From AVI film to DVD: best format?

[Ron P.]

I checked some of my DV files and they all show a data rate of 3512.11kps. These are the original source video files from my Sony DCR-TRV120. When you render a project to a video file, then you set the data rate, which is referred to in VS as the Bit Rate. Data Rate and Bit Rate are interchangeable. For more information on Data Rate or Bit Rate there's plenty of reading found on Wikipedia
http://en.wikipedia.org/wiki/Bit_rate

[maxfrost01]

Hi, Ron

I'm getting these different bit rates on captured SD video which has NOT been rendered.
Looking more closely, I am even getting different data rates on footage from the same mini-DV tape! One section I captured reports 1829.97 and the next (captured from the same tape) shows a data rate of 3404.87.

And does data rate determine quality? Do these figures mean that the first section is only half the quality of the next?

How come it varies?

Thanks,

[GuyL]

The encoder determines the data rate. There are variable data rates and fixed data rates.

For variable rates, the encoder (built into the camera, or using software for rendering like VS), examines the scene to determine the lowest bit rate it can use and not lose quality. For instance, if the scene is static with not a lot going on then a low bit rate will work just fine while a fast moving scene with lots of changes will require a higher bit rate because there is more "data". This is to try and keep the file size smaller than it otherwise would need to be.

If you have a fixed rate then the video will be encoded with the fixed data rate for its entire length.

[maxfrost01]

So therefore a low bit rate does not indicate low quality? It indicates little action in the footage?

[GuyL]

No, not really. That is too simple .

A low bit rate could be low quality but it is relative in the case of a variable bit rate.

For instance, if you encode MPEG2 at a 6000 bitrate then some of the footage with be below 6000 if the encoder believes the quality will be the same.