You can't ever smart render 25p to 50p if that is what you are trying to do, because the underlying data is changed (two output frames for each input frame). Smart render only applies if each video frame will be unchanged. Rewrapping and trimming, cutting or joining don't change the way each frame is coded. The frames are passed through without decoding.

EDIT

I assumed that you would be creating a new interpolated frame in going from 25p to 50p, but I suppose you could smart render it if you just repeated a frame. But why would you do that?

"I realized that closed gops is required for smart render an mpeg program steam"

Smart render is usually understood to mean that MOST frames are transmitted unchanged, and only frames in the vicinity of cuts will be recoded to fix up those frames which look back or forward to frames that no longer exist. A cut on an i-frame should be passed through without recoding because that frame doesn't rely on information in other frames.

Some so-called smart render software will only put cuts on i-frames and therefore does not have to recode at the cut.

Sorry, i was not understandable.
When i wrote HDV 25p preset can do smart render the input file was also in 720/25p format.
When i change that preset framerate to 50p, render some test video to that 50p format, and this is the video what i try to smartrender to 50p format.

So when i use smartrender i always take care that resolution, fps, etc. is the same of course.

Now i try to render 1280x720 50 fps videos to mpeg2 TS from vegas.
It works. But this file cannot smart render again exactly to the same format (render template)

Why?

I suspect it's just the precaution on programmers side: they forbid smart render for "unknown" formats. Technically it's possible, but not in current Vegas version.

So a program stream cannot be an "unknown" format?

Why not? Program stream is just a container.

Because with program stream it works great.

I'm surprised you would get a ts to smart render at all.
Vegas does not correct stream or GOP errors, so your source must have been absolutely pristine t start with.

Broadcast streams containing the usual number of errors often won't open in Vegas at all without a pass through vrd, much less smart render.

It's all about my own materials.
As i wrote earlier, Stereoscopic player works better with TS format. PS playback is often jerky, cannot seek, or freeze sometimes.
That's why i need TS. But would be good, smart rendering to a new TS, when i do some editing, cut, etc. I like to erase the original files, and only have transport streams.

You can smart render any MPEG-2 stream, if you use Womble to actually make the cuts.

How?

Well, do your edits in Vegas. Use just a single video track, with its audio. Then, save it as an EDL text file.

Download the EDL to Womble converter

EDL to Womble.

and run that. It creates a Womble project file. Open that in Womble and smart render to your output. It will not re-encode, except at the cut points, as already described in previous posts. This always works, and it works with any MPEG-2 source that Vegas can edit.

Thanks, maybe i will try.
Too bad it's not a free app.

Some "program streams" I created couldn't even been read by Vegas. It was not proper mpeg-2 video, just reencoded screen capture with weird resolution/fps, but whatever - it was not working. And, you know, I was after easy editing format, with smart rendering as additional bonus, but it doesn't really work for my workflow. I turned to h264 streams in mp4, and without smart rendering.

As for your situation, you have transport stream in the beginning and want transport stream in the end. You can convert transport stream into program stream with some muxer and smart render it into another program stream. What stops you from converting resulting program stream into transport stream with help of those same muxers you use at the beginning?