Andrew Palfreyman wrote:
> Chris -
>
> I address your points below. When I refer to "Tailor", I mean FutureTel's frame-accurate MPEG editing engine, which is integrated into both the VideOh! and the Video Sphinx Pro products. Tailor is a cut-and-paste non-real-time editor. Tailor includes support for special effects, two of which (Fades and Titling or both) are integrated into ClipView 2.0. The current implementation of Effects is a complete re-encode (but a careful one, in the VBV sense) over the effect duration.
> You might also like to read my reply to Halstead York on this topic.
>
> At 12:02 AM 10/3/98 PDT, Chris O'Leary wrote:
> >My concern is that you have to accept one of several limitations when
> >you talk about editing MPEG. The first limitation is that editing a
> >standard MPEG stream will likely cause a video buffer overflow - which
> >will mean that the stream will be rendered illegal and cannot be played
> >back from that point on.
>
> Correct, but Tailor takes pains about this.
>
> >You can get around in several ways. You can lower your bit rate or inject blank frames, but this will impact quality.
>
> Correct, but Tailor does not do either of these things.
>
> >You could also re-encode the clip from the point of the edit,
> >but that can be a hassle, especially when you are dealing with longer
> >clips.
>
> Correct, but Tailor does not do this either.
>
> >The third option is to do what is called an I-frame only encode.
> >This is to encode the sequence using only MPEG I-frames and not P-frames
> >and B-frames. The problem is that an I-frame only encode is basically
> >the same as a motion-JPEG encode. The point of MPEG is that is looks
> >for opportunities to compress both within (intraframe) and between
> >(interframe) frames. With an I-frame only encode you aren't using any
> >interframe compression, so your file won't be as small as a standard
> >MPEG file. A fully-encoded stream with I, P, and B frames could be 5 to
> >10 percent of the size of a comparable I-frame only or motion-JPEG
> >encode. The point of MPEG is that its files are smaller than
> >motion-JPEG files but are of comparable quality.
>
> Correct, but Tailor is a full IBP editor, so the above does not apply.
>
> >The bottom line is that MPEG editing is possible, but is very hard to
> >ensure that the file will be small, high-quality, legal, and not have to
> >be re-encoded.
>
> Then I guess we did the very hard thing.
>
> Cheers,
> Andrew
-- SCA - Padrhaig ne Killkenny "Duine nach dtéann leis an slua" Mundanely - Chris Peters http://www.cyburban.com/~chatelaine The Canton of Northpass http://www.cyburban.com/~celticbard My website (always under construction!)