Problem on Sony Vegas Pro 9.0c at DVinfo.net

Matias Sanchez · November 29th, 2009, 04:14 AM

Hi.
I'm editing avchd files recorded with my Canon HF S100. Sony Vegas 9.0c makes a fast smart rendering proccess over the video (with no recompresion), until a reencode is needed (transitions). After that, the rest of the video is reencoded too. (very slow)

Does anyone know anything about this?

Thanks.

Perrone Ford · November 29th, 2009, 05:55 AM

Yes, we do. Was that your question?

Matias Sanchez · November 29th, 2009, 09:07 AM

How to prevent unnecesary recompression after transitions?

Perrone Ford · November 29th, 2009, 09:23 AM

We can't answer that question because the rendering is absolutely necessary on transitions. It's that way in every NLE ever made.

Matias Sanchez · November 29th, 2009, 09:59 AM

Quote:

Originally Posted by Perrone Ford

We can't answer that question because the rendering is absolutely necessary on transitions. It's that way in every NLE ever made.

I said "after" transitions..Perhaps this Vegas version needs a fix.

Perrone Ford · November 29th, 2009, 10:41 AM

Sorry, but your wording was not very clear. "After transitions" could mean a number of things. After transitions are put on the timeline, after transitions further down the timeline, etc.

What transitions have you put on the timeline? Can you post a screenshot of your timeline?

Matias Sanchez · November 29th, 2009, 04:36 PM

I split de video file in Vegas. I put a transition effect (2 seconds duration)in the timeline between both segments.

Before rendering proccess gets the transition effect, Vegas doesn't recompress anything (Smart rendering) but transition. My question is: Why does Vegas remain recompressing all the video after transition??

Predrag Vasic · November 30th, 2009, 05:19 PM

So, for example, you have two clips. They are 35 seconds each. You create a cross-fade transition between the two clips, duration of which is one second (30 frames). When Vegas goes to render this thing, it zooms right through the first 34 seconds of the first clip (nothing to encode, just copy all data across), then slows down, renders the transition (1 second), then continues on to re-render the entire second clip of 35 seconds, even though only first 1 second of that clip has changed, and everything else is the same.

If this is the scenario, I can see why it happens. Since AVCHD is a long GOP codec, it creates keyframes every so often and all frames in between are interdependent. When you cut a keyframe out of that stream, all subsequent interdependent frames have to be re-rendered. The problem is, Vegas should be able to recognise where the keyframes are, and only re-render until the next keyframe.

It is possible, though, that Vegas is actually doing exactly that, but those keyframes are far between each other. AVCHD standard allows for keyframes to be 300 frames apart (10 seconds), so it is possible to find a situation where a cut (or transition) is made right after a keyframe, and the next one doesn't happen for the next 10 seconds, forcing a re-render of the entire segment.

I'm a Mac guy, so I don't have Vegas. Anyone with AVCHD experience with Vegas care to chime in?

November 29th, 2009, 04:14 AM	#1
Matias Sanchez Tourist Join Date: Nov 2009 Location: Murcia (Spain) Posts: 4	Problem on Sony Vegas Pro 9.0c Hi. I'm editing avchd files recorded with my Canon HF S100. Sony Vegas 9.0c makes a fast smart rendering proccess over the video (with no recompresion), until a reencode is needed (transitions). After that, the rest of the video is reencoded too. (very slow) Does anyone know anything about this? Thanks.

November 29th, 2009, 05:55 AM	#2
Perrone Ford Inner Circle Join Date: Nov 2006 Location: Tallahassee, FL Posts: 4,100	Yes, we do. Was that your question? __________________ DVX100, PMW-EX1, Canon 550D, FigRig, Dell Octocore, Avid MC4/5, MB Looks, RedCineX, Matrox MX02 mini, GTech RAID, Edirol R-4, Senn. G2 Evo, Countryman, Moles and Lowels.

November 29th, 2009, 09:23 AM	#4
Perrone Ford Inner Circle Join Date: Nov 2006 Location: Tallahassee, FL Posts: 4,100	We can't answer that question because the rendering is absolutely necessary on transitions. It's that way in every NLE ever made. __________________ DVX100, PMW-EX1, Canon 550D, FigRig, Dell Octocore, Avid MC4/5, MB Looks, RedCineX, Matrox MX02 mini, GTech RAID, Edirol R-4, Senn. G2 Evo, Countryman, Moles and Lowels.

November 29th, 2009, 10:41 AM	#6
Perrone Ford Inner Circle Join Date: Nov 2006 Location: Tallahassee, FL Posts: 4,100	Sorry, but your wording was not very clear. "After transitions" could mean a number of things. After transitions are put on the timeline, after transitions further down the timeline, etc. What transitions have you put on the timeline? Can you post a screenshot of your timeline? __________________ DVX100, PMW-EX1, Canon 550D, FigRig, Dell Octocore, Avid MC4/5, MB Looks, RedCineX, Matrox MX02 mini, GTech RAID, Edirol R-4, Senn. G2 Evo, Countryman, Moles and Lowels.

November 30th, 2009, 05:19 PM	#8
Predrag Vasic Regular Crew Join Date: May 2009 Location: Manhattan Posts: 131	To make it perfectly clear So, for example, you have two clips. They are 35 seconds each. You create a cross-fade transition between the two clips, duration of which is one second (30 frames). When Vegas goes to render this thing, it zooms right through the first 34 seconds of the first clip (nothing to encode, just copy all data across), then slows down, renders the transition (1 second), then continues on to re-render the entire second clip of 35 seconds, even though only first 1 second of that clip has changed, and everything else is the same. If this is the scenario, I can see why it happens. Since AVCHD is a long GOP codec, it creates keyframes every so often and all frames in between are interdependent. When you cut a keyframe out of that stream, all subsequent interdependent frames have to be re-rendered. The problem is, Vegas should be able to recognise where the keyframes are, and only re-render until the next keyframe. It is possible, though, that Vegas is actually doing exactly that, but those keyframes are far between each other. AVCHD standard allows for keyframes to be 300 frames apart (10 seconds), so it is possible to find a situation where a cut (or transition) is made right after a keyframe, and the next one doesn't happen for the next 10 seconds, forcing a re-render of the entire segment. I'm a Mac guy, so I don't have Vegas. Anyone with AVCHD experience with Vegas care to chime in?

November 29th, 2009, 09:07 AM	#3
Matias Sanchez Tourist Join Date: Nov 2009 Location: Murcia (Spain) Posts: 4	How to prevent unnecesary recompression after transitions?

November 29th, 2009, 04:36 PM	#7
Matias Sanchez Tourist Join Date: Nov 2009 Location: Murcia (Spain) Posts: 4	I split de video file in Vegas. I put a transition effect (2 seconds duration)in the timeline between both segments. Before rendering proccess gets the transition effect, Vegas doesn't recompress anything (Smart rendering) but transition. My question is: Why does Vegas remain recompressing all the video after transition??