Speaking of other people writen software ... is there no viable alternative to Virtual Audio Cable?
KC7NOA > Date: Tue, 27 Nov 2012 12:49:08 -0800 > From: [email protected] > To: [email protected] > CC: [email protected] > Subject: Re: Topband: Remote SDR Receive only setup > > It is very good that you have given the ham community a well > done sound over IP program. There already was a program like > this called IP Sound written by SM5VXC, however, the OM seems > to have vanished, and his last release has been passed around > the internet. It will be good to get a supported program > again. > > I could never get IP Sound below 150 to 200 ms at my QTH. > Perhaps it was limited by my computer. One of the problems > with VOIP programs is that the designer seems to think that > the figure of merit is how low he can reduce the data rate. > It seems logical that doing this will increase the absolute > latency (even with no processor delays) and will also increase > the processing workload for the computer. > > I also tested Remote Rig, which has its own hardware. It could > get down to about 100 ms on a good day. The problem you have is > that if you make the buffer size small to get good latency, you > increase drop outs. I can get pings of less than 20 ms, MOST of > the time. The problem is that I will get a non zero number of > 200 or 300 ms pings. You end up having to trade off latency for > drop outs. > > I will try out your software and see how it compares to IP Sound > and Remote Rig. > > Rick N6RK > > > DF3CB wrote: > >> I have found that this limits latency to something like 50 ms and the > >> audio is relatively high fidelity because the standard 56k codex is > >> quite good, compared to any kind of VOIP, which is optimized for, guess > >> what, voice, not weak signal CW. In general, you cannot get this kind > >> of latency over the internet, and if you could, it would require BOTH > >> the remote internet and the control point internet to have low latency. > > > > I can agree to some point. However, it's a fact that most of the latency > > is > > not generated on the internet line itself but on your own (client) > > computer > > and in particular with soundcard processing of the remote audio. I am also > > operating my station fully remote-controlled for DX, the station is 30km > > away from home. I've gone very deep into the problems around latency (it's > > almost a science) and developed my own VoIP software called RemAud > > (available at http://df3cb.com/remaud/). Another important factor are the > > right audio buffer sizes. More to read about that at > > http://df3cb.com/remaud/concept.php. > > > > The internet line latency can be as low as 20ms in my environment but can > > be > > as high as 80 or 100ms in the evening time. Not much to do about that. But > > I > > was surprised how long soundcard processing can take. I measured it and > > found out that there is a steady soundcard buffer overrun on my computers > > adding another 50 or even 200 or 300ms latency. The soundcards are not > > able > > to process a high number of small audio chunks - necessary for low latency > > - > > in an appropriate time. What I do with my software is to watch the number > > of > > audio chunks going into the soundcard and counting the number of processed > > audio samples at the same time. If a certain buffer overrun, set by a > > software parameter, is exceeded I begin to omit some of the incoming audio > > chunks and let them **not** process by the soundcard. This doesn't play > > any > > matter for CW or SSB. It might for digital modes. You might not even > > notice > > the dropped-out audio samples but latency can be absolutely reduced and > > minimized. (To whom it may concern, the next step are ASIO soundcard > > hardware drivers). > > > > I've also experimented with other VoIP software and different Codecs, > > compressed and uncompressed and my favorite is PCM, 8kHz needing a rather > > low internet bandwidth and reaching an estimated radio audio quality of > > 95%. > > > > 73 Bernd DF3CB > > > > > > _______________________________________________ > > Topband reflector - [email protected] > > > > > > > _______________________________________________ > Topband reflector - [email protected] _______________________________________________ Topband reflector - [email protected]
