[mpeg2] Re: MPEG encoding latency

[Ralph Metzler <rjkm@convergence.de>]

Frank Rosengart writes:
 > Stig R Kristiansen wrote:
 > 
 > > Hi all,
 > > 
 > > I'm considering using the MPEG2 encoder board for Linux fom BMK-Elektronik
 > > in a video conference setup.
 > > What kind of encoding latency/delay should I expect? Anyone have any idea?
 > 
 > It's about between one and two second for encoding/multicasting/decoding 
 > with Siemens/Hauppauge/TT-DVB-card @ 4MBit/s
 > 

AFAIR, the people from Visiontech claimed the encoding latency is less
than a frame. So, the encoded frame should come out of the encoder
pretty much directly after it has finished.
Of course the buffer of the encoder, the network and the buffer of the
decoder add a lot of delay which results in the one or two seconds
mentioned above.

If you want less latency one could experiment with the buffer sizes
and driver polling behavior or even write the data directly from the 
encoders DMA buffer to the network driver.
There was some discussion about the zero copying network patch 
on the kernel list. Once this is stable and established in standard
kernels one might think about introducing a similar scheme for multimedia
applications.


Ralph