Digger
Guest
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 Posted:
Sat Dec 25, 2004 12:13 pm Post subject:
Re: avi / mpeg2 files |
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Suggestions:
1. Today's breed of smart renderers can combine scenes, add transitions, and
produce fully qualified DVDs in less time than it takes to compose this
reply. For smart rendering to be of benefit, all video files used for
combining scenes must be identically formatted. The lesson herein is to use
exact same capture format and bitrate for all archived video -- don't change
video bitrates, formats, or mix and match differing video parameters (upper,
lower, interlace, etc). Any differences in format between 2 or more files
may trigger undesirable re-compression while rendering.
2. Capture video as I-Frame only (no IBP color compression). This will
forcibly preserve the original color content of each frame. If for some
reason it later becomes necessary to re-compress, there is now a fudge
factor (I-Frames) already built into the file footage. One cannot
completely eliminate frame degradation, but, damage can be mitigated by
capturing I-Frames only.
3. Use a constant bit rate (CBR) -- exact same bitrate setting for each file
archived -- do not use variable bit rates (VBR) for archival purposes. I
recommend 8 to 9 kbps as standard video bitrate for up to 1 hour of
contiguous video. As mentioned earlier, when bitrates differ between mpg
files (scenes), the differing scenes must be re-encoded (re-compressed) and
rendered to a common bitrate...ultimately degrading overall output quality.
4. Audio is typically re-multiplexed (mux'd) during use of authoring or
editing software. Thus, other than inherent latency or bad source issues,
audio transforms are easily accomplished independent of video compression.
Changing audio format or bitrate will not, of itself, force video
re-compression; final output is rendered with audio transforms intact. In
the interest of broadest possible compliance, consistency, and reliability,
LPCM & Dolby Digital (AC-3) are the only audio formats commonly mandated by
both NTSC, and PAL/SECAM. I would recommend LPCM as the audio format of
choice, but you will need to research this further and choose a format based
upon your own best needs. I personally would not archive audio as MPEG-1,
2, or 3, but once again, it really is a matter of personal preference.
I also utilize mpeg-2 for archival purposes; beginning early in 1999 and
using hardware encoders. Barring initial learning curves, I have been more
than satisfied with the results and with the recent availability of consumer
grade dual-layer media, life simply gets better and better.
Hope something here will be of help in your quest,
--
Digger
"Victor Eckhardt" <victor_eckhardt@hotmail.com> wrote in message
news:exzzDIi6EHA.3236@TK2MSFTNGP15.phx.gbl...
| Quote: | To save space, I'm intending to store my AVI files as MPEG2 on data DVDs.
How well will I go later in editing the mpeg's; or should I convert back
to AVI? Appreciate any advice
Victor
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