[AG-TECH] sending vic pre-encoded video

[Christoph Willing]

On 07/02/2009, at 1:44 AM, Gurcharan S. Khanna wrote:

> hi,
>
> i just wanted to clarify how AG vic works. it seems to want a
> raw digital stream to encode in h.261, h.264, or whatever. it
> does not accept a stream that's already encoded, like mpeg2,
> mpeg4, mjpeg, etc. is that correct?
>
> i understand that the AGDV for windows and the DVservices for
> linux do accept HDV (mpeg2) as part of those modules. are they
> the only add-ons that do so?
>
> anyone working on adding mp4 support for the HDV modules which
> currently support mp2?


Gurcharan,

The problem with doing anything with the firewire port mpeg2 streams  
(like converting to mpeg4 etc.) is the inherent 1/2 to 1 second  
latency incurred inside the camera when encoding the mpeg2 stream in  
the first place. Any further processing we choose to perform (like  
mpeg2 -> mpeg4 conversion) may cause even further latency.

What we really need to be able to do is grab the camera video _before_  
its encoded into mpeg2 i.e. before any latency is built into the  
signal. This signal is available on some cameras as a 1920x1080 YUV  
type signal via an HDMI connector - hence the previous talk about the  
Blackmagic Intensity HDMI capture card which can capture this signal.

Work on it this patchy - lack of a Linux driver is the main stumbling  
block here. Some initial work by Doug with the Blackmagic card on OSX  
indicates the single threaded nature of standard vic may be a  
bottleneck preventing full frame rate at 1920x1080. Perhaps a  
multithreaded version of vic (like the UQVislab HDV enabled vic) would  
work at full frame rate but integrating that into the standard vic  
code would require a lot of effort. That integration was always  
planned but we ran out of time/budget. Its not clear who could afford  
that effort at the moment.


chris


Christoph Willing                       +61 7 3365 8316
QCIF Access Grid Manager
University of Queensland