Audio/Video Out of Sync

[MacFH - C E Macfarlane]

Thanks for your reply, please see below ...

> -----Original Message-----
> From: get_iplayer [mailto:get_iplayer-bounces at lists.infradead.org] On
> Behalf Of tellyaddict
> Sent: 13 August 2016 21:51
> To: get_iplayer
> Subject: Re: RE: Audio/Video Out of Sync
> 
> > That successfully shoots down my tentative explanation, but
> > unfortunately doesn't supply a better one.  Based on your superior
> > knowledge of both GiP, and the BBC system, what is your understanding
> > of why these problems started to occur about a month ago, bearing in
> > mind that I've seen at least one in a DASH download as well (the night
> > before last, last night's downloads were error free).

Just FYI, all overnight downloads have been error-free since that one.

> I wouldn't really say that I have any superior knowledge on this. My best
> guess on why these problems suddenly started about a month ago would
> be...
> All of the segmenting, playlist creation etc will be done by some software
at
> Akamai if they are doing the packaging. It's possible that maybe they have
> done a software update that has introduced a bug into their encoding
> systems.

Yes, but ...

> From what Jim said it sounds like Akamai have been doing this for
> the BBC for quite a while and in the past their software has processed
things
> without any problems.

... and, as Jim has said, it's a legacy system, so why would they be
changing it?  It's not impossible of course, but doesn't seem likely if it's
deprecated and due to be discontinued anyway.

Briefly, I'll go into more detail than I have previously about my
experiences with this issue.  I am using v2.95 on Linux.  I first started to
notice problems around Wimbledon, when I had one Linux NAS doing my normal
overnight downloads of everything except the tennis, and the other NAS doing
the tennis full-time.  I noticed that if I had two HLS downloads going at
once, one on each NAS, then inevitably I seemed to get problems with one or
the other or both, whereas if the Wimbledon NAS was downloading HLS, but the
other was downloading non HLS, nearly always it seemed alright.  At first I
thought this was due to trying to download two things at once on my low ADSL
bandwidth, but a week or less later others started to post about similar
problems, so now I suspect that I was simply one of the first to encounter
the current problems.

Given the coincidence with Wimbledon and now the Olympics, I think you can
see why I thought server loading might be an issue.  However, I note that
Jim has said that loading on ALL (my caps) servers was below capacity, by
which I presume he meant the Akamai ones as well as the BBC ones, so we are
still left short of an adequate explanation.  The only thing further I can
think of is that the putative change on the Akamai servers which you suggest
may actually have been the introduction of extra capacity for Wimbledon and
the Olympics, and this change, designed to thwart problems before they could
occur, somehow introduced the current problems as collateral damage.  I
guess we'll never know, but it sure is frustrating for everybody.

Also, I'm unclear from the release notes if the deprecating of the RTMP and
HLS timeout options means they are currently being ignored, or are still
effective.

PS (can be ignored by most):  In case further detail is useful to anyone
working on this issue, I'll give the download options which, rightly or
wrongly, were/are being used:
	Normal Download NAS goes through the four PVR search lists
previously mentioned, a sequence of the following options ...
		Radio HQ:	type radio, radiomode dashhigh
		TV HQ:		type tv, tvmode flashhd,hlshd
		Radio LQ:	type radio
		TV LQ:		type tv
	... as well as any one-off PVR jobs that have been added, which for
radio would usually be at normal quality, while TV ones would often have the
following options:
				type tv, tvmode
flashhd,hlshd,flashvhigh,hlsvhigh
	Wimbledon NAS (has to be HLS because RTMPDump falls over downloading
files greater than 4GB):
				type tv, tvmode hlsvhigh, no-tag, raw 
Additionally the following global options were and are still set (including
several that are now deprecated):
				rtmpdump /opt/share/bin/rtmpdump
				exclude pets,reversions,shorts,short
edition,strange hill high
				excludecategory Sign
Zone,Learning,Primary,Secondary,Children's
				hlsradioopts --timeout 100
				hlstvopts --timeout 100
				isodate 1
				refreshexclude BBC Radio 1,BBC 1Xtra,BBC
Three,CBBC,CBeebies
				rtmpradioopts --timeout 100
				rtmptvopts --timeout 100