Streaming Video Quality

WildBlue wrote on 2/4/2003, 10:35 PM

Hi. I'm finding that when trying to stream a short video of an outdoor fall scene (lots of leaves rustling and someone walking towards the camera) the minimum bitrate that is even barely acceptable is 512kbps (I'm using the default templates in Vegas 4 beta). This seems true for both Windows Media Player and Quicktime. Is this the experience of other people? Does anyone have a sense of whether most cable or DSL modems will be able to view a 512kbps streaming video?

Comments

SonyDennis wrote on 2/5/2003, 10:36 AM

For what it's worth, "natural" scenes (leafs, wheat blowing in the wind, water, fire, etc) are historically the hardest scenes for a video compressor to deal with. They contains tons of detailed motion that if messed with, are very visible to the human perception system which has been "tuned" on the same types of pictures for millions of years. They are also typically "moving" everywhere in the picture, unlike an indoor scene or talking head. That's why, in any high-end DVD review magazine, the scenes they usually use to watch for compression errors involve fast moving explosions with lots of fire. Fast moving scenes are also hard to compress, but we're used to things getting blurry during fast transitions, so errors there are not as easy to detect. Don't mess with Mother Nature.
///d@

WildBlue wrote on 2/5/2003, 12:08 PM

Thanks, I appreciate the advice. It makes a lot of sense.

mikkie wrote on 2/5/2003, 1:35 PM

If this helps...

512 is getting up there for a lot of folks.

When you're trying something with that type of background, if the video has a bit of noise it can sort of force the encoding software to retain more of this movement detail - the compression works by trying to ignore anything static, & you're forcing it to pay more attention. I admit this is counterintuitive but it works.

Try Realmedia. Realmedia has long had the habit IMO of having a softer background.

Do 2 pass variable bit rate encoding, even if it means a slower encoder like that for winmedia 9.

Try going from a full frame video to a compressed 320 x 240 (let the compression software resize it). Again, maybe counter intuitive, but you're giving the encoder more information to deal with, even if it throws half away.

Try cutting the frame rate down, allowing more bitrate to quality. Try moving your keyframes wider appart (allows more bitrate & smooths motion). Try setting the quality levels lower/smoother (with realmedia 9 you can edit the XML audience files to access this). Try brightening things up - most encoders have more of these problems the lower the light levels.

Try capture/encoding in one step. At low bitrates Real seems to do a bit better in this regard then winmedia, but both can yield better results then compressing existing video on your drive.

Finally, check out the DiVX folks, forums etc... Even if you decide not to try DiVX, you'll find a bit of info on breaking up your video and rejoining it. If I visualize your scene correctly, an example might be to encode with smoothness set very high, noise filters way up -> find where your subject starts to come closer & you need more focus -> encode with settings that make this look good -> use the same bitrate for both *halves* -> put the two together using something like asftools or rmeditor (DO NOT recompress).

mike