In article
<>, CJB
<> wrote:
> ubject: Tech: BBC Radio 3 Lossless Stream

> The BBC is currently testing a lossless stream of Radio 3 in flac
> format. The problem is how can this be captured? The obvious choice
> would be ffmpeg and there is protracted discussion here


Apologies if this is seen as too OT at present, but just to inform

I've been using a version of ffmpeg to capture the flac test stream since
10th April. I should make clear I'm doing this in co-operation with some
people at the BBC to help assess how well it works, etc. I put up one
*provisional* result here

The upper graph shows the peak audio level during each 0.1 sec chunk of a
section of a flac capture. The lower graph indicates how much this differs
from a sample-aligned 320 aac capture (obtained using gip). In essence the
lower graph shows a sample-by-sample 'diff' of the two versions.

Note that the lower graph is plotted to show how much *below* the flac
version this 'diff' is. So if the top graph shows, say, -20dBFS at some
point and the lower one -40dB at this time, the 'diff' is at -60dBFS. I'm
still mainly focussing on capturing info and assessing how to analyse it.
But the results tend to confirm the expectation that the flac stream is
good. I'm certainly enjoying *listening* to it. :-)

The situation wrt ffmpeg is fluid. But the way I did this is described in
some threads on the R3 flac test in the uk.comp.os.linux newsgroup during
the last couple of weeks.

Look in particular at the postings by Andy Furniss. e.g. on 9th April which
let me build a version of ffmpeg that does the job nicely here. FWIW I now
also 'tee' into a file the reports ffmpeg outputs as this helps me track
when any TLS/HTTP/DASH hiccups occur.

Note also that - despite some initial comments on a BBC webpage (now
amended) - the trial will only run for about another couple of weeks.

I would, however, recommend people try out the flac stream. And then send
positive feedback to the BBC about it. If enough people say they want it,
that increases the chance that flac might become established rather than a


Armstrong Audio
Audio Misc

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