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Topic: Wavpack Hybrid Question? (Read 3731 times) previous topic - next topic
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Wavpack Hybrid Question?

I have been experimenting with Wavpack Hybrid mode at 384kbps.  Sound quality is quite astounding and makes sense for me as my FLAC files are using up so much HD space.

This format is quite new to me and I am facinated as to why - when I unpack the file back into Wav format, as is one of the interesting perks of Wavepack - my new PCM file is 2116Kbps.  That is huge!!

Is there something I should be doing to control this?  And BTW, is this new PCM file actually a true wav file without any loss?

Many thanks for any help or suggestions.

Wavpack Hybrid Question?

Reply #1 –
No idea about your bitrate problem.
You might want to specify what tools and commands you're using.

Quote
And BTW, is this new PCM file actually a true wav file without any loss?

It depends whether it was able to compress the audio losslessly at the given bitrate.
If not, and you did not specify for it to generate a correction file, then no.

Quote
-bn = enable hybrid compression, n = 2.0 to 23.9 bits/sample, or
                                 n = 24-9600 kbits/second (kbps)

The default operation of WavPack is pure lossless, which means that the .wv file contains all the information that was in the original .wav file. The hybrid mode allows the user to specify a target bitrate for the output file, either in kilobits per second (kbps) or bits per sample. If the track can be losslessly compressed without exceeding the specified bitrate, then it will be and WavPack will report the compression as lossless. If lossless compression would exceed the specified bitrate, then 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. WavPack will report this as "lossy" compression. Although the option accepts bitrates as low as 24 kbps, the actual value that WavPack can achieve is usually much higher than that. For example, with CD-audio sampled at 44.1k the lower limit is about 196 kbps.

-c = create correction file (.wvc) for hybrid mode (=lossless)

If the -c option is specified (in addition to the -b option), then WavPack will generate an additional file that will contain the information that was discarded to generate the lossy .wv file. This file will have the same name as the .wv file but will have the extension .wvc (the 'c' is for "correction"). When WvUnpack is used to restore the .wav file, it will attempt to find the .wvc file in the same directory as the .wv file. If it is found then the decompression will be lossless and will be reported as such, otherwise lossy decompression will be reported (assuming that any information was actually discarded during the original compression). If -c is specified but no actual information is discarded, the correction file will be deleted. The extra overhead involved with having these two files instead of a single pure lossless file is usually less than 1% of the original .WAV file and can be as low as 0.25% at high bitrates. Note that CRCs are stored for both the lossy and lossless versions, so error detection works correctly whether the .wvc file is used or not.


http://www.wavpack.com/wavpack_doc.html

Wavpack Hybrid Question?

Reply #2 –
This will happen if you convert to WAV 32bit. Try foobar WAV - fixed point and you will always get 1410k.

The PCM file is bit-identical to the source - lossy .wv or .wv + .wvc (lossless).
 

Wavpack Hybrid Question?

Reply #3 –
Quote
This will happen if you convert to WAV 32bit. Try foobar WAV - fixed point and you will always get 1410k.

The PCM file is bit-identical to the source - lossy .wv or .wv + .wvc (lossless).
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Problem solved!  Thanks!!