Hi David, 52bits per 30ms might work out nicely.
30ms at 2400baud is 72 bits. If we use a 16 bit uw there are still 4 bits to spare. I don't think FEC is that important when using an existing FM system. For more advanced work with TDMA that will help, but I think that would require its own format and mode anyway, no need to mix those two up. (Execpt use the same codec2 mode for convenience) I think the code changes for such a mode would be relativly simple. fmfsk is currently fixed at 96 bits per frame, but that can be fixed relativly easy and a new frame format should be easy to add. (Basicly its size is between the 800XA and 2400A/B) Regards, Jeroen On 02/24/2019 07:52 PM, David Rowe wrote: > Hello Jeroen, > > The experimental quantisation I'm working on is flexible, you can trade > off the number of VQ stages and frame rate (10,20,30 ... ms). > > In order to get a FreeDV mode on the air, I've settled on 52 bits every > 30ms (1733 bits/s). You'll need syncronisation and maybe FEC on top of > that. > > The work-in-progress code is here: > > https://github.com/mozilla/LPCNet/tree/dr_exp_quant > > - David > > On 25/02/19 03:31, Jeroen Vreeken wrote: >> Hi David, >> >> How 'fixed' is the 'around 2000 bits/s' number? And do you have some >> idea of the frame size you are going to use? >> (e.g. 40ms or something different?P >> I really liked the sound of the new modes and would like to test them on >> UHF with a mode based on 2400B. >> If we take the current 2400B frame and strip the padding (not needed if >> not doing TDMA) and protocol bits (can be doing in the data channel with >> the alternate UW) you get 80bits of usefull data per 40ms frame which >> translates nicely to 2000bits/s. >> >> If you end up on something different it can probably still be done by >> changing the framing some more (e.g. larger frame than just 96 bits). In >> that case I would like to prepare the fmfsk code and framing code for it >> and start testing a bit. >> >> Regards, >> Jeroen >> >> On 02/24/2019 05:08 AM, David Rowe wrote: >>> Hi Mike, >>> >>> Unfortunately the masking model work didn't lead to a viable Codec 2 mode. >>> >>> I think a LPCNet codec might suit your application well, I'll have a >>> release in the next few weeks for you to play with (around 2000 bits/s). >>> >>> Jean-Marc Valin (the author) has ported the code to C and to run on >>> general purpose CPUs, and we have some done some optimisation for >>> ARM-NEON. It's real time on a modern smart phone, and has scope for >>> further optimisation (help wanted here!) >>> >>> You don't need any special libraries, and it doesn't (really) need >>> training for specific speakers, although you could re-train if you >>> wanted to. >>> >>> Cheers, >>> David >>> >>> On 23/02/19 19:40, Mike Dawson wrote: >>>> Hi Codec2 list, >>>> >>>> I'm working together with Samih, looking at shrinking Khan Academy and >>>> other educational content for our offline library app. I've been trying >>>> to figure out optimal codec2 encoding / decoding parameters. >>>> >>>> We know who the speaker is in each clip. As far as I can understand, the >>>> best approach for us to achieve optimal results with a fixed speaker >>>> set, with having access to the original would be using the masking model >>>> outlined here: https://www.rowetel.com/?p=4454. Is this masking model >>>> per speaker, or per clip? >>>> >>>> I haven't managed to get the masking model running yet, but I made a >>>> basic script ( >>>> https://gist.github.com/mikedawson/1d66a1d35bd1538b2a9950246ef061a2 ) to >>>> generate comparison tables using a basket of clips and different >>>> parameter combinations. The audio from 4 Khan Academy clips with >>>> different codec2 settings is here: >>>> >>>> https://www.ustadmobile.com/files/codec2/out/ >>>> >>>> Using VP9 compression, the video in a 3.5 min clip can be shrunk to just >>>> under 100kB. If we used 2.4kbps codec2 for the audio, we could get the >>>> audio to around 70kB. As there are around 15,000 videos (only in >>>> English), codec2 could save a huge amount of space and bandwidth. That >>>> makes it around 60-70% smaller than the smallest 'mobile friendly' mp4 >>>> version from Khan Academy. >>>> >>>> On the LPCNet topic: this is definitely interesting, but will need >>>> further investigation. The examples from the masking model sounded >>>> pretty good. One obstacle I can see is the size of the training file. >>>> The app has to work offline and we have to keep the app size itself as >>>> small as possible. Perhaps with a limited speaker set, and no need to >>>> work on untrained files, this would not be so bad. We would also need to >>>> get the model to work with Tensorflow lite. Finally, in many places >>>> where low bandwidth and device space is an issue, the phones themselves >>>> often have limited capacity (Android 4.4 is still very much alive). >>>> >>>> Any further suggestion on what would be the current recommended / >>>> optimal approach for a fixed set of speakers would be much appreciated! >>>> We're very excited about the potential of this to make this education >>>> content more accessible. >>>> >>>> Thanks! >>>> >>>> -Mike >>>> >>>> CEO >>>> Ustad Mobile >>>> >>>> Email: m...@ustadmobile.com >>>> Web: www.ustadmobile.com >>>> Twitter: @ustadmobile >>>> Facebook: www.facebook.com/Ustad.Mobile >>>> >>>> >>>> _______________________________________________ >>>> Freetel-codec2 mailing list >>>> Freetel-codec2@lists.sourceforge.net >>>> https://lists.sourceforge.net/lists/listinfo/freetel-codec2 >>>> >>> _______________________________________________ >>> Freetel-codec2 mailing list >>> Freetel-codec2@lists.sourceforge.net >>> https://lists.sourceforge.net/lists/listinfo/freetel-codec2 >> >> >> _______________________________________________ >> Freetel-codec2 mailing list >> Freetel-codec2@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/freetel-codec2 >> > > _______________________________________________ > Freetel-codec2 mailing list > Freetel-codec2@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > _______________________________________________ Freetel-codec2 mailing list Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2
