InfoMagic Internet Tools 1995 April/Internet Tools.iso/dos_win/winsock/maillist/94-04.Z/94-04/text0084.txt

Text File | 1994-04-30 | 4.3 KB | 99 lines

In article <[e-mail]> [e-mail] (Francisco Diaz Catalan) writes:
>From: [e-mail] (Francisco Diaz Catalan)
>Subject: Programming a videoconferencing system
>Date: Mon, 4 Apr 1994 10:28:51 GMT

>We want to build a program that periodically takes a digitalized image
>(we say, for example, every fifty milliseconds) an sends it over a
>windows socket (we use Microsoft Windows 3.1).

>We firstly thought to put it in a callback function accesed at
>interrupt time, in a DLL. We tried to use the multimedia timer
>services (timeSetEvent), but due to limitations imposed to the timer
>callback functions, it did not work.

>We don't want to post messages to a window because of the lost of
>precission it suposes.

>Does anybody out there know how to avoid the limitations of this kind
>of callback functions?

>Is there another form, perhaps totally different, for doing this?

Are you using Video for Windows for this? If so, were you planning on using
frame captures or stream captures?

I'm afraid that you are stuck with posting a message from the timer callback
to a window. 50mSec might be a bit agressive, though.

The Video for Windows Capture app does it's preview mode this
way, though it sets the timer to 100mSec. There should be no "loss of
precision" though, of course, there will be some latency. (But there will be
latency going over the net, too...)

If you are concerned with proper synchronization, you are better-off using the
stream capture functions, rather than frame capture. (VFW Capture uses frame
captures for "preview" and single-frames, but uses stream capture for file
capture.)

With stream capture, you specify the frame rate you want, and your callback
or window will receive formatted buffers with embedded time information. It is
*not* guaranteed that every requested frame will be provided, but you will
have the time code to know if there are missing frames and to keep things in
sync. Note that you do not need to use a timer in this case, as the timing is
done by the driver in this case. It is also very accurate. Most VFW capture
drivers get an interrupt for every field or frame, and simply read the MM
timer to determine if a particular field or frame needs to be captured or not.
This is much better than going in asynchronously via a timer in your app.

Sorry if I'm being a bit sketchy or inaccurate - I only know VFW from the
driver side out. I've never actually *written* a VFW app, but I have written a
capture driver (for the I/OMagic PCMCIA capture card).
_____________________________________________________________________
Jon Tara|Internet:   [e-mail] | Kibo told me I could say
        |CompuServe: 76477,3422          | "53-X" here.

From [e-mail] Sat Apr  2 18:39:05 1994
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Date: Sat, 2 Apr 94 16:39:05 +0200
From: Uli Mittermaier <[e-mail]>
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Sender: ses
References: <[e-mail]>
Subject: Re: Telnet server wanted

In <[e-mail]> [e-mail] (Dave Maher) writes:
>     I am currently running winsock.dll servers such as ftp, rcp, www, etc..
>but cannot find a telnet server. I realize that telnetting to DOS is not a
>widespread thing, but is there a program _somewhere_??


I know only of a Telnet-Server for DOS that 'sits' on top of a packet-
driver. It's called 'The WATTCP TELNET Server'. The author is Erick Engelke
[e-mail]. (Information taken from the doc-file
of the program.)

Available at:

Host: ftp-ns.rutgers.edu
Dir:  /pub/msdos/wattcp
File: telnetd.zip


Best regards,
Uli Mittermaier

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