Optimal Bitrate Settings

[Brazil]

Hello all,

Just a quick question and I am sure that the answer is a fairly subjective one but I would like to know at what point increasing the bitrate for an avi using Divx 5.1 becomes worthless. I sometimes fill up one DVD-R with a single film with a bitrate of about 2300. This film was the first Lord of the Rings. The quality is obvioulsy amazing. I dont set the bitrate myself I just decide the file size of the avi though GKnot. So is there a point where simply increasing the avi file size and therefore the bitrate becomes a waste of time with no noticeable visual improvement?

The reason why I ask is because I bought an Archos AV320 (which never seems to get a mention on this site although it really is a great portable Divx player) and that one of the latest rips I did which has a 2433kb bitrate film at 608x480 has a little difficulty keeping the sound and video in sync due to the large bitrate.

Thanks for any responses,

Ben.

[SeeMoreDigital]

Sorry Ben. There's no such thing as an 'optimal bitrate setting'. There are just too many variables!

I find it strange that you chose to encode LOR at 604x480 pixels. Especially if you are viewing it on the Archos AV320.

The Archos is a fine little player but it really has not got the processing power to decode such large image pixel frame sizes at high bitrates!

You could either try encoding at lower bitrates, say below 900kbps or halve the resolution to 360x240/288.

Cheers

[Brazil]

Thanks for your reply.

The film I did at 608x480 wasn't Lord of the Rings. All of my files are 640X352. It was just one film which was a full screen film which I did at 608X480.

But my question still stands, is there a point where increasing a bitrate really makes no difference to the quality of the film?

Thanks again,

Ben.

[SeeMoreDigital]

It's impossible to forward a reply as we all respond to an image in different ways. So when it comes to watching encoded moving images, the answers you're looking for, become even more subjective!

I personally can't see the point of using DivX above 4000kbps. As at this bitrate we are close to the lower end of DVD (Mpeg2) bitrates!

It all depends what kind of monitor you view your encodes on too. I encode most of mine for widescreen TV viewing, which means I don't necessarily have to encode them using the high bitrates required for PC viewing!

Each to their own.

Cheers

[Beastie Boy]

Brazil, since you are using GKnot all you need to do is carry out a Compression Test to see how much the movie is being compressed at the current settings.

If the indicated percentage is close to or above 100% then your bitrate is too high. Essentially anything below 100% indicates that the encoder could theoretically produce a better output with less compression if a higher bit rate or lower frame size was used. If the percentage indicated is above 80% then you would probably get a better looking movie by increasing the resolution so that more detail is shown.
Bear in mind that there are a lot of factors that affect the compressibility of a movie like filters, resizing method etc.

If you want a straight answer to a straight question without subjective opinions then this is the only thing to do.

Cheers, Beastie.

[SeeMoreDigital]

Aaaarh, me hearty!