Post by thread:[PICLIST] [OT] Audio Compression

Help. I'm trying to reproduce low fi of 300 to 8Khz while using a minimal amount of flash memory to do so. I also want to keep the code simple, and within the confines of an 8 bit processor if possible. I've looked at MP3 and other compression techniques, but most of them require a large amount of processing. First a sanity check: If I want 3 minutes of 8 bit sound reproduced with the max freq. of 8Khz I'll get: (180 seconds) * (8 bits) * (16000 pulses/ second) = 23.04 megbits of memory required right? Is there an easy method to half, quarter, or more this audio info to save on memory space? Thanks, Tim Crist -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

There are various simple compression schemes available. Most use some variation of the VSDC method (Variable Slope Delta Compression) wherein you store nybbles which contain the deltas between samples (DC), or the slope required to get to the next sample (VSDC). You can also look at thowing away near silence by using an escape code and RLL (run lengh limiting) compression as used in Fax machines and the like. Also look at the various formats for compression in WAV files to see if one of them meets your needs. (somewhere on http://support.microsoft.com) Robert Tim Crist wrote: {Quote hidden}> > Help. > > I'm trying to reproduce low fi of 300 to 8Khz while using a minimal amount > of flash memory to do so. I also want to keep the code simple, and within > the confines of an 8 bit processor if possible. > > I've looked at MP3 and other compression techniques, but most of them > require a large amount of processing. > > First a sanity check: If I want 3 minutes of 8 bit sound reproduced with > the max freq. of 8Khz I'll get: > > (180 seconds) * (8 bits) * (16000 pulses/ second) = 23.04 megbits of memory > required > > right? > > Is there an easy method to half, quarter, or more this audio info to save on > memory space? > > Thanks, > > Tim Crist > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

Tim Crist wrote: {Quote hidden}> > Help. > > I'm trying to reproduce low fi of 300 to 8Khz while using a minimal amount > of flash memory to do so. I also want to keep the code simple, and within > the confines of an 8 bit processor if possible. > > I've looked at MP3 and other compression techniques, but most of them > require a large amount of processing. > > First a sanity check: If I want 3 minutes of 8 bit sound reproduced with > the max freq. of 8Khz I'll get: > > (180 seconds) * (8 bits) * (16000 pulses/ second) = 23.04 megbits of memory > required > > right? > > Is there an easy method to half, quarter, or more this audio info to save on > memory space? Yes. Use a skilled sound engineer and good recording equipment. If you have a decent analog "compressor" to compress the dynamic range of the sound, especially speech, and a REAL good microphone, you can get excellent quality at 8bit 5000Hz or even 2000Hz. I have personally recorded CD music to 8bit 10kHz and almost sounded CD quality, but you need to know all the tricks. You didn't mention if this was speech?? If so, a trained speech person (Radio DJ etc) will help a huge amount and usually have their own mic and know all the tricks for pop suppresion and leveling. Contact local small recording studios, they have local speech people on file for pay per hour stuff. If you state your exact needs i'm sure there are lots of people here with experience who can offer suggestions. :o) -Roman -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Hi, there is an AN in the new issue of "Embedded control handbook" with a PIC of 16C series, and schematic, and theoretical background, etc. etc. I should search the number but I you need I can. Regards, Imre +-----------------------------------------------------------------------+ | The information transmitted is intended only for the person or entity | | to which it is addressed and may contain confidential and/or | | privileged material. Any review, retransmission, dissemination or | | other use of, or taking of any action in reliance upon, this | | information by persons or entities other than the intended recipient | | is prohibited. If you received this in error, please contact the | | sender and delete the material from any computer. | +-----------------------------------------------------------------------+ On Mon, 13 Aug 2001, Robert Rolf wrote: {Quote hidden}> There are various simple compression schemes available. Most use some > variation of the VSDC method (Variable Slope Delta Compression) wherein > you store nybbles which contain the deltas between samples (DC), or the > slope required to get to the next sample (VSDC). > > You can also look at thowing away near silence by using an escape > code and RLL (run lengh limiting) compression as used in Fax machines > and the like. > > Also look at the various formats for compression in WAV files to see if > one of them meets your needs. (somewhere on > http://support.microsoft.com) > > Robert > > > Tim Crist wrote: > > > > Help. > > > > I'm trying to reproduce low fi of 300 to 8Khz while using a minimal amount > > of flash memory to do so. I also want to keep the code simple, and within > > the confines of an 8 bit processor if possible. > > > > I've looked at MP3 and other compression techniques, but most of them > > require a large amount of processing. > > > > First a sanity check: If I want 3 minutes of 8 bit sound reproduced with > > the max freq. of 8Khz I'll get: > > > > (180 seconds) * (8 bits) * (16000 pulses/ second) = 23.04 megbits of memory > > required > > > > right? > > > > Is there an easy method to half, quarter, or more this audio info to save on > > memory space? > > > > Thanks, > > > > Tim Crist > > > > -- > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > email listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email @spam@listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body > > > .. > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics