README.md (4967B)
1 libresample 2 =========== 3 4 Real-time library interface by Dominic Mazzoni 5 6 Based on resample-1.7: 7 http://www-ccrma.stanford.edu/~jos/resample/ 8 9 Two licenses available: 10 License: LGPL - see LICENSE-LGPL.txt 11 License: BSD - see LICENSE-BSD.txt 12 13 History: 14 15 This library is not the highest-quality resampling library 16 available, nor is it the most flexible, nor is it the 17 fastest. But it is pretty good in all of these regards, and 18 it is quite portable. The best resampling library I am aware 19 of is libsamplerate by Erik de Castro Lopo. It's small, fast, 20 and very high quality. However, it uses the GPL for its 21 license (with commercial options available) and I needed 22 a more free library. So I wrote this library, using 23 the LGPL resample-1.7 library by Julius Smith as a basis. 24 25 Resample-1.7 is a fixed-point resampler, and as a result 26 has only limited precision. I rewrote it to use single-precision 27 floating-point arithmetic instead and increased the number 28 of filter coefficients between time steps significantly. 29 On modern processors it can resample in real time even 30 with this extra overhead. 31 32 Resample-1.7 was designed to read and write from files, so 33 I removed all of that code and replaced it with an API that 34 lets you pass samples in small chunks. It should be easy 35 to link to resample-1.7 as a library. 36 37 Changes in version 0.1.3: 38 39 * Fixed two bugs that were causing subtle problems 40 on Intel x86 processors due to differences in roundoff errors. 41 42 * Prefixed most function names with lrs and changed header file 43 from resample.h to libresample.h, to avoid namespace 44 collisions with existing programs and libraries. 45 46 * Added resample_dup (thanks to Glenn Maynard) 47 48 * Argument to resample_get_filter_width takes a const void * 49 (thanks to Glenn Maynard) 50 51 * resample-sndfile clips output to -1...1 (thanks to Glenn Maynard) 52 53 Changes in version 0.1.4: 54 55 * Added BSD license, with support from all authors and contributors. 56 57 * Uploaded to GitHub: http://github.com/minorninth/libresample 58 59 Usage notes: 60 61 - If the output buffer you pass is too small, resample_process 62 may not use any input samples because its internal output 63 buffer is too full to process any more. So do not assume 64 that it is an error just because no input samples were 65 consumed. Just keep passing valid output buffers. 66 67 - Given a resampling factor f > 1, and a number of input 68 samples n, the number of output samples should be between 69 floor(n - f) and ceil(n + f). In other words, if you 70 resample 1000 samples at a factor of 8, the number of 71 output samples might be between 7992 and 8008. Do not 72 assume that it will be exactly 8000. If you need exactly 73 8000 outputs, pad the input with extra zeros as necessary. 74 75 License and warranty: 76 77 All of the files in this package are Copyright 2003 by Dominic 78 Mazzoni <dominic@minorninth.com>. This library was based heavily 79 on Resample-1.7, Copyright 1994-2002 by Julius O. Smith III 80 <jos@ccrma.stanford.edu>, all rights reserved. 81 82 Permission to use and copy is granted subject to the terms of the 83 "GNU Lesser General Public License" (LGPL) as published by the 84 Free Software Foundation; either version 2.1 of the License, 85 or any later version. In addition, Julius O. Smith III requests 86 that a copy of any modified files be sent by email to 87 jos@ccrma.stanford.edu so that he may incorporate them into the 88 CCRMA version. 89 90 This library is distributed in the hope that it will be useful, 91 but WITHOUT ANY WARRANTY; without even the implied warranty of 92 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 93 Lesser General Public License for more details. 94 95 Permission to use and copy is also granted subject to the terms of the 96 BSD license found in LICENSE-BSD.txt. 97 98 Redistribution and use in source and binary forms, with or without modification, 99 are permitted provided that the following conditions are met: 100 101 * Redistributions of source code must retain the above copyright notice, this 102 list of conditions and the following disclaimer. 103 104 * Redistributions in binary form must reproduce the above copyright notice, this 105 list of conditions and the following disclaimer in the documentation and/or 106 other materials provided with the distribution. 107 108 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 109 ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 110 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 111 DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR 112 ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 113 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 114 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON 115 ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 116 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 117 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.