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Topic: *Ultra* low bitrates (Read 4646 times) previous topic - next topic
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*Ultra* low bitrates

I recently get a recording of the famous Orson Welles War of the Worlds Radio broadcast and wanted to compress it down to show some internet friends. At an hour long, this meant serious compression. Thankfully, the source material was low-fi enough that it didn't suffer from downsampling to 8 khz mono, then I put it through Vorbis q-1 and got a 4.5 MB file out, perfect for internet distribution, and it sounds great.

I'm not sure if the mods would be okay with posting it, I *think* it's still under copyright, so I'll err on the safe side until I'm informed otherwise.
 

*Ultra* low bitrates

Reply #1 –
Try Speex.

*Ultra* low bitrates

Reply #2 –
That was my temptation at the time, but I didn't have access to a speex encoder at the time. Besides, there are a lot of sound effects and music that aren't handled very well by speex at such low bitrates. I did a comparison on a soundboard recording from my church if you're interested. Though to be fair, the recordings in the comparison are at 22 and 11 khz, which speex is not optimized for. I was actually doing the test to see how well Speex would fare on compressing sound from old LucasArts games for the ScummVM project.

*Ultra* low bitrates

Reply #3 –
Then again, there is always Garf's work in this area.

*Ultra* low bitrates

Reply #5 –
aoTuV beta 2 has a -q -2 mode.

*Ultra* low bitrates

Reply #6 –
I love outrageous copyright terms.

I'm all for the preservation of intellectual property, but at a certain point it tends to become ridiculous, no?

*Ultra* low bitrates

Reply #7 –
I like to use a sampling rate of 8khz and -q -1 for streaming, this gives a nice under 12kbps vbr stream with landline telephone like quality. I know speex can do better, but only with human voice. Add anything to the speech, and the artifact is quite annoying. Its like that in all speech based codecs so i'm not complaining

But vorbis keeps a much more familiar sound, more "consistent", not too "metallic" or "weird" form time to time.

Under that... well Garf's experiments were nice but quality suffers a LOT. Vorbis at under 6kbps reminds me of mp3 at 8kbps. Still discernable, i suppose
She is waiting in the air

*Ultra* low bitrates

Reply #8 –
Quote
aoTuV beta 2 has a -q -2 mode.

only works for 44.1 kHz

*Ultra* low bitrates

Reply #9 –
Give the HE-AAC a try, haven`t disapointed me yet.

*Ultra* low bitrates

Reply #10 –
Quote
Quote
aoTuV beta 2 has a -q -2 mode.

only works for 44.1 kHz

If you use the GT3 encoder it has q -2 for 6 KHz and 8 KHz (though you get horrible artifacting unless you use stereo encoding, even for mono material).