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Wavpack hybrid and archiving
RD
post Feb 8 2003, 04:15
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Hey everyone,

I just started playing around with wavpack's hybrid lossy compression mode.
I don't fully understand how it differs from the mp3/aac/mpc compression modes.

The author of wav pack says:
"WavPack will begin carefully discarding the least significant portion of the audio information to stay within the limit. Every effort is made to keep this inaudible, including the use of joint stereo, dynamic bit allocation and noise shaping."

Does this mean that wavpack has and uses a psycho-acoustic model like mp3? Does it use short block and long blocks like mp3? My guess is "NO" is the answer to both of these questions. But does anyone know for sure?

If the answer is no the long/block short block thing, then it would seem that wavpack hybrid would have 0 (zero) problem with transients unlike lame....

Also the author says:
"320 kbps gives audibly transparent operation in the vast majority of cases . . ..at bitrates above 320 kbps, the measured quality of the hybrid mode rises rapidy (about 1 dB less added noise for each 14 kbps."

Have any of you tested wavpack at 320 kbps... how good is it? as good as mpc insane ? What if any types of artifacts does it have?

I need to archive a lot of files on cd-r and I want about a 4:1 compression ratio. So I am thinking that if I raise the bitrate by 3x14 (namely, 320+42 = 362kbps) it should give 3db less noise than 320, and a 4:1 compression ratio.

Or am I crazy to think that 362 kbps wavpack hybrid compression is high enough quality for archiving?

Thanks for all help,
Rob
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bryant
post Feb 8 2003, 06:37
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I don't know if you saw this thread, but it might answer some of your questions. I also don't know if mmortal03 carried his tests any further:

http://www.hydrogenaudio.org/forums/index....=ST&f=19&t=4875

Because WavPack's lossy mode is based on the same principles as lossless compression, the quality undoubtedly increases as the bitrate is raised until you get an exact match. This is not true of MP3 or Vorbis, and I think that even with MPC you can't get lossless just by throwing more bits at it. This means that at some bitrate WavPack's lossy mode will surpass the quality of the other lossy codecs, but where exactly that happens is not clear.

Whether or not WavPack at 360 kbps would be a good choice for archiving CDs depends on other factors besides just audio quality. Currently, WavPack has pretty primitive seeking and tagging, it has no hardware support, and even though it is completely open source, it certainly is not a "standard". And, unlike true lossless, if you ever decide to transcode to something else you won't be starting with the original (of course, this is true of any lossy format).
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RD
post Feb 8 2003, 19:11
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Thanks for the info.

Btw, have you tweaked the joint stereo modes because the link you gave mentioned there may be a problem with it. mmortal says he uses regular stereo...

Thanks again,
RD
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john33
post Feb 8 2003, 20:08
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I haven't done any definitive testing, but I have encoded quite a bit of stuff at 320kbps, high quality, but otherwise, default settings and they sound pretty good to me. smile.gif I believe the regular stereo is default now, IIRC.


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mmortal03
post Feb 9 2003, 09:53
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I will have to look into it again, don't take this harshly, but I lost interest for some reason. I'm glad to hear about others using it though. I may play around with it some this week, who knows...


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NumLOCK
post Feb 9 2003, 12:32
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QUOTE
This is not true of MP3 or Vorbis, and I think that even with MPC you can't get lossless just by throwing more bits at it.

Well, with MP3 you cannot go above 320kbps, which is highly lossy, but with MPC you could just store ~16bits per subband sample, if I'm not mistaken. That would be near-lossless.


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RD
post Feb 12 2003, 21:16
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Thanks for the replies guys... maybe if I do more testing i'll post the results
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LordofStars
post Feb 12 2003, 21:44
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I have used wav pack lossy for quite a while now. I usually encode at about 350kbps and store the "repair" information in zip files on a cd with the .pac on a seperate cd's.


@numlock So your saying that mpc with 16bits per sfb and 21 sfb (mp3 uses 21 is mpc different?) mpc should be near lossless at 331?


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penvzila
post Feb 19 2003, 00:56
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QUOTE (NumLOCK @ Feb 9 2003 - 03:32 AM)
QUOTE

Well, with MP3 you cannot go above 320kbps,

?????????????


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