Thanks for the reply. We are currently using AMBE (4Kbps) for our Traffic/Weather Channels. If you have ever had a chance to hear the service, you will know that AMBE does not do us well. I understand that 2Kbps is low quality, but any poorer than AMBE? If can get a decent quality for other low bandwidth talk channels, such as about 10-16Kbps and have it sound rather clean, then I would be gaining a bit of growth in the areas I'm seeking. None of this would be Music, understand. Music needs it's bandwidth... just voice only channels like: - Emergency Announcements - Barkers (This channel is not yet scheduled for Air - Traffic/Weather - ...etc Thanks again for the reply. ____________________________________________________________________________________________ Terry Carr Manager, Broadcast Applications XM SATELLITE RADIO 1500 Eckington Place, NE (Flr-2, Ops Mgt) Washington, DC 20002 Phone: (202) 380-4081 - Fax: (202) 380-4768 ________________________________ From: Jean-Marc Valin [mailto:Jean-Marc.Valin@USherbrooke.ca] Sent: Sun 11/27/2005 4:55 PM To: Carr, Terrance Cc: speex-dev@xiph.org Subject: Re: [Speex-dev] Question from XM Radio You can try the Ogg DirectShow filter to get Windows support for Speex: http://www.illiminable.com/ogg/> My goal is to find a promising codec for 2Kbps.You should be aware that the 2 kbps mode has quite poor quality in Speex, a bit similar to the LPC10 vocoder.> - Has there been any successful satellite streaming projects using > Speex?Not that I know of.> - Has there been any projects having a decoder embedded in an ICNot that I know of.> - If none of the above, what type of processing power for real-time > Encoding/Decoding are we talking. Does anyone have real-time > encoding/decoding software yet?The source code can be compiled as fixed-point and I would think the complexity is somewhere in the 5-10 MIPS range for encode+decode (decoding is cheaper than encoding). Jean-Marc -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.xiph.org/pipermail/speex-dev/attachments/20051127/38c58caa/attachment.html
On Sun, 2005-11-27 at 17:11 -0500, Carr, Terrance wrote:> Thanks for the reply. We are currently using AMBE (4Kbps) for our > Traffic/Weather Channels. If you have ever had a chance to hear the > service, you will know that AMBE does not do us well. > > I understand that 2Kbps is low quality, but any poorer than AMBE?If AMBE is 4 kbps, then most likely yes.> If can get a decent quality for other low bandwidth talk channels, > such as about 10-16Kbps and have it sound rather clean, then I would > be gaining a bit of growth in the areas I'm seeking.10-16 kbps is different and Speex is probably more useful there. Jean-Marc
> On Sun, 2005-11-27 at 17:11 -0500, Carr, Terrance wrote: >> Thanks for the reply. We are currently using AMBE (4Kbps) for our >> Traffic/Weather Channels. If you have ever had a chance to hear the >> service, you will know that AMBE does not do us well. >> >> I understand that 2Kbps is low quality, but any poorer than AMBE? > > If AMBE is 4 kbps, then most likely yes.> >> If can get a decent quality for other low bandwidth talk channels, >> such as about 10-16Kbps and have it sound rather clean, then I would >> be gaining a bit of growth in the areas I'm seeking. > > 10-16 kbps is different and Speex is probably more useful there.AMBE has a pretty long history for low-bandwidth satellite speech (the predecessor IMBE is used in the Inmarsat-M system, and AMBE is used in the Inmarsat Mini-M and M4 at 3.6kbps and Iridium at 2.4 kbps). A few years ago I did an evaluation of 4kbps speech codecs for a low-earth-orbit satellite operator (now defunct). AMBE+ at 4kbps was intended to be a "toll quality" codec, with MOS scores similar to ACELP 8kbps. It was clearly better than the couple of other 4kbps codecs which we tested, and MUCH better than LPC10. Now, AMBE builds in forward error correction, which gives the most redundancy to the most important vectors in the encoded speech. This is optimized for circuit mode systems, where all bits are delivered, even if some are in error. This sort of FEC is useless in packet systems where the data is either delivered correct or not at all. If XM is running speech in a packet mode, perhaps AMBE is not handing the loss of blocks of data data well. This might not be the fault of the codec itself, but an issue with the way that it is integrated into the system. Speex is unually flexible in its choice of bit and sampling rates, and you certainly have the ability to produce higher quality speech than you can get from AMBE. But, as Jean-Marc points out, you will need a higher bitrate to do this. - Jim