rendering increases size?

gmes29 wrote on 3/4/2008, 2:35 AM
going back to my synchronization post (for the second time), i have 2 3-hour videos - one was complete the other broken up into 2 parts. i created a project for the 2 part video where i reduced the volume of the smaller clip and matched up the frames of both clips so they were now in sync. once i did that, i rerendered the video to mpeg-2 (same format as original video and with no special fx) so i'd have a single file instead of 2. when it was done, the resulting size was 8+gb. the other 3 hr video however was only 3+gb. further problems arose after i edited the rerendered video and tried to make movie to another mpeg. the estimated time of completion ended up cranking up all the way to 10 hrs which is ridiculous and a lot longer than any other video i've ever rendered from within vms. any ideas why the 2 clip video ended up being almost 3 times the size of the other 3 hr video?

Comments

owlsroost wrote on 3/4/2008, 3:36 AM
VMS does NOT smart-render MPEG so it will re-compress the MPEG file to whatever bitrate the render template uses - which is almost certainly much higher than the original files, hence the larger file size.

Why not render the final output from the original source files instead of rendering to an intermediate file and then editing it again ?

Because of the re-compression problem, VMS isn't the ideal tool for MPEG editing - apps like Womble MPEG Video Wizard and VideoReDo can edit MPEG without re-compression (as can the Vegas Pro 8). There are also some freeware MPEG editing apps around - have a look at [url=http://www.videohelp.com/tools/sections/video-editors-mpg-dvd] for a list.

Tony
Chienworks wrote on 3/4/2008, 3:37 AM
The size of compressed video files depends on the length and the bitrate. You didn't mention what bitrates the original files were or the birate of the rendered file. I'll take a guess though that the finished file had a bit rate about 3 times as high as the source files.

Combining the two MPEG clips into a single MPEG clip is probably a bad idea with no benefit. Vegas can continue working with your project containing two source files just as easily as a single file. It won't slow you down or cause problems working with the two original files. It won't help you to have them combined in to one. On the other hand, rendering from MPEG to MPEG can lose a lot of quality, so there's a distinct disadvantage in doing so.
gmes29 wrote on 3/4/2008, 10:09 AM
now i'm confused. in the other thread i mentioned how i rendered to avi from the original mpg thinking avi was compressed and therefore there'd be no data loss and someone had said that no re-encoding is done going from mpg to mpg which is why i'm going to mpg now (faster creating a disc in dvd-a). so since clip 2 of the 'broken' video was taken from the same source as the complete video (both 3 hrs), why would the bitrate change going from mpg to mpg if no re-encoding occurs? could it have something to do with clip 1 coming from a slightly different source than clip 2 (hence the different volume)?
Chienworks wrote on 3/4/2008, 11:45 AM
Vegas studio always reencodes when rendering from MPEG to MPEG.
gmes29 wrote on 3/4/2008, 12:20 PM
thanx Chien.
a couple more things..
how do i check the current bitrate?? i tried playing clips 1 and 2 in WMP and clicked on Properties off the menu and the bitrate was shown as '-' (dash/minus sign). why was there not a number there?

how do i control/change (if possible) the bitrate used at rerender time?
Himanshu wrote on 3/4/2008, 7:40 PM
GSpot provides good information about media files, including bitrate.