On Wed, 18 May 2005, Matt wrote:
> I am looking for a way to output dvd's without having to move data
> (sneaker-net style) to a mac every time I want to make one.
At the risk of sounding silly why not put the Mac on the network? ;)
Actually sneakernet can be faster - moving a 120GB Firewire drive
50 feet in 30 seconds is a fantastic transfer rate :-) :-)
> I have used mpeg2enc and it seems serviceable as does dvd-author.
So far I've been able to retain using mpeg2enc for the encoding and it
does a very good job once you have grasp on the options to use and
how to pre-process/filter the incoming data (when doing analog->digital
conversions).
> The questions:
> 1. Is anyone else using this for work that one would call professional,
> and is it working out? We are doing animation work, largely computer
For myself I've moved more and more of the acquisition, initial
processing and eventual authoring *to* the Mac.
For generation/compositing there's Motion at the entry level and
Shake at the high-end but Shake is quite expensive (but is available
for Linux I believe).
> generated 3d stuff, so the encoding is critical. My experience says that
> animations always seem to suffer more than video during encoding. And my
Hmmm, ok - generating animations (modeling/compositing) isn't
something I've worked with a lot. I do see a lot of animation but
from the viewpoint of analog->digital conversion and trying to
cleanup/retouch/salvage/etc the video into something watchable. That
type of analog material when digitized is extremely hard to
denoise/cleanup.
I assume you're familiar with the usual caveats for computer generated
video: no thin lines, avoid highly saturated colors especially reds
(i.e. be broadcast safe - computer monitor != TVset), avoid excess
luma (too bright), avoid superblack (too dark), use 24000/1001fps
progressive and 2:3 pulldown instead of 30000/1001 fps (more discussion
about that below), avoid small fonts (less than 14points), observe
the titlesafe and action safe regions, ...
Oh - and avoid JPEG at any stage of the process! Use a lossless (PNG,
PPM, etc) format during the creation process. The use of a lossy
intermediate format loses enough information that the encoded MPEG-2
output often looks poor.
and so on and so forth :)
> quicky customer demos, but less than perfect for dvd generation. Not
> horrible, just not great and usually not up to apples compressor. As a
> note I have been using mencoder for my dvd tests up till now.
I've only used Apple's compressor program when there wasn't a way
around it ;) NOT that it's bad - it's very good - but it's not
scriptable from a bash script and it has some limitations that I find
irksome - it doesn't appear to allow me to specify cropped D1 output
if I want 704x480 instead of 720x480, doesn't implement DPME (Dual
Prime Motion Estimation) which I find helps improve the picture when
not using B frames, the choice of GOP size is limited (most of
the entries in that menu always remain grey'd out).
One thing I am looking forward to in DVDSP4 is the new Compressor
2.0.x which can do HD resolutions (both MPEG-2 and H.264) - that
will be fun to play around with.
Mencoder's rate control wasn't as good as mpeg2enc's the last I heard.
For quite a while (even fairly recently) folks were having trouble
getting 100% compliant streams out - sometimes it would work, other
times the standalone players would object to the files. Your Mileage
May Vary of course :-)
> 2. I have already noticed that mpeg2enc does not appear to perform 2
> pass encoding. Is this really a detriment?
Not really. For a 1 pass encoder it's one of the better ones (the
rate control has become amazingly good - little overshoot and quick
recovery). It's also quite fast - the bottleneck is rarely if ever
the encoder but instead the filtering/pre-processing.
About all I've seen two pass encoding do is almost double the encoding
time <grin>
> 3. I currently am working on a project where about 16 seconds of video
> ends up looking like 17MB of data encoded with good visual qualities
> (8500 Kbps). Not that I currently need it, but won't this eventually
> lead to a serious time limitation if a project goes the distance?
How long of a project is it planned to be? With the right options
you should be able to get down to ~7500 and get 85-90 minutes on a
single layer piece of media.
Were you generating the data at 24 or 30fps? You can save ~20% on
the bitrate (or viewed another way you can keep the same bitrate and
get a ~20% increase in quality ;)) by using the film rate (well,
24000/1001 ;)) instead of 30. That would also make converting to the
25fps ("PAL") format simpler - a modest speedup instead of going from
30 to 25.
> Realistically that is looking like an hour of video on a single layer
> disc, is that about right?
Closer to 75 minutes depending on the number of menus (and
if the are motion menus or not), how many transitions are used,
the audio rate and so on.
When DVD media makers say "2hrs" they're figuring an average bitrate
around 5000Kb/s or so. The 1 hr figure assumed the max (~10Mb/s)
DVD rate. So 8500 would be somewhere in the middle.
Dual layer media has come down a lot in price. A few months ago
it was $11 per disc, now it's around $4.50 or so. I keep a few DL
discs around just in case a project ends up being too large - rather
than drop the quality/bitrate down I'll increase the rate, add in an
extra trailer/specialfeature or maybe an alternate sound track, slide
shows, etc.
> 4. Obviously compatibility with hardware players is a clear concern, and
> I have read the dv-to-dvd.txt, so those tips are in my head. Are there
> any other pitfalls a person should be aware of when mastering a dvd with
> these tools?
The obvious (and it is a VFAQ - Very Frequently Asked Question ;))
one that comes to mind is that you can NOT append/catenate multiple
files seamlessly with dvdauthor - you'll have stutter/stops/gaps and
so on at the join/splice points(depending on the player used). DVDSP
has no problem joining multiple files together in a single track.
So if you were planning on creating the content in smaller pieces and
adding them together in the timeline, well - you may need to work
with DVDSP a little while longer. OR alternatively set things up with
subshells, etc to generate a single monolithic rendering&encoding job.
The other thing which I do fairly often is 'multi' and 'mixed' angle
DVDs. Trivial to do with DVDSP but not with the other tools as far
as I know (mpeg2enc can generate .m2v files suitable for multi-
angle DVDs). Are you going to need multiple audio tracks? Multiple
subtitle streams?
> I will be aquiring the dvd books suggested by Mr. Schultz asap. With
> blue ray and the rest, I suspect we will be changing technologies again
> pretty quickly. But until then...
I'll probably get a blu-ray recorder for data storage as soon as
possible. But in a few weeks I'll be experimenting with authoring
HD-DVD - one of the new features in DVDSP4...
Cheers,
Steven Schultz
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