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I have closed the forums to new postings because there was not enough discussion, I answered nearly all the questions, and I no longer work on Kino. Please use the forums provided by your Linux distribution. Meanwhile, I will leave this open in read-only mode to serve as a knowledge base.


Subject: "dvgrab from multiple camcoders in the same time" Previous topic | Next topic
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Top Linux Digital Video dvgrab Topic #701
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Peter Szabo (Guest)Mon Sep-19-05 07:36 AM

  
#701, "dvgrab from multiple camcoders in the same time"


          

Hi!

I have a Sony and a Canon camcoder, and I use dvgrab 1.7. Both camcoders are plugged in using firewire. How do I tell dvgrab to start grabbing from the Sony camcoder? Is it possible to do grabbing the same time from both camcoders? I tried --guid, but it didn't work: the data received from one camcoder started appearing on the LCD of the other camcoder.

Thanks,

Peter

  

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Replies to this topic:
RE: dvgrab from multiple camcoders in the same time, ddennedy, Sep-25-05 04:58 PM, #1
      RE: dvgrab from multiple camcoders in the same time, Thomas (Guest), Dec-30-05 05:23 PM, #2
           RE: dvgrab from multiple camcoders in the same time, ddennedy, Jan-05-06 01:26 PM, #3
                RE: dvgrab from multiple camcoders in the same time, anubis4d, Jun-12-09 06:12 PM, #4
                     RE: dvgrab from multiple camcoders in the same time, ddennedy, Jun-14-09 05:32 AM, #5
                          RE: dvgrab from multiple camcoders in the same time, anubis4d, Jun-14-09 07:08 AM, #6

ddennedySun Sep-25-05 04:58 PM
Member since Jun 26th 2006
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#703, "RE: dvgrab from multiple camcoders in the same time"
In response to Reply #0


          

Only running two instances of dvgrab using version 2.0 lets you capture from both cameras at the same time. In dvgrab 1.7, if you want to capture from a specific camera, then --guid lets you control to which camera to send the play command, which apparently is working. However, beyond that, for the dv data, the guid does not matter, only the isochronous channel matters. Most cameras broadcast over channel 63, which is what dvgrab defaults to. However, in the odd case that one camera sees the other and has switched to another channel, then dvgrab 1.7 may not know. Channel usage is not very obvious and you need a utility like plugreport, which comes with libavc1394 source to lookup that info. However, more than likely, it has not switched from channel 63, and linux 1394 is not playing nicely enough with your camera to receive the data. Does it work okay on each camera if only one is plugged in at a time?

Needless to say, you have entered an advanced territory here, and need to dig in deeper with 1394 specifics in order to sort out the details. On the other hand, with dvgrab 2.0, I have attempted to make it easier and work more automagically in the advanced territory.

+-DRD-+
Lead Kino Developer

  

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Thomas (Guest)Fri Dec-30-05 05:23 PM

  
#723, "RE: dvgrab from multiple camcoders in the same time"
In response to Reply #1


          

How many cameras can be captured from at once on one firewire card, theoretically? practically? Can this number be increased by adding more firewire cards? What kind of system would be needed to capture from 3 cameras at once?

What would be the major obstacles to overcome in writing an app that can do live switching between multiple cameras to one recorded file? Is anyone working on such an app?

T

  

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ddennedyThu Jan-05-06 01:26 PM
Member since Jun 26th 2006
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#724, "RE: dvgrab from multiple camcoders in the same time"
In response to Reply #2


          

>How many cameras can be captured from at once on one firewire
>card, theoretically? practically?

Since DV devices are set to use 100 mb/s, sadly only 2 both theoretically and practically. However, I have seen some Canopus DV converters that can be set to a data rate of 400 mb/s with a DIP switch, and then you can use up to 6. However, most firewire cards have only 4 isochronous receive contexts, which limits it. There is a special multichannel receive mode for which you would need to do some custom programming using libraw1394 as dvgrab does not use that mode.

>Can this number be
>increased by adding more firewire cards?

Yes, also there are multi-port/channel firewire cards that combine the hardware of two firewire cards into one.

>What kind of system
>would be needed to capture from 3 cameras at once?

Just a low end PC by todays standards would work fine. Capture is very low overhead. The biggest bottleneck is perhaps the disk subsytem to write multiple streams at ~3.6 MB/s each.

>What would be the major obstacles to overcome in writing an
>app that can do live switching between multiple cameras to one
>recorded file? Is anyone working on such an app?

I do not know of anyone working on it. Should not be too hard to start with dvgrab 2.0 source code, but I am unable to work on it at this time.

+-DRD-+
Lead Kino Developer

  

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anubis4dFri Jun-12-09 06:12 PM
Member since Dec 19th 2007
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#1078, "RE: dvgrab from multiple camcoders in the same time"
In response to Reply #3


          

is there a PRACTICAL way to do it TODAY?
maybe by using a script or something, I need to capture 2
cameras simultaneously into 2 independent files, the bitrate
is not a problem because I will pepare a raid setup for this,
actually I was thinking about SDD disks to get more speed, and
have an option for pipe all into mpeg files.

I am not a coder, just a user.
Marquitux

http://www.anubis4d.com.ar   

  

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ddennedySun Jun-14-09 05:32 AM
Member since Jun 26th 2006
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#1080, "RE: dvgrab from multiple camcoders in the same time"
In response to Reply #4


          

dvgrab is a practical way - if it works as expected.  Just run
2 instances of dvgrab using the -guid option. You don't need a
raid to write ~7 MiB/s. If it does not work as expected, then
it is not practical because you either have to debug it or
hire someone like me to debug it.

+-DRD-+
Lead Kino Developer

  

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anubis4dSun Jun-14-09 07:08 AM
Member since Dec 19th 2007
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#1081, "RE: dvgrab from multiple camcoders in the same time"
In response to Reply #5


          

how do I use the GUID option, do I have to use several cards
or with one the GUID number will identify each port?

how can this be automated with a script?

  

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