[Vorbis] Vorbis encoding at half speed

[Ross Levis]

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 at xiph.org] On Behalf Of xiphmont at xiph.org
Sent: Wednesday, 4 January 2017 1:17 p.m.
To: IHARA Hiroka
Cc: vorbis at 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 at 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 at 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.
>>
>>
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