AVI files rendered a second time

Eric Ken wrote on 7/4/2006, 6:49 AM
Dose anyone edit there vision tracks and make a rendered AVI and then lay and mix the sound to the rendered track?

Also is there any serious loss of quality if a rendered AVI file is rendered again?

I find it much easier to carry out the work in two sessions rather than trying to do the sound work with all the vision tracks on the screen. However, I am concerned that there may be some loss of quality doing it this way.

Any advice on this will be greatly appreciated.

Eric Ken

Comments

Chienworks wrote on 7/4/2006, 7:04 AM
If you render to uncompressed AVI there will be no loss.
If you render to DV .avi then do your second render to DV .avi there will be no loss.
If your source is DV .avi and you do cuts-only editing then there will be no loss.
In all other cases, if you render using SONY's DV codec the loss will be so minimal as to be undetectable even through dozens of generations.

The major loss occurs the first time you enter a particular codec, or when you switch codecs. The major loss due to DV compression occurs in your camera. After that SONY's codec retains the image quality very very well. If your source is better than DV and you render to DV, then render again to MPEG2 for DVDs then you will take a noticeable hit, mostly in strong reds and contrasting color edges. MPEG is much more compressed than DV so rendering MPEG -> MPEG always loses some amount of quality and is often very noticeable.

What you might want to consider doing with Vegas 6 is to render a single video file from your original project, create a new project with this single file, add your audio to it, then when you're done drag the original project into the new one as a nested timeline. Then you can mute the single video track and render using the original video clips with your audio.
TheHappyFriar wrote on 7/4/2006, 8:11 AM
I just render parts (as I finish them) to a new track. I almost always have the audio already laied out. it's much easier to see where the audio goes when you alread have scene's/etc visually cut instead of going through everythging all over again.
Stuart Robinson wrote on 7/4/2006, 3:14 PM
You could render to a loss-less AVI CODEC.

I use HUFFYUV - http://en.wikipedia.org/wiki/Huffyuv - it's free, fast and flexible (no constraints regarding image size). Officially it's a Win32 CODEC but there is a 64-bit version if, like me you use x64.

It's also a good way to archive footage in a loss-less format if quality is critical. You can encode to MPEG or whatever at a later date.
Jay-Hancock wrote on 7/5/2006, 7:39 AM
Chienworks - good info, thanks.
Eric Ken wrote on 7/5/2006, 4:05 PM
Thank you for your detailed answer about AVI files, it will enable me to set up a work flow system in my post-production studio.

Eric
teaktart wrote on 7/6/2006, 12:11 AM
I got myself in a dilemma here....

"The major loss occurs the first time you enter a particular codec, or when you switch codecs".......

I rendered my avi/project to mpeg2 @24p trying to squeeze1:37 minutes worth of material onto a dvd. DVDA3 says it won't fit so I went back into V6 and hoped I could just re-render the mpeg2 without the 10min section I deleted. Am I going to take a big quality hit?


"MPEG is much more compressed than DV so rendering MPEG -> MPEG always loses some amount of quality and is often very noticeable."

Yes, I sure notice the reds are way more saturated when dropping from dv>to mpeg. But with the above mentioned problem with wanting to just cut a section and re-render will those reds get even worse or will the process use my previously rendered files for all but the changed area? I don't quite understand when you can make minor adjustments and re-do and not lose quality.

My render on a fast new machine for the 24p 2pass VBR with a couple of simple transitions, and color correct,and some other audio fx is taking 12-13hr. for the 1 1/2hr project so having to go all the way back to the avi>mpeg render is what I'd like to avoid if possible, and not lose any quality....(I should be fair here to my machine and mention that my render times are while rendering two different Vegas projects of equal timeline length of about 1hr 30 min.)

Thanks,

Teaktart
mbryant wrote on 7/6/2006, 3:25 AM
The problem is that Vegas doesn’t do any “smart rendering” with MPEG (as it does with DV). If you make any change it will re-encode the entire project. So if you re-render from the MPEG it will mean an additional generation and thus quality loss. Whether the loss is significant to you or not depends on your display, your eyes, etc. But clearly it will be best for you to re-render from the original avi.

Or you could use other software which doesn’t re-render everything, like Womble.

Or you could prepare the files you have, and use DVD shrink to shrink it to size… I’m not sure quite how it works (it must need to re-encode) but it tends to do a good job.
rs170a wrote on 7/6/2006, 3:37 AM
...DVDA3 says it won't fit ...

Teaktart, I ran into the same problem just last week with 2 different projects (similar length to yours). I knew that the mpeg files were under the maximum so I ignored the message. DVDA 3 went ahead and burned them without any problems.

Mike
teaktart wrote on 7/6/2006, 10:38 AM
RE: rs170a
Interesting that you had the same size issue. When I click on the mpeg file it said 4.17GB and when I added the AC-3 file it didn't seem to change the size. However, when I put that on my DVDA timeline it reads 4.8GB so I couldn't fit my project, weird.

The second file which I burned said 99% @4.7GB even though it was a couple of minutes longer than the first disc. It burned but, when I went to watch it it completely froze up about 8 minutes from the end so the encoding didn't work correctly even though the burn said "successful". Guess you got lucky with your burn and I didn't!

So, how do I get anywhere near the so called 2 hrs per disc? I did the 2-pass VBR hoping to keep better quality and have a more efficient use of the encoding in the hope that I could cram my 1:37 minutes onto the disc but so far no luck and hence my dilemma with having to re-encode from the AVI according to the post above.

If I hit the DVDA "Opimize" button (I rendered avi>mpeg in Vegas)would this re-encode again and lose quality or would this be a workaround that wouldn't sacrifice quality but would make it fit?

My video is in a somewhat low-light environment so keeping the color quality is becoming the challenge as well.

What a long process and this isn't even HDV material just plain old SD DV...!

Teaktart

p.s. to MBryant: "use DVD shrink to shrink it to size"
is this a seperate program or is this the "optimize" within DVDA?
rs170a wrote on 7/6/2006, 11:35 AM
teaktart said:
Guess you got lucky with your burn and I didn't!

Hard to say. I use this bitrate calculator (it's a zipped file) for anything over an hour.

...when I added the AC-3 file it didn't seem to change the size.

How big was the AC3 file after rendering? Was the total still under the 4.3 GB limit? Keep in mind that you have to look at the file details to see the "real" size. For example, I just looked at a folder of videos that said 599 MB. When I look at the actual total though, it came out to 628 MB.

...it completely froze up...

Were you using a computer DVD drive or a regular player?

So, how do I get anywhere near the so called 2 hrs per disc?

I've done this several times using the bitrate calculator I mentioned above.

If I hit the DVDA "Opimize" button, would this re-encode again...

It probably would but I'll leave a definitive answer to one of the DVD experts here :-)

Lastly, DVD Shrink is a tool that can be used to shrink "prepared" DVD (VIDEO_TS & AUDIO_TS) files that are too large to fit on a regular DVD. For example, you could "prepare" your files that you rendered out in Vegas at a CBR of 8 MB. You know that would be too large but you "prepare" it anyway. Then use DVD Shrink on those files to get them to fit a standard DVD. Works like a charm :-)

Mike
Stuart Robinson wrote on 7/6/2006, 1:46 PM
A few things; in my experience Womble files have compatibility issues; my Pioneer players have problems with basic joins and crash on transitions. VideoReDo is much more reliable, except there are no transition options. Neither re-render, only the I frames before and after cuts.

Another thing to remember, 1Gb on a hard disk is not the same as 1Gb on an optical disc, the latter is actually smaller.

1h 37m on a DVD-5 should be easy and quality excellent (you're not compressing too much). Use the bitrate calculator mentioned above and you should be OK, but don't re-render from your MPEG, go back to the source if you can.

"My render on a fast new machine for the 24p 2pass VBR with a couple of simple transitions, and color correct,and some other audio fx is taking 12-13hr."

What are the specs of your machine? That seems to be a long, long time. I rendered 2h 35m of 25fps PAL with two-pass VBR encoding and all the best quality settings in under four hours last night.
teaktart wrote on 7/6/2006, 10:14 PM
I'm a bit confused on the changing sizes of a file...hmmm, need clarification on how to check that.

The AC3 file is on the other machine but it shouldn't be that big a file if its the audio to the 1:37 video...

My disc froze on a set top player and no amount of button pushing on the remote would move it forward...

I have a dual core AMD Athlon 64 x 2 machine with 10K system drive and a SATA Raid, 4GB RAM, etc so it should a fast machine. I was rendering two projects simultaneously so maybe that bogged me down on the process time?

Tried to download DVD Shrink and the webpage isn't working tonight but I'll try later, thanks for that tip.

I'm lazy enough to want to just let a program re-calculate for me instead of using a bitrate calculater, comments? pro/con?

Thanks for all your help with this!

Teaktart

p.s. How do you add the links to a post so they work and are Blue in color, I'm new to this? thanks
mbryant wrote on 7/7/2006, 5:51 AM
If I hit the DVDA "Opimize" button (I rendered avi>mpeg in Vegas)would this re-encode again and lose quality or would this be a workaround that wouldn't sacrifice quality but would make it fit?

Optimize just shows you what needs to be re-encoded and what doesn't. If you then click on fit to disc yes it will re-encode.

p.s. How do you add the links to a post so they work and are Blue in color, I'm new to this?

See here
Stuart Robinson wrote on 7/7/2006, 4:42 PM
>I'm a bit confused on the changing sizes of a file...hmmm, need clarification on how to check that.<

A blank DVD-R is 4.7Gb (it says so on the packaging!) but in actual fact, in computer terms where 1 kbyte is 1024 bytes, the maximum you can get on a disc is 4.37Gb. If you use Windows Explorer, look at a file size of, for example 4.5Gb and think "that'll go", in actual fact it won't. In addition, the DVD authoring program will add a little overhead, so when burning DVD-Video the video and structure added together have to be under 4.37Gb.

>My disc froze on a set top player and no amount of button pushing on the remote would move it forward...<

The problem with DVD authoring is that it could be any number of things. It's unlikely you exceeded the maximum data rate but it could be a capacity issue.

>I'm lazy enough to want to just let a program re-calculate for me instead of using a bitrate calculater, comments? pro/con?<

Well, this is just my opinion but DVD and MPEG files are picky to begin with so if you just try to squash an existing file the chances are it will become less compliant. The bitrate calculator is easy to use and in my experience is usually spot-on, you'll have to completely re-render the file though.
teaktart wrote on 7/8/2006, 11:45 AM
Stuart, thanks for the explanation, makes sense.... although it reminds me of those stickers on rear view mirrors that say "objects are not the actual size they appear to be"..or something like that!

Looks like it may be a more efficient work flow to render my original timeline to AVI first so I have that to go back to if I need to make any adjustments later on and can just render a new mpeg that hopefully wouldn't take as long to render (especially in this case with using original clips on timeline with effects, and conversion to 24p, which added significantly to render time)
So in this case, I'll render first to standard AVI then let DVDA "fit to disc" and see how that comes out.
As you mentioned I'm right up against the time/space issue @4.37GB even though the "video structure" should be minimal as I have a "single movie" without any kind of menu .

Thanks again,
Teaktart