[MPlayer-users] Re: Again on 5.1 vorbis encoding

[marcogi at libero.it]

On Mon, 6 Jan 2003 marcogi at libero.it wrote:

> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> On Sun, 5 Jan 2003, Alessio Sangalli wrote:
>
> > I've got the idea. I'll try to encode in separate steps so I can
> > compare
> > the file sizes of the ac3, pcm, vorbis data in 5.1 and stereo modes.
>
> I did this just yesterday. Here what I got:
>
> $ du -m
> 205     stream.ac3
> 218     3.ogg
> 221     4.ogg
> 258     5.ogg

I remade encoding test from ac3 5.1 to 6 channel vorbis, since previus
ones were wrong encoded.
I forgot to specify sempling rate to oggenc so it defaults to 44100
while .wav file was 48000 Hz.
I'm very sorry.

Now test results.

Original AC-3 file:
205 MB - File length:  74m 31,0s

ATSC A/52 aka AC-3 aka Dolby Digital stream, 48 kHz,,
complete main (CM) 3 front/2 rear, LFE on,,
384 kbit/s reserved Dolby Surround mode

Wave file created using:
mplayer -channels 6 -ao pcm ...

Vorbis files encoded using:
oggenc -q <quality> -C 6 -R 48000 -o file.ogg file.wav

Here what I got:

Quality | Avg bitrate (kbps) | File size (MB)
----------------------------------------------
  0     |    181,9           |   98
  1     |    244,2           |   131
  2     |    327,3           |   175
  3     |    378,5           |   202
  4     |    386,9           |   207
  5     |    458,4           |   245


The problem with these 6 channels vorbis files is that mplayer plays they
incorrectly. About firsts 95 secs are played correctly, but after that
only 2 rear channels are earable.
Someone can reproduce this? Am I doing something wrong?

--
Regards,  Marco Gigante
Student at Pisa University - Computer Engineering