I am making a Digital Dictation Machine and I need a solution to digitize the voice, compress it and store it on a flash chip. It should then also be able to decompress it and play it back through a d/a. I need to control it using I2C. Questions: 1) Which are the latest voice compression algorithms out there?. i know of a-law u-law, but what about the ones used in cell phones and other new ones. 2) I found "voice band audio processors" at ti, are these suited to my application? Although they dont provide for external memory access, could I use them for the compression atleast? 3)Another path would be to use a general purpose DSP chip and then program it. This way i could get the peripheral support and still get compression. Since this is a portable application, i plan to use the 5000 (low power)series. Could you help me narrow down this choice to a specific chip or how should i estimate my processing needs. 4) any other useful information would be great: Kunal
Voice Compression for digital storage and playback
Started by ●June 18, 2004
Reply by ●June 18, 20042004-06-18
Kunal wrote:> I am making a Digital Dictation Machine and I need a solution to > digitize the voice, compress it and store it on a flash chip. It > should then also be able to decompress it and play it back through a > d/a. I need to control it using I2C.What Is I2C? I have much to learn.> Questions: > 1) Which are the latest voice compression algorithms out there?. i > know of a-law u-law, but what about the ones used in cell phones and > other new ones.You too have much to learn. A- and mu-law compress dynamic range, not storage requirements.> 2) I found "voice band audio processors" at ti, are these suited to my > application? Although they dont provide for external memory access, > could I use them for the compression atleast?That depends on what they process. What do their descriptions say?> 3)Another path would be to use a general purpose DSP chip and then > program it. This way i could get the peripheral support and still get > compression. Since this is a portable application, i plan to use the > 5000 (low power)series. Could you help me narrow down this choice to a > specific chip or how should i estimate my processing needs.If A programmable processor is "another path", what had you in mind for the first path? Will TI's routines be useful for that? What you want to do is part of what many telephone answering machines do. Perhaps you can find out how some of them do it. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●June 18, 20042004-06-18
> > Questions: > > 1) Which are the latest voice compression algorithms out there?. i > > know of a-law u-law, but what about the ones used in cell phones and > > other new ones. > > You too have much to learn. A- and mu-law compress dynamic range, not > storage requirements. >It is my understanding that a-law mu-law does reduce storage requirements by representing 16 bit samples in 8 bits. Not that it is very good compression :)
Reply by ●June 18, 20042004-06-18
yo wrote:>>>Questions: >>>1) Which are the latest voice compression algorithms out there?. i >>>know of a-law u-law, but what about the ones used in cell phones and >>>other new ones. >> >>You too have much to learn. A- and mu-law compress dynamic range, not >>storage requirements. >> > > It is my understanding that a-law mu-law does reduce storage requirements by > representing 16 bit samples in 8 bits. Not that it is very good compression > :)I suppose that's a saving. Anyhow it stores 12 bits of dynamic range in 8 bits of storage space. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●June 18, 20042004-06-18
"Jerry Avins" <jya@ieee.org> wrote in message news:40d36d0c$0$3027$61fed72c@news.rcn.com...> Kunal wrote: > > > I am making a Digital Dictation Machine and I need a solution to > > digitize the voice, compress it and store it on a flash chip. It > > should then also be able to decompress it and play it back through a > > d/a. I need to control it using I2C. > > What Is I2C? I have much to learn.I2C = 'Inter-IC' - Philips's two wire bus for comms between ICs. Leon
Reply by ●June 18, 20042004-06-18
The GSM vocoder gets voice down to 13 kbit/s (Search for 'Regular Pulse Excitation - Long Term prediction'). ulaw/alaw are 64 kbit/s. Last I was working with GSM, c.4 years ago, they (ITU-T) were talking about a 8 kbit/s vocoder. I think 3G networks are using an adaptive multi-rate vocoder. Have fun, Syms.
Reply by ●June 18, 20042004-06-18
Leon Heller wrote:> "Jerry Avins" <jya@ieee.org> wrote in message...>>What Is I2C? I have much to learn. > > > I2C = 'Inter-IC' - Philips's two wire bus for comms between ICs. > > LeonThanks. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●June 19, 20042004-06-19
A lot of the tiny MP3 players out there can also record/compress from mic input. For a dictation machine you could code to as low as 16kb/s with useful results. If you want to roll your own instead of hacking a bought device, the MP3 player chips are easy to find and well documented, and I believe Microchip and TI (at least) have apnotes showing how to use their products in that application, and TI also have MP3 (and other) libraries for their DSPs (ask them). There are more efficient compression methods, but they generally take way more code and horsepower for the compression process, and MP3 is way more universal anyway. Of course there are no/low-cost PC-based MP3 dictation machines out there, but I assume you need to be independent of a PC or laptop? On 18 Jun 2004 13:17:39 -0700, kunalshenoy@hotmail.com (Kunal) wrote:>I am making a Digital Dictation Machine and I need a solution to >digitize the voice, compress it and store it on a flash chip. It >should then also be able to decompress it and play it back through a >d/a. I need to control it using I2C. > >Questions: >1) Which are the latest voice compression algorithms out there?. i >know of a-law u-law, but what about the ones used in cell phones and >other new ones. > >2) I found "voice band audio processors" at ti, are these suited to my >application? Although they dont provide for external memory access, >could I use them for the compression atleast? > >3)Another path would be to use a general purpose DSP chip and then >program it. This way i could get the peripheral support and still get >compression. Since this is a portable application, i plan to use the >5000 (low power)series. Could you help me narrow down this choice to a >specific chip or how should i estimate my processing needs. > >4) any other useful information would be great: > >KunalTony (remove the "_" to reply by email)
Reply by ●June 19, 20042004-06-19
"Jerry Avins" schrieb> Leon Heller wrote:> > > > What Is I2C? I have much to learn. > > I2C = 'Inter-IC' - Philips's two wire bus for comms > > between ICs.You might have an I2C bus in your PC, as this is IIRC used for temperature measurements (CPU, mainboard), perhaps as well for dynamic fan control. You might want to have a look at http://www.philipslogic.com/products/i2c/ Regards Martin
Reply by ●June 20, 20042004-06-20
Symon wrote:> The GSM vocoder gets voice down to 13 kbit/s (Search for 'Regular Pulse > Excitation - Long Term prediction'). ulaw/alaw are 64 kbit/s. Last I was > working with GSM, c.4 years ago, they (ITU-T) were talking about a 8 kbit/s > vocoder.There's Enhanced Full Rate and Half Rate CODECs in GSM these days. Note that teh GSM codec does stuffliek comfort noise detection and generation which the OP may not desire (coder detects type of background noise, and decoder plays correct background noise when no speech bits are transmitted or received). Thomas
