Dear All, Floor 1 decoder uses FLOOR_fromdB_LOOKUP table. The purpose of this table is not clear to me. It is also not explicitly explained in the vorbis specification. As i have understood is that it is used to dequantise the "Y" values which are decoded from the bitstream during curve synthesis. Is this correct ? If so why does the table have only 256 elements ? This would imply that the "Y" value decoded from the bitstream should has a range from "0" to 256. ? Does the encoder ensure this ? In section 1.3.2.8 of the vorbis specification "However, floor vector values can span ~140dB (~24 bits unsigned)" . What is this referring to ? Is it the final ( dequantised ) floor vector ? warm regards, Sameen -- ___________________________________________________________ Sign-up for Ads Free at Mail.com http://promo.mail.com/adsfreejump.htm -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.xiph.org/pipermail/vorbis/attachments/20050914/e6ea9986/attachment.htm
Hi! szerda 14 szeptember 2005 08.04-kor sameen eajaz ezeket a bolcs gondolatokat fogalmazta meg:> As i have understood is that it is used to dequantise the "Y" values > which are decoded from the bitstream during curve synthesis. Is this > correct ?No, actally the floor values are the quantizers and the residue is the quantized value. Hence residue*floor=original values with quantization error.> If so why does the table have only 256 elements ? This would imply that > the "Y" value decoded from the bitstream should has a range from "0" to > 256. ? Does the encoder ensure this ?The encoders I know of do so.> In section 1.3.2.8 of the vorbis specification "However, floor vector > values can span ~140dB (~24 bits unsigned)" . What is this referring to > ? Is it the final ( dequantised ) floor vector ?Yes (the ratio between the smallest and the largest value in the FLOOR_fromdB_LOOKUP table).> warm regards, > > Sameenbye Denes -- --- What kills me, doesn't make me stronger.