Duration time stamp jumps around in VLC playing downloaded radio.

[Jeremy Nicoll - ml get_iplayer]

MS <jmstanfield at gmail.com> wrote:

>When playing radio programmes I've downloaded using get_iplayer in VLC 
>the duration time jumps around instead of displaying an accurate fixed 
>time, it constantly changes (usually in the region of 2-3 mins longer 
>than the real duration). The playing time works correctly, each second 
>ticking over at the correct rate, and the audio plays fine.

For an application to estimate the duration of something recorded/converted
at a fixed sample rate is easy, but if the file has a variable bit rate the
ionly way an app can work out the duration is to scan though the whole file
working out how long it would take to play.

So... maybe the way downloads are being converted to MP3 has changed, or
maybe the way VLC makes its estimates has changed.  Do you have any other
softare that you could use to see what it thinks the duration of some item
is?


>I can fix this by re-encoding the downloaded MP3 file with Lame, e.g. 
>below. Once this is done the duration time works normally showing an 
>accurate fixed time as you would expect.
>
>lame -V 2 InFile.mp3 OutFile.mp3

Is that by any chance converting to a fixed bit-rate?

>...Download complete
>avconv version 0.8.9-4:0.8.9-0ubuntu0.12.04.1, Copyright (c) 2000-2013 
>the Libav developers built on Nov  9 2013 19:08:00 with gcc 4.6.3
>[flv @ 0x153a9c0] max_analyze_duration reached
>[flv @ 0x153a9c0] Estimating duration from bitrate, this may be inaccurate
>Input #0, flv, from '/my/edit/path/to/file.partial.mp3.flv...

... and that's the problem.  It's guessing because it can't tell for sure
without simulating the whole play process.  But why?


-- 
Jeremy Nicoll - my opinions are my own.