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Topic: Ogg Managed Bitrate & Quality (Read 1937 times) previous topic - next topic

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  • Tom Servo
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Ogg Managed Bitrate & Quality
Hi!

I tried to encode Moby's James Bond theme in OGG using the managed bitrate mode. I'm using the parameters -m 32 -M 160 -b 64, to try to achieve a good sounding 64kbit OGG.

But I have a weird quality issue. If you know the song, you know it begins with some low piano notes and some talking, which sound great, but when the synthies start, the cutoff frequency slides damn low and raises slightly more and more during the song plays. What causes that effect? Because when I encode songs with these settings with start immediately with loud sounds at the beginning, this doesn't happen. Is it related to any sort of prediction function (wild guess coz i dont know how OGG works)? Same happens to Jump'n'Shout from Basement Jaxx, which starts with a couple of seconds of low volume sounds. Those were the only two I tried with managed bitrates.

I'm atm at work, I'll upload some samples when I'm back home.

Thanks, Tom!

  • tangent
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Ogg Managed Bitrate & Quality
Reply #1
Sounds like an adaptive, but I didn't think Ogg Vorbis used that.

But why are you using bitrate management anyway? -q 0 should give you better quality.

  • Tom Servo
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Ogg Managed Bitrate & Quality
Reply #2
Was rather a try. I thought it keeps the bitrate more to the nominal than -q 0.

As said, if the song starts in low volume I get that cutoff freq fall with a slow raise. Same happens if a low passage happens in the song. If the song is e.g. full volume all the time, it's neat quality.