Trim in VegasPro without loosing quality (if possible)

pats2265 wrote on 9/25/2018, 11:57 PM

I have some original video footage that is in mp4 format. Most of it I want to cut out. For the sake of discussion, say of video 55 min is fluff (can be cut) and 5 min is what I want to keep. I'm using Sony VegasPro v10 x64 on Win7 if that matters.

If I see that the video is mp4 format 640x480 as an example, but might be other formats. My current approach is to do the following:

(1) Set the properties of the vegas file to match the source, so if the source is 900x600, then I change the properties of the vegas project to match that. If it is 640x480 then change the vegas file to match that.

(2) When rendering, use custom rendering. I currently am using MainConcept (*.mp4) with Default Template and then select custom size to match the source. So the render format is identical the the source format both in file type, and in size.

My goal/attempt is to somehow cut out parts of the video I no longer want to reduce the file size when archiving the video.

My question is this:

If I do the above steps, will I have good results at not loosing source image quality?

The reason I ask, is that I want to do further editing on the "trimmed video" so I want to know if I need to keep the original video around or if I can delete it after I have re-rendered and trimmed a 40 min video to 5 mins.

NOTE: Vegas has another feature that might be better suited. I forget how to use it now, but it allowed me to say copy all of the original footage to another project but only what I was referring to (adding some number of frames to the start and end of each video clip). This is the feature I think would be better suited for what I'm trying to do. So if you know this answer please share it.

NOTE: Searching on the internet turned up these links:

https://vegasaur.com/smart-trim
Trim video but render it as original https://forums.creativecow.net/docs/forums/post.php?forumid=24&postid=982620&univpostid=982620&pview=t
How to trim videos without losing quality (YouTube)
How to cut/edit video without re-encoding

Comments

i am erikd wrote on 9/26/2018, 12:50 AM

You wrote: (2) When rendering, use custom rendering. I currently am using MainConcept (*.mp4) with Default Template and then select custom size to match the source. So the render format is identical the the source format both in file type, and in size.

Are you also factoring in bit rate? Also, I think you are saying you used the identical codec as the original as well so if that is true AND you are maintaining at least the same bit rate as the original, then you shouldn't have anything to worry about IMO.

On the other hand. Why remove the other content in the first place? Do you have hundreds of hours of this content that would possibly warrant deleting part of the original content?

Musicvid wrote on 9/26/2018, 2:14 AM

Vegas does not smart-render mp4; that is just asking too much for an NLE.

Instead of an encoder, you want a muxer. The go-to choice in Windows is VideoRedo.

There is a free trial.

NickHope wrote on 9/26/2018, 3:26 AM

My method for smart rendering using ffmpeg is in this post: https://www.vegascreativesoftware.info/us/forum/smart-rendering-in-a-batch-with-ffmpeg-gh4-etc--101381/

It does include compensating for repeat frames at the start and end of the trimmed clips, which is something you might not need. Also, the script develops over the course of the thread, so be sure to note the later comments.

Musicvid wrote on 9/26/2018, 5:28 PM

Nick, does your script recreate new Ref frames at cut points, or is the current GOP unclosed as in dos concatenation?

NickHope wrote on 9/26/2018, 10:08 PM

Nick, does your script recreate new Ref frames at cut points, or is the current GOP unclosed as in dos concatenation?

@Musicvid I don't know but I guess it does. How could I inspect a trimmed file to find out? It just does whatever ffmpeg does with a line like this:

ffmpeg -ss 00:00:02.603 -i input.MP4 -c copy -t 00:00:17.384 output.mp4

john_dennis wrote on 9/26/2018, 10:27 PM

@ Nick Hope

"How could I inspect a trimmed file to find out?"

This is the way I do it.

john_dennis wrote on 9/26/2018, 11:25 PM

When I ran your script on a random file from my camera it started two B-frames before the IDR.

Musicvid wrote on 9/27/2018, 8:25 AM

Looks like it concatenated, which Kelly always said works fine. Being a bit of a purist, I might point out that keyframe indexing as for chapter marks, subtitles, etc. would probably be lost.

NickHope wrote on 9/27/2018, 11:05 PM

When I ran your script on a random file from my camera it started two B-frames before the IDR.

Same here.