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List:       linux1394-user
Subject:    RE: Reg. Mutiple Channel Recv Mode.
From:       <dilip.vamanan () wipro ! com>
Date:       2007-04-05 6:16:28
Message-ID: A23A58A8CC5ED24EB7A3A44D059C0DD3327719 () blr-m3-msg ! wipro ! com
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Thanks Pieter for the info, 

I would like to know how the Sync Mechanism is possible with the buffer fill mode. \
While I was using the Buffer Fill Mode for receiving the IIDC Camera Stream, I could \
find that the "Sync" is lost for most of the frames displayed in the application.

In the case of Per Packet Buffer, Managing Sync for the display was easier.

Regards,

	Dilip
 

-----Original Message-----
From: Pieter Palmers [mailto:pieterp@joow.be] 
Sent: Thursday, March 29, 2007 1:33 PM
To: Dilip Vamanan (WT01 - Embedded Systems)
Cc: linux1394-devel@lists.sourceforge.net; linux1394-user@lists.sourceforge.net
Subject: Re: Reg. Mutiple Channel Recv Mode.

dilip.vamanan@wipro.com wrote:
> 
> Now has anybody actually tried listening to two channels and suceeded 
> ?. I am sorry, i couldnt find any information regarding any projects 
> which has used the same also.

I have this laying around...

Pieter


> 
> Kristian has suggested me to go with two handlers. The risk of DMA 
> getting filled up is also there then.
> 
> Regards,
> Dilip
> 
> 
> 
> -----Original Message-----
> From: Pieter Palmers [mailto:pieterp@joow.be]
> Sent: Wed 3/28/2007 10:46 PM
> To: Kristian Høgsberg
> Cc: Dilip Vamanan (WT01 - Embedded Systems); 
> linux1394-devel@lists.sourceforge.net; 
> linux1394-user@lists.sourceforge.net
> Subject: Re: Reg. Mutiple Channel Recv Mode.
> 
> Kristian Høgsberg wrote:
> 
> > On 3/28/07, dilip.vamanan@wipro.com <dilip.vamanan@wipro.com> wrote:
> > 
> > 
> > > Hello Friends,
> > > 
> > > I am planning to use the linux1394 drivers for hobby project. I
> > > receive the Isochronous data coming from the AV harddisk using  
> > > "raw1394_iso_recv_init", DMA receive Mode. The driver behaves 
> perfectly and  >>I am able to see real time streaming video on the 
> screen.
> > > 
> > > Now I am planning to support two AV HDDs at the same time. So I 
> decided
> > > to go for "raw1394_iso_multichannel_recv_init". From the  >>API 
> documentation, I cannot go for the DMA receive mode here. So the data  
> > > may be coming in the user application lately. Is their any specific 
> reason  >>by which we cannot use Mapped Memory here ?
> > > 
> > > 
> As far as I know, DMA memory mapping is always used by raw1394. The 
> difference between the modes is that one is 'DMA buffer fill' and the 
> other is 'packet per (DMA) buffer'.
> 
> The OHCI spec says: "A context to be enabled for multiChanMode, shall 
> also be enabled for bufferFill and isochHeader modes. If multiChanMode 
> is enabled without bufferFill and isochHeader, the resulting behavior 
> is undefined."
> 
> For more info see:
> http://download.intel.com/technology/1394/download/ohci_11.pdf
> Receive modes: page 151-...
> Multichannel receive: page 159-...
> 
> > The multichannel receive mode isn't really useful for streaming, 
> it's  >typically just used for async stream packets.  What I'd suggest 
> is to  >just use two raw1394handle_t's and receive one stream to one 
> handle  >and the other stream to the other handle.
> > 
> > 
> It might be inefficient, but you could use multichannel mode to avoid 
> running out of receive DMA contexts.
> 
> Pieter
> 
> 
> 
> 
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