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Musepack encoder, Modification to write MPEG Audio Layer 1/2
S_O
post Dec 5 2010, 21:54
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Hello,
several years ago it was said that changing the MusePack encoder to mp2 output wonīt take very long. But AFAIK nobody has ever released a musepack-based mp2-encoder so far.
Because I need a high-quality mp2-encoder (for authoring DVDs) I tried it myself:

I was able to modify the encoder in a way it outputs a 448kbit/s MP1 file, if the bitrate musepack wants to encode is higher, the last subbands are just cut off, otherwise the frame is padded with 0. The problem is now: After just one musepack frame (=three layer1 frames) the bitrate is decreased dramatically: Beginning from band 5 only 2 bits are assigned for each subband, the lower ones also have 8 bits max. It doesnīt matter at what quality I try, itīs the same for thumb to insane.
Otherwise the output file will play fine (very noticeable artifacts because of low effective bitrate (about 200kbps layer1, stereo, 44100khz), but otherwise it seems to work).
Is here anybody familiar with the MusePack encoder able to tell why there is this bitrate drop? I havenīt done anything special, just disabled MS coding, changed the scalefactors, created a function to write MPEG layer1 bitstream and modified the allocate function not to use unsupported quantizers (resolution is increased in that case) and that allocation is limited by maximum bitrate (thatīs not causing the problem). Thatīs it. Unfortunately the source code is not very structured/readable so I donīt see what Iīm missing.
Any ideas?
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S_O
post Dec 6 2010, 15:52
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TooLAME isnīt developed for a long time now, also the development of itīs successor twoLame seems to be stopped for some years already. Both encoders donīt provide the quality of MusePack. MusePack has a more advanced encoder, allowing much higher quality. Of course the mp2 bitstream format does not allow all MusePack features (M/S stereo, huffman, PNS, true VBR,...), but you should be able to encode mp2 files about the same quality as musepack with a major bitrate increase (like 256 - 320 kbps comparable to musepack standard).
I need the encoder to author DVDs containing music. Unfortunately LPCM causes problems with several players and there is also no free, high-quality AC-3 encoder around. MusePack based MP2 seems to be good choice too me.

I found out that the problem are the SMRs returned by "Psychoakustisches_Modell", beginning from the second call of that function they are much too low. Unfortunately I havenīt found a reason why. Any ideas?
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alexeysp
post Dec 7 2010, 15:47
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No offence, but I think you're wasting your time. I seriously doubt that there could be any audible difference between TooLAME at 384 kbps (maybe even lower) and the thing you're trying to make.

In any case, claims like

QUOTE (S_O @ Dec 6 2010, 16:52) *
Both encoders donīt provide the quality of MusePack. MusePack has a more advanced encoder, allowing much higher quality.


certainly demand for a proof (especially considering we're talking about bitrates around ~400 kbps).
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