[mpg123-devel] [ mpg123-Bugs-3582628 ] High pitched sound distortion

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Bugs item #3582628, was opened at 2012-11-01 23:09
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>Category: mpglib
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Thomas ()
Assigned to: Nobody/Anonymous (nobody)
Summary: High pitched sound distortion

Initial Comment:
Introduced somewhere between 1.12.1 and 1.13.4, a problem with mpg123
produces a high-pitched distortion in the attached file.

In the first syllabe of the first word spoken in the attached file,
there is a high pitched distortion when played with mpg123 1.13.4, as
well as the latest 1.14.4. It plays fine with 1.12.1, or with OS X's
built-in mp3 decoder.

This was tested on MacOS X 10.8.2, but I don't beleive this to be
system dependant.


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>Comment By: Thomas ()
Date: 2012-11-02 12:42

Message:
Hi,

In fact, I was using the mpglib, not mpg123. I entered the wrong
category, sorry for the confusion.

I could narrow down the source of the problem. Below is the sequence
of mpg123 lib calls I do when I open an mp3 file. The problem appeared
when I added a mpg123_scan call, to get a more accurate value of the
length for certain mp3 files.

  mpg123_init
  mpg123_new
  mpg123_open
  mpg123_getformat
> mpg123_scan
  mpg123_length
  mpg123_format_none
  mpg123_format
  decode audio...

With this mpg123_scan call, there is a blip at the beginning of the
decoded audio. I can work around this by closing, and reopening the
file, like this:

  mpg123_init
  mpg123_new
  mpg123_open
  mpg123_getformat
  mpg123_scan
  mpg123_length
> mpg123_close
> mpg123_open
  mpg123_format_none
  mpg123_format
  decode audio...

This is either a problem with mpg123 lib, or with its documentation.

Thanks for looking into this.


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Comment By: Thomas Orgis (sobukus)
Date: 2012-11-02 02:03

Message:
Sorry, I cannot reproduce that on GNU/Linux x86-64; does the distortion
also show when decoding to WAV with mpg123 -w out.wav and playing that?

You are also on x86-64 architecture, right? Does the distortion change when
switching decoders (mpg123 --cpu generic)?

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