Bit rate vs Frame rate

[zok4me2000]

I have reviewed the forum messages but maybe its just me, I just don't get it. I fully understand frame rate and why you need to pay attention to this - but bit rate (fixed / variable)? Can someone explain this in street language without all the hub-bub. Why would you want to play around with this? What is it that you gain?

[yoda313]

BITRATE is essentially the amount of video information you can store in a video file. The more bitrate the better the picture assuming you have a quality source.

A simple comparison to do is to convert a captured video file to different bitrates. In general your original file will look the best. With each reduction in bitrate it will get more washed out.

This is not a technical explanation just kind of the jist of it.

[David K]

And the bigger the resolution of the video (720 x 480 for example is bigger than 320 x 240) the more bitrate you need to make the video look smooth and sharp.
So whereas 2 mbps would certainly give you a good looking video for a 320x240 resolution video, you might need up to 6 mbps for a 720x480 resolution video. (The amount of bitrate needed varies with the different codecs (for example, mpeg 2 versus XviD). The more efficient the codec (like XviD) the less bitrate it needs to maintain quality at a given resolution.

[mats.hogberg]

Also, the way most video codecs work, they take one frame, then for a number of frames, all that gets encoded is the difference from the previous. Where nothing much changes between frames, not much bitrate is needed to describe these changes between 2 consecutive frames. OTOH, a high action scene, very much is changed between 2 frames, This takes many bytes to describe. A CBR (fixed bitrate) uses the same amount of bits to describe these changes, no matter if they are needed or not, resulting in "a waste" of bits where nothing happens on screen, and a shortage (resulting in lower picture quality) in the high action scenes. A VBR encode can use the bits where they are needed, and hold back on them where they not. Mostlt this is done with multipass encodes, where the encoder first takes a look thru the whole movie to see where the action is, and where nothing much happens, then uses the # of bits it's told to use where they are best needed.

/Mats

[zok4me2000]

OK, I think I got it. What I do read in-between the lines is that it only makes sense to consider the bit rate when compression is applied, and for all recording media compression is the name of the game. So pretty much you need to give this serious consideration.

Can I assume that all encoding software allows the user to adjust the rate? What about whole packaged software(capture/edit/re-encoding/authoring) like ULEAD, PINNACLE and others? Is this an adjustable value provided?

[David K]

(No issue of bitrate control in capturing camcorder DV (Digital Video) because that is fixed by the tape, but that's a different issue.)
The all-in-one programs should have some bitrate settings for encoding (typically to mpeg for DVD). But they tend to have less options than the dedicated encoding software you will see mentioned here.

[mats.hogberg]

Can I assume that all encoding software allows the user to adjust the rate? What about whole packaged software(capture/edit/re-encoding/authoring) like ULEAD, PINNACLE and others? Is this an adjustable value provided?

Some packages, targeting the newbie, hides the bitrate (and other) settings behind terms like LP (Long Play) or HQ (High Quality) or other "dumb down" terms. Avoid those. A fine grained control over encoder setting are, as you've quite correctly deduced, essential to the quality of the final product.
Over all, a dedicated encoder offers more tuning than any "all-in-one" apps. My recommendeation is to go for dedicated apps as much as possible.

/Mats

[zok4me2000]

All of nailed it for me - Much thanks!

[thecoalman]

Ulead Video Studio is completely customizable, even for resolutions outside of the DVD spec. Movie Factory may have less non-standar doptions but I really don't know.