[mythtv-users] trandcoding messes up 6 channel audio slow audio playback

Jean-Yves Avenard jyavenard at gmail.com
Fri Dec 31 04:46:24 UTC 2010

On 31 December 2010 11:51, Bryan Clingman <bryan at clingman.org> wrote:

> It's the same problem discussed here:
> http://www.mythtvtalk.com/playback-half-speed-after-transcoding-13472/
> and several times on this list (including myself)
> Anyway, the patch is attached.  This works by making the audio as
> follows:

Is see that the patch has:
// ugly hack.

and it surely is :)

> left_transcoded = left/2 + center/2;
> right_transcoded = right/2 + center/2;

> The patch is an UGLY hack, but it works for the short term.  Hopefully
> at some point the AC3 stream can just be copied to the transcoded file.

I've put this on my todo list, it's actually a trivial thing to do, I
just wasn't aware that mythtranscode had such limitation so I never
actually bothered looking into the source code..

Mythtv 0.24 also offers downmixing capabilities, so rather than doing
your loop and using fixed coefficient downmixing, you could use the
mythtv downmixer class instead, your code would be greatly simplified

I guess we would have a transcoding option to leave the audio stream
as-is (LPCM or AC3/DTS etc...)


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