Generational degradation at DVinfo.net

Sam Houchins II · May 11th, 2019, 08:01 AM

Too many generations of rendered versions leading to loss of resolution / sharpness / detail.

Source is 4k XAVC-S. Output to be 1080 available online.
2-hour session, 3 cams x 2 recorded sessions, + 120 ppt slides
Tasks to accomplish = color correcting, synchronize, choose multicamera cuts, crop and motion track, apply overlays, mix in previously edited takes from the 1st session.

In the past, I'd edit an entire project left to right on the timeline, with the intent of rendering the whole once the whole was finished. Consequently there was no generational degradation, but I was tortured with unnoticed and unintended glitches in distant surrounding edits due to user error with ripple effect or track adjustments that suited one clip while mangling another.

Plan to mitigate my bumbling was to do more renders of "completed" sections to lock those edits down while I proceeded down the timeline to other sections.

Glitch in that plan was that those renders were still more or less only drafts in the process, that then received other layers of edits, which were then locked down with another render, sometimes cumulatively combined with newly compiled sections.

1. Must I avoid multiple renders at all cost, because there is no way to avoid generational loss? Early on I used the Sony XAVC / XAVC S, XAVC S Long 3840x2160-29.97p template for rendering sectional drafts.

2. Once a portion of 4k footage has had cropping or motion tracking applied so as to uses less than 4k of that portion of the clip (as little but no less than 1080), should that portion thereafter only be rendered as 1080?

3. At one point midway, I switched to Sony AVC/MVC Internet 1920x1080 template, but ended up with still more generations of edits and renders that followed. Was that fatal?

4. I've not yet delved into proxies(?). Dunno if there's a helpful use down that path.

Thanks in advance.

George Dean · May 11th, 2019, 08:42 AM

If you are working with 4:2:0 8 bit, Three options that come to mind are MagicYUV, UT Video and uncompressed. I very seldom go more than 2 generations (maybe 3 at the very most) so I keep it simple and easy and use Avid DNx.

If you are working in 422/444 10 bit that may knock out MagicYUV. But if you are using 8 bit pixel format it doesn't matter about the 10 bit/bit depth, because Vegas will process it at 8 bits.

I would prefer to keep everything at 4kUHD until the very end, but depending on what you are doing it may not matter.

Proxy is good for getting a smoother playback of the timeline, but will not help with gen loss.

You can also use nesting, but that may become complex, but if you use nesting, there is no generation loss because nothing is rendered until the end. There is a way to edit/modify a nested project but it involves running 2 instances of Vegas and for a large project with many sections that you want to isolate it could become wild, loading 1 or 2 to edit, then closing those and opening another 1-2 to avoid the ultimate limit of your system running multiple instances.

I think it would also depend on what type of changes you will make to a 2nd generation as to weather it is better to go with whatever! Regardless, if you keep the project you made for section one to render the 1st generation and find you need something alter, you can always go back, change the project and re-render and that then is the new/edited 1st generation.....I'm not sure I explained that very well.

Sam Houchins II · May 11th, 2019, 01:17 PM

Quote:

Originally Posted by George Dean

You can also use nesting, but that may become complex, but if you use nesting, there is no generation loss because nothing is rendered until the end.

Thank you for bringing up nesting!
Something else that I knew existed out there in some form or other for something or other, but looking it up today looks like it would have been an excellent fit for this.
Thanks!!

George Dean · May 11th, 2019, 02:27 PM

Quote:

Originally Posted by Sam Houchins II

Thank you for bringing up nesting!
Something else that I knew existed out there in some form or other for something or other, but looking it up today looks like it would have been an excellent fit for this.
Thanks!!

I don't know how nesting works behind the interface. When you add a .veg to the Project Media bin it will post a small window that says it's rendering. What this refers to I don't know. I thought is might be a proxy, but I can not detect any difference in quality between that shown in the timeline that is nested compared to the original. I also can not tell any difference in between rendering out the original compared to the rendered out nested project, so my assumption has always been the final render has not lost any quality by nesting it.

There are few cautions when using or editing certain audio. I would recommend doing a search in the index Vegas help for 'Project Nesting'. It never effected me but I think it may have to do with 5.1 surround and/or editing in Acid/Sound Forge, neither of which I do anymore.

May 11th, 2019, 08:01 AM	#1
Sam Houchins II Major Player Join Date: Jun 2003 Location: Fredericksburg, VA Posts: 282	Generational degradation Too many generations of rendered versions leading to loss of resolution / sharpness / detail. Source is 4k XAVC-S. Output to be 1080 available online. 2-hour session, 3 cams x 2 recorded sessions, + 120 ppt slides Tasks to accomplish = color correcting, synchronize, choose multicamera cuts, crop and motion track, apply overlays, mix in previously edited takes from the 1st session. In the past, I'd edit an entire project left to right on the timeline, with the intent of rendering the whole once the whole was finished. Consequently there was no generational degradation, but I was tortured with unnoticed and unintended glitches in distant surrounding edits due to user error with ripple effect or track adjustments that suited one clip while mangling another. Plan to mitigate my bumbling was to do more renders of "completed" sections to lock those edits down while I proceeded down the timeline to other sections. Glitch in that plan was that those renders were still more or less only drafts in the process, that then received other layers of edits, which were then locked down with another render, sometimes cumulatively combined with newly compiled sections. 1. Must I avoid multiple renders at all cost, because there is no way to avoid generational loss? Early on I used the Sony XAVC / XAVC S, XAVC S Long 3840x2160-29.97p template for rendering sectional drafts. 2. Once a portion of 4k footage has had cropping or motion tracking applied so as to uses less than 4k of that portion of the clip (as little but no less than 1080), should that portion thereafter only be rendered as 1080? 3. At one point midway, I switched to Sony AVC/MVC Internet 1920x1080 template, but ended up with still more generations of edits and renders that followed. Was that fatal? 4. I've not yet delved into proxies(?). Dunno if there's a helpful use down that path. Thanks in advance.

May 11th, 2019, 08:42 AM	#2
George Dean Regular Crew Join Date: Oct 2015 Location: Navajo County, Arizona Posts: 109	Re: Generational degradation If you are working with 4:2:0 8 bit, Three options that come to mind are MagicYUV, UT Video and uncompressed. I very seldom go more than 2 generations (maybe 3 at the very most) so I keep it simple and easy and use Avid DNx. If you are working in 422/444 10 bit that may knock out MagicYUV. But if you are using 8 bit pixel format it doesn't matter about the 10 bit/bit depth, because Vegas will process it at 8 bits. I would prefer to keep everything at 4kUHD until the very end, but depending on what you are doing it may not matter. Proxy is good for getting a smoother playback of the timeline, but will not help with gen loss. You can also use nesting, but that may become complex, but if you use nesting, there is no generation loss because nothing is rendered until the end. There is a way to edit/modify a nested project but it involves running 2 instances of Vegas and for a large project with many sections that you want to isolate it could become wild, loading 1 or 2 to edit, then closing those and opening another 1-2 to avoid the ultimate limit of your system running multiple instances. I think it would also depend on what type of changes you will make to a 2nd generation as to weather it is better to go with whatever! Regardless, if you keep the project you made for section one to render the 1st generation and find you need something alter, you can always go back, change the project and re-render and that then is the new/edited 1st generation.....I'm not sure I explained that very well. __________________ Best Regards.....George