Bringing PNG Sequence into NTSC fps in a Video Editor

lwaxana · Post by **lwaxana** » Mon Apr 12, 2010 4:59 pm

As an experiment to work in the best quality until the final compression, I tried exporting a png sequence from AS. When I brought it into Sony Vegas Movie Studio, I had to enter a numerical value for the number of seconds each image is on screen. If I use PAL settings of 25 fps, I can specify that each image should show for .04 seconds. And it works great.

But if I use NTSC settings of either 29.97 or 30 fps, the division isn't clean. If I round at all, it flashes a black screen between the images.

Am I missing something here? I thought that as a workaround, I could bring the images in in PAL settings and then export to NTSC settings. But I wonder if that would introduce timing problems? I also saw a thread about free image sequencers and wonder if I should try a separate program for sequencing and then do the rest of the editing in Vegas Movie Studio.

Does anyone have some insights on this?

rylleman · Post by **rylleman** » Mon Apr 12, 2010 9:58 pm

Sounds easier to just use ffmpeg for the stiching;
ffmpeg -i imagesequence_%04d.png -r 29.97 -y output.avi
Could of course tweak it with codecs and stuff.

J. Baker · Post by **J. Baker** » Mon Apr 12, 2010 10:58 pm

It's usually best to use 24 fps. Then if you are going to make it interlaced, you just do a 3/2 pulldown in your mpeg2 (DVD) encoder. Or a DVD player will do automatic 3/2 pulldown.

slowtiger · Post by **slowtiger** » Mon Apr 12, 2010 11:08 pm

While importing a PNG sequence, the video editor should treat each PNG as a single frame of video - no matter at which FPS. After that you should be able to change the FPS setting without interpolating frames. Vegas should be able to do this.

lwaxana · Post by **lwaxana** » Tue Apr 13, 2010 12:13 am

Thanks for your replies!

Rylleman--I was not aware of ffmpeg. I will look into that more. Thanks! :D

J Baker--thanks for the tip about 3/2 pulldown! 24 fps is the frame rate I've grown used to so I'm glad to hear that dvd players will automatically pulldown. That should make things easier for me.

Slowtiger--Yeah, I would expect Vegas to be able to do this. I contacted Vegas tech support so hopefully they'll explain a convenient way to do this.

lwaxana · Post by **lwaxana** » Tue Apr 13, 2010 5:03 pm

Ugh. I just heard back from technical support. "Vegas currently has the ability to set this parameter by time but not by literal frame. This makes an interesting product suggestion." Well at least I know now that I need to look at other methods. :)

rylleman · Post by **rylleman** » Wed Apr 14, 2010 9:55 pm

lwaxana wrote:... "Vegas currently has the ability to set this parameter by time but not by literal frame. This makes an interesting product suggestion."...

I've seen this odd behavior in a few video apps, that they uses seconds instead of frames for time measure. Strange when frames is the core of moving pictures...