Re: Two Pass Encoding

Yo Fabio,

> Hi,

> a little question about two pass encoding that flyes in my head from a
> long time:

> In the first pass of a two pass encoding is necessary give to transcode
> program all the parameters of final transcoding?

> For example, if I have to transcode a video that needs some filtering
> and resize, in the first pass is mandatory to give all the options, like
> bitrate, resampling, filtering etc, etc?

In the first pass does the codec determine types of frames (I/P/B) and
writes additional information to be able to match the wanted filesize
in the second pass.
Thus bitrate has nothing to do with two pass encoding. (Maybe average
bitrate, from which you can calculate filesize.)

Both passes work on the same input - the frames should be naturally
the same. So you have to apply all the filters if you wish the second
pass to do what it should - match the desired filesize.

But in fact you cannot do anything wrong when you do not apply all the
filters in the first pass. The result will be just filesize different
from desired value and maybe some wrong decisions on types of frames.
But the resulting video will be coded in the second pass, thus giving
you all you wanted.

Naturally, it is better to use the same input for both passes.

> Thanks a lot! :)

> ciao.

> 	Fabio.

   Picasso Pablo