[mythtv-users] I'm in....

Steve Davies steve at one47.co.uk
Sat Nov 15 07:10:03 EST 2003


Jelle wrote:
> 
> What about this: Make a 'low delay uncompressed audio/video' mode, lets
> call it the 'fastpath'. The fastpath is more restrictive than the normal
> path but has a very low latency (mainly for channel surfing...). Accept
> restrictions, such as requires a faster CPU/memory bandwidth, and only
> when frontend and backend are on the same machine, and only if backend
> and frontend drivers support the fastpath feature, and maybe no OSD,
> etc. For low CPU power systems, maybe even disable all
> compression/recording/pausing on this backend if the fastpath is in use.

I like the sound of this. I was under the impression that the delay was 
already adaptive, backing off a little more whenever a frame is not available 
in time.
> 
> Example: If the backend and frontend are on the same system and if they
> both support this feature, then allow the backend and frontend to
> allocate a chunk of shared memory for a doublebuffered uncompressed
> frame. In the backend, the thread/process that has the uncompressed
> frames first can then memcpy() the uncompressed frame to the shared
> memory, before any compression is started on it. And the frontend can
> then resize&copy it onto the screen (of course, with the right
> semaphores for the shared memory, and something similar for the audio).
> That should result in a latency that comes pretty close to using xawtv
> directly.
> 

With the above in mind, does anybody see any benefit in using domain sockets 
to improve throughput and reduce latency if the front/back-ends are on the 
same server? This might be a cheap (in effort) alternative to a shared-memory 
alternative. If nothing else, it might reduce the system load by a couple of 
percent...

Steve
-- 
Steve Davies                   steve at one47.co.uk

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