Hi all,
I routinesly rips my CDs to WAV and then convert to ogg vorbis format
for use in my car and portable player. I don't usually notice anything
amiss, but on the last track of Mike Oldfield's "Music of the
Spheres"
album ("Musica Universalis", at the very end crescendo), the converted
.ogg file exhibits terrible distortion (sounds like digital clipping).
This does not occur with MP3 or WMA formats. I used a quality factor of 4.
Does oggenc raise the amplitude (to cause digital clippiing)? Any
idea why this happens?
Also, my previous experience with ogg vorbis format is that it provide
nice, seamless gapless transitions between tracks. However, on this
same Mike Oldfield album, I can hear a click and discontinuity between
certain tracks. Since this is a continuous symphonic piece that
spans across tracks, this is annoying. What is it with this album
that taxes the capability of the vorbis encoder?
-Ti
On Wed, Aug 13, 2008 at 1:18 PM, Ti Kan <ti at amb.org> wrote:> Hi all, > > I routinesly rips my CDs to WAV and then convert to ogg vorbis format > for use in my car and portable player. I don't usually notice anything > amiss, but on the last track of Mike Oldfield's "Music of the Spheres" > album ("Musica Universalis", at the very end crescendo), the converted > .ogg file exhibits terrible distortion (sounds like digital clipping). > This does not occur with MP3 or WMA formats. I used a quality factor of 4. > > Does oggenc raise the amplitude (to cause digital clippiing)? Any > idea why this happens?No, but it does lose precision. What is happening is not that Vorbis is amplifying, it's that the other encoders are attenuating when near clipping. Vorbis does not do this; it is capable of representing and outputiing digital signals of > +0dB, and most players just clip it.> Also, my previous experience with ogg vorbis format is that it provide > nice, seamless gapless transitions between tracks. However, on this > same Mike Oldfield album, I can hear a click and discontinuity between > certain tracks. Since this is a continuous symphonic piece that > spans across tracks, this is annoying. What is it with this album > that taxes the capability of the vorbis encoder?A DC offset or alot of subsonics that aren't being modelled because they're inaudible? (That's a guess). What do the beginning waveforms look like? Monty
Thanks Monty and Ulrich for the reply, I figured out what the problem was. It wasn't the files themselves, it was the Winamp player! I tried changing the vorbis encoding quality factor to 6.6, no difference. I tried quality factor of 10, still no difference. I didn't set any replay gain. These files are ripped into WAV (and flac) directly and converted into vorbis using oggenc. Then I changed to using foobar2000 for playback, and there is no more distortion and no more glitches between tracks. FWIW, xmms on Linux also exhibits track-gap glitches with this album, but I don't hear the distortion at the last track. I've used xmms and Winamp regularly and this is the first time I noticed these problems. Curiously, they work fine with the WAV and flac versions of this album. Something about the way they handle vorbis files? I dunno... -Ti