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Tiny encoder in lossy mode sounds differnent to wavpack, Tiny encoder lossy mode analysis
cram
post Feb 24 2010, 10:52
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I have been running some tests on the performance of the wavpack algorithm for low bit rates and sample rates using the command line versions of the software.

e.g. wavpack -b24 file.wav file.wv

These have been performed at 16k sample rate and 11k sample rate as my application requires big reduction in the data file size. The command line algorithm states that 24 is the most compression available (although i have noticed that tiny encoder can go lower).

On the whole i have been pretty impressed with the lossy mode of the algorithm and found some suitable settings for my application.

My target hardware however requires fixed point maths so I have now implemented the tiny encoder 4.40 to perform the compression.

The issue that i have discovered is this version of the algorithm does not sound the same. There are additional distortion products when using the Tiny encoder which are not present on the command line version of wavpack.

I have tried using v4.40 of the command line version in case it was a version issue but this seems to perform as well as the latest wavpack version.

I have tried the command line version of Tiny encoder 4.40 and this does also have the distortion products which leads me to believe that they are specific to the implementation.

e.g. tinypack -b2.0 file.wav file.wv (at 16kHz)

My concern is that the lack of resolution (or dynamic range) forced by a fixed point implementation has led to a compromise of the algorithm's performance.

1) has anyone else encountered this issue?
2) Is it just a known issue that the fixed point Tiny Encoder does not function as well as the floating point version?
3) Does anyone have any ideas in which areas the discrepancy in the algorithms performance could be occurring and if modification of the source code could improve the issues.

Any comments or suggestions would be much appreciated.

many thanks
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