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GT3b2 with HF Reduction, Discussion
SebastianG
post Mar 23 2004, 16:40
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Group: Developer
Posts: 1318
Joined: 20-March 04
From: Göttingen (DE)
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Split from here.

Please tell me some details about your HF boost reduction strategy.

Maybe my posting at
Ogg Vorbis - General
is of some interest.

edited: had some troubles posting the link ;)

bye,
Sebastian

This post has been edited by dev0: Mar 26 2004, 15:06
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QuantumKnot
post Mar 26 2004, 00:56
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Posts: 1245
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Just to clarify my position on graphs versus ABXing. I use frequency responses, graphs, spectrogram subtraction sometimes during my tunings to see what effect some modification has. However, in the end, I always do my own private listening tests to see if I have reduced something or not before I release it for external testing. And since my hearing and equipment is not that good, I often have to rely on other people like harashin, nyaochi, guruboolez, etc. to do ABX/ABC-HR tests to judge whether this encoder is an improvement or nor over the official encoder. Hence I believe, as tigre pointed out above, that empirical analysis such as spectrograms are only useful during tuning, bugfixing, etc. but ABX/ABC-HR tests should be used as the final judge of an encoder since that is ultimately what a perceptual encoder is used for.....compressing audio for our listening.

My impression is that you are judging my encoder based on looking at the frequency response of original/compressed white noise. In my opinion, that is not an accurate or fair way of judging any perceptual coder. Sure, looking at these graphs can reveal the underlying behaviour but when it comes to perceptual quality, nothing can replace ABX/ABC-HR testing.

I don't claim I know everything or a lot about Vorbis internals. I am not a Vorbis developer by trade and I admit I don't know half of what people like Garf, nyaochi, aoyumi, etc know about Vorbis internals. I stress time and time again in the other threads that I am learning as I go. I have 30% confidence that my tunings will actually work until I get external testers who very graciously perform listening tests with their expertise and equipment. Only till then am I moderately confident, based on their comments. The HF reduction code in this version of GT3b2 came from my own tuned version, QKTune beta 3.2. Since I got positive comments from the listening tests people did that there was a degree of HF hiss/boost reduction in certain transients, compared with the original coder, then I applied the patch to GT3b2, as a proof of concept.
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