tag:blogger.com,1999:blog-5096278891763426276.post2389194395439975685..comments2024-03-13T19:12:58.863+02:00Comments on absorptions: Time-coding audio filesOona Räisänenhttp://www.blogger.com/profile/08764440174916554983noreply@blogger.comBlogger9125tag:blogger.com,1999:blog-5096278891763426276.post-91569877523572643272015-10-19T09:22:58.375+03:002015-10-19T09:22:58.375+03:00I wrote it in MuseScore, it's called 'Utop...I wrote it in MuseScore, it's called 'Utopia IV'.Oona Räisänenhttps://www.blogger.com/profile/08764440174916554983noreply@blogger.comtag:blogger.com,1999:blog-5096278891763426276.post-7119236442405833542015-10-19T05:22:35.247+03:002015-10-19T05:22:35.247+03:00Where'd you get that sound sample? It's pr...Where'd you get that sound sample? It's pretty coolAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-5096278891763426276.post-36671264105065882362015-06-30T12:25:24.203+03:002015-06-30T12:25:24.203+03:00Another way would be to add a section in the wave ...Another way would be to add a section in the wave file containing a table listing the timestamps of samples every second. It would increase the file size, but it wouldn't affect the data and would/should be ignored by wave file editors and players. The table section would have to be generated alongside the generation of the wave file, and then added to the wave file afterwards. Tim.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-5096278891763426276.post-24057532200941714032015-04-15T00:23:44.816+03:002015-04-15T00:23:44.816+03:00To other readers: this is a very old trick - https...To other readers: this is a very old trick - https://en.wikipedia.org/wiki/Robbed-bit_signalingAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-5096278891763426276.post-14881407983475730052014-06-12T05:36:56.205+03:002014-06-12T05:36:56.205+03:00Spread spectrum signalling does work well for this...Spread spectrum signalling does work well for this.<br /><br />We use m-sequences for through-water comms and range measurement, providing time of flight resolution of about 0.2 milliseconds, with a signal that can be detected at -6dB SNR. We often detect on multiple ADC channels with only a single input channel connected, just from the ADC crosstalk!<br /><br />It also survives lossy compression well. I regularly use pre-canned MP3s of test signals playing back from my mobile phone through air into the receive hydrophone for testing. Spread spectrum is very tolerant to channel fading (ie what lossy audio codecs do in suppressing un-noticable frequencies), so long as correct phase is retained (which it is, otherwise music would sound terrible!)Rodney Thomsonhttps://www.blogger.com/profile/11854209436110515025noreply@blogger.comtag:blogger.com,1999:blog-5096278891763426276.post-86236710921248651702014-06-09T16:25:43.105+03:002014-06-09T16:25:43.105+03:00Thanks, very interesting insight.Thanks, very interesting insight.Oona Räisänenhttps://www.blogger.com/profile/08764440174916554983noreply@blogger.comtag:blogger.com,1999:blog-5096278891763426276.post-26929449104817060232014-06-09T15:51:43.488+03:002014-06-09T15:51:43.488+03:00Consider using spread spectrum noise in the backgr...Consider using spread spectrum noise in the background. Your data could be sent as alternating Walsh Codes. A simple Walsh-Hadamard transform would then make it possible to extract the time from a background noise level. This ought to be more resilient. Jake Brodskyhttps://www.blogger.com/profile/10353058180710930885noreply@blogger.comtag:blogger.com,1999:blog-5096278891763426276.post-26521138266922722562014-06-09T15:30:46.203+03:002014-06-09T15:30:46.203+03:00Is this supposed to be communications channel audi...Is this supposed to be communications channel audio or is this supposed to be music? <br /><br />If the former, consider using a subcarrier with WWVB tones and encoding (100 Hz). There are lots of chips out there that can pick this up and it is usually benign enough that you can filter it out of most audio streams. However, it takes an entire minute to send the time.<br /><br />The LSB stealing trick is not new. I have seen it used with T1 carriers. If you ever have to choose T1 framing methods, take a look at the difference between a plain Super Frame and an Extended Super Frame. The ESF frames have 4 KBPS channels which steal the LSB of several circuits. Jake Brodskyhttps://www.blogger.com/profile/10353058180710930885noreply@blogger.comtag:blogger.com,1999:blog-5096278891763426276.post-34420185752200364042014-06-09T08:48:28.432+03:002014-06-09T08:48:28.432+03:00Hi Oona, What if you use the TC as the dither inst...Hi Oona, What if you use the TC as the dither instead of using noise?drkimhttps://www.blogger.com/profile/06314213966971943534noreply@blogger.com