刘品今天推荐了一个speech codec：hawkvoice

今天没时间了，改天详细研究一下。

先留个链接吧。。。。。

http://hawksoft.com/hawkvoice/

简介：OpenLPC 1.8~1.4kbps Speech Codec

今天测试了一下：

官方测试文件链接如下

http://hawksoft.com/hawkvoice/codecs.shtml

Source Codec 链接

https://files.cnblogs.com/gaozehua/openlpc.fp.zip

个人分析：openlpc效果是差一些的。因为算法比较简单，在量化上估计损失大点，起到提高压缩比作用。代码就一页，代码量不大，不能说这个能说明什么问题。但是他没有做太多的算法级升级，应该是在LPC10中做深度的量化分析。hawksoft主打好像是game，由于军方早期的codec质量不好，现在类似军方游戏的codec也像那方面模拟。音质差一点不重要，只要能听懂就可。以后做详细分析。

引用：

“

HawkVoice™ codecs

Here are actual voice samples that were compressed and decompressed with the codecs included with HawkVoice. The original u-law encoded samples were encoded and decoded back to u-law for comparison.

This sample is about 5 seconds long, with a male and female speaker. Each sample is 43 KB and available in .au or .wav format.
[.au] [.wav] Original u-law encoded 
[.au] [.wav] 32 Kbps Intel/DVI ADPCM codec 
[.au] [.wav] 13.2 Kbps GSM codec 
[.au] [.wav] 4.8 Kbps LPC codec 
[.au] [.wav] 4.5 Kbps CELP codec 
[.au] [.wav] 3.0 Kbps CELP codec 
[.au] [.wav] 2.4 Kbps LPC10 codec 
[.au] [.wav] 356 bps - 2.4 Kbps VBR-LPC10 codec, averaged 1905 bps 
[.au] [.wav] 2.3 Kbps CELP codec 
[.au] [.wav] 1.8 Kbps OpenLPC codec 
[.au] [.wav] 1.4 Kbps OpenLPC codec 
[.au] [.wav] 2.4 Kbps fixed point LPC10 codec $ 
[.au] [.wav] 1.8 Kbps fixed point OpenLPC codec $ or LGPL 
[.au] [.wav] 1.4 Kbps fixed point OpenLPC codec $ or LGPL 
$ fixed point code is available for license, contact Phil Frisbie, Jr. for details

This sample is about 25 seconds long, with several male and several female speakers. Each sample is 200 KB and available in .au or .wav format.
[.au] [.wav] Original u-law encoded 
[.au] [.wav] 32 Kbps Intel/DVI ADPCM codec 
[.au] [.wav] 13.2 Kbps GSM codec 
[.au] [.wav] 4.8 Kbps LPC codec 
[.au] [.wav] 4.5 Kbps CELP codec 
[.au] [.wav] 3.0 Kbps CELP codec 
[.au] [.wav] 2.4 Kbps LPC10 codec 
[.au] [.wav] 356 bps - 2.4 Kbps VBR-LPC10 codec, averaged 1224 bps 
[.au] [.wav] 2.3 Kbps CELP codec 
[.au] [.wav] 1.8 Kbps OpenLPC codec 
[.au] [.wav] 1.4 Kbps OpenLPC codec 
[.au] [.wav] 2.4 Kbps fixed point LPC10 codec $ 
[.au] [.wav] 1.8 Kbps fixed point OpenLPC codec $ or LGPL 
[.au] [.wav] 1.4 Kbps fixed point OpenLPC codec $ or LGPL 
$ fixed point code is available for license, contact Phil Frisbie, Jr. for details

Here are some performance results calculated with codectest.exe, version HVDI 0.9, on a Pentium III system using the short five second voice sample above:

CPU cycles per second for 8KHz sample rate sound.
Compression % is compared to 16 bit PCM.

             encode     decode     compression
u-law:         42K        40K          50%
ADPMC:        407K       330K          75%
GSM:          2.0M       950K          89.7%
LPC:          2.5M       1.0M          96.3%
CELP 4.5K:    24-52M*    4.4M          96.5%
CELP 3.0K:    25-47M*    4.0M          97.7%
LPC-10:       6.4M       3.5M          98.1%
CELP 2.3K:    24-45M*    3.8M          98.2%
OpenLPC 1.8K: 2.9M       1.8M          98.6%
OpenLPC 1.4K: 2.9M       1.9M          98.9%

*Note on CELP encoding: CELP uses a codebook
of 256 speech patterns.  The CELP encoding
performance listed shows figures from a codebook
search of 32 up to the full 256 entries.

Here are some performance results for fixed point codecs on a Pocket PC with a PXA250 400MHz X-Scale (ARM) CPU using the long 25 second voice sample above:

CPU cycles per second for 8KHz sample rate sound.

              encode      decode
LPC-10:       19.0M       13.2M
OpenLPC 1.8K:  8.1M        9.8M
OpenLPC 1.4K:  8.2M        9.8M

HawkNL, HawkNLU, and HawkVoice are trademarks of Phil Frisbie to help protect these open source projects.

”