>At 09:58 AM 11/16/2002 +0000, you wrote:
>When down loading onto a PC something you had "filmed" with a
>digital video camera would you expect the file to be created in real
>time on the PC?
By real time, I assume you mean, will it play as a video, at the speed it
was recorded at ...like a Tape recording in a VCR...the answer is yes.
>So that a piece of video that takes 5 minutes to
>view would take 5 minutes to down load.
I am not sure if you mean download from your camera to your hard drive, or
download from a web server to somebodies computer. In either case the time
it takes to watch the video is not really related. A video file is just
like any other file when it comes to downloading it. All digital files are
made up of machine code = ones and zeros, and all file sizes are measured
the same way. Windows only knows the difference between an Excel file and a
video file by it's extension. Other then that both are fundamentally just
ones and zeros.
How long it takes to download from your camera to your PC will depend on
the file size which is in flash memory, and what you are using as a
connection between the two ...such as Firewire or USB ( 1or2). These will
be similar in speed to a Network transfer .
However, if you mean how long will it take to download a particular video
file, that you have put on a web site, then
the time it takes to download the file from the server it is located on,
will depend on the file size, the Internet connection of the server, and
the Internet connection of the person who is downloading the file. For
example, suppose you have a 3 megabyte file. You upload it to your web or
ftp site, which is located on your ISPs, or domain hosting server, which
has a high speed Internet connection. Once on the Server it is available
for download.
You have a high speed DSL connection, and can now download that file in a
minute or two. But your friend is still on a dial up 56K connection and
they only can connect at 40K. It is going to take them around 20 minutes to
bring in that same 3 megabyte file.
>Is it possible to down load
>faster that it takes to view the video?
Yes it is. You would expect this when downloading from your camera to your
hard drive but not necessarily when downloading from a web page to a hard
drive. In the latter case, It will depend on the file size and the Internet
connection. To determine the download time of a particular file, simply
look at the file size relative to the server upload, and the client
download connection. Whichever connection speed is the slower, represents
the speed it will download to the client at.
Video file sizes can be, and usually are, enormous. The better the quality
the bigger the file. When capturing a TV broadcast on a PC, at the highest
quality, the result can easily be 7 GB to 14 GB per hour of recording! That
is the size in it's raw perfect state. Once encoded down to a more
manageable size, it can become 600 megs or even less. But there will be a
quality degradation. This is no different then in what is done when turning
audio wav files, into the popular mp3 files. Wav to mp3 is a 11 to 1
reduction in file size.
There are two ways you can download a video. The first way is to simply put
it in a zip file, or other archive, and then let it download to the clients
hard drive, just like any other file. Or just have the client right click
on a particular video file link, and select "save to hard disk" from the
context sensitive menu. Once it is on the hard drive, they can, if
necessary, extract from archive, and then play it. This insures that it
plays normally. You don't have to worry about playback being jerky. All the
information is on the clients hard drive.
The other way, is streaming video. This works by downloading part of the
video and then buffering it in a cache after which it will start playing it
while downloading the next segment. Windows Media Player and Real Audio do
streaming audio and video. This format is popular on web pages.
The faster the speed of the server and the client, the better this will
work. I routinely watch video replays on the CSPAN TV network that go on
for hours at a time, and it works fine for me. However, I have a very fast,
3 to 10 MB per minute broadband connection, and the CSPAN servers are very
fast.
The windows media video format with the wmv extension is a very good format
for streaming video. Using something like Movie Maker, that comes with
Windows XP, or ME, you can create video files that are designed to be
streamed, at a particular speed, of your choosing...like 56K. Keep in mind
that the slower the speed, the smaller the file size, the worse the
quality. But even the worst quality can be acceptable as long as you are
watching it on a tiny little computer window being streamed from a web page.
Here is an example of all this. I recorded a 30 minute TV broadcast with my
Matrox Marvel TV video capture card at these settings.
704X480
30 frames/sec
1.930 MB/sec
CD Quality audio
The file size totaled around 3.5 GBs. Yes, that is Gigabytes!
I edited 10 minutes out of it, and re-encoded it to mpg-1 down to a file
size of around 112 megabytes. Then I used Movie Maker to create a streaming
video file for 56K and got it down to 8.2 megs. Then I uploaded it to a
fast COX web server here
http://members.cox.net/golden-retriever/friends.htm
Picture quality is pretty poor but it works for what it was intended.
Another example is here on this link at bottom of the page. This is only 24
seconds of video so I could make the quality very high while keeping the
file size small = 2.2MB.
http://members.cox.net/golden-retriever/goldens.htm
You will have no trouble in seeing the difference in the video quality.
I hope this helps but you are probably just as confused as when we started!
:) Don't let it discourage you, that is just the nature of working with
video. Video is a dynamic technology, that changes on a weekly bases, and
is a black hole when it comes to upgrades! It is one of those things that
require your confused participation, in order to acquire some level of
competence. :)
Rode
The NOSPIN Group
http://freepctech.com
>Any help appreciated as I am very new to this and I lack an
>understanding of the basics.
>
>Tony Beckett - Rutland, UK
PCSOFT's List Owner's:
Bob Wright<[log in to unmask]>
Drew Dunn<[log in to unmask]>
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