iplayer audio to lpcm

[Jim Lesurf]

I
> > >> Thanks, I'll look at the above. One of the things I'm curious about
> > >> is the relative performance (in terms of quality, etc) of ffmpeg
> > >> versus avcodec. I come to this from being a long term user of
> > >> ffmpeg, but knowing nothing about the forking or its effects. Given
> > >> my past I tend to go for using ffmpeg as my first intent. But
> > >> would/will change if it is advantageous.
>

> Bringing this sharply back on topic...

> IIRC, DTT, DSAT and iPlayer are basically fed with the same quality
> source. iPlayer caps live from the full fat source signal, with
> automation to tell it when to start and stop, except where something
> has been preloaded for immediate availability. Not intimately familiar
> with the latest incarnation setup but I'll read some docs and confirm
> with people who do, I'm also curious now.

> IMO any significant difference in sound is going to be down to relative
> codec efficiency, not due to huge differences in the TX chain. iPlayer
> desktop uses AAC-LC, DSAT is MP2 and AAC for HD, DTT the same albeit at
> lower bit rates.

In general terms, that's what I'd be expecting. Particularly when my
favourite source material for comparisons has tended to be proms concerts
where I can compare R3 with BBC4, for example. However there can still be
curious differences as I've found and reported on previous webpages on
audiomisc.

And I know that at one time the R3 'listen again' differed from the 'live'.
e.g. a tendency to be able to second-guess converting the input stream at a
different level. Not sure that's still the case, though. Nor for other
'stations'.

However one of the points I want to test is to compare how the 'Flash'
decoder you're using when using a webpage and browser compare with what
something like ffmpeg makes of the source material. I've asked about
various aspects of this in the past. But TBH aspects of it are a black box
even for BBC people! Too much outsourcing and no source code they can all
check, I fear. :-/

Jim

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