R
Rowetel
rowetel.com · Personal blog · on HN since 2008
David Rowe writes about open source radio and speech coding projects like Codec 2, plus home engineering projects such as an electric car.
What HN saysCommenters point to it for Codec 2 as a low-bitrate voice option on devices like the ESP32, and one has followed the blog since 2008.
32HN people shared it
21linked it in comments
40stories submitted
810story points
3 years agolast shared
2008people per year2026
Most-shared posts
- 1Post 4525 people · first shared 2017
- 2Busting Teenage Partying with a Fluksometer4 people · 10 points · first shared 2012 · discussion on HN
- 3Wordpress3 people · first shared 2019
- 4Codec2: GNU low-bitrate speech codec (2400 bits/second)2 people · 47 points · first shared 2010 · 15 comments on HN
- 5Subset Vector Quantiser2 people · 14 points · first shared 2021 · discussion on HN
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- 10Open IP over VHF/UHF Part 51 people · 123 points · first shared 2021 · 23 comments on HN
- 11Open IP over VHF/UHF1 people · 122 points · first shared 2020 · 49 comments on HN
- 12Codec 2 700C1 people · 70 points · first shared 2017 · 19 comments on HN
- 13Measuring HF noise around a city1 people · 48 points · first shared 2022 · 14 comments on HN
- 14GMSK Modem Simulation1 people · 8 points · first shared 2014 · discussion on HN
- 15Open Source Low Rate Speech Codec (Part 1)1 people · 4 points · first shared 2011 · discussion on HN
What HN people wrote when they linked it
squarefoot · 2024-04-19
> It would also be great to have this running on ESP32 or similar
ESP32 has its own port of the Codec2 library, which allows intelligible communications using very low bandwidth (a few kb/s). It could make the ideal solution for creating small cheap intercoms scattered around a small area using WiFi, or employing very low bandwidth radio connection such as LoRa for wider coverage. I still didn't see any real application, beside a few simple proof of concept videos on YouTube, though.
More info:
http://www.rowetel.com/?page_id=452
https://www.arduino.cc/reference/en/libraries/esp32_codec2/
mmastrac · 2019-03-29
I've been waiting for someone to do this* with audio and/or video. Amazing work.
Also worth reading this related link: https://www.rowetel.com/?p=6639
There's some really exciting progress that could be made in this space. The page mentions that they could use it as a post-processing filter for Opus for better decoding to avoid changing the bitstream. It could also be useful as a way to accommodate for packet loss and recover "just enough" to avoid interrupting the conversation.
* encoding audio through a neural network for network transmission
LeonM · 2018-06-23
I've been reading David Rowe's blog [0] since 2008, there are some other really interesting projects and products on it. One of my favorites back then was his home build electric car.
[0] https://www.rowetel.com/
lifthrasiir · 2022-06-28
How about Codec 2 [1]? I think it delivers a comparable performance to Lyra etc. while not using ML, and has multiple ESP32 ports already. Maybe it might be usable for less powered devices.
[1] https://www.rowetel.com/?page_id=452
tgsovlerkhgsel · 2021-08-10
1 k bytes per second. You can [1] squish it down to 1 kbit/s but it will become hard to understand accurately at that point, even under good conditions, and hopeless if there is noise. Opus simply doesn't support bitrates below 6 kbps.
[1] https://www.rowetel.com/?page_id=452
kragen · 2021-03-02
The LPCNet decoder for Codec2 enables high-quality voice calls at 1700 bits per second since 02019: http://www.rowetel.com/?p=6639
Why doesn't this article mention LPCNet or Codec2?
throw0101a · 2020-01-07
I'm of the opinion that Codec 2 [0][1] should pause on trying to perform better at lower and lower bit rates, and put some work into higher ones.
Getting down to 700 and even 450 b/s is neat and all, but there seems (to me) to be a gap between 4000 and 10000 b/s in the patent-free space.
* [0] http://www.rowetel.com/?page_id=452
* [1] https://en.wikipedia.org/wiki/Codec_2
dahauns · 2018-06-23
Aside from the seriously impressive WaveNet based results, I think the article doesn't do the codec itself enough justice.
I mean, low-bitrate speech codecs have been around for some time (hey, vocoders are the oldest kind of audio codecs in history!), and I grew skeptical when they started to compare with mp3 and opus.
But looking at this page Codec2 really holds its own when compared to AMBE and especially MELP, two of the most prominent ultra low-bandwidth speech codecs used today:
https://www.rowetel.com/?p=5520
gnaffle · 2011-08-05
Can anyone confirm that there are toner cartridges that stop working after a set number of pages? I thought this only applied to inkjets. My (10 year old) laser printer will happily print until the pages become unreadable - and then some more and some more after shaking the toner cartridge.
I think an open source laser printer would be an insanely cool hardware project. Although probably not cost effective due to the complexity, at least you would know exactly why the paper jams occur!
But you never know, the IP0X open source hardware project has had great success with getting chinese manufacturers to produce affordable hardware: http://www.rowetel.com/blog/?page_id=440 some of which can compete with very expensive "mainstream" offerings.
peterbmarks · 2023-02-02
I'd like to see a comparison with codec2 https://www.rowetel.com/wordpress/?page_id=452
hatsunearu · 2021-03-01
http://www.rowetel.com/wordpress/?page_id=452
Take a look at this too. Also runnable on low power devices. And there was some work of using AI to enhance the codec2 encoded bits too.
ddevault · 2021-03-01
Yeah, with Codec 2 setting the gold standard, I don't find this very impressive. I find this more intelligible at one-third of the Lyra bitrate:
http://www.rowetel.com/downloads/codec2/hts2a_1300.wav
Codec 2 does a better job of isolating the parts of sound which are most necessary to intelligible speech, without necessarily caring too much about preserving the original qualities of the speaker's voice or environment.
Fun fact: Codec 2 can be used to transmit voice over IRC:
https://github.com/asiekierka/voirc
gorkish · 2020-12-28
I have used Digium's T1/E1 cards with VPMOCT or VPMADT hardware echo cancellers, but I have since switched to using https://www.rowetel.com/wordpress/?page_id=454 OSLEC for EC as it is simply better and requires much less tuning.
est31 · 2019-06-25
> the audio quality is incredible, though required compute power is ridiculous.
LPCnet gives similar quality with much less compuation needed:
http://www.rowetel.com/wordpress/?p=6482
https://people.xiph.org/~jm/demo/lpcnet/
https://people.xiph.org/~jm/demo/lpcnet_codec/
vackosar · 2019-05-18
Impressive, the Codec 2 can go down to 0.7kbps! http://www.rowetel.com/downloads/codec2/hts1a_700c.wav
zamadatix · 2019-05-18
http://www.rowetel.com/wordpress/?page_id=452 is a bit more exotic but should sound way better even though it caps out at 3.2 kbps.
flashman · 2016-03-01
This dad used remote power monitoring to bust his daughter throwing a party at home while she was supposed to be staying with family: http://www.rowetel.com/blog/?p=2381
jasonjayr · 2015-10-30
Codec2 is an open source speech codec, shooting for 700 - 3200 bit/s, specifically for digital voice over radio.
http://www.rowetel.com/blog/?page_id=452
follower · 2010-10-29
If you still have an interest in telephony you might want to look at http://www.rowetel.com/blog/ and his work on the Mesh Potato http://www.villagetelco.org/about/mesh-potato/.
It's an open source hardware project to create an easily deployed developing world "village telephony" system.
Some really good content.
drowe67 · 2008-07-19
Re 27 (hardware/software hybrids) there is a good example: The Free Telephony Project: http://rowetel.com/ucasterisk
A community has been working on Open Hardware designs for IP telephony - embedded Asterisk boxes. The technology is now in mass production, and several commercial products are being spun out of the original, community based work.