Rich Felker <dalias@aerifal.cx> writes:
On Wed, Feb 06, 2008 at 06:27:47PM +0100, Michael Niedermayer wrote:
On Wed, Feb 06, 2008 at 12:08:37PM -0500, Rich Felker wrote:
OK since there seems to be a disagreement (to put it lightly :) as to what the current NUT framework can do for synchronizing timing between a transmitter and receiver, I'd like to lay down the hypotheses and reasoning I'm working from. Maybe others disagree on the basic assumptions or haven't though of them. So, here it goes:
Transmitter side:
Key assumption is that frames are actually transmitted according to dts. In a VBR transmission with immensely excessive bandwidth, or a pure CBR (e.g. uncompressed, single-stream) transmission, this can be done almost exactly. In CBR with buffer restraints, obviously it will not be exact.
It is sufficient that the mean difference between dts and actual transmission time be constant over intervals of time whose length is on the order of the maximal length of time in which transmitter and receiver clocks can be expected to remain within an acceptable error relative to one another.
This is too vague to argue about it.
It's trivially true for any live broadcast or broadcast with a fixed channel bitrate.
Nobody uses fixed channel bitrate. A multiplex has a fixed bitrate dictated by the modulation. This fixed bitrate is then shared by 10-15 independent channels. It is even common to over-allocate the bitrate somewhat, since it is highly unlikely that all channels will need peak rates at the same time. -- Måns Rullgård mans@mansr.com