless" is very subjective. It depends on how closely you look, the size of the screen, how far you are from it, how good your TV is, ambient lighting, how good your eyesight is, etc.

[rgr]

In Kdenlive it's very simple because I can select CRF 15 from a slider when exporting, and I don't have to know what bitrate to set in order to make sure the output file will be visually lossless. But because Kdenlive doesn't have the features I need, I have to use Movavi Video Editor. And with Movavi I have to set a bitrate, because it doesn't have CRF mode.

A long time ago I exported such a video losslessly, converted ffmpeg with CRF17 set and entered the obtained bitrate into the program

[ProWo]

Use clever FFmpeg-GUI to encode, so while encoding you can see the actual bitrate, choosen from the encoder at the given CRF.


[Attachment 82559 - Click to enlarge]

[codemaster]

In Kdenlive it's very simple because I can select CRF 15 from a slider when exporting, and I don't have to know what bitrate to set in order to make sure the output file will be visually lossless. But because Kdenlive doesn't have the features I need, I have to use Movavi Video Editor. And with Movavi I have to set a bitrate, because it doesn't have CRF mode.

A long time ago I exported such a video losslessly, converted ffmpeg with CRF17 set and entered the obtained bitrate into the program

I was trying to avoid lossless export. 1080p or 4K encoded with UT Video or ProRes, doesn't even fit in my 1 TB hard drive. Plus, the editor I use now doesn't even have lossless export.

With clips from a standard definition camera it was easy to preserve visual quality. I edit them in Vegas Pro and export a virtual .avi with DebugMode FrameServer, then encode with x264 in CRF mode, with CRF 18-15. No large intermediary files, no risk of setting the bitrate too low, and good encoding speed (20-30 fps).

But with 1080p or 4K clips from a phone camera, that have variable frame rate, it's not that easy. Because I have to use an editor that:
- can handle variable frame rate source clips
- can use hardware decoding and encoding for creating proxy clips at a decent speed
- creates small standard definition proxy clips that fit even on a 120 GB SSD
- can use hardware encoding for exporting, so that encoding speed will not be too slow

Because with software encoding, the encoding speed would be only 3 fps for 1080p, and less than 1 fps for 4K. Leaving no good way to preserve visual quality, as I am forced to choose Intel QSV and AMD VCN encoders, setting the same bitrate that the source clips have, which could result in more degradation than with x264 CRF 15.

[4kblurayguru]

The problem is that when I export a video from a NLE

export lossless, uncompressed or dnxhr/prores
then use separate encoder to encode

how can I find out what bitrate is equivalent?

specific bitrate not important, you encode for playback device. Different video will have different bitrate.

The easiest solution is to just set 17 Mb/s for 1-pass

What is the delivery? online, broadcast, local or BD? For online I recommend crf 18 / "slow" speed / high profile / level 3.1 / 720p res / 30fps / max bitrate 6Mbps.

doesn't even fit in my 1 TB hard drive

Buy new hard drive, 4tb minimum

the editor I use now doesn't even have lossless export

use other NLE, with uncompressed or dnxhd export

But with 1080p or 4K clips from a phone camera, that have variable frame rate, it's not that easy

GIGO
play videos as recorded

[jagabo]

At least some of Intel's QSV h.264 encoders support constant quantizer encoding. A sample ffmpeg command line:

ffmpeg -y -i "input.mp4" -c:v h264_qsv -preset:v slow -q:v 12 -an "output.qsv12.mkv"