Quality loss when rendering mini-DVD

[Johan Lundqvist]

So the “no recompression required” should’t blink on the preview screen during rendering. So I guess, during rendering – the preview screen should not show any movie at all, just the “no recompression…”-sign.

I have now been sitting for hours trying different settings on a small test-movie (26 secs completely uncut), but the best I can get is the blinking of the “no recompression…”. The sign is never steady for more than like 1/100 sek. If I try settings that I know are wrong, the “no reco…” never shows at all and the rendering goes much slower.

If I right-click my 26 sec movie in the project media window and choose “properties”, I get this:

Accessed: den 18 september 2008, 22:34:22
Attributes: Archive

Streams
Video: 00:00:26,400, 25,000 fps interlaced, 720x576x32, MPEG-2
Audio: 00:00:26,368, 48 000 Hz; Stereo, MPEG

ACID information
ACID chunk: no
Stretch chunk: no
Stretch list: no
Stretch info2: no
Beat markers: no
Detected beats: no

Other metadata
Regions/markers: no
Command markers: no

Media manager
Media tags: no

Plug-In
Name: mcplug.dll
Folder: C:\Program Files\Sony\Vegas Pro 8.0\FileIO Plug-Ins\mcplug
Format: MainConcept MPEG-2
Version: Version 2.0 (Build 4349)
Company: Sony Creative Software Inc.

I’m trying different settings in project properties and custom settings in templates before rendering, and I have no imagination left. You were talking about changing the bitrate or the GOP. What is GOP (and how do I change it) and how do I know what bitrate my original file has? During rendering, I usually use the default options on varable bitrate. The only setting I have found where it says GOP is in the custom template where it says “insert sequence header before every GOP”, “use closed GOPs” and “length of GOPs”.

From what I understand, the PAL Standard/IMX Widescreen option should be used in project properties, but I have to have the “upper field first” (because the original file comes from the mini-DVD). I have tried lower field first (which is usually default) but then the rendered file looks truly awful.

[John Rofrano]

Is the original footage widescreen? What miniDVD camera are you using? Would it be possible to post a few seconds of a file from the camera? Maybe someone here can detect what the correct settings to use are. You might also want to contact the camera manufacturer and ask them for the specs on the MPEG-2 stream that they use.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[Johan Lundqvist]

I use a Sony DCR-DVD205. It’s bought in Sweden (Europe) where i live. Iv’e formatted the disc to shoot in 16:9 so the original footage is in widescreen. I’d love to post a few seconds from a file – any good suggestion where I can put it?

Thanks for your help!

[Johan Lundqvist]

I have a friend who can help me to put up the 4 sec file on the internet tomorrow.

I have found this information in Vegas help menu:

“When you render video to any of the following formats, unedited video frames are passed through without recompression:

DV AVI

DV MXF

IMX MXF (IMX 24p MXF is not supported for no-recompress rendering)

HD MXF

HDV

In order to perform rendering without recompression, the width, height, frame rate, field order, and bit rate of the source media, project settings, and rendering template must match. Frames that have effects, compositing, or transitions applied will be rendered.”

I actually don’t understand what the above means. When you select “Render As”, there is no option that says “IMX MXF” for example. I use MainConcept MPEG-2 and as template I first select DVD Architect PAL Widescreen video stream. I then have to make a custom setting in the template – “Upper field first”. Is this the same as “IMX MXF”?

[John Rofrano]

What that says is if the streams match in resolution and bitrate, the source will not be re-compressed. The trick is knowing the attributes of your source MPEG-2 file. I did some searching on the web and one review site said that in SP mode your camera tops out at 8.5Mbps. You might want to try setting the MPEG-2 bitrate to 8,500,000 and see if that helps.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[Johan Lundqvist]

I have now tried – in “Render As…”, custom template – to change the bitrate. I´ve tried constant bit rate: 8 500 000 as well as variable bit rate with 8 500 000 as maximum. None of this changes anything (the “No Recompression…”-sign is not constant during rendering). The “No Recompression…”-sign shows for like 1-4 times when I render my 26 sec movie-clip.

This is really starting to feel hopeless. I just want the “No compression…”-sign to be constant during rendering so I know that there is no quality loss in the picture from the original file. Perhaps I’m trying to do something impossible. Or perhaps there is a bug in Vegas. I mean – why would the “No Recompression…” just blink a few times during rendering? If the sign bothers to appear at all – why is it not constant? It’s the same clip and it’s pure an not changed in any way! I can’t find information anywhere about “No Rec..”-sign just showing up very fast like on my screen.

Perhaps people with Mini-DVD:s dont care about editing, but I do. And when the picture quality is not very good from the start, I surely do not want the quality to be worse just because I edit my movies without effects and add some music.

I’ll try to link to a 4 sec clip tomorrow. The clip I will link to was created on my harddrive when importing a DVD Camcorder disc in Vegas. It’s not been processed by Vegas other than that and it has not been edited in any way.

Good night and thank you for your help!

[John Rofrano]

> Perhaps people with Mini-DVD:s dont care about editing, but I do. And when the picture quality is not very good from the start, I surely do not want the quality to be worse just because I edit my movies without effects and add some music.

That’s why people who want to edit should not buy a miniDVD camera. I realize it’s hard for you to admit this to yourself, but you purchased the wrong camera for your needs. I’ve been doing more reading on it and apparently, Sony didn’t even try and trick you and ship editing software with this model. They have basically said it’s a “soccer mom” camera. You have to realize that and move on.

I would highly recommend that you buy a cameras that shoots in a format that is meant to be edited. MiniDV uses a 25Mbps data rate and your camera uses 8Mbps. That’s a big difference (3x) and while bitrate isn’t the only thing that determines quality, it is a big contributor.

You could try convert all of your footage to DV Widescreen and edit with that. This might preserve the footage better. You will loose some color information because of the difference in the way MPEG and DV store color but it’s worth a try.

Here is one final thing to try:

1. Start a new project.
2. Set your project properties to match one of the MPEG files by going into the Project Properties using the Match Media Settings button. (it’s the yellow folder to the right of the project dropdown)
3. Drop the same MPEG file on the timeline.
4. Then Render to MainConcept MPEG-2 using the Default Template!

The Default Template gets it’s properties from the project. Since you matched the project to the media, this just might use the proper format and not recompress.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[Johan Lundqvist]

I like the Match Media Settings function, and it works perfectly! The project settings turn out to be the same that I set manually before, but that was to be expected after my 15 hours of work on this problem. Like I thought, Match Media Settings sets the template of the project to PAL Standard/IMX Widescreen, and the field order to upper field first. Rendering to MainConcept MPEG-2 using the Default Template is not, however, working fine at all. It looks horrible after rendering with that template. The Default Template does not seem to comply with the project settings at all. It uses Aspect ratio 4:3 (!), and LOWER field first (!). Because the field order differs from the project settings, the picture looks very strange. And the 4:3 aspect ratio is obviously totally wrong. Needless to say – the “No compression…”-sign is not shown at all during rendering with the default temple.

So – my last hope is that someone (perhaps you John?) can have a look at this 4 sec clip and try to find the right rendering-settings for MainConcept MPEG-2 in Vegas (so that rendering is done without any recompression). The Match Media Settings function does the job in Project Settings – it�s all about finding the rendering-settings i guess.

Here is the clip: https://www.svardmail.se/johan/Unedited.mpg

Thanks!

(I´ve tried to put a few copies of the 4 sec clip after each other on the timeline and then render them to one file. If I use the best rendering settings that I can come up with, the “No recompression…”-sign blinks a couple of times in the preview window during rendering.)

[John Rofrano]

> my last hope is that someone (perhaps you John?) can have a look at this 4 sec clip and try to find the right rendering-settings for MainConcept MPEG-2 in Vegas

Well… it really helps having the file because I figured it out. I looked at the file in GSpot and it said it was in DVD VOB format with AC3 audio. (which actually makes perfect sense since this camera shoots video that can be directly played in a DVD player) Since Vegas can’t output AC3 audio in an MPEG file I knew that we needed to start with a template that didn’t include audio. Then I opened the file in Womble and that confirmed that the audio was AC3 but also told me that the bit-rate was 9.1Mbps Variable. We already knew from using the Match Media button that the MPEG was Upper Field First. With those three pieces of information I was able to create a render template that did not require recompression.

Here’s how:

1. Start with the DVD Architect PAL Widescreen video stream template
2. Press the Custom… button
3. Select the Video tab
4. Change the Field Order to Upper Field First
5. Change the Maximum (bps) to 9,100,000
6. Select the System tab
7. Check Save as separate elementary streams (very important)
8. Change the Template name to PAL Widescreen (No Recompress)
9. Press the Save icon
10. Press OK

You should now have a new template called PAL Widescreen (No Recompress) that will render without recompression to a .m2v file. The secret was rendering to m2v as an elemental stream that can be used to build the VOB again for DVD. If you go back and render the audio as AC3 and drop the M2V file into DVD Architect it will act just like an MPG file and create a button with video and audio.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[Johan Lundqvist]

Wow, you made it! You are a genious, thanks!

I thought all my problems were solved, but unfortunately I have discovered a new problem when I use the new settings…

I have made a few projects in Vegas and I tried to render one of them with the new settings. It worked out fine during the rendering process and the “No Recompression”-sign was constant in the preview-window for most of the time. Sometimes the sign disappeared for a very short time on places where I had made cuts in Vegas, but I didn’t expect this to be a problem. However, this really turned out to be a problem.

When I rendered with my previous settings, there was some loss in quality during rendering. The quality loss was however stable throughout the rendered file and there were no special “quality-dips” on places where I had made cuts.

Now, there are on many occasions severe “quality-dips” on places where I have made cuts. This means that the picture quality now is excactly the same throughout most of the movie – but on places where I have made cuts in Vegas, it’s much worse than it was before. You look at the movie and its like “oh, yes, the picture quality is not altered at all” and then there is a cut made in Vegas and its like “what just happended there, it looked horrible”.

This can be seen if you use the 4 sec clip I put on the internet.

For example: Take the 4 sec clip and put it 10 times after each other in Vegas. Then render with the new settings. At first the “No recompression…”-sign blinks one time (this does not seem to affect the quality though) and then its constant during the whole rendering process. BUT – if you then try to do a few cuts in the project, you’ll notice that the “No recompression”-sign starts blinking when you render. It blinks every time you’ve mad a cut. If you look at the movie after rendering, you’ll notice that the quality-loss is severe around some of the cuts (not all perhaps, but some). Unfortunately this 4 sec clip hasn’t got much motion in it – but I can assure that it looks much worse when you’ve make cuts during motion.

Do I make straight cuts? Well, I don’t know how to make them more straight. I highlight the part I want to get rid of by pressing the left mouse-button and draw the mouse over the unwanted area. Then I push the delete button.

And if there is nothing wrong with my cutting technique, is there anything left to be done when it comes to settings?

Is it possible to make cuts in a project and still have the “No recompression”-sign constant during rendering? If not – is there any way to make the quality loss smoother around the clips?