[vlc-devel] commit: stream: Add a new method for buffering access: A*Immediate method. (Pierre d'Herbemont )
pdherbemont at free.fr
Thu Jun 5 21:46:35 CEST 2008
On Jun 5, 2008, at 9:29 PM, Rémi Denis-Courmont wrote:
> Le jeudi 5 juin 2008 22:08:05 Pierre d'Herbemont, vous avez écrit :
>> However, nowadays caching at our level doesn't seems to have a big
>> impact (we are only caching at most 4Mo), and the kernel doesn't seem
>> to trash that much packet, plus disk cache has increased.
> 4 Mb is a lot more than the "bandwidth" of typical network jitter. 0
> Mb is
> infinitely less.
> Even sitting idle, my cable modem connection shows about 25ms of
> packet delay
> variation. That's more than the typical network packetization time
> (20 ms),
> which is also an intrinsic latency. For audio, 50 ms is not
> Using TCP, the jitter will be a lot longer due to head-of-line
> Using wireless networking will also increase delay variation.
Well, we don't really care about 25ms variation given that we have a
pts delay of 900ms, so a really big caching is done much far after in
the decoding chain.
>> I think that this caching may have been useful 10 years back, but is
>> not anymore.
> For disk I/O, it may be irrelevant because the hardware and the
> system read ahead. But VLC caching has hidden packet delay variation
> which is
> inherent to packet switched network (IP). Sure, we could cache a lot
> typically some tens of milliseconds, but we can't remove caching.
My point is, this caching isn't relevant as there is a much bigger one
More information about the vlc-devel