[Speex-dev] Quick survey for Speex 1.2
jean-marc.valin at usherbrooke.ca
Tue Nov 14 03:12:37 PST 2006
> 1) The voice quality of ouput after coding and decoding in WB mode is
> unacceptable using the SVN fixed-point code,
> while the ouput of floating-point code is good.
> The test flow is input-->coder---->decoder---->.wav file--->player.
> The quality decrease of the decoder output is notable to ears.
> according to above test, some fixed-point codes must need to be corrected.
> What's your experience with current fixed-point code?
Indeed, your file triggers a problem with the fixed-point code. It
doesn't happen with all files, so I'm not sure yet if it's a regression
(if you've tested with other versions, I'm interested in what you find).
I'll be investigating the issue and will fix this as soon as I can.
Thanks for reporting the problem.
> 2) The rtp profile is not clear
> In the svn directory /doc, draft-herlein-speex-rtp-profile-02.txt is the
> latest draft.
> According to the chapter 5,
> "The encoding and decoding algorithm can change the bit rate at any 20
> msec frame boundary, with the bit rate change notification provided
> in-band with the bit stream. Each frame contains both "mode"
> (narrowband, wideband or ultra-wideband) and "sub-mode" (bit-rate)
> information in the bit stream. No out-of-band notification is
> required for the decoder to process changes in the bit rate sent by
> the encoder."
> The "sub-mode" can be calculated from the size of coded frame if "mode" is
> But the "mode" is not contained in the coding ouput (note it's not the ogg
> case) according to the source code.
> How does the decoder know the "mode" from RTP package?(it's assigned
> directly in the decoder in current svn sources)
The mode/bit-rate is detected automatically by the decoder because it's
encoded in the first few bits of each frame. The encoder can change
bit-rate at any time without telling the decoder. Can you be more
precise as to what isn't clear?
> What's the use of file rtp.txt in /doc directory? and its relationship with
The IETF stuff has been really, really slow. I'm still looking for
someone who knows enough to help me finalise all this.
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