|
|
Posted by Neil Smith [MVP Digital Media] on 01/07/07 20:39
On Sun, 7 Jan 2007 05:41:04 -0800, "PTravel"
<ptravel@travelersvideo.com> wrote:
>> I've just done some editing from video taken on the memory card of a
>> friend's digital still camera. The results were surprisingly good for
>> viewing on a relatively small screen. But not so good if you want to
>> project the film on to a 100 inch screen with a video projector. Even my
>> miniDV (once edited and put on to a DVD) doesn't go too well on very large
>> screens, it's not as good as commercial DVDs, for example.
>
>You must have a pretty crappy miniDV camcorder, then. Commercial DVDs have
>a data rate limited to under 10 megabits per second, whereas DV-25 (which is
>the standard use by miniDV) has a data rate 2.5 times as great.
>DVD camcorders do single-pass on-the-fly transcoding. Producing an mpeg
>file from a DV-codec-encoded AVI can be done in software, can be
>multiple-pass, not constrained to real-time, etc. Yes, the end result is
>the same amount of compression. The quality of the video will vary
>dramatically.
PTravel, while I obviously agree with your general points about DVD
compression and editing of DVD source material, I'd like to return to
your comment about commervial DVDs if I may.
Compression is a large part but not the only part of the story here.
Commercially mastered DVDs will generally have come from either film
source or from a full quality camera source using 4:2:2 or even 4:4:4
colour resolution.
As you know, DV cameras of the type the OP's discussing are going to
be 4:1:1 - so the DV-AVI will have full NTSC resolution for luma, but
only 1/4 that vertically in the colour space (with PAL DV that changes
to 1/2 resolution in X and Y)
That can be useful to account for why even home produced DVDs from
DV-AVI don't ever get to the quality of a commercial product, because
you have 1/4 the vertical resolution for colour rendition (or half and
half for PAL, with a similar effect)
OP if you want to read about this, there are basic reference articles
like http://en.wikipedia.org/wiki/Chroma_subsampling#4:2:1
Cheers - Neil
------------------------------------------------
Digital Media MVP : 2004-2007
http://mvp.support.microsoft.com/mvpfaqs
Navigation:
[Reply to this message]
|