World Service podcast bit rates

[RS]

>From: Vangelis forthnet Sent: Wednesday, August 16, 2017 02:58

Thanks Vangelis for your helpful comments and explanations.

>Since 95% of BBC WS Radio content is "talk-radio",
>I find 96kbps to be more than adequate for the task...

I don't disagree.  We have survived with much lower bandwidths in the past. 
One programme I listen to regularly is Moneybox on Radio 4.  If I've 
remembered correctly for a long time its podcast was at 16kbit/s.  I think 
it is probably made in a tiny studio with Paul Lewis sitting too close to 
the microphone, because now you can hear his every breath.

>Considering it's a "World" service, meaning they have
>to cater for a global audience, 96kbps is a fine compromise
>between quality and bandwidth costs...
>And even HE-AACv1 at 48kbps sounds acceptable for
>those parts of the world with very expensive/slow Internet access...

We must be grateful for all the modes the BBC provides, because they are 
there for the benefit of devices the BBC wants to support, not for our 
benefit.  Even so it would be nice if there were always one mode without 
SBR.

>Programmes with copyrighted music (or other)
>content are excluded from the podcast treatment,
>in the rare occasions they do make it to podcast,
>music tracks are truncated to just 10sec excerpts...

I had forgotten about the restriction of music in podcasts.  It was probably 
part of the reason Desert Island Discs didn't have a podcast for so long.  I 
listened to one about a year ago, and it struck me the clips were rather 
short, but it didn't occur to me that was the reason.

>(I am only joking here, but several of your recent
>posts seem to be inquisitive of overseas BBC Radio
>bitrates, are you planning a retirement to Majorca, Richard?)

I don't have any immediate plans to move to another country, but if I did it 
would be a consolation that I could still listen to BBC radio.  If I comment 
on the politics of copyright licensing I am in danger of going way off 
topic.  In my view the Television Without Frontiers Directive does not go 
anywhere near far enough.  The EU Commission seems to be much closer to the 
mark with its argument that national copyright licences partition the single 
market and are therefore unlawful.  Unfortunately the UK may not be in the 
EU by the time anything happens.

>> if HE-AAC with SBR

>... HE-AAC always comes with SBR,
>HE-AAC = AAC-LC + SBR

>> is played on a player that does not support SBR
>> half the bandwidth is lost.
>>I have been wondering how best to deal with that.

>Yet another topic that you're recently concerned with...
>It does appear as though you're the owner of
>a hardware device that is incapable of fully rendering
>HE-AACv1...

>FWIW, in 2017, 99% of software players on all
>modern OSes can play back fully HE-AACv1.
>Even browsers like Firefox 52.3.0ESR does on
>this old Vista laptop...

I am sure you are right that there are many software players which will play 
AAC-LC and HE-AAC v1 without problem.  It is a different matter when it 
comes to hardware players (portable players or satellite receivers). 
Finding players which will reliably play AAC-LC for up to 3 hours is not 
simple.  I was lucky with SanDisk.  There was a new version of the firmware 
which fixed a problem with AAC-LC about 2 months after I asked.  My Triax 
satellite receiver will play AAC television sound, whether stereo or AC3, 
from satellite, from its own recording, and from external sources for hours 
on end without problem.  When it comes to playing AAC-LC/M4A files on the 
Music tab it will start playing and then stop after a time which is 
repeatable for each file, but varies from one file to another with no 
obvious pattern.  I have not received any reply from Triax support.  Since I 
use it as the interface to my surround sound amplifier I have to convert 
files to MP3 if they are to play reliably.

In both cases the player is only claimed to support AAC-LC, so it would be 
unreasonable to ask the supplier to make it support HE-AAC.

My Panasonic blu-ray player only supports MP3 and FLAC.

>HE-AACv1 (previously known as aacp/aac+)
>is even natively supported on most cheap mobile phones,
>where you need good sound quality at reduced
>bandwidth (because BW is expensive there...).

The specification for my phone says it plays eAAC+, which I gather is HE-AAC 
v2.  I have not checked it with the Fraunhofer tests.  The specification for 
my previous phone says it plays AAC/M4A, so it probably does not support 
HE-AAC v1.  They are not the devices I want to use.

>If your device does not support HE-AACv1,
>have you contacted its vendor by any chance?

>I often transcode HE-AACv1 m4a encodes
>to mp3 files with ffmpeg, here's an example:

I am intrigued that you are way ahead of me in transcoding HE-AAC v1 to MP3. 
You must have had a reason for doing it.  When the --aactomp3 option was 
withdrawn, several people asked for help in creating a --preset or --command 
to do it.  I suspect I am not alone in finding MP3 better supported than AAC 
by some players.

>I can assure you the MP3 transcode has full audio
>bandwidth preserved!

When I was trying to do it I did find a free software spectrum analyser to 
check, but I couldn't get it to hear the file I wanted to analyse.  I have 
since spotted that VLC has an uncalibrated spectrum analyser at
Audio Visualisations Spectrum

>> the latest episode of Science in Action, p05bdb8p.


>get_iplayer --type=radio --pid=p05bdb8p -i | FindStr versions =>

>versions:       original,podcast

>get_iplayer --type=radio --pid=p05bdb8p -i | FindStr modes =>

>modes:          original: 
>dafmed1,dafmed2,dafmed3,dafmed4,daflow1,daflow2,daflow
>3,daflow4,hafmed1,hafmed2,haflow1,haflow2,hlsaacmed1,hlsaaclow1

>which is consistent with what I wrote earlier...

and is the same as I got.

>But for the "podcast" version (not the MP3 file, this is an .m4a
>file fetched by GiP) it would appear they apply geo-filtering :-(

>verpids:        original: p05bdbfp
>verpids:        podcast: p05c1hf1

>http://open.live.bbc.co.uk/mediaselector/5/select/version/2.0/mediaset/pc/vpid/p05c1hf1

>yields different stream data based on geo-location;
>no signs of dashhigh/dashstd/hlsaacstd over here;
>but then again, who really wants "talk-radio" @320kbps?

I agree.  I thought it was weird to limit the original version to 96kbit/s 
while making the podcast version (which in this context refers to content 
rather than mode of delivery) at 320kbit/s.  In fact the same podcast 
version modes are created for non-World Service programmes (matching the 
version original modes), but that is still weird because the highest bit 
rate the podcast itself is offered at is 128kbit/s.

There were two points I wanted to make with my post.  Firstly anyone having 
problems with the new World Service PIDs may be able to get round them by 
downloading the podcast if there is one.  Secondly the podcast may offer 
higher quality for those whose players do not support HE-AAC v1.

Best wishes
Richard