Is quality lost when editing mpeg vs. .AVI?

Ponderer · Post by **Ponderer** » Sat Jan 15, 2005 6:42 pm

I've got space problems folks. One of the projects I'm working on is simply taking 10 years of family video and securing it for posterity's sake. However, I would like to go back later and catalog it into different sections (i.e. Christmas, Family vacations, etc.). But as I capture these tapes onto my PC in .AVI format I'm losing space quickly. If I convert them to mpeg2 format for storage purposes and then go back later to catalog them, will I have less quality videos than if I edited straight from .AVI? Please tell me I can convert to mpeg!!!!

jwarner · Post by **jwarner** » Sat Jan 15, 2005 7:02 pm

You could always add an external USB hard drive to archive you original captured files.

I bought an Ultra Housing and 120 gb HD for about $150 that work great for that purpose. Since it's only spinning when I connect it to archive or backup files, it's very secure from virus's and hardware failures. I can also easily move it and its file from PC to PC.

Ponderer · Post by **Ponderer** » Sat Jan 15, 2005 8:10 pm

Thanks for the idea. Unfortunately....I'm talking about my external HDD. My internal HDD is only 60GB and the external HDD is 80GB, but I'm still managing the space issue. .AVI is just so cumbersone!

jwarner · Post by **jwarner** » Sat Jan 15, 2005 8:33 pm

Hmm - can't answer your original question since I did the same as you but captured to MPEG-2 in the first place. I now have about 40 hours worth of MPEG's (about 80gb) archived on my external hard drive.

I use the other 40gb's for system backups.

Maybe it's time you sprung for a larger drive? You could install your external drive in your system and spring for a 200gb drive for the external enclosure. You can get 200gb for around $100 US now...

After all the work it takes to capture these files, I'd sure want to archive the original versions someplace safe!

THoff · Post by **THoff** » Sat Jan 15, 2005 8:47 pm

High-quality real-time MPEG encoding is difficult and extremely resource intensive. You will get better quality if you capture as DV or AVI with lossless or near-lossless codec, and transcode to MPEG when making your disks. Since these are probably priceless family memories, I would spring for a larger drive rather than sacrifice quality.

jwarner · Post by **jwarner** » Sat Jan 15, 2005 10:32 pm

High-quality real-time MPEG encoding is difficult and extremely resource intensive

Unless you have a hardware MPEG encoder.

My captures were done with an ADS DVDXpress box which did all the work. All my PC had to do was write the file to my hard drive at the rate of 2 MB/hour.

jchunter_2 · Post by **jchunter_2** » Sat Jan 15, 2005 11:50 pm

Ponderer,
I did a series of resolution tests covering avi vs mpeg2 resolution using fixed and moving test patterns. I was unable to detect any visible difference in resolution at a 720 x 480 frame size whether captured as avi and converted to mpeg2 or vice versa. Moreover, I was unable to detect any visible difference when mpeg2 or avi was repeatedly edited and rerendered up to ten times.

These tests did show significant degredation in resolution when video files were converted to the wrong frame type. The worst distortion occurred when converting Upper Field First or Lower Field First to Frame Based.

THoff · Post by **THoff** » Sun Jan 16, 2005 12:08 am

jwarner wrote:
High-quality real-time MPEG encoding is difficult and extremely resource intensive
Unless you have a hardware MPEG encoder.

My captures were done with an ADS DVDXpress box which did all the work. All my PC had to do was write the file to my hard drive at the rate of 2 MB/hour.

Yes, my comments were directed at anyone considering doing on-the-fly capturing in MPEG format using their system's CPU, not using a specialized ASIC/DSP. I'm also not saying that it's not possible, I'm just saying you need a fast system to do it.

Incidentally, both ATI's and NVIDIA's high-end video cards have video encoding capabilities. NVIDIA's 6800 chips can do MPEG1, MPEG2, and even MPEG4 at better than DVD resolution -- I'd really love to see support for this feature in UVS and other programs.

Ponderer · Post by **Ponderer** » Tue Jan 18, 2005 4:23 am

You know, one of the problems of a forum like this is that, if you have a question, the possibilities of answers range from basic all the way to expert and/or you get a redirect because all the vets are tired of answering the same old question (which is totally understandable). So the answer you are looking for may get lost in the stuff that's flying over your head as you process through the replys.

I truly appreciate the great answers and time that everyone spent answering my question. But, after reading them all and reading a bunch of other posts, I've come to the conclusion that the "Basic" answer to my question was "...if you can capture the video in mpg2 format then you can edit your project in mpg2 format. If you capture in .AVI, then it's best to do your project in .AVI." It sounds like there is not very much quality difference as long as the video is captured "correctly". Is this a supportable conclusion on the basic level?

kebrinton · Post by **kebrinton** » Tue Jan 18, 2005 4:52 am

Ponderer,

If you come to forum just a few times and read, you'll soon distinguish the knowledgeable from the opposite.

If you capture in .AVI format, you'll run the least risk of loss of data during the transfer. Then you can immediately create a new project and render the .AVI file to .MPEG2 format, which will take about 1/3 the space. Finally you can delete your .AVI file. [For the proper steps before rendering, read the first post in the forum.]

I think most of us respect the rather astonishing findings of jchunter, which were spelled out in great detail in the old forum (now closed): You don't risk perceptible quality loss if you work with .MPEG files.

Did you say you had to get rid of the old family video sources, for some reason? By all means, hang on to them. No need to have .AVI files if you can go back to the source someday in the future.

Good luck!

Keith

kebrinton · Post by **kebrinton** » Tue Jan 18, 2005 5:17 am

jchunter has retrieved the old information. It's here:

http://phpbb.ulead.com.tw/EN/viewtopic.php?t=861

in a new post.

david reece · Post by **david reece** » Tue Jan 18, 2005 1:45 pm

my 4 pence worth on this.

If i capture as direct MPG2 picture is ok for CBR but with VBR with fast movement it goes pixelated around a person moving about.

However the same clip from DV.AVi to MPG2 no such problems exist.

I have an ATI RADEON(tm) X600 PRO 256 mb.

I know it is long winded buy i think you get better quality this way than doing direct MPG2 capture.

Also bnear in mind people have experienced problems with audio/visual synhc using direct MPG2 both in VS7 & 8.

However if you edit an MPG2 file later you will get some degradation in the video quality i have found.

At the end of the day go with what you feel is best.

gordonwd · Post by **gordonwd** » Tue Jan 18, 2005 4:54 pm

You also have to consider the quality of the original source material. You are never going to get better quality out than you put in. I have found that the quality of old VHS tapes taken with an old VHS camcorder is not that great to begin with, especially when compared with those taken with newer DV camcorders. Capturing them with my Dazzle device that converts directly to MPEG and then editing in VS8 results in a DVD that looks just as good as the original tapes, especially when viewed on a standard TV screen.

Doug G

Ponderer · Post by **Ponderer** » Wed Jan 19, 2005 3:46 am

The part about getting a good capture with AVI and then converting to mpeg2 is what I'm looking for. I don't care about capturing directly to mpeg. I just want to get enough space back so I'm not continually playing "move the video files" to maximize enough disk space to use VS8 on my current project.

maddrummer3301 · Post by **maddrummer3301** » Wed Jan 19, 2005 5:08 am

10 years of video will be quite alot of work to convert and edit.

If the videos are VHS tape then contacting a professional service for
advice would be a way to go.

The pro's can dub the tapes and advise on how to store them and also
the expected shelf-life of the old and dubbed tapes.
In a few years, as technology only gets better there will be better storage
methods for the consumers and the pros.

A good dvd recorder,. Sony or Panasonic will give good results for a large
project with many videos.

MD