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Subject: RE: Re[4]: LOW_WATER and high bitrates
From: Nielsen Linus (ext) (Linus.Nielsen_at_elema.siemens.se)
Date: 2002-08-01


> Hello Nielsen,

It's Linus, actually. :-)

> Is the playing time written somewhere in the mp3 file or
> calculated by filesize/bitrate?

For CBR files it is calculated from the bitrate and the file size, for VRB
files it is calculated from the frame count and the file size from the Xing
VBR header. This is of course only for the current daily build version and
not for the 1.1 version. That is why I asked what firmware you are using.

> NLe> What makes you think we read the whole file before playing it?
>
> Is my english so bad? ;) I know that we don't do this now.
>
> To calculate an average bitrate (my whole mail was about that), we can
>
> 1. read sync words, bitrates in mp3frames and calculate an
> average so far while playing (in the code that copies data from hdd to
ram)
>
> 2. read the whole file before playing as described in id3.c:
>

3. Read the Xing/Fraunhofer VBR header and use that to calculate the VBR
time.

> The DSP plays the stream without us saying him the bitrate
> of the mp3 frames. Yes. That's not the point.
> How could that help to get an average bitrate of the VBR
> file in the rockbox program?

I am silly. I read "volume" instead of "value". My bad. :-)
I thought you meant the Auto Volume feature.

/Linus



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