Audio/Video Out of Sync

[Jim web]

In article <604314c0-d408-a82b-4520-89052e20b135 at soulman1949.com>,
Alan
Milewczyk <alan at soulman1949.com> wrote:
> On 07/08/16 09:32, Jim web wrote:
> > In article <5a2b1ab9-4c80-350b-e082-eadc3de1b1f3 at soulman1949.com>,

> >
> > If there is a synch problem due to missing chunks at some point, does
> > that persist or accumulate to the end of the file? i.e. if the synch
> > is correct at the end, does that indicate that it was probably OK
> > thoughout?

> I don't use the PVR as I find it's too much of a fag adding and removing
> programmes for download so I use a combination of a batch file which
> reads a text file containing the PIDs I want to download. 

FWIW I've also written a simple (ROX filer) front-end that lets me drop a
file onto it which lists the PIDs and my chosen transfer methods.

[snip]

> ... As you say the latter is much slower - I'm getting between 30Mbps
> and 100Mbps for HLS but using Flash the same programmes take, on
> average, four times longer than HLS.

Much the same here. FWIW I now leave the relevant machine fetching in
parallel with watching or listening to something as I eat breakfast. I
use the same machine to fetch as I do to play the results into the TV and
audio setup. It seems happy to spin both plates at the same time when
this is needed.


> I sympathise for anyone in your situation where you have constraints on
> your downloading schedule, a real hassle.

Well, I can download things during the day. But as you'd expect, getting
the 'hd' TV files can rapidly add up. So by default I try to fetch TV files
before 9am. That usually gives me 1 - 2 hours. So it is mainly a matter of
being organised. ( Not my best suit! :-) ) However at present I'm trying to
keep up with the Proms. One of my most 'busy' periods for TV.

I am coping so far. Just spend a while going through the proms on tv
webpage choosing the pids for the next few 'morning batches'.

> >
> > This does drift OT. But it has reminded me that one long-term
> > wish/thought I've had is to work out how to take an iplayer TV version
> > of a Prom and replace its audio stream with the 320k R3 version during
> > the music. However even if I knew how to do this, again I think synch
> > would drift. Tests some years ago showed clock drifts between TV and
> > radio.
> >
> > Jim

> I think you'll be giving yourself a massive task trying to synchronise
> radio and TV outputs, I couldn't imagine the time it would take to do
> that task!

Yes. That's what has put me off it! I did some years ago write a
cross-correlator program to do a time synch measurement of the offset
between bbc iplayer and freeview files. Did this to get results I put on
the web at the time. Part of an early comparison of TV versus R3 for the
Proms audio. So I could revive that and have a go. But not a trivial task.

As a result it has been for some years in my box marked "awaiting a supply
of round tuits"...  :-)  But the current problems brought it back to mind.
May find it useful sometime.

Jim

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