NVEnc Preview

[Dan64]

This script is working

import vapoursynth as vs
from vapoursynth import core
import subprocess
import ctypes

ffmpeg = r'E:\VideoTest\TestSubs\ffmpeg.exe'
source_path=r'E:\VideoTest\TestSubs\TestVideo.mp4'
# Loading Plugins
core.std.LoadPlugin(path="E:/VideoTest/TestSubs/BestSource.dll") #from https://forum.doom9.org/showthread.php?t=184255
#current color space: YUV420P8, bit depth: 8
#resolution: 1280x536, fps: 25, color matrix: 470bg, yuv luminance scale: limited, scanorder: progressive
clip = core.bs.VideoSource(source=source_path) #this clip is not not needed, just to get width and height
# Setting detected color matrix (470bg).
clip = core.std.SetFrameProps(clip, _Matrix=5)
# Setting color transfer info (470bg), when it is not set
clip = clip if not core.text.FrameProps(clip,'_Transfer') else core.std.SetFrameProps(clip, _Transfer=5)
# Setting color primaries info (BT.709), when it is not set
clip = clip if not core.text.FrameProps(clip,'_Primaries') else core.std.SetFrameProps(clip, _Primaries=1)
# Setting color range to TV (limited) range.
clip = core.std.SetFrameProp(clip=clip, prop="_ColorRange", intval=1)
clip = core.std.SetFrameProp(clip=clip, prop="_FieldBased", intval=0) # progressive
# set output frame rate to 25fps (progressive)
clip = core.std.AssumeFPS(clip=clip, fpsnum=25, fpsden=1)

clip = core.std.BlankClip(clip)

w = clip.width
h = clip.height
Ysize  = w * h
UVsize = w * h//4
frame_len = w * h * 3 // 2 #YUV420

command = [ ffmpeg, '-i', source_path,'-vcodec', 'rawvideo', '-pix_fmt', 'yuv420p',  '-f', 'rawvideo', '-']

pipe = subprocess.Popen(command, stdout = subprocess.PIPE, bufsize=frame_len)

def load_frame(n,f):
    try:
        vs_frame = f.copy()
        for plane, size in enumerate([Ysize, UVsize, UVsize]):
            ctypes.memmove(vs_frame.get_write_ptr(plane), pipe.stdout.read(size),  size)
        pipe.stdout.flush()
    except Exception as e:
        raise ValueError(repr(e))   
    return vs_frame

try:
    clip = core.std.ModifyFrame(clip, clip, load_frame)
except ValueError as e:
    pipe.terminate()
    print(e)

clip.set_output()

I used for testing the following file: https://filebin.net/trb7yof9h0g335e0

It seems that the problem was related to mod 8 and to conversion to YUV420P810.

But at least now we have a version working with ffmpeg, I'm testing the NVEnc version...