[Speex-dev] Speex for sampling freq >48KHz

devilal sharma devilal_sharma at yahoo.com
Mon Mar 27 05:01:40 PST 2006

I chose speex initially because i had some work in VQ on speex i.e. modifying split VQ to GMM based parametric VQ and I thought If I train the GMM based VQ codebooks with audio signal and then do audio coding with speex, I probably get a better(smaller) residual signal even with speex. But I couldnt get that.
I was trying to get a lossless bitstream by MUXing the speex-bitstream and the entropy encoded error signal from speex. 

I still have 2 months time but I need to do some useful and fundamentally strong work(even if  its  a small improvement). I can work day and night, But want to come up with some results. Results could be anything which make sense.
If you could suggest me some work in order to improve even a small part in lossless coding, I would be grateful.

I am sorry for any act of not respecting you in the past. I consider you at the top in guiding me.

Thanking you,


Jean-Marc Valin <Jean-Marc.Valin at USherbrooke.ca> wrote: > I have one doubt again, that is Vorbis use DCT/MDCT based algorithm
> and also use psychoacoustic model so this is lossy codec. 

Speex is also a lossy codec.

> And I dont think it ca regenerate a better matching waveform than
> speex. 

At bit-rates above 32 kbps, Vorbis tends to produce better results than
Speex, even for speech. The only advantages of Speex over Vorbis at
these high rates is the lower latency and lower encoding complexity.

> Then there comes FLAC which is the perfect answer to my question, I
> suppose. But my concern is this that FLAC use simple prediction
> algorithm and doesnt use any CELP based algo which could have model
> the waveform coding by having a large codebook and comparing the
> residual signal and selecting the codebook index.

FLAC is entirely different. You need to choose between perfect quality
and low bit-rate. FLAC isn't better or worse than Speex. If you can't
decide between the two, then you've obviously have no idea what your
after in the first place.

> For this, shall I start understanding and modifying FLAC itself in
> case I need to do something for lossless coding or I can try on Speex
> and than apply entropy coding.
> I am getting quite good(comparable) results for audio signal(44.1KHz)
> if use speex and separate entropy coding.

You apply entropy coding to the Speex bit-stream or you encode the Speex
error to make a lossless codec (which I already mentioned is a stupid

> Please suggest me clearly as I have very small time left to wrap up my
> work to submit.

To be honest, that's the least of my problem. If you were clear in the
first place and listened to advice I already gave, you might have been
better off already.


Devi Lal Sharma
Final Yr. Dual Degree(Communications)

Mobile: +91-9986423985(I am currently in bangalore)
email: devilal_sharma at yahoo.com, devilal at gmail.com
Yahoo! Messenger with Voice. PC-to-Phone calls for ridiculously low rates.
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