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Posted by Jim S on 01/08/07 00:05
"Neil Smith [MVP Digital Media]" <neil@nospam.com> wrote in message
news:hnl2q21sl0njrhepq8p67te69o1i6fqfiv@4ax.com...
> 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
Thanks for this explanation Neil. I have noticed considerable differences
between the quality of video on commercial DVDs, but some of the more recent
DVDs are of a better quality than I can produce from my miniDV camcorder.
However, the difference is only really noticeable when I project the images
on to very large screens, such as 120". I also think that the equipment from
which the video is played needs to be of the best quality to ensure good
results. For example, the use of HDMI connections between the equipment is
desirable.
Cheers, Jim
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