[linux-dvb] Re: [PATCH] fix for stream corruption on budget /Nova-T cards

[Jon Burgess <mplayer@jburgess.uklinux.net>]

Holger Waechtler wrote:


> why do you want to do PID filtering on the RPS? it's done in software in 
> the current Nova driver anyway...
I thought Robert was hinting that you could get the device to DMA the 
data straight into an output buffer which then gets returned to 
usermode, without needing to do any data copying. This sounds feasible 
for receiving the whole TS.

The usermode code could directly mmap() the DMA buffer. The userspace 
would need to be made aware of the circular nature of the buffer unless 
the driver can play games with file pointer to make it look like a 
linear file. A backwards seek() would be impossible if the data has 
already been overwritten and data would get lost if the usermode didn't 
keep up with the stream.

I haven't looked at the details of the demux code, perhaps it already 
does something like this for TS streaming.

Receiving an individual PID needs filtering which I think can only be 
done sensibly using an copying the data to another buffer.

	Jon









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