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Non Linear Editing and SONY VEGAS - video quality

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Xavier Dolz
Non Linear Editing and SONY VEGAS - video quality
on May 18, 2014 at 3:20:16 am

Hello
I have a doubt about NLE - Non Linear Editing and SONY VEGAS.
My question is simple, but I am not sure about the reply.
Does my video file lose quality when I edit it in SONY VEGAS?
For example, I record a video from my computer screen and I get a mp4 file.
Now I put that file into the SONY VEGAS, add text, add stuff and now I render it.
I guess the SONY VEGAS render is a second generation file?
and my first mp4 was the first generation?
To illustrate the example I can mention video cassettes in which every copy was a second, third, fourth... generation and so on, and every generation was more degraded with worse quality.
I am wondering if this happen also in SONY VEGAS with video files that are edited in the timeline.
As far as I know, NLE software provide non destructive editing, so allegedly files shouldn't lose quality and we shouldn't have generations stuff here, right?
Not sure about this, so if someone could give me some clues I'd be grateful.
Cheers


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Norman Black
Re: Non Linear Editing and SONY VEGAS - video quality
on May 18, 2014 at 4:30:23 am

Vegas does not really degrade source video by simply editing. Where you lose quality is when you encode again. How much you lose depends on your encode settings.

Video encoding is not lossless unless you encode to uncompressed and those files are only good as intermediates. They are HUGE. All other encoding algorithms are lossy. Period. It has nothing to do with the editor and is all about compressing the file.


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Steve Rhoden
Re: Non Linear Editing and SONY VEGAS - video quality
on May 18, 2014 at 7:15:24 am

Norman is correct, this has nothing to do with Sony Vegas.
Putting it simply: The more you render a video file into a
more compressed format, the worse it gets at every render.

Steve Rhoden
(Cow Leader)
Film Editor & Compositor.
Filmex Creative Media.
http://www.facebook.com/FilmexCreativeMedia
1-876-461-9019


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John Rofrano
Re: Non Linear Editing and SONY VEGAS - video quality
on May 18, 2014 at 1:24:34 pm

[Steve Rhoden] "Putting it simply: The more you render a video file into a more compressed format, the worse it gets at every render."
Yes, but we should also point out that it is not nearly as bad as the VHS tape example that was given. Back in the days of analog tapes there was significant loss to where the 3rd generation copy was probably unwatchable. With digital video, you can render and re-render even with a lossy codec and you will not see a visual loss in quality until after many, many renders and then only if you are using low bit-rates.

Here is an example of a video I'm working on for an upcoming Boris TV episode that I rendered 10 times to MainConcept AVC using the Internet HD 1080p template with no changes other than turning on CUDA processing because I'm too lazy to wait for my CPU. ;-)

This is a frame grab from the original video:



This is a frame grab from the video after 10 renders to MainConcept AVC | Internet HD 1080p (12Mbps):



This is a frame grab of the difference between the two videos:



This should dispel all myths about people being afraid to render one or two generations to MP4. That file was rendered 10 times! That means that I rendered it, dropped that render back onto the timeline and rendered it again, dropped that render back onto the timeline and rendered it again, for 10 times.

The difference was taken by placing the original video on a track above the 10th rendered video and changing the track composite mode to Difference. You can see there are some slight artifacts around the edges of the title but nothing the human eye can detect by just looking at the video.

Feel free to do your own tests. The whole lossy codec thing is really nothing to worry about at high bit rates. It's only when re-rendering low bit rates do you see a noticeable loss in quality.

~jr

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



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Norman Black
Re: Non Linear Editing and SONY VEGAS - video quality
on May 18, 2014 at 2:24:51 pm

[John Rofrano] "This should dispel all myths about people being afraid to render one or two generations to MP4"

Nice demo. Yes, AVC is as good as anything out there. There is nothing that forces serious loss in the codec. It all comes down to encoding settings.

I can also confirm that Mainconcept AVC does very well on multi-generation renders. I only tested 5 gens, on a high frequency detail video clip (outside on a trail with lots of brush around). Sony AVC did not fare as well. I was testing at around 30Mbps. You need a lot of bitrate to preserve that images with high frequency detail.


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Xavier Dolz
Re: Non Linear Editing and SONY VEGAS - video quality
on May 19, 2014 at 1:28:59 am
Last Edited By Xavier Dolz on May 19, 2014 at 1:30:38 am

Hi, thanks a lot for the replies, amazing information I got with all this, specially thanks to John, really, I was not expecting so much quality after 10 renders !!! my God, 10 renders :D so... having fear for 2 renders in a mp4 has no sense, thanks a lot.
The other day saw an article in which was published the timeline of Gravity, the movie with George Clooney, and I saw it was made with Avid Media Composer. As far as I know, both, VEGAS and AVID are both NLE, so I don't know if Hollywood is using the AVID because provide more quality also in multiple generation renders?
Mainconcept AVC seems to be the key to get the best quality in multiple generation renders, so I'll do my tests with it.
Thanks a lot for this very useful info!


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John Rofrano
Re: Non Linear Editing and SONY VEGAS - video quality
on May 19, 2014 at 3:21:14 am

[Xavier Dolz] "The other day saw an article in which was published the timeline of Gravity, the movie with George Clooney, and I saw it was made with Avid Media Composer. As far as I know, both, VEGAS and AVID are both NLE, so I don't know if Hollywood is using the AVID because provide more quality also in multiple generation renders?"
Hollywood uses Avid Media Composer because it has outstanding media management. As you can imagine, creating a feature length film involves 1000's of video files. Media Composer is very good at keeping track of large projects that are being worked on by teams of editors. The quality is the same as Vegas Pro.

~jr

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



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Stephen Mann
Re: Non Linear Editing and SONY VEGAS - video quality
on May 20, 2014 at 4:05:02 am

To expand on Steve's first reply - ALL re-compression degrades quality regardless of which NLE you use. But as John pointed out, a few recompressions won't be noticeable by the average user.

Steve Mann
MannMade Digital Video
http://www.mmdv.com


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Steve Rhoden
Re: Non Linear Editing and SONY VEGAS - video quality
on May 21, 2014 at 7:15:23 am

That is true, most of the time it wont be visible to the
naked eye. However when you re-compress multiple times and
try to reduce the size of a video file, it then has a nasty look.

Steve Rhoden
(Cow Leader)
Film Editor & Compositor.
Filmex Creative Media.
http://www.facebook.com/FilmexCreativeMedia
1-876-461-9019


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John Rofrano
Re: Non Linear Editing and SONY VEGAS - video quality
on May 21, 2014 at 12:42:31 pm

[Steve Rhoden] "However when you re-compress multiple times and try to reduce the size of a video file, it then has a nasty look."
Yes, resizing and reducing the bit rate over and over again will produce some nasty results. At some point when the bit rate gets low enough, you won't have enough bits to accurately represent the image and that's when it starts to fall apart.

~jr

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



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