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64kbps mp3 encoding for streaming broadcast
post Jan 14 2013, 20:13
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I'm in the process of beta testing a stream for internet radio broadcast. We are looking to stream in mp3 as it's still the most universally accepted format for opening from a URL or hyperlink, at least until we develop our standalone app and flash player on the site.

That said, we were toying with 128kbps 44k lame and like how it sounds, but have concerns for mobile users and data usage. So we'd like to go with a 64kbps stream instead and lower the overhead for everyone. Right now, running the lame converter at 64kbps 44k joint stereo just doesn't sound good. Lots of high end artifacts as expected. Cutting the sampling frequency down to 22k helps but I'm losing a lot of high end.

I've listened to other services using this bit rate, and they sound a lot better. I listen to Radio.com quite a bit and their stations are encoded 64kbps AAC or MP3 by default. Even when switching the player to MP3 in settings, it sounds really clean. Honestly nothing like a 64kbps lame encoded stream that I'm used to.

I'd really like to get this quality out of my converter at that bit rate for mp3, but have no idea how they are doing it. Can anybody here make any suggestions on Lame settings that will really get me the most bang for the bit at 64kbps in stereo? I'm using Edcast (Oddcast) with the latest lame dll for encoding.


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post Jan 15 2013, 17:16
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From http://lame.cvs.sourceforge.net/viewvc/lame/lame/USAGE:
At lower bitrates, (like 24 kbps per channel), it is recommended that
you use a 16 kHz sampling rate combined with lowpass filtering. LAME,
as well as commercial encoders (FhG, Xing) will do this automatically.
However, if you feel there is too much (or not enough) lowpass
filtering, you may need to try different values of the lowpass cutoff
and passband width (--resample, --lowpass and --lowpass-width options).

I am not sure if those settings are exposed through edcast. Personally I would avoid 64Kbps MP3 if possible.

We may end up implementing HE-AAC from the get go..

That might be a good choice. My old non-smartphone phone from 2006(Samsung ZV50) was able to decode HE-AAC natively without additional software...

This post has been edited by LithosZA: Jan 15 2013, 17:22
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