How to use NVencC as external encoder in VirtualDub 2 ?

[spapakons]

Hello!

I appreciate the quality of x265vfw, but unfortunately the rendering is done in software and is very slow. If I don't do any other video processing in the same time AND the VirtualDub progress window is in focus, I can get up to 25-30fps for SD video or 10-12fps for 1080p. If the progress windows is not in focus, or even worse I do some other processing at the same time, the speed can drop to 2-3fps or even below 1fps. Changing the priority from normal to high from the progress window makes very little difference. If I change the VirtualDub priority in Task Manager to high it might slow down the whole computer for very little improvement in speed.

As you realize I cannot dedicate the computer to render a single video in VirtualDub 2! I have tried to use Fastflix to convert my video to HEVC (MKV), with the NVEncC program and I was amazed! I am talking over 150fps in SD video and over 70fps in 1080p. However, Fastflix doesn't have any editing capabilities, unless I see the start/stop points in VirtualDub and copy them to Fastflix. Even then, it is not very precise. Also Fastflix offers simple resize and cropping. It has no other effects. I would appreciate if I could edit the video in VirtualDub and export using NVEncC as external encoder.

I want the input video to be output at the same resolution as the original (either 720x576 SD PAL or 1920x1080 HD), at VBR with specific bitrate (say 4000K for SD video). I tried this syntax and I get an error:

--vbr 4000 --preset quality --profile main --raw --input-res %(width)x%(height) --fps %(fpsnum)/%(fpsden) --input-csp yuv420p -i - -c hevc  -o "%(tempvideofile)"

I tried to set the Decode Format to either NV12 or YV12 in VirtualDub, it didn't work. I tried many times to correct the syntax, always fails. I hate guesswork, so if you are kind enough, please give me the EXACT syntax I should use so I can copy-paste it. Also tell me if I need to change any setting in VirtualDub before explorting the video. Please also tell me what I should change to export to AVC instead of HEVC.

I also have FFMPEG, what is the EXACT syntax to use FFMPEG to export same videos to either AVC or HEVC with NVEnc hardware acceleration?

I use Aften for AC3 Stereo 192Kbit audio and MKVmerge to create the final MKV file.

Million thanks in advance!

[buzz1891]

regarding If the progress windows is not in focus - try to uncheck 'Background I/O priority' in status window

[spapakons]

It is not checked. When starting to render the video the progress window has checked the input video and output video by default. I uncheck them both to speedup the rendering. As long as the progress window is on top (focused), the speed doesn't drop much, unless of course I am processing some other video in the background. If the progress window loses focus, such as when I browse the web, the speed drops considerably. Is there any way to prevent that and make VirtualDub rendering at the maximum speed possible? I hope this won't make the whole computer crawl! I would like to use it for other stuff while VirtualDub is busy.

[spapakons]

When I bought my Intel Core-i7 3770 3.4GHz (overclocked to 3.7GHz) CPU second hand to upgrade from my Intel Core-i3 3220 3.3GHz, the CPU cooler wasn't available, so I used my old Core-i3 cooler which could not dissipate enough heat and my Core-i7 was running hot. I didn't have any issue until a few weeks ago, so I just ignored the higher temperature. From start of June we have high temperatures here in Athens, Greece reaching 38-40 degrees Centigrade, so eventually my Core-i7 reached the threshold of 105 degrees where it slows down to protect itself from overheating and it was operating at 1.4-1.5GHz! The impact on hardware accelerated video rendering (such as running Handbrake with nVidia HEVC) was small, but without hardware acceleration (such as running VirtualDub with the x265vfw codec) was huge! Hence the very few fps and the overall system delay. Yesterday I replaced my old Core-i3 CPU cooler with a Coolermaster Gamma Archer which has a lot better heat dissipation, so now I can use VirtualDub with 8-10fps, if the progress window is not in focus, or 24-28fps if the progress window is in focus. Much better from the old underclocked values, but I would appreciate if there is a trick to force maximum performance even if the progress windows is not in focus.

Thanks.

[jagabo]

There's no reason a VirtualDub should run slower in the background than when it's in the foreground. VirtualDub is not well multithreaded so you may not get good throughput when filtering. But whether it's in the foreground or background doesn't matter. I don't normally use VirtualDub for anything except previewing AviSynth scripts. But a quick test shows it encoding at the same speed in the background and foreground.

Process priority determines which processes get more CPU when multiple processes are requesting CPU time. If your computer is otherwise idle a process gets all the CPU time it can use. You shouldn't run user process at more than normal priority. That is reserved for device drivers and realtime processes.

I normally run encoders at low (idle) priority so they only get CPU time when the system an other processes don't need it. Since my computer idles at 0 to 1 percent CPU encoding isn't slowed by this unless I run some other CPU hungry process. I can barely tell an encoding is going on if I use the computer for other things at the same time. I'm on 8 core 16 thread CPU now. But the situation was the same since single core computers.

[spapakons]

Unfortunately, it makes a big difference if the progress window is in focus or not. So I let other applications working in the background and make sure the VirtualDub progress window is in focus. When it is, I get rendering speed of over 15fps. If it is in the background it goes down to 3-5fps since usually the CPU is busy with other applications. One workaround is not to save the video directly from VirtualDub but frame serve into a .vdr file and then open this file in Fastflix via Avisynth. Fastflix has the drawback that it hardly keeps the bitrate I set making the resulting video larger than the target file size. If I want to fit as good as possible a blank DVD disc when creating an AVCHD folder I must save directly from VirtualDub.

In case it makes any difference, I use x264, x264vfw and x265vfw codecs.

[jagabo]

Unfortunately, it makes a big difference if the progress window is in focus or not.

It's not supposed to work like that. I don't know what's set up wrong on your computer.

[spapakons]

Well, I am not 100% sure, but I think I fixed it. In VirtualDub Preferences, Threading section I changed the default Video Compression Threads setting from 0 to 1 hoping it would improve performance and I also set the Video filter threading from Auto to 8 threads. I put both back to default values, 0 and Auto and now I have reasonable rendering speed of 12-15fps even if the progress window is not in focus. However, the computer is not busy doing other processing at the moment. I will confirm it when I have it busy.

[spapakons]

When computer is idle, I get good reasonable speed even if the progress window is not in focus. If the computer is busy with other applications, the speed still drops but it is better now that my CPU is cooler and running at 3.7GHz. One workaround is to frame serve to another application such as AVStoDVD or Fastflix, not save the video directly from VirtualDub.

[jagabo]

Note that the original VirtualDub's filtering is single threaded. So if you're filtering that may become your bottleneck. VirtualDub2's filtering is multithreaded. I'm not sure how well it works since I don't use its filtering.

[spapakons]

Yes, I know if I use filters (the whole point of using VirtualDub) the rendering will be slower from 35fps, for example, to 20fps. That's not my issue. The problem is that it doesn't stay at 20fps if you do something else (even reading your email) and the progress window is not in focus. This is not convenient at all. I want to use my computer while VirtualDub is rendering. I don't want to dedicate it to VirtualDub just to finish earlier. A small drop, say to 15fps wouldn't mind, but we are talking about as low as 5-6fps or even less if the CPU is busy with other applications. I cannot have the VirtualDub progress in focus all the time, unless I am not using the computer. Thankfully other applications that I frame serve to don't have this issue and VirtualDub is serving them as fast as possible. I have seen speeds over 80fps while using filters like resize, crop and logoaway.

[jagabo]

Saw this story about hybrid CPUs running programs slower in the background:

https://aloiskraus.wordpress.com/2024/02/08/hybrid-cpu-performance-on-windows-10-and-11/

[spapakons]

My CPU is third generation Intel Core-i7 3770, so it is certainly no hybrid. I had seen that before, that VirtualDub slows down when the progress window is not in focus, but I wasn't using other applications back then, only 3 or 4 VirtualDub instances, so it wasn't that obvious. I thought the slowdown was because of the many instances and of course whichever progress window was in focus was speeding up. It seemed logical to me. However, lately I use Handbrake, AVS Video Converter and other applications at the same time and it is ridiculous to see these applications mostly unaffected if not in focus and VirtualDub slowing down to 1/3 or less of the speed it has when in focus. As I already said the workaround is not to compress the video directly in VirtualDub (Save video) but frame serve it to another application to do it (Start Frame Server), so in effect the other application takes control of the process and keeps VirtualDub active and as fast as it can, it doesn't slowdown.

PS: In case you were wondering, other applications don't accept .vdr files directly (only TMPGEnc 2.5), so I have to use an AviSynth script to open the .vdr file (without any filters, just open it) and create a .avs file. The other applications open this .avs file so they get frames from VirtualDub indirectly. Anyway, the job is done, so I don't care about the two steps (start frame serving in VirtualDub and then open the .vdr file with AviSynth).

[jagabo]

If I remember correctly, by default VirtualDub encodes at low priority when in the background. If you're running other CPU intensive tasks in the foreground you expect VirtualDub to run slowly. You can configure the program to encode at normal priority. I'm not at a computer with VirtualDub installed right now but I believe the setting is in the CPU section of the preferences.

[spapakons]

I have set Normal priority when encoding. I see normal priority both on the progress window and in Task Manager. Setting the priority to high in progress window makes no difference, probably this is when two or more instances are running which has higher priority. Setting the priority to high in Task Manager might make VirtualDub a little faster but makes the whole computer crawl, so I rather keep it at normal.

PS: I am using x264 or x265 compression, just in case it matters. I don't know if the issue exists for other codecs such as DivX or VP8.