Re: Slow seeking in MP3 files using ExtAudioFile
Re: Slow seeking in MP3 files using ExtAudioFile
- Subject: Re: Slow seeking in MP3 files using ExtAudioFile
- From: Stephen Davis <email@hidden>
- Date: Tue, 20 Jan 2009 14:45:40 -0800
On Jan 20, 2009, at 2:25 PM, Jens Alfke wrote:
On Jan 20, 2009, at 1:56 PM, Markus Fritze wrote:
MP3 is a streaming format, to find a sample position inside the
file this reading is required. However, iTunes 5 or later,
GarageBand and Logic write some additional information into the MP3
file, which allows you to find the position without reading
everything.
Interesting! Are there any APIs for reading this, or at least
something describing the format and how to find it?
It's the XING header which you can probably find documented somewhere.
However, it is not actually sufficient b/c it is a fixed-size 256-
entry table so it is not accurate to a packet boundary and gets less
accurate the longer the file is. Since ExtAudioFile exposes a "go to
this packet" API, it has to calculate reality, not the vague notion of
it that the XING header represents.
stephen
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