From: "Craig A. Schultz" <[EMAIL PROTECTED]>
Subject: Re: Back-To-Back Capture
RealForum wrote:
> From: "Gurpratap Virdi" <[EMAIL PROTECTED]>
> Subject: Back-To-Back Capture
>
> Hi,
>
> I am using the Real Producer Plus ActiveX control in my application to
> capture and encode files in real-time from my capture card. I need to
> capture video in chunks of 30 minutes however there must not be any time gap
> between the two files eg. if I have one capture from 6-6:30 this capture
> should stop precisely at 6:30 and the next one should begin at exactly 6:30
> so I can later paste these clips together without loosing any time I have a
> few questions about this:
>
> - At the moment when I call the stop function in the Real Producer Control,
> it takes about 13 seconds for it to stop before it can start capturing
> again. I believe this delay is caused because it is writing data from the
> temp file to the destination file. Is there any way I can get around this
> problem?
I haven't tried it using the ActiveX control but having done it using the
SDK and coding it myself, I would think it not likely a general application can
do it. Basically what you need is an application that can at a random
point say
that, this buffer from the recording device goes to this file and that the next
buffer will go to the next file. In some cases you are talking about
millisecond intervals between buffers arriving for processing. But, that
is not
to say it can't be done in a general application, just difficult and I
think you
are lucky that it is only 13 seconds! ;-) BTW, this is how I get around the 2
Gig problem.
> - To get around the start-stop overhead I set the capture time to a large
> value (say 5 hours) and every half an hour I make a copy of the temp file. I
> then paste a header from an existing rm file (without this real player does
> not recognize the file) to the beginning of the temp file. When I play this
> file in Real Player it works great, however when I try to cut out the
> segment I need using rmeditor, rmeditor gives me the error: "The specified
> input file is invalid" Why does rm editor fail to open the file even though
> real player can play it fine?
Probably because the player might not be reading all the data that is
in the
header or somewhere or just ignores it even if it is there but that the editor
may not only require that it be there but that it be correct. You could
think of
it as CRC codes used to verify data, if you make a cut in the middle of a line,
the CRC check will fail. The line may be a perfectly valid line but it is not
the same as what was originally there. I do not know this to be the exact case
this time but I have seen it so often before that I would doubt that it is not
also the case this time.
> - Assuming I can get around the 13 sec gap problem, when I try to paste 2
> files together, at the junction the audio starts immediately however there
> is a lag before the video appears. I believe this is because real player
> waits for a key frame. Is there a way to get around this interruption in
> video?
If you need split second shifts from one to the other, video will be your
biggest problem. I ran into the same thing when I was trying to paste video
together. After a while I wa able to use a Hex editor to get audio files to be
understood even by editors but I was never able to do that with video and
had to
dig to find where to splice the two and it was never the same for any two
files.
I could be a bone head and just not have a clue as to what is going on but
that is what I ran into and how I dealt with it. Things helped when I made a
cheap and dirty splicer (very dirty!) using information in the G2 System SDK.
In there you will find information regarding the rm media file format.
Basically it is a sub-set, or super-set depending on your point of view, of the
tagged information file format. I think you will find it rather easy to work
with but still, I think you will run into problems with video.
Hope this helps,
Craig
> - Is the rm file format public? Where can I get it from?
>
> Thanks in advance!!
> Gurpratap Virdi
>
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