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Subject: Re: Recording problem

Re: Recording problem

From: Jens Arnold <arnold-j_at_t-online.de>
Date: 2005-11-02

On 02.11.2005, Bluechip wrote:

>> > > Or Rockbox does a similar workaround like the Archos
>> > > firmware does: It tracks the frames of incoming mp3 data.
>> > > In case of a mismatch the MAS
>> > gets
>> restarted. Results in a minor glitch in the recording, but
>> will hardly
>> > get
>> >> noticed, as rare as it happens.

>> > I mostly record concerts, typically 2-4 hours at a go.
>> > Less than half my files make it through MP3Fixer
>> > unscathed.
>> > It's not rare in my experience.

>> No, misunderstanding:
>> The workaround would cause a minor glitch every few hours
>> (that's something I could live with and call rare), when the
>> bit loss occurs. Without, your recording is toast after that,
>> or has to be rescued with Jens' very special tool.

> From where does one obtain a copy of Jens' tool?

>From nowhere so far. This isn't because I don't want to disclose
the sources, but because the tool is far from user-friendly.
All it can do is to shift a certain range of bytes within a file
by a certain number of bits.

It is possible to repair recordings suffering from the MAS
glitch with it, but the procedure isn't automatic. First, one
would need to analyse the broken recording with a hex editor,
and find the exact starting point(s) of the glitch(es), and the
shift amount. Then this tool can be used to undo the bitshift(s)
in the file, effectively repairing the recording.

I tested this method with a few of my lengthy test recordings,
and repaired them successfully. It might happen that a small
glitch remains at the point(s) where the bit shift(s) originally
started, but in my tests I didn't notice any remaining glitches.

You see, the method is tedious, but maybe it's still worth a try
for valuable recordings.

Regards, Jens
Received on Wed Nov 2 21:45:34 2005


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