Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion.

Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules.

 

Go Back   Doom9's Forum > Capturing and Editing Video > Avisynth Usage

Reply
 
Thread Tools Search this Thread Display Modes
Old 16th February 2012, 07:22   #1  |  Link
nhope
partially-informed layman
 
Join Date: Jan 2002
Location: Bangkok, Thailand
Posts: 314
MVtools scene detection for a clean cut? (1080-50i to 720-30p)

I have a bunch of HDV 1080-50i clips on my Sony Vegas Pro timeline and I'm converting them to 720-30p UT video codec format to mix with footage originating from HDV 1080-60i by frameserving to the following script, then VirtualDub. It will later be rendered to H.264 for the web.

Code:
AviSource("d:\fs.avi")
AssumeTFF()
ConvertToYUY2(interlaced=true, matrix="Rec601")
QTGMC(SubPel=2, EdiThreads=2)
super = MSuper(levels=1, pel=2)
MFlowFps(super, QTGMC_bVec1, QTGMC_fVec1, num=30000, den=1001)
Spline36Resize(1280,720)
AssumeFPS(29.97)
The quality is great. However at some of the scene changes in the 30p output I get a clean cut, but at others I get a blended frame. This is not a big deal as the eye generally glosses over these rapid transitions between scenes, but I was wondering if there is a smarter way to do it whereby I always get a clean cut?

I guess one solution might be to duplicate a frame instead of blending at those transitions, but I fear that might look less smooth during playback.

I guess another solution might be to drop a frame, although that would make the video shorter and I would prefer to retain the overall length of the video so I can still sync 50i and 30p to audio on my timeline.

So it seems the ideal solution might be to somehow detect which transitions are going to render a blended frame, and then at those transitions to generate a new frame by either looking just backwards at the preceding clip, or just forwards at the following clip, depending which of those 2 clips' ends is closer to the cut. I hope that makes sense!

Possible? Or should I just live with the blended transitions?
nhope is offline   Reply With Quote
Old 16th February 2012, 08:20   #2  |  Link
Didée
Registered User
 
Join Date: Apr 2002
Location: Germany
Posts: 5,391
Code:
MFlowFps(super, QTGMC_bVec1, QTGMC_fVec1, num=30000, den=1001, blend=false )
__________________
- We´re at the beginning of the end of mankind´s childhood -

My little flickr gallery. (Yes indeed, I do have hobbies other than digital video!)
Didée is offline   Reply With Quote
Old 16th February 2012, 09:11   #3  |  Link
nhope
partially-informed layman
 
Join Date: Jan 2002
Location: Bangkok, Thailand
Posts: 314
Damn it, I was hoping the solution would be really complicated.

Thanks Didée!
nhope is offline   Reply With Quote
Old 16th February 2012, 14:17   #4  |  Link
TheSkiller
Registered User
 
Join Date: Dec 2007
Location: Germany
Posts: 632
Some tips:

1) Avoid AssumeFPS(29.97)
It's not exactly the right frame rate. It might seem over-the-top but it's a difference whether a video is marked as 29.970000000000 fps or 29.970029970029970(...) fps which is the real NTSC frame rate, 30000/1001.
Use AssumeFPS(30000,1001). In fact you can omit this line because the frame rate was converted to 30000/1001 by MFlowFps already.

2) If "d:\fs.avi" is your raw HDV source (YV12) then the matrix parameter in ConvertToYUY2() won't do anything at all! It is only used for conversions between any YUV color space and RGB.
If you need to do a conversion from Rec709 to Rec601 coefficients then you need to use ColorMatrix.

Code:
ColorMatrix(mode="Rec.709->Rec.601", clamp=0)
Edit: However, your destination seems to be HD which means you should not convert to Rec601.

Last edited by TheSkiller; 16th February 2012 at 16:08.
TheSkiller is offline   Reply With Quote
Old 17th February 2012, 05:37   #5  |  Link
nhope
partially-informed layman
 
Join Date: Jan 2002
Location: Bangkok, Thailand
Posts: 314
Thanks for you reply TheSkiller.

Quote:
Originally Posted by TheSkiller View Post
1) Avoid AssumeFPS(29.97)
It's not exactly the right frame rate. It might seem over-the-top but it's a difference whether a video is marked as 29.970000000000 fps or 29.970029970029970(...) fps which is the real NTSC frame rate, 30000/1001.
Use AssumeFPS(30000,1001). In fact you can omit this line because the frame rate was converted to 30000/1001 by MFlowFps already.
That's a good point. I had to leave AssumeFPS in for one of my earlier conversion scripts, so that found its way into this one. The frame rates used in Sony Vegas Pro only go to 3 decimal places. As this footage is going back into Sony Vegas Pro, I guess 29.97 might be OK, but as you say, I can leave it out anyway.

Quote:
2) If "d:\fs.avi" is your raw HDV source (YV12) then the matrix parameter in ConvertToYUY2() won't do anything at all! It is only used for conversions between any YUV color space and RGB.
If you need to do a conversion from Rec709 to Rec601 coefficients then you need to use ColorMatrix.

Code:
ColorMatrix(mode="Rec.709->Rec.601", clamp=0)
Edit: However, your destination seems to be HD which means you should not convert to Rec601.
My source is actually a frameserved RGB AVI stream. I have found that matrix="Rec601" gives the correct result when rendering to UT video codec in VirtualDub, even though everything is HD (1808i to 720p).
nhope is offline   Reply With Quote
Old 17th February 2012, 06:40   #6  |  Link
poisondeathray
Registered User
 
Join Date: Sep 2007
Posts: 5,551
Quote:
Originally Posted by nhope View Post

My source is actually a frameserved RGB AVI stream. I have found that matrix="Rec601" gives the correct result when rendering to UT video codec in VirtualDub, even though everything is HD (1808i to 720p).
But how are you determining the "correct result" ? The preview in vdub? It's using Rec601 converting to RGB for display (usually incorrect for HD material)

ie. You are frameserving RGB from vegas but converting to YUY2 (rec601) in the script; vdub is using Rec601 to convert to RGB for display, not Rec709. But when you view this on some other device or HD workflow , it will most likely use Rec709 for display
poisondeathray is offline   Reply With Quote
Old 17th February 2012, 07:00   #7  |  Link
nhope
partially-informed layman
 
Join Date: Jan 2002
Location: Bangkok, Thailand
Posts: 314
Quote:
Originally Posted by poisondeathray View Post
But how are you determining the "correct result" ?
By comparing the rendered UT Video Codec file against the original HDV files in Sony Vegas Pro. Rec601 is the same. Rec709 is different.
nhope is offline   Reply With Quote
Old 17th February 2012, 07:03   #8  |  Link
poisondeathray
Registered User
 
Join Date: Sep 2007
Posts: 5,551
Quote:
Originally Posted by nhope View Post
By comparing the rendered UT Video Codec file against the original HDV files in Sony Vegas Pro. Rec601 is the same. Rec709 is different.

So you render UT 422 out of vdub with the script , then re-import into vegas?

The problem is vegas is converting UT 422 to RGB using Rec601, not treating it as Y'CbCr

Why not do whatever you have to do in vegas, before you frameserve out? This way you don't face several uncessary colorspace conversions ?

EDIT: sorry nevermind, I see what you are doing, you're mixing it back in a vegas project with 60i footage

Last edited by poisondeathray; 17th February 2012 at 07:14.
poisondeathray is offline   Reply With Quote
Old 17th February 2012, 07:39   #9  |  Link
nhope
partially-informed layman
 
Join Date: Jan 2002
Location: Bangkok, Thailand
Posts: 314
Actually I'm rendering to Ut Video Codec RGB (URLG). Since Vegas works internally in RGB, there is no conversion happening on import to Vegas.
nhope is offline   Reply With Quote
Old 17th February 2012, 07:53   #10  |  Link
nhope
partially-informed layman
 
Join Date: Jan 2002
Location: Bangkok, Thailand
Posts: 314
Back to the original point, the mvtools documentation implied that blend=false might actually simply repeat frames at scene changes. So it concerned me that there might be a bit of a "jolt" at scene changes. But I'm finding that there is no such repeated frame, at least in the case of my 50i to 30p script. Motion is totally smooth amd cuts are clean. So that's great!
nhope is offline   Reply With Quote
Old 17th February 2012, 10:07   #11  |  Link
Gavino
Avisynth language lover
 
Join Date: Dec 2007
Location: Spain
Posts: 3,435
Quote:
Originally Posted by nhope View Post
the mvtools documentation implied that blend=false might actually simply repeat frames at scene changes. So it concerned me that there might be a bit of a "jolt" at scene changes. But I'm finding that there is no such repeated frame, at least in the case of my 50i to 30p script.
Repeated frames are necessary only when increasing the frame rate. When decreasing, the issue does not arise.
__________________
GScript and GRunT - complex Avisynth scripting made easier
Gavino is offline   Reply With Quote
Old 17th February 2012, 11:56   #12  |  Link
nhope
partially-informed layman
 
Join Date: Jan 2002
Location: Bangkok, Thailand
Posts: 314
Ah OK. Thanks Gavino. That makes sense. I'll look out for that in another project where I'm planning to convert PAL to NTSC (both interlaced) in a similar manner.
nhope is offline   Reply With Quote
Reply

Tags
blend, cut, mvtools, scene detection, transition

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 17:24.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.