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#1
Posted to rec.audio.pro
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Objective means for comparing audio codecs and settings
I~m working with a team developing streaming audio-video systems. We
need to make some competitive comparisons of our audio codec. I~m thinking that pure frequency response won~t cut it, because supposing all codecs are sampling at 32 kHz, there won~t be much difference shown between say, 64 kbps and 96 kbps. I do know from personal experimentation with MP3 that 192 kbps sounds ^pretty good^, higher is of course better, and below 128 kbps it starts to sound bad, but mostly getting effects like transient smearing, which you wouldn~t expect to get from sine waves or sweeps. I suppose one could normalize the encoded output of any complex bit of sound, e.g. speech, music, typical TV noises (it is for sending broadcast TV signals mostly), and then subtract it from the original signal to get a residual, but this seems highly subject to correct level matching, time alignment, blah blah blah. Suggestions (question mark) my keyboard~s gone all screwy on me ! Thanks. |
#2
Posted to rec.audio.pro
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Objective means for comparing audio codecs and settings
Drily Lit Raga wrote:
I~m working with a team developing streaming audio-video systems. We need to make some competitive comparisons of our audio codec. I~m thinking that pure frequency response won~t cut it, because supposing all codecs are sampling at 32 kHz, there won~t be much difference shown between say, 64 kbps and 96 kbps. I do know from personal experimentation with MP3 that 192 kbps sounds ^pretty good^, higher is of course better, and below 128 kbps it starts to sound bad, but mostly getting effects like transient smearing, which you wouldn~t expect to get from sine waves or sweeps. I suppose one could normalize the encoded output of any complex bit of sound, e.g. speech, music, typical TV noises (it is for sending broadcast TV signals mostly), and then subtract it from the original signal to get a residual, but this seems highly subject to correct level matching, time alignment, blah blah blah. Suggestions (question mark) my keyboard~s gone all screwy on me ! Thanks. Call Spirent or Agilent. -- Les Cargill |
#3
Posted to rec.audio.pro
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Objective means for comparing audio codecs and settings
"Drily Lit Raga" wrote in message
I~m working with a team developing streaming audio-video systems. As if we don't have enough of those already! We need to make some competitive comparisons of our audio codec. How have the subjective comparisons worked out for you? In some sense, you should know the answer to the question if you are developers, because you should know what you did to your product to improve it when it didn't sound good enough. I~m thinking that pure frequency response won~t cut it, because supposing all codecs are sampling at 32 kHz, there won~t be much difference shown between say, 64 kbps and 96 kbps. As a rule, codecs have had good frequency response for tones and sweeps for a long time. The next stage of complexity after simple frequency response testing is testing with complex multiones. As codecs have improved over the years, this has also improved. I do know from personal experimentation with MP3 that 192 kbps sounds ^pretty good^, higher is of course better, Not that much better, after 192. and below 128 kbps it starts to sound bad, Agreed. ut mostly getting effects like transient smearing, which you wouldn~t expect to get from sine waves or sweeps. Seems like bursts of carefully-tuned multitones might be a productive way to go. |
#4
Posted to rec.audio.pro
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Objective means for comparing audio codecs and settings
ut mostly getting effects like transient smearing, which you wouldn~t expect to get from sine waves or sweeps. Seems like bursts of *carefully-tuned multitones might be a productive way to go. see: http://www.avisoft.com/compression.htm Mark |
#5
Posted to rec.audio.pro
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Objective means for comparing audio codecs and settings
On Oct 15, 11:50*am, Mark wrote:
ut mostly getting effects like transient smearing, which you wouldn~t expect to get from sine waves or sweeps. Seems like bursts of *carefully-tuned multitones might be a productive way to go. see:http://www.avisoft.com/compression.htm Mark Interesting! I wonder how my colleagues will respond to the variations in intelligibility of a series of mouse, bat, cricket and cockroach chirps? hmmmm 8^) some of them might get hungry.... Actually it was an intersting web site, thx! DLR |
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