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@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
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