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Topic: Manual SBR (Read 6096 times) previous topic - next topic
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Manual SBR

Hi y'all !

I downloaded a song - "Under The Bombs" from Think Twice - from the goodies section of F-Communications. Unfortunately it sounded a bit dull and I noticed that the encoder which has been used to encode this 128kbps file limited the bandwidth to 14 kHz.

So, this is what I did:
- Opened MP3 in Cool Edit (window #1)
- copied the whole track (window #2)
- applied an FFT bandpass filter: 10-12 kHz
- created new window (window #3)
- generated a full-scale sine on both channels with a frequency of 4000 Hz and a duration of 360 seconds (window #3)
- copied this sine (window #3) to the clibboard
- switched to window #2 and set the pointer to 00:00
- Edit -> Mix Paste -> Modulate with Clibboard
- FFT highpass filter at 13 kHz (window #2)
- copied current wave to clibboard (window #2)
- switched to window #1 and set the pointer to 00:00
- Edit -> Mix Paste -> Overlap (Mix) with Clibboard

Et voila. I shifted the 10-12 kHz content to 14-16 khz and mixed it with the original. "Manual subband replication" so to speak. The result sounds much better.

A "before/after" example is attached to this message  (600 KB).

have fun,
Sebastian

edit: fixed a typo

Manual SBR

Reply #1 –
Interesting...  For those of us who are less technical, is there a less complicated way to generate harmonics?  It does seem to improve the sound.  Subjectively anyway.

Manual SBR

Reply #2 –
Would it be possible to create an impulse from the process you did?
"To understand me, you'll have to swallow a world." Or maybe your words.

Manual SBR

Reply #3 –
Quote
Interesting...  For those of us who are less technical, is there a less complicated way to generate harmonics?  It does seem to improve the sound.  Subjectively anyway.
[a href="index.php?act=findpost&pid=245266"][{POST_SNAPBACK}][/a]


Well, this is only a hack. The content is shifted exactly 4 kHz upwards which is likely to fail in restoring harmonics at the correct multiple of the fundamental frequency. But in case of the quite noisy percussions it works.

I don't know if there is a less complicated way to do this. (I think not)


Sebastian

Manual SBR

Reply #4 –
Quote
Would it be possible to create an impulse from the process you did?
[a href="index.php?act=findpost&pid=245268"][{POST_SNAPBACK}][/a]


An impulse response ?

No, you cannot shift a frequency band up/downwards via a convolution.


Sebastian

Manual SBR

Reply #5 –
Interesting!
Is the "high frequency reconstruction" method used by NCTU MP3 decoder a similar one?

Manual SBR

Reply #6 –
Quote
Interesting!
Is the "high frequency reconstruction" method used by NCTU MP3 decoder a similar one?
[a href="index.php?act=findpost&pid=245325"][{POST_SNAPBACK}][/a]


From what I can tell is the NTCU HF reconstruction system extrapolating the log frequency envelope - which seems to be more sophisticated than this hack. But I'm actually not aware of how they compute the samples they put under this envelope.

The effect is similar, though (since it creates new content above the original cut-off frequency)


Sebastian

Manual SBR

Reply #7 –
Hi,
How to open the msbr-before and msbr-after (.OCG) files
Regards


Quote
Hi y'all !

I downloaded a song - "Under The Bombs" from Think Twice - from the goodies section of F-Communications. Unfortunately it sounded a bit dull and I noticed that the encoder which has been used to encode this 128kbps file limited the bandwidth to 14 kHz.

So, this is what I did:
- Opened MP3 in Cool Edit (window #1)
- copied the whole track (window #2)
- applied an FFT bandpass filter: 10-12 kHz
- created new window (window #3)
- generated a full-scale sine on both channels with a frequency of 4000 Hz and a duration of 360 seconds (window #3)
- copied this sine (window #3) to the clibboard
- switched to window #2 and set the pointer to 00:00
- Edit -> Mix Paste -> Modulate with Clibboard
- FFT highpass filter at 13 kHz (window #2)
- copied current wave to clibboard (window #2)
- switched to window #1 and set the pointer to 00:00
- Edit -> Mix Paste -> Overlap (Mix) with Clibboard

Et voila. I shifted the 10-12 kHz content to 14-16 khz and mixed it with the original. "Manual subband replication" so to speak. The result sounds much better.

A "before/after" example is attached to this message  (600 KB).

have fun,
Sebastian

edit: fixed a typo
[a href="index.php?act=findpost&pid=245262"][{POST_SNAPBACK}][/a]
 

Manual SBR

Reply #8 –
Quote
Hi,
How to open the msbr-before and msbr-after (.OCG) files
Regards
[{POST_SNAPBACK}][/a]


Those files with the ".ogg" extension are [a href="http://www.hydrogenaudio.org/index.php/Vorbis]Ogg Vorbis[/url] files.
It's among others an alternative to MP3.

I'm sure there's an Ogg Vorbis plugin for your audio player of choice. (For WinAMP there is for sure) You might also want to try out the Foobar2000 player. It has built-in support for a large amount of various formats (among other nice features)


SebastianG