Query re BBC On Demand Radio

[Vangelis forthnet]

On Tue Feb 17 15:53:30 GMT 2015, Prisca wrote:

> I don't fully understand how get_iplayer works
> what is likely to happen at the end of February 
> when the WMA/AAC streams for on demand radio are turned off. 
> Will this have any impact on get_iplayer?
> I've never really figured out where the streams I download 
> actually come from.

On Tue Feb 17 19:06:22 GMT 2015, Prisca wrote:

> My query really related to how/where get_iplayer obtained 
> the radio links and whether it would still be able 
> to download radio programs after the switch off.

Hi Prisca :-)

The wma streams are being phased out as we speak; 
I can't find wma-OD streams for newly broadcast content 
on Radios 1 & 2 (e.g. pid=b0528kgc) - Radio 3 programmes 
continue to have a WMA-OD version (e.g. pid=b052gzr7) 
at the time of writing.
 GiP 2.91 doesn't search for WMA streams (by default) 
in any case; use the --mediaselector=4 switch to try and 
grab any remaining available wma-radiomodes, but the app 
that is used (MPlayer) for dumping isn't reliable...
 It isn't true they are axing the AAC AOD streams; one mode 
of delivery (via the RTMP protocol) will be discontinued 
sometime during this current year 2015 - they (the Beeb) 
have been very vague in their statements... This mode is 
what in GiP terms is referred to as "flashaac" radiomode.
 The RTMP protocol delivery will be phased out in favour 
of a HTTP protocol delivery - this is suported currently by 
two technologies:
1. AdobeHDS (targeting desktops/laptops) & 
2. AppleHLS (targeting mobile devices).
A third one (MPEG-DASH) is currently experimental 
and under development, but they seem to like it a lot...
 When the RTMP AOD streams die, it's hard to tell what'll 
happen. GiP already has support for the AppleHLS 
streams (main method for accessing Live TV); try them by 
using --modes=hlsaac with your radio fetches; 
sadly, it takes a lot longer to download compared to the 
flashaac ones...
 GiP lacks support currently for AdobeHDS streams; 
there are solutions available for the more savvy - eventually 
FFmpeg (a helper app used by GiP) will incorporate 
support for such streams...
 Be sure that the dev of GiP keeps an eye on the changes 
the BBC implements and tries his absolute best to come up 
with solutions - have faith!
(What is ominous with these new methods is that they 
leave room for DRM encryption - if to be implemented, I 
fear this would be the definite end of GiP ... :-(  ).
 As to "where the streams are coming from", I'm afraid 
I'd bore you with a lot of "techie" talk - In a nutshell, 
the files are uploaded by the Beeb on networks of 
storage servers, called CDNs - then they are streamed to 
the clients devices (e.g. your PC browser or your iPad) via different 
streaming techniques.
When you tell GiP to fetch a radio programme 
(by providing a pid string), GiP queries various BBC servers to 
acquire needed metadata that will grant it access to the CDNs 
where the files are stored - then, depending on the streaming 
method, will invoke the suitable helper app (rtmpdump, ffmpeg, 
mplayer) to start saving the stream onto your disk - further apps 
are then used so that in the end you get a playable and tagged 
file for your listening pleasure!
 
Cheers,
Vangelis.