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Subject: Re: Re[2]: LOW_WATER and high bitrates
From: Paul Suade (paul.suade_at_laposte.net)
Date: 2002-07-31


The MAS issues a SYNC FRAME so it might be used by the SH1 to be aware,
provided that the SH1 can catch it..

----- Original Message -----
From: "Uwe Freese" <mail_at_uwe-freese.de>
To: "Eric Linenberg" <rockbox_at_cool.haxx.se>
Sent: Wednesday, July 31, 2002 8:52 PM
Subject: Re[2]: LOW_WATER and high bitrates

> Hello Eric,
>
> Eric Linenberg wrote on Wednesday, July 31, 2002, 6:10:00 PM:
>
> EL> I think a good solution to this problem would be to have dynamic
> EL> watermarks. After learning what bitrate the song is at. Dynamically
> EL> adjust the watermark to reflect this. VBR file could be a bit of a
> EL> problem though.
>
> Are we reading the data from disk and sending it to the mp3
> decoder without noticing mp3 frames or are we aware of the mp3frames? (I
> think the first one.)
> How can I find the beginning of an mp3-frame (and find the header)?
>
> If that is possible, I think we should update the bitrate-field of the
> id3tag-struct by making it the average of the ones that were found by
> now, like:
>
> double bitrate_sum = 0.0;
> double frames_read = 0.0;
>
> void DEI3(void) {
>
> // reading data from disk
>
> // get bitrate of actually read frame
>
> bitrate_sum += bitrate_this_frame;
> frames_read += 1.0;
> mp3entry.bitrate = (int)(bitrate_sum / frames_read);
>
> }
>
> (double to prevent overflow)
>
> The playing time should also be updated while playing the song.
>
> I'd prefer this instead of reading in the whole file before playing it
> (it takes too long). And I think it'll give a really good average value
> very quickly.
>
> Bye, Uwe.
>



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