VS1063a OGG Vorbis encoding quality setting effects

[Aidan]

Hi,

I have been testing OGG Vorbis encodings on the VS1063a with a sample rate of 48kHz, and different quality settings and I wanted to confirm the effects of the quality setting.

In my tests, with a quality setting of 10 (maximum), I see noise drop off around 22kHz. With quality set to 8, it is just under 20kHz. Additionally, going down to quality level 7, it drops further down to around 19kHz.

Is this the expected behavior, and are there any effects in the lower frequencies as a result of lowering the quality, or does it primarily effect the higher frequencies?

Any help would be much appreciated.

Thanks,
Aidan

[pasi]

Yes, this is by design and expected.

Lower quality setting tries to produce a lower bitrate, and reducing the highest frequencies encoded is one of the employed ways to do that.

Lower frequencies are not restricted other than due to quantization and intensity stereo limit frequency changing according to the quality setting.