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Highly Compressed Richard Hamming's Lectures (vaclavkosar.com)
68 points by vackosar on May 18, 2019 | hide | past | favorite | 21 comments

These sound terrible. The lowest-quality audio from Youtube is about 10x the size (which is still small), but at least it doesn't sound like a rescued wax cylinder recording from the turn of last century.

I had hoped from the title that this would be a summarized or edited cut of the salient points from these lectures. My limited resource these days is not bandwidth or disk space, but time.

These are encoded with Speex, the precursor to opus. If you actually want to download the audio, you can use youtube-dl to get opus encoded audio-only recordings directly:

    > youtube-dl -F "https://www.youtube.com/watch?v=AD4b-52jtos1"
    [youtube] AD4b-52jtos: Downloading webpage
    [youtube] AD4b-52jtos: Downloading video info webpage
    [info] Available formats for AD4b-52jtos:
    format code  extension  resolution note
    249          webm       audio only DASH audio   51k , opus @ 50k, 16.97MiB
    250          webm       audio only DASH audio   57k , opus @ 70k, 17.50MiB
    171          webm       audio only DASH audio   99k , vorbis@128k, 31.57MiB
    251          webm       audio only DASH audio  106k , opus @160k, 32.55MiB
    140          m4a        audio only DASH audio  132k , m4a_dash container, mp
     4a.40.2@128k, 43.56MiB
    160          mp4        194x144    144p   69k , avc1.4d400c, 30fps, video on
     ly, 10.50MiB
    278          webm       194x144    144p   86k , webm container, vp9, 30fps,
     video only, 22.85MiB
    133          mp4        322x240    240p  121k , avc1.4d400d, 30fps, video on
     ly, 17.77MiB
    242          webm       322x240    240p  153k , vp9, 30fps, video only, 26.6
    18           mp4        352x262    small , avc1.42001E, mp4a.40.2@ 96k, 114.
    43           webm       640x360    medium , vp8.0, vorbis@128k, 136.89MiB (b
The lowest quality version (opus @ 50k) is around 17mb compared with this author's 1.5mb speex version.

I store these in an archive in my syncthing directory. I don't have to think about running out of space on mobile or too much cost for the cellular downlink.

Thank you! these are very cool.

> you can save some bandwidth in exchange for recording quality by using high compression of Speex algo

how about using opus[0], the comparison chart[1] shows that opus is supposedly significantly better even at a lower bitrate.

[0]: https://www.opus-codec.org/

[1]: https://www.opus-codec.org/comparison/

actually I encoded the files to 4kbps but opus goes only to 6kbps?

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.

Impressive, the Codec 2 can go down to 0.7kbps! http://www.rowetel.com/downloads/codec2/hts1a_700c.wav

Codec2 has even lower vitrate modes than speech or opus.

wow, looks very good! It seems it my have even better support in players. I should try it out.

I really like the idea, but I find Speex distorts the audio way too much in a way that makes it hard to understand afterwards. I'm willing to sacrifice as much quality as I can as long as the speech remains easy to understand, but after that, any space savings aren't worth it.

I cannot recommend highly enough, You and Your Research. Great life and career advice from a great man near the end of his life.


Thank you for your service, sir.

Why are people thanking the OP?

Cool how you CAN compress 47 minutes of audio down to 1.6MB if you're willing to accept awful sound quality, sure. Why though? I mean, why thank the OP for their service? I don't get it.

Because processing power,bandwidth, storage space, battery capacity are not limitless resources. Computing power has been massively increased over the last few decades and yet we don't often see the 1000x increase in performance that we really should as developers have often squandered that performance.

The closer we get to pushing the limits of physics, while still expecting computing to be faster, higher resolution, etc. We should commend any efforts to make computing more efficient and less resource intensive.

Speex is cool technology from what I can tell, but it's not exactly designed to run on a Commodore 64. E.g. it's used for the voice compression of commands sent to Siri.

What it saves in bandwidth, it pays in processing power.

But anyway, that still doesn't explain why posting these files is so cool that the post shot to the top of HN.

>> that still doesn't explain why posting these files is so cool that the post shot to the top of HN.

This article shot to the top because of at least three things:

1. It was well written.

2. It had to do with cool tech in a complicated problem space.

I only know those two.

Hopefully the Speex algorithm uses Hamming Code.

Well the SpeeX Codec Manual mentions a 'Hamming window'...

It's barely decipherable.

Because he made a funny joke.

Oh I see! Fair enough.

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