rendering time weird behaviour

marcinzm wrote on 5/28/2024, 3:56 PM

Hello,

I have noticed weird rendering time behaviour. I will describe you based on example.

I have two videos:

a) 4K 50p 200 Mbps 4:2:2 10bits XAVC - duration: 50 minutes in single raw file - overall duration 22 minutes after editing

b) 4K 50p 1500 Mbps 4:2:2 10bits Prores - multiple raw videoclips - overall duration after editing 11 minutes

I noticed that rendering time for a) was more than 3 hours. Rendering time for b) was 30 minutes.

As you can see that rendering time for a) is much longer than a). If I had 22 minutes in b) example the rendering time would be 1 hour.

Do you think that the problem is when we render single file which is very long (in my case it is 50 minutes), and we split this single file into small events, Vegas must search the pointer after these splites, and it must take time for Vegas to search this pointer, that's why the rendering time is much longer than if we render project after editing which contains many multiple videoclips which are short and we split them either.

Are you agree with me that we should avoid longer raw files for editing to avoid longer rendering time?

Regards
Marcin

Comments

RogerS wrote on 5/28/2024, 7:43 PM

That isn't unexpected.

Was a also HEVC? The more compressed a file is the harder it is to read and the longer it will take to render. ProRes is lightly compressed and doesn't even use GPUs to decode it. If you use proxy files to make say 10-bit 422 files playable when you render it has to work from the originals which may not decode in anywhere near real time.

The length of the original file is irrelevant assuming the length after editing is the same.

john_dennis wrote on 5/28/2024, 7:56 PM

XAVC is a compressed acquisition codec used to allow cameras to write video at relatively low bit rates to memory cards. The resulting video is much more difficult to decode than Pro Res (an editing codec meant to be read and decoded from fast hard drives). If you converted your XAVC to Pro Res before editing, the render times per minute would be closer, but you will have lost the time it takes for the conversion.

marcinzm wrote on 5/29/2024, 7:23 AM

So, let's sum up the issues.

ProRes codec is easy to decode that's why rendering time of project which contains ProRes files will be significally shorter than rendering events encoded in HEVC / XAVC, because HEVC and XAVC encoded files are harder to decode.

Dexcon wrote on 5/29/2024, 7:58 AM

A huge downside of ProRes is that ProRes file sizes are big to huge. A 202Mb UHD AVC file just rendered to ProRes with a file size of just over 1 GB using the ProRes 422 render format. If using the ProRes UHD HQ render format, the file size for that same event is 3.4GB - but I doubt that the HQ format would be necessary for an AVC transcode.

It then becomes a decision based on the balance between available HDD/SSD free space and rendering speed - as well as mentioned by john_dennis the time needed to first transcode to ProRes. And you'd probably need a bulk rendering feature/app for a large project otherwise it will be individually rendering event-by-event in VP - a bit of a turn off with 2,000+ video events as I often have for the one project. Obviously this isn't a problem with a limited number of video events.