Re: Wav to Mp3 leads to an mp3 file that has a longer duration

Ok, thanks.

But would it be possible to
- add silence samples at the end of the wav file so that is is a multiple
of 1152
- convert it to an mp3
- and get the exact same number of samples with no change between wav
duration and mp3 duration

Because I just test with a wav file that is 8640000 samples = 7500 * 1152
and when I convert it to an mp3, I get 8641152 samples

Thanks again for your insights


-----------------------------------------------------------------------
*Martin RATINAUD*
-----------------------------------------------------------------------


On Mon, Dec 16, 2019 at 5:30 PM Måns Rullgård <[email protected]> wrote:

> Martin Ratinaud <[email protected]> writes:
>
> > Hi Måns and thanks very much
> >
> > Though it seems the resulting file is 7939544 samples
> >
> > and 7939544 / 1152 = 6891.965277777777
> >
> > So it's not a multiple of 1152 unless I'm missing something ?
>
> That difference is due to a rounding error in the stream length
> calculation.
>
> > On Mon, Dec 16, 2019 at 3:48 PM Måns Rullgård <[email protected]> wrote:
> >
> >> Martin Ratinaud <[email protected]> writes:
> >>
> >> > Hi all,
> >> >
> >> > I'm converting a file called vocals.wav to vocals.mp3
> >> >  vocals.wav
> >> > <
> >>
> https://drive.google.com/file/d/1he1eCJag1G8iGkgL932jy_mXuLT_khGM/view?usp=drive_web
> >> >
> >> > For this I'm using this command
> >> >
> >> > ```
> >> > sox vocals.wav vocals.mp3
> >> > ```
> >> > and here is the result of the corresponding files
> >> >
> >> > - original file
> >> > ```
> >> > soxi /Users/martin/Downloads/split-test/vocals.wav
> >> >
> >> > Input File     : '/Users/martin/Downloads/split-test/vocals.wav'
> >> > Channels       : 2
> >> > Sample Rate    : 44100
> >> > Precision      : 16-bit
> >> > Duration       : 00:03:00.00 = 7938000 samples = 13500 CDDA sectors
> >> > File Size      : 31.8M
> >> > Bit Rate       : 1.41M
> >> > Sample Encoding: 16-bit Signed Integer PCM
> >> > ```
> >> >
> >> > - converted file
> >> > ```
> >> > soxi /Users/martin/Downloads/split-test/vocals.mp3
> >> >
> >> > Input File     : '/Users/martin/Downloads/split-test/vocals.mp3'
> >> > Channels       : 2
> >> > Sample Rate    : 44100
> >> > Precision      : 16-bit
> >> > Duration       : 00:03:00.04 = 7939544 samples = 13502.6 CDDA sectors
> >> > File Size      : 2.88M
> >> > Bit Rate       : 128k
> >> > Sample Encoding: MPEG audio (layer I, II or III)
> >> > ```
> >> >
> >> > You can see that the duration is not the same which is weird and the
> number
> >> > of samples also changed.
> >> > In fact, 1544 samples have been added to the beginning of the file
> >> >
> >> > If I try to launch `sox -V vocals.mp3 vocals-trimmed.mp3 trim 1544s`
> it
> >> > does not work
> >>
> >> MP3 files have to have a multiple of 1152 samples.  This can't be
> >> avoided.  If the input isn't such a multiple, it will be padded by the
> >> encoder.
> >>
> >>
> >
> > _______________________________________________
> > Sox-users mailing list
> > [email protected]
> > https://lists.sourceforge.net/lists/listinfo/sox-users
> >
>
> --
> Måns Rullgård
>

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