Converting to Opus: 44.1 kHz resampled to 48 kHz |
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Converting to Opus: 44.1 kHz resampled to 48 kHz |
 Jan 21 2013, 02:19
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#26
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 Group: Developer Posts: 295 Joined: 22-November 10 From: Japan Member No.: 85902  |
QUOTE (C.R.Helmrich @ Jan 21 2013, 06:35)  Yes, I expected Opus to resample to 48 kHz internally. The question was more: if it does, will the CELT coder know that the input was upsampled from 32 kHz by the Speex resampler, and limit its encoding bandwidth to 16 kHz (the bandwidth of the original input file), or is the 20-kHz bandwidth of high-bitrate CELT hard-coded regardless of the input sampling rate? Input sample rate doesn't seem to be get passed to the encoder (although it is used in the calculation of default bitrate, when user doesn't provide it via --bitrate). |
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Jan 21 2013, 03:55
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#27
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Xiph.org Speex developer Group: Developer Posts: 431 Joined: 21-August 02 Member No.: 3134 |
QUOTE (C.R.Helmrich @ Jan 20 2013, 16:35) Yes, I expected Opus to resample to 48 kHz internally. The question was more: if it does, will the CELT coder know that the input was upsampled from 32 kHz by the Speex resampler, and limit its encoding bandwidth to 16 kHz (the bandwidth of the original input file), or is the 20-kHz bandwidth of high-bitrate CELT hard-coded regardless of the input sampling rate? Opus doesn't actually have a mode for 16 kHz bandwidth (only 12 and 20). However, the new 1.1-alpha release has new code (it may not be 100% reliable) to avoid wasting bits on frequencies that aren't present in the signal being coded. |
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Jan 21 2013, 18:40
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#28
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 Group: Developer Posts: 618 Joined: 6-December 08 From: Erlangen Germany Member No.: 64012 |
Thanks, guys. I'll wait for the 1.1 beta then. Too scared of alphas.
Chris -------------------- If I don't reply to your reply, it means I agree with you.
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Jan 21 2013, 18:44
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#29
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Group: Members Posts: 1315 Joined: 3-January 05 From: Argentina, Bs As Member No.: 18803 |
Chris, feel free to submit problematic samples for 1.1a. Experienced ears are required.
Also I'm planning to organize unofficial test of Opus 1.1a vs stable here on HA. This post has been edited by IgorC: Jan 21 2013, 18:47 |
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Mar 14 2013, 15:55
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#30
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Group: Members Posts: 148 Joined: 2-May 07 Member No.: 43131 |
Why 48kHz?
If the lowpass frequency is 20kHz why not resample everything to 40kHz instead of 48. Or why not a higher lowpass setting at higher bitrates? I doubt that 20kHz is a hard limit to everyone anyway. Some might hear a few kHz higher if its loud enough |
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Mar 14 2013, 16:05
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#31
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 Group: Developer Posts: 2986 Joined: 2-December 07 Member No.: 49183 |
QUOTE (mzso @ Mar 14 2013, 18:55) why not resample everything to 40kHz instead of 48. A more complete list of common audio sample rates is: ... |
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Mar 14 2013, 21:58
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#32
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Group: Members Posts: 82 Joined: 11-December 06 Member No.: 38563 |
Doesn't the CELT layer work strictly at 48 kHz regardless of input sample rate?
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Mar 15 2013, 18:28
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#33
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 Group: Members Posts: 736 Joined: 17-September 06 Member No.: 35307 |
I think the CELT layer in Opus (possibly not in the old CELT codec) works also at 24kHz sampling rate (12kHz bandwidth) - and this is used at least for the 8-12kHz part of the spectrum in the hybrid mode.
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Mar 15 2013, 18:51
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#34
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Xiph.org Speex developer Group: Developer Posts: 431 Joined: 21-August 02 Member No.: 3134 |
QUOTE (Dynamic @ Mar 15 2013, 13:28) I think the CELT layer in Opus (possibly not in the old CELT codec) works also at 24kHz sampling rate (12kHz bandwidth) - and this is used at least for the 8-12kHz part of the spectrum in the hybrid mode. No that is incorrect. In Opus, the CELT layer *always* works at 48 kHz, even if it's only coding a small part of the spectrum. |
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Lo-Fi Version | Time is now: 25th May 2013 - 00:22 |
