Audio/Video Out of Sync

[MacFH - C E Macfarlane]

Please see below ...

> -----Original Message-----
> From: get_iplayer [mailto:get_iplayer-bounces at lists.infradead.org] On
Behalf Of Alan Milewczyk
> Sent: 07 August 2016 10:00
> To: get_iplayer at lists.infradead.org
> Subject: Re: Audio/Video Out of Sync
> 
> On 07/08/16 09:32, Jim web wrote:
>>
>> In article <5a2b1ab9-4c80-350b-e082-eadc3de1b1f3 at soulman1949.com>, 
>> Alan Milewczyk <alan at soulman1949.com> wrote:
>>>
>>> I have a very stable 200Mbps connection so I decided to test just how 
>>> bad the situation actually is. Overnight I carried out a download of 
>>> 124 sample programmes drawn from BBC's One, Two and Four which were 
>>> broadcast between Monday and Friday. Of this sample, only 63 were 
>>> downloaded without fault (60 hlshd, 3 hlsvhigh). The remaining 61 had 
>>> at least one segment missing (58 hlshd, 3 hlsvhigh). A dreadful
situation.

Agreed.

I'm currently finding lots of 'blips', for want of a better word, in music
programmes downloaded at 320kbps.
For example, I can definitely recall them in most recent episodes of ...
	Caithream Ciuil	(Gaelic language  -  Gael/Scot folk and folk-pop)

While, because of the way the nightly PVR overwrites the log of the previous
night, and the fact that I rarely listen to a programme the day after it is
downloaded, I can't be certain that these are caused by similar errors in
the downloads, it seems very likely to me.  FTR, I've checked the log of
last night's run (which, unusually, is still running) and, so far, there are
no errors.

>> It is particularly annoying for me that it has arisen during the Proms.

Agreed.

>> Particularly annoying for a musical concert where synch is vital.

Agreed.

>> 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?

Dunno, I've been too busy to have yet watched any of the Proms I've
downloaded this year.
 
> I don't use the PVR as I find it's too much of a fag adding and removing
programmes for download 

If you were going to use it directly for every programme, so that you had to
run an individual --pvr-add or --pvr-queue command for everything, I'd
agree, but its use for one-off programmes/series is not too maintenance
heavy.  See below ...

> so I use a combination of a batch file which reads a text file containing
the PIDs I want to download. With this "dropped segments" situation I've
started to pipe the output to an error file. As some programmes might not be
watched for a while, at least this gives me notification of a problem so I
can try again for faulty programmes using RTMPDump/Flash. 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.

I do use the PVR, from a Linux NAS box.  I have four files controlling
regular downloads  -  radio highest quality, TV highest quality, radio
normal quality, and tv normal quality.  These are just a series of text
files containing individual search terms on separate lines, and the Linux
equivalent of a batch file runs a PVR command to set up the relevant PVR
item.  Additionally, if I see a series that I want to hear or watch, I run a
suitable PVR command manually to add it.  Then, the PVR runs overnight to
download the programmes to hear or watch over the coming days.

As with both our methods the biggest fag is likely to be looking up the PID
of a programme on the treacle slow BBC website, I can't see that my method
is going to be any more labour-intensive than yours?  You look up an
individual PID and put it in a file, I look up  a PID and run a command.

> It's a real eyeopener scanning the error file, some programmes have
multiple dropped segments - I've not bothered trying to play the files to
see how bad the synch issue actually is, I've re-downloaded using Flash.

Yes,  on occasion I've seen a great many errors also.  One of the things
that concerns me about this is that the current 2.95 script no longer
recognizes many of the options I've been using, and I think some of the
ignored options may be related to the increase in the incidence of errors:
	WARNING: Deprecated option(s) found in /root/.get_iplayer/options:
	WARNING: rtmpdump = /opt/share/bin/rtmpdump
		Understandable when rtmpdump ceases to work, but currently
it does still work, so this option shouldn't yet be being ignored.
	WARNING: excludecategory = Sign
Zone,Learning,Primary,Secondary,Children's
		???
	WARNING: hlsradioopts = --timeout 100
	WARNING: hlstvopts = --timeout 100
		AIUI, HLS is now the default download method, so why are
these options now being ignored?  What with the abysmal local bandwidth in
the Highlands, and the greater demand on the BBC's servers during events
such as Wimbledon and the Olympics, the greater tolerance that these options
provided is even more necessary than before, but they are being ignored, and
there is an increase in error rate, which leads me to suspect that these
things may be related.
	WARNING: isodate = 1
		I haven't looked up why this is being removed, but ISO dates
have the great advantage of sorting in chronological order.
	WARNING: rtmpradioopts = --timeout 100
	WARNING: rtmptvopts = --timeout 100
		Understandable when rtmpdump ceases to work, but currently
it does still work, so these options shouldn't yet be being ignored.
	WARNING: Deprecated options will be removed in a future release

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

It does sound to me as though Jim would benefit from setting up an overnight
PVR run, if he hasn't already.  It's not clear from his post whether he has.

>> 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.
> 
> 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.  Each to his own, but I would rather go and buy a CD/DVD of the work
concerned, and this would have the major advantage of buying just the piece
most wanted, without any of the other pieces in the same Prom, and without
the obligatory coughing brigade, and without the pseudo-intellectual verbal
diarrhoea that is used to fill in so much of the broadcast programmes.