Re: new-B: xternal card for AD conversion?
- From: "Richard Crowley" <rcrowley@xxxxxxxxx>
- Date: Sat, 4 Mar 2006 03:47:44 -0800
"arrya deefmon" wrote ...
Thank you, I have now read some reviews of the Canopus ADVC on your recommendation and I still don't understand what file extension I end up with after the proprietary Canopus chip has transferred the video/sound.
The Canopus products (and many others from other vendors)
convert analog video (composite or Y/C) into DV (Digital
Video) via Firewire/1394.
Note that there are other ways of digitizing video/audio.
Particularly the method that digitizes/compresses analog
video & audio directly into MPEG, etc.
One user said the only problem is 1 hour = approximately
13GB,
13.7GB/hour is the standard for DV-encoded video.
which seems wrong to me. A DVD movie is about 2.2G per hour
MPEG is variable-rate and 2.2GB/hour is likely toward
the high end. It could be compressed even more than
that.
Note that DV and MPEG are two different ways of
compressing digital video. DV is compressed ~5:1
in the camcorder, while MPEG is compressed up to
10x more than that. Video frames are compressed
separately and independently in DV
MPEG does not contain all the frames. It contains only full frames every 5~10 frames, and "difference information" about what changes inbetween frames. This is called
"temporal compression" It makes the files smaller
so they can fit many hours on a 4.7GB (single-layer)
DVD disc.
This is good. But the flipside of that coin is that the video quality suffers due to irretrievably discarding the majority of the video information. Commercial
DVDs are hand-encoded where skilled humans decide, scene-by-scene, how much to compress the
video to stay within the "budget" of the overall disc
size vs. how much they want to cram in there.
The kind of MPEG encoders most of us use at home
are not this good and produce results which may look
as good as commercial DVDs, but also has the potential
to look significantly worse, depending on the content
of the video and the static compression ratio setting
you selected (or the software selected for you).
which are VOB files if I follow this correctly. (Mpeg2 is VOB?)
VOB files contain MPEG2 with the "VOB" file name
extension.
Also, several users stated they used Scenalyzer, Tempgen, Nero, etc in some hours long serialized combinational process in order to end up with a
movie. I didn't quite follow this either.
If you want to just take analog video and make a DVD
disc from it, perhaps the easiest is to just use a stand-
alone DVD recorder. No computer required. As easy
to use as any VCR.
Or, if you just want to take over-the-air (OTA) video,
edit out the commercials, and make DVDs of your
favorite TV show, one of the MPEG encoding boxes
(or boards) may be more convienent for you.
As with most things, there are tradeoffs between the smaller size and lower quality of MPEG vs. larger size and higher quality of DV. The temporal compression
of MPEG files also means that the video must be de-
compressed and re-compressed if you do most any
kind of editing to the video. This decompression and
recompression almost always results in additional
loss of quality. But if you are only removing commercials
from cable or satellite TV (which was likely MPEG
compressed already) you can probably get away with it.
I mentioned my audio card, a LynxOne with digital clock synch on BNC because I assumed I would want to clean up the sound, specifically 60Hz hum, in some kind of editor.
DV stores audio as uncompressed PCM 48K samples
per second by 16-bits. This makes it very easy to edit/
process, etc. MPEG stores audio in a compressed form
(similar to MP3), and processing it (like removing 60Hz
hum, etc.) is more problematic.
If the S&V are locked I don't see how to do that.
The audio and video are locked by digitizing both of
them in the encoding device (The ADVC box/board or
the MPEG encoding board, etc.) It is not practical to
use your separete audio card unless you are using professional video encoding equipment where the sampling rate clocks can be synced together using your BNC connector.
You said you wanted to use Firewire or USB which led
us to believe you were looking for a more consumer-
priced solution.
Note that it is FAR EASIER to eliminate the 60Hz hum
before you digitize the audio than having to do it in
"post-production".
I'd also like to remove the commercials and credits to save space. Can you recommend software for this?
Many people seem to like applications like Video-Re-Do
to do simple editing (like removing commercials) from
MPEG-encoded files.
This is where the rebuilding of the file takes so much time?
This is the tradeoff. You can avoid the transcoding (what
you are calling "rebuilding') between DV and MPEG if you
encode/record directly in MPEG. But you have to live with
the limitations. If you are just removing commercials, this
may be the best solution for you.
Could you pause the recording on the pc during the initial
transfer and then FF/CUE the VCR and start again recording to avoid this?
Probably. It depends on what software application you are
using to do the recording (whether DV or MPEG). There
are many different applicaitons with different featues available
for either MPEG or DV recording.
If your video source is a VCR (like VHS, etc.) then your
video may already be low enough quality that using DV
is overkill, and MPEG may be a better compromise.
Also, if you had to render in some absurd overnight process
It only takes overnight if you are running a 300MHz computer
(0.3 GHz). Is your computer really that slow? If you are
doing something that requires quick turnaround time, maybe
you should be investigating more expensive commercial solutions. Most of us don't have the kind of time crunch it takes to get the news ready for the 6pm broadcast, etc.
could you open two instances of software and play out the
non-destructive edit program in real time and record it in a loop as the Canopus ADVC 100 is a two way set up?
You will need to re-state what you are trying to do here
before I can respond. If you have the video in your computer
as a file already, why would you need to use the ADVC or
any other conversion box?
And I guess my budget it about $250usd.
Then you are likely looking at a lower-end solution like an
MPEG encoder. ADVC and other DV-encoding devices
tend to be higher-priced than that. Clean up the 60Hz
before going into the converter (whether MPEG or DV).
.
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