Vegas Cannot Decode MPEG2 ?

PunchNBurn wrote on 12/2/2003, 8:16 AM
I am having a real hard time using Vegas as an editor. I am importing MPEG2 media captures but they are almost completely uneditable in Vegas. The timeline continuously re-calculates the thumbnails and the previewer is WAY off. Makes it kindof hard to edit video when you can't determine where you are!

Any ideas why Vegas is having problems with MPEG2 media? Is this a problem with the MainConcept Codec?

Its not a performance problem. My hardware has plenty of horsepower, very low CPU usage, no HD problems, fairly high end video card, etc.

Comments

vonhosen wrote on 12/2/2003, 8:22 AM
Vegas is primarily a DV editor. Editing MPEG files is not easy because of the temporal compression they use. The MPEG stream is made up of GOPs (Groups Of Pictures) These comprise of I,B & P frames. The I frames are compressed similar to JPEGs & the B & P frames are not full frames they contain only info of the changes from the previous or next frame. Depending on whether you are using NTSC or PAL it is likely that you are only getting a frame with full info every 15 or 18 frames. hence it makes them difficult to edit easily. You should only cut MPEG files on an "I" frame or your editor is going to need to force "I" frames/create new GOPs.
Jsnkc wrote on 12/2/2003, 8:22 AM
Without getting into a long post about I-frames and B-frames and things like that basically you are having problems because MPEG-2 is a highly compressed format. If you use Uncompressed AVI or at least AVI-DV files you will have much faster editing. Try rendering your MPEG-2's to AVI-DV files then edit with those.
PunchNBurn wrote on 12/2/2003, 9:15 AM
Thanks to both. That answers my question. I am doing the captures myself and I CAN encode as AVI but the file sizes are huge. Even with two 160GB disks I'm running into space problems. I thought MPEG2 would work better. MPEG2 files are not only much smaller but also re-encode MUCH faster. I am getting 1.6:1 encoding time for MPEG2 but much higher ratio for AVI files. I have to encode to MPEG2 for imput to DVDA.

Would forcing the capture encoding to all I-Frames help?
Jsnkc wrote on 12/2/2003, 9:19 AM
If you capture all I frames your file sizes will be huge also. That is why MPEG can create smaller file sizes. There are only some I Frames which store the entire picture, and the other B and P frames store only what is diffrent between the I frames so it doesn't need to keep as much information and then you get the smaller file sizes. With the AVI-DV you should get about 1hr of video to be about 13GB.
Rogueone wrote on 12/2/2003, 9:21 AM
Can you record the source files into the DV AVI format? It takes approximately 13 GB per hour of video. Uncompressed AVI will take way too much space. Edit the DV AVI files, then render into MPEG2 for import into DVDA. You can also record source files into MPEG1, but the encoding time to convert it to MPEG2 is a really long process. DV AVI is really the best format for working with Vegas.

Rogue One