mpg quality to raw avi quality

auggybendoggy wrote on 9/2/2003, 7:18 PM
Can anyone explain why my mpg 1 or 2 quality is not near as smooth as my
raw avi quality? When I render a file it seems its a little less smooth and is completely noticable.
My thoughts are that if a motion picture can be compressed to a dvd and still keep such great quulity then why shouldn't we dv owners.

Perhaps theres timing issues involved that make it imposs w/o EXPENSIVE equipment.

Auggy

Comments

Former user wrote on 9/2/2003, 7:22 PM
A motion picture is not compressed on $300 software. They use hardware compressors that cost several thousand dollars.

But given that, you can still make a very good MPEG2 file with software. MPEG1 is by nature, I believe, always less quality.

Dave T2
auggybendoggy wrote on 9/3/2003, 7:01 AM
Dave,
I have tried everything in the options to make the best mpg2 video and no matter what its just not as smooth. Is this always the case? Perhaps I don't know the difference of dvd (professional) because I never saw the original which also may be much smoother.

Jpg can be so good that you can't tell the difference from an original uncompressed tif file. Then again I don't believe the picture quality is what suffers. It's simply the smooth motion.

Anyone else have some wisdom on this.

Auggy
TheHappyFriar wrote on 9/3/2003, 7:31 AM
I haven't had any problems with my mpeg-2's being un-smooth. Are you playing them on a DVD player or from your computer?
gold wrote on 9/3/2003, 8:35 AM
The very nature of digital video hinges on lossy compression; it will never be as good as the original analog. If your AVI is not compressed as much as the mpeg 1 or 2 then it would be of higher quality [MJPEG and mpeg 1 are similar and don't utilize frame to frame difference compression of mpeg2]. Thus mpeg2 would give better quality than mpeg1 if the total compression were identical [however, a 5:1 mpeg1 would be superior to a 100:1 mpeg2]. Content has a lot to do with it. Mpeg2 cannot tolerate zooms well as they mean that there is little common area frame to frame. Mpeg1 works on a standalone frame basis and has no problem with zooms. Best source of info is the look under the hood of the different codecs....
Chienworks wrote on 9/3/2003, 9:18 AM
What bitrate are you using when you create your MPEG file? If you bitrate is too high then your player might simply be unable to read the bits from the file fast enough to display every frame. With my DVD player i can playback about 4Mbps from a CD-R, but if i go up to 4.5 then it starts skipping badly. It can handle about 9Mbps from a DVD-R but anything above that starts skipping too. If you're playing the files on your computer then its possible that the computer can't handle decoding the data above a certain rate. When the bitstream is too fast, the player will skip occasional frames in order to catch up with the stream.
riredale wrote on 9/3/2003, 12:49 PM
A DV avi can be compressed using MPEG2 at a bitrate of about 8Mb/sec to look pretty much identical to the original DV avi. If there is little video noise in the original, then the bitrate can be substantially reduced--Hollywood DVDs typically run in the range of 4-6Mb/sec. I don't think these low bitrates are because of better encoding, since you can get software encoders such as CinemaCraft that are very good, but rather the low bitrates are due to the noise-free source images (35mm film).

I did a project a few months back that had over two hours on a DVD-R blank. That much material means a low bitrate is necessary(~4.5Mb/sec). Even so, the results were excellent once I did a video-noise-reduction pass over the source material before encoding.
gold wrote on 9/3/2003, 3:01 PM
I somehow missed that the avi was dv; if 25 Mbs dv--common on consumer grade cameras, this is a compressed, lossy format to begin with; so your dvd should be as good as the avi. Now if your avi were uncompressed capture using a dps reality, video toaster, targa 3000, etc. and your source were NTSC video straight from the camera rather than tape; there is no way your dvd could compare in quality.
Adam Wilt is sort of a defacto standard and he likes dv so I may be overly pessimistic in that I deal oftimes with scientific quality video rather than just what a human perceives from a movie, see his insights
http://www.adamwilt.com/DV-FAQ-tech.html#DVformats
auggybendoggy wrote on 9/3/2003, 6:40 PM
im looking on it on my pc. I'll try messing with the bitrates some more.
I don't think its the comp. The motions loss is stable throughout the video.
I am getting in a dvd burner this week -
by the way if anyone hasnt got one tigerdirect has em for 119.00 bucks

not too bad.

I'll keep everyone posted

Thanks for the help all
gold wrote on 9/4/2003, 7:45 AM
What is the source of your video? What is the type of subject matter? Mpeg2 handles fixed backgrounds with small sprites moving across the background well via motion compensation [mpeg 4 does it even better] other motions it doesn't like as well. If your video is coming from a camera that outputs dv then there is a feature in the dv compression codec that is different from mpeg for motion compression that is implemented in some dv cameras that may not make the jump to mpeg2 well [can't remember the name off hand but it may be selectable--it affects the size of i frames relative to p and d frames tending to sacrifice i quality while increasing p content]. Another general reference is
http://www.newmediarepublic.com/dvideo/compression/adv08.html