Subject: Re: [ecasound] Fade in and fade out
From: Kai Vehmanen (k_AT_eca.cx)
Date: Tue Nov 04 2003 - 01:47:43 EET
On Mon, 3 Nov 2003, Julian Dobson wrote:
> I was hoping to avoid having to use an external program to measure the
> playtime of the file before-hand, as I've had problems doing this due to
> VBR in the source (for example ecalength reports 1529.861s for a song
> which is only 254s actual length - and mp3check reports 382s; MP3::info
> correctly reports 254s, at least for this song). And this is why I was
Yep, this is a real problem. But the only real solution is to decode the
whole file and see how many samples come out. And this is slow.
> hoping that there was some way of processing ecasound's internal buffer
> or secondary buffer.
> I guess I may have to look into writing a LADSPA plug-in to do this.
The problem is that a single singal processing component only sees the
current sample or a block of sample, it does not have access to the whole
file (which might be gigabytes long and not fit to the memory, etc). This
limitation applies both to Ecasound as well as LADSPA plugins. In any case
you will need a two-stage processing to make the tail-fade.
I'd recommend that you implement a more robust ecalength that decodes the
whole file and reports how much data did the decoder provide. Using this
info you can make a realiable fade-out.
-- http://www.eca.cx Audio software for Linux!
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