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List:       vorbis
Subject:    Re: [Vorbis] Vorbis encoding at half speed
From:       "Ross Levis" <ross () stationplaylist ! com>
Date:       2017-01-04 0:33:56
Message-ID: 000301d26622$3d25e2e0$b771a8a0$ () com
[Download RAW message or body]

When the source is stereo, the code is down mixing stereo to mono before the output \
to vorbis_analysis_wrote.  I can't duplicate any problem here but there must be some \
issue in the code.

Thanks anyway.

-----Original Message-----
From: Vorbis [mailto:vorbis-bounces@xiph.org] On Behalf Of xiphmont@xiph.org
Sent: Wednesday, 4 January 2017 1:17 p.m.
To: IHARA Hiroka
Cc: vorbis@xiph.org
Subject: Re: [Vorbis] Vorbis encoding at half speed

Echoing Hiroka, who is likely on the right track.

Simply telling the encoder 'one channel' and then passing stereo data will not \
convert the stereo data to mono.  The encoder encodes whatever it is given...

Monty

On Tue, Jan 3, 2017 at 6:51 PM, IHARA Hiroka <ihara_h@live.jp> wrote:
> Hello Ross,
> 
> The attachment appears at least to me as a valid monaural Vorbis audio.
> 
> It says in its header that there is only one audio channel, no stereo 
> mapping is in use, and there is only one audio vector per frame.
> 
> Actually it does not sound well, in a way that makes me wonder if two 
> channels are unexpectedly merged into one... (thus it might sound like
> half-speed)
> 
> I guess there is something wrong with the encoder setting you are 
> using, or with the original stream to be transcoded.
> 
> You might want to supply more pieces of information which you think 
> are relevant to the transcoding process (original stream, encoder 
> settings and so on).
> 
> Regards,
> 
> Hiroka
> 
> --
> 
> Hiroka IHARA
> 
> Department of Information and Communication Engineering, The 
> University of Tokyo
> 
> ihara_h@live.jp
> 
> On 2017年01月04日 07:31, Ross Levis wrote:
> > I'm using a Windows development component which uses vorbis.dll, ogg.dll, \
> > vorbisenc.dll for encoding an Ogg Vorbis file.  It's all working well except for \
> > one user occasionally has a 1 hour file appear as 2 hours and it plays at half \
> > speed.  It is being converted from stereo to mono before feeding the encoder with \
> > a channels=1 configuration. 
> > Here is an example file which will be available for a few weeks.
> > http://stationplaylist.com/temp2398/Hour2.ogg
> > 
> > Any ideas why this should occur sometimes but works fine other times?
> > 
> > Ross.
> > 
> > 
> > _______________________________________________
> > Vorbis mailing list
> > Vorbis@xiph.org
> > http://lists.xiph.org/mailman/listinfo/vorbis
> 
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