Setting Bitrate Higher Than Original AVI's - Worth It Ever?

[Slug]

Gspot tells me that the average bitrate for this AVI is 128kbps - I noticed that the average DVD bitrate is 4000-6000, and that at that point, a dvdr can hold 2 hours of video.

So, at 128kbps, will I A) Not lose any quality from this AVI and B) Be capable of storing a ridiculous amount of minutes on the dvdr?

It just doesn't seem to make sense in my head. The video is quite nice quality, and it seems unlikely that this will work as nicely as I figure it will. Is the avi bitrate able to be so much lower without sacrificing much quality just because of the codec? Will a 128kbps mpeg2 just look attrocious?

[Dhruv]

So, at 128kbps, will I A) Not lose any quality from this AVI and B) Be capable of storing a ridiculous amount of minutes on the dvdr?

A: Well everytime a video file is converted from one format to another, a little quality will be sacrificed regardless if the bitrate is the same or higher than the source. Normally this loss of quality is hardly noticable so I wouldn't worry too much about it.

B: Yup, you'll only find it difficult to store more minutes worth of video/audio on a DVDR if you use a high bitrate setting.

Is the avi bitrate able to be so much lower without sacrificing much quality just because of the codec? Will a 128kbps mpeg2 just look attrocious?

Yes, the codec and way it was encoded is what determines the filesize. Mind you, if you were to play a DivX on a giagantic television you'll be able to see a huge difference between the original source and the DivX.

Not quite sure how it'll look. I'd say try to encode to that, and preview the mpeg2 on your computer, if it doesn't look totally horrible then burn it and have a look on your television.
Regards,

[mats.hogberg]

AVI (DivX, XviD...) bit rate has no relation to what bit rate to use when you reencode it to mpeg2. Whenever you reencode, you'll get a copy that is more or less worse than the original. The higher the bit rate used, the closer to the original it will be (but never 100%).

/Mats

[sterno]

Is the avi bitrate able to be so much lower without sacrificing much quality just because of the codec? Will a 128kbps mpeg2 just look attrocious?

Yes and yes.

At a guess, your AVI file that looks nice at 128k is probably a relatively low-resolution DivX (or some other MPEG4 variant like xvid), maybe even with a nonstandard framerate. If it's done correctly, MPEG4 encoding will almost always look better at lower bitrates than MPEG2. Your MPEG2 file will also have to follow standards on resolution and frame rate, which may be higher - even if it MPEG2 just as efficient it could still look terrible because you're trying to encode more data in to the same space.