TransPCM—use Float16/24 to reduce bit-depth, also promotes compression, 2012-05-29: beta v0.1.1 / formerly HalfPrecision / ref.: IEEE 754-2008 Options

[Nick.C]

When I first became aware of the Float16 type I found it interesting in terms of maybe having potential as a possible lossy storage type.

Attached is a processed version of the sample in this thread which has been decoded back to PCM. The processing is as follows (at this stage as there is no player that I am aware of):
Input file Sample [PCM] > FLOAT16 > [PCM] > Output File.

The conversion from integer to Float16 reduces the number of significant bits of the 24-bit sample to (a maximum of) 11. There is therefore an amount of added noise due to truncation. The added noise has been noise shaped using SG's adaptive noise shaping method as used in lossyWAV.

Original Sample

Lossy Float16 Processed Sample [edit] removed due to TransPCM executable / foobar2000 Float16 playback availability, 29th May 2012. [/edit]

If the 24-bit coded sample is encoded with FLAC (wFormatTag left as 0x0001 as FLAC does not handle Floating Point samples and wBitsPerSample is left as 24) there is a saving of in excess of 20% in filesize.

I don't see any practical advantage using this storage type for native 16-bit PCM.

This post has been edited by Nick.C: May 29 2012, 21:36

[Nick.C]

HalfPrecision beta 0.1.0a attached. [edit] Superseded. [/edit]

Changelog:

• Change to -P, --precision parameter. Takes a value in the range -8<=n<=0, i.e. new_mantissa_precision = old_mantissa_precision + n.
• Modifications to Float32 and Float24 handling - now uses -P, --precision parameter to reduce mantissa bits as for Float16.
• Optimisation of uLaw and ALaw encoding / decoding.

This post has been edited by Nick.C: Dec 23 2011, 08:21