diff options
Diffstat (limited to 'src/wavpack/readme.txt')
| -rw-r--r-- | src/wavpack/readme.txt | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/src/wavpack/readme.txt b/src/wavpack/readme.txt new file mode 100644 index 00000000..4ccbdf42 --- /dev/null +++ b/src/wavpack/readme.txt @@ -0,0 +1,68 @@ +//////////////////////////////////////////////////////////////////////////// +// **** WAVPACK **** // +// Hybrid Lossless Wavefile Compressor // +// Copyright (c) 1998 - 2006 Conifer Software. // +// All Rights Reserved. // +// Distributed under the BSD Software License (see license.txt) // +//////////////////////////////////////////////////////////////////////////// + +This package contains a tiny version of the WavPack 4.40 decoder that might +be used in a "resource limited" CPU environment or form the basis for a +hardware decoding implementation. It is packaged with a demo command-line +program that accepts a WavPack audio file on stdin and outputs a RIFF wav +file to stdout. The program is standard C, and a win32 executable is +included which was compiled under MS Visual C++ 6.0 using this command: + +cl /O1 /DWIN32 wvfilter.c wputils.c unpack.c float.c metadata.c words.c bits.c + +WavPack data is read with a stream reading callback. No direct seeking is +provided for, but it is possible to start decoding anywhere in a WavPack +stream. In this case, WavPack will be able to provide the sample-accurate +position when it synchs with the data and begins decoding. The WIN32 macro +is used for Windows to force the stdin and stdout streams to be binary mode. + +Compared to the previous version, this library has been optimized somewhat +for improved performance in exchange for slightly larger code size. The +library also now includes hand-optimized assembly language versions of the +decorrelation functions for both the ColdFire (w/EMAC) and ARM processors. + +For demonstration purposes this uses a single static copy of the +WavpackContext structure, so obviously it cannot be used for more than one +file at a time. Also, this decoder will not handle "correction" files, plays +only the first two channels of multi-channel files, and is limited in +resolution in some large integer or floating point files (but always +provides at least 24 bits of resolution). It also will not accept WavPack +files from before version 4.0. + +The previous version of this library would handle float files by returning +32-bit floating-point data (even though no floating point math was used). +Because this library would normally be used for simply playing WavPack +files where lossless performance (beyond 24-bits) is not relevant, I have +changed this behavior. Now, these files will generate clipped 24-bit data. +The MODE_FLOAT flag will still be returned by WavpackGetMode(), but the +BitsPerSample and BytesPerSample queries will be 24 and 3, respectfully. +What this means is that an application that can handle 24-bit data will +now be able to handle floating point data (assuming that the MODE_FLOAT +flag is ignored). + +To make this code viable on the greatest number of hardware platforms, the +following are true: + + speed is about 5x realtime on an AMD K6 300 MHz + ("high" mode 16/44 stereo; normal mode is about twice that fast) + + no floating-point math required; just 32b * 32b = 32b int multiply + + large data areas are static and less than 4K total + executable code and tables are less than 40K + no malloc / free usage + +To maintain compatibility on various platforms, the following conventions +are used: + + a "char" must be exactly 8-bits + a "short" must be exactly 16-bits + an "int" must be at least 16-bits, but may be larger + the "long" type is not used to avoid problems with 64-bit compilers + +Questions or comments should be directed to david@wavpack.com |