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  1. Member
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    Oct 2017
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    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:

    Code:
    --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!
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  2. regarding If the progress windows is not in focus - try to uncheck 'Background I/O priority' in status window
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  3. Member
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    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.
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  4. Member
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    Oct 2017
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    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.
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  5. 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.
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  6. Member
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    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.
    Last edited by spapakons; 13th Jul 2024 at 17:18.
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  7. Originally Posted by spapakons View Post
    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.
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  8. Member
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    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.
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