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Posted by PTravel on 01/08/07 00:42
"Jim S" <Jim S@jimsplace.com> wrote in message
news:45a18abe$1@clear.net.nz...
>
> "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
Neil's post hasn't shown up on my news server or on google groups, so I'll
have to respond to it here.
Neil's explanation is interesting and, of course, accurate. I would only
add this: the DVDs that I author, though not of commercial DVD quality,
approach them very closely (at least commercial DVDs that use video source
material -- "film look" is an entirely different issue). I view them on my
52" RPTV (which has 700 line resolution), as well as a video monitor and
standard televisions.
I use tmpgenc for transcoding, and can see significant (meaning readily
viewable) differences depending on the transcode settings of the software.
Tweaking tmpgenc to produce maximum quality, I get very high quality DVDs
that come very close (but are still discernible as different from) the
original DV-codec-encoded AVI source. However, it also takes up to 24 hours
to do a double-pass, 10-bit precision, deep-motion search transcode of 2
hours of source material on my 3 GHz P4 with 1 gig of RAM. There's simply
no way that a DVD camcorder can remotely approach this kind of quality using
single-pass real-time on-the-fly transcoding.
>
>
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