multiple rendering ruin quality? at DVinfo.net

Spike Spiegel · January 27th, 2006, 11:54 AM

I don't know if this is a myth, but I've heard it several times. Does multiple rendering sessions of the same video project file (with color corrections, etc) kill the quality of the raw video after each rendering run? Or is this just a myth?

Devlyn Hukowich · January 27th, 2006, 12:56 PM

The only time that multiple renderings will not cause quality issues is if you are working with uncompressed video. In other words video that is not compressed in any way, full resolution, 4:4:4 YCrCb. Which alas DV is not.
Now having said that a couple of passes is not going to cause any major quality issues, but choose the order for operations carefully. Perform compositing first, as any problems will show in edges, especially with green or blue. And colour correction last. Everything else can go in the middle. Also remember this would only be true where everything is not being done in the same timeline and not rendered out between passes.
Just remember that uncompressed DV is an oxymoron, all DV is compressed as is most video that we work with (that includes DigiBeta, YCrCb 4:1:1 with 1:3 DCT)
Keep rendering passes to a minimum and you will be OK.

Steven Gotz · January 27th, 2006, 07:22 PM

Sorry folks, but this is a case of using the wrong words, or attaching the wrong meaning to the word "render".

In Premiere and Premiere Pro, the word render means to create preview files. To create a new AVI file requires an "export".

So, you can render all you want without losing quality. If, however, you export to a new AVI, then add effects to that, export again, then add more effects, you will soon be disappointed in the quality.

If, however, you render, add effects, render again, nest a sequence in a sequence, render again - then there is no quality loss added each time. You still lose one generation when you export, but not until you export.

Spike Spiegel · January 27th, 2006, 10:19 PM

Hi Steven, yeah I meant export. I'm not talking about reexporting exported files with effects. I have 17 min worth of footage in my work area, I modded them graphically only with the color correction filter. My question is, will the raw footage be harmed if I keep rexporting multiple times, from the raw footage..?

Steven Gotz · January 27th, 2006, 11:05 PM

The raw footage is never, I repeat, never touched. Ever. The Premiere Pro project files are merely references to the original. You can export 1000 times in 1000 different ways and never make a change to the original.

Only if you export, then use that file in a project and make more changes, then export... etc - then you will have problems.

Spike Spiegel · January 28th, 2006, 02:52 AM

gotcha, glad to hear that, thanks for clearing that up!

January 27th, 2006, 11:54 AM	#1
Spike Spiegel Major Player Join Date: Feb 2005 Location: Los Angeles, CA Posts: 429	multiple rendering ruin quality? I don't know if this is a myth, but I've heard it several times. Does multiple rendering sessions of the same video project file (with color corrections, etc) kill the quality of the raw video after each rendering run? Or is this just a myth?

January 27th, 2006, 12:56 PM	#2
Devlyn Hukowich Regular Crew Join Date: Mar 2004 Location: Toronto, ON Canada Posts: 40	Multiple renders The only time that multiple renderings will not cause quality issues is if you are working with uncompressed video. In other words video that is not compressed in any way, full resolution, 4:4:4 YCrCb. Which alas DV is not. Now having said that a couple of passes is not going to cause any major quality issues, but choose the order for operations carefully. Perform compositing first, as any problems will show in edges, especially with green or blue. And colour correction last. Everything else can go in the middle. Also remember this would only be true where everything is not being done in the same timeline and not rendered out between passes. Just remember that uncompressed DV is an oxymoron, all DV is compressed as is most video that we work with (that includes DigiBeta, YCrCb 4:1:1 with 1:3 DCT) Keep rendering passes to a minimum and you will be OK. __________________ Devlyn Hukowich TwoBit Digital Inc. Video and Computer Geek P4 3.06GHz, 2GB RAM, Matrox RT.x100, dual head display

January 27th, 2006, 07:22 PM	#3
Steven Gotz Trustee Join Date: May 2002 Location: Clermont, FL Posts: 1,520	Using the wrong terms Sorry folks, but this is a case of using the wrong words, or attaching the wrong meaning to the word "render". In Premiere and Premiere Pro, the word render means to create preview files. To create a new AVI file requires an "export". So, you can render all you want without losing quality. If, however, you export to a new AVI, then add effects to that, export again, then add more effects, you will soon be disappointed in the quality. If, however, you render, add effects, render again, nest a sequence in a sequence, render again - then there is no quality loss added each time. You still lose one generation when you export, but not until you export. __________________ Steven Gotz http://www.stevengotz.com

January 27th, 2006, 11:05 PM	#5
Steven Gotz Trustee Join Date: May 2002 Location: Clermont, FL Posts: 1,520	The raw footage is never, I repeat, never touched. Ever. The Premiere Pro project files are merely references to the original. You can export 1000 times in 1000 different ways and never make a change to the original. Only if you export, then use that file in a project and make more changes, then export... etc - then you will have problems. __________________ Steven Gotz http://www.stevengotz.com

January 27th, 2006, 10:19 PM	#4
Spike Spiegel Major Player Join Date: Feb 2005 Location: Los Angeles, CA Posts: 429	Hi Steven, yeah I meant export. I'm not talking about reexporting exported files with effects. I have 17 min worth of footage in my work area, I modded them graphically only with the color correction filter. My question is, will the raw footage be harmed if I keep rexporting multiple times, from the raw footage..?

January 28th, 2006, 02:52 AM	#6
Spike Spiegel Major Player Join Date: Feb 2005 Location: Los Angeles, CA Posts: 429	gotcha, glad to hear that, thanks for clearing that up!