Xvid to DVD - does codec affect final result

[JayT]

Hi to all,

Ive been converting AVI films Xvid/DivX to DVD for a while now with great results, but a question has sprung to mind which i hope ppl out there can answer if i can explain it right.
When a conversion is made from Xvid to DVD for example does it matter which Xvid Codec you have installed on your PC as far as quality goes, i tend to think that the answer would be yes, if this is correct ,can altering the Xvid settings improve the final conversion quality without tweaking your present AVI to DVD software. Thanks in Advance ... Jay T

[bugster]

AFAIK, the answer is yes, the xvid codec used can affect the final output quality. In fact whatever codec is used to decode the source for display for whatever format can have an effect.

The reasoning behind this? The encoder needs to be fed with full frames of video, not compressed video, in order to encode it to mpeg-2 or whatever format you are aiming for. In order to achieve this the software uses the default system decoder in order to uncompress the source material. Obviously this is not displayed, simply stored in memory untill the encoder requires it. Therefore the quality of the decode stage can affect the encoder in that if the decoder does a poor job and so feeds 'bad' quality frames to the encoder, it is working with flawed source to start with and re-compressing it into another format won't make it any better!


This is all theory/educated guesswork but makes sense to me, hopefully it does to you too

[junkmalle]

Note that many codecs have filtering options that effect the decoded image. For instance, XVID has deblocking and "film effect" filters. Not to mention that sometimes one codec can't properly decode another's data (early XVID releases had often had problems decoding DIVX data, and vice versa). So, yes, the codec can make a difference.

[JayT]

Thanks both for the info, so in theory with ref to Xvid Codec, applying maybe the Deblocking filter within the codecs settings could improve the final conversion result.

[junkmalle]

Thanks both for the info, so in theory with ref to Xvid Codec, applying maybe the Deblocking filter within the codecs settings could improve the final conversion result.

Yes, the deblocking filter could help a badly macroblocked source.