[MPlayer-dev-eng] [RFC] auto adjustment of playback speed

[Nico Sabbi]

Il Friday 18 April 2008 20:11:16 Uoti Urpala ha scritto:
> On Fri, 2008-04-18 at 10:03 +0200, Nico Sabbi wrote:
> > This patch implements (quite naively) an auto-adjustment mechanism
> > of the playback speed based on the proportion between the real
> > delta_time elapsed from the beginning of the playback and the
> > delta_reference_clock found in the multiplex.
> > At the moment the only mux that carries this information is
> > MPEG-TS and only if demuxed by demux_ts.c.
> > 
> > The patch is just in an initial state, but I'd like to know if this
> > code is (or resembles) what Uoti and Rich had in mind when they
> > objected to my commit in ds_fill_buffer() a couple of months ago.
> 
> This is still fundamentally flawed. You can't match timing with a server
> based on just the _contents_ of the stream from the server. Those will
> be exactly the same even if the server clock is slower or faster than
> yours. Your code would behave exactly the same if the stream came from a
> file. Trying to "synchronize clocks with a file" is obviously nonsense.

do you mean that mplayer needs to know the sender's real clock?
or I'm missing something? In the mpeg reference model there's no
dependency on the sender clock: the decoder is supposed to use
only the PCR present in the stream to drive the decoders.

> 
> If for example the demuxer ran in a separate thread and immediately read
> all data available from the server then an approach like this could work
> (at least in theory, I didn't read the actual code as it was obvious it
> could not work overall). But it doesn't; what the demuxer has seen does
> not depend on how much data the server has sent but on how much data
> MPlayer has wanted to read. The only case where the server speed would
> have any effect on the behavior of this code would be if MPlayer is
> delayed because the buffer already ran completely empty and a read
> blocked.
> 

then what's the right way to proceed (keeping in mind that I can't get the
server's clock)