NVENC 2pass tested

[sophisticles]

A while back i ran across a site on how to encode using ffmpeg and the author claimed that NVENC supported true 2 pass encoding and gave a command line example of how to do it. I could never get the command given to work, and evidently neither could anyone else based on the comments section and the author walked back the claim,

Fast forward some time and I was building Handbrake from scratch on Ubuntu when I accidentally built it with NVENC support on Ubuntu? QSV and NVENC do not show up in the official HB builds on Linux, nor in the nightly builds that I have tried but if you build it from source, there it is. Even more surprising is that they appear to have found a way to do a true 2 pass NVENC, at least on Linux.

Attached is some quick encodes I did, I decided to do a Netflix style test encode, 2 pass for all encodes at 15 MB/s, which is what Netflix uses for their 4k offerings. I have also attached the source for comparison, as well as a couple of "cheat" encodes, where I applied a little sharpening using one of sharpen filters built into HB; x264 was encoded using the very fast preset and x265 used the ultra fast preset.

The source file can be downloaded from http://download.blender.org/mango/dcp/tos_dcp_test_04.zip and in terms of encoding speed all encodes finished at roughly 5fps, I think this system may be decode bottleneck regarding jpeg2000 source, because the uncompressed y4m version places back smoothly but the jpeg2000 in an MXF container stutters and uses up all 12 threads at max of this R5 1600.

[pandy]

Where is you commandline?

[sophisticles]

There is no command line, this was done within the Hand Brake GUI.

[poisondeathray]

Can you look at the log file ? I would like to try 2pass nvenc to get it working. Maybe there is a special switch. AFAIK, it's only an internal 2pass with the higher quality preset. Or maybe they added it with the newer cards ?

Or, can you check the diff between 1 pass and 2 pass . I can get 2passes to encode , but I don't see any difference with nvenc on windows . It's bit for bit identical . Also there is no actual log file/ stats file written out on the 1st pass (it's blank) , whereas various other encoders have that data written for the 1st pass used in the 2nd pass . So basically the 2nd pass just overwrites the 1st pass with the same thing

[pandy]

There is no command line, this was done within the Hand Brake GUI.

isn't handbrake provide log with command line - correct me if i'm wrong - not using handbrake but i assume it is just gui/wrapper for other tools.

[sneaker]

HandBrake isn't like MeGUI, StaxRip, RipBot etc. that mostly combine AviSynth with a bunch of CLI tools. It's a single .exe (well, two, one GUI version and one CLI version) based around libav/ffmpeg. But the GUI does have a log (CTRL+L).

[pandy]

HandBrake isn't like MeGUI, StaxRip, RipBot etc. that mostly combine AviSynth with a bunch of CLI tools. It's a single .exe (well, two, one GUI version and one CLI version) based around libav/ffmpeg. But the GUI does have a log (CTRL+L).

Well, you can turn dos batch to exe, python can be turned to exe - question is if Handbrake use NVidia NVEnc API in unique way or just use other tools.

[sr55]

HandBrake does not support 2-pass with NVENC. When you enable -2, the first pass is basically doing nothing. It's a bug that it even allows it.
We use ffmpeg under the hood for nvenc integration + a little direct API calls into NVENC. Nothing special going on here.

NVEnc does have this sudo 2pass vbr mode but it appears to be more of a frame level analysis. So, it's not the traditional two pass you'd see with x264/5