Even, Roni a écrit :
Jean-Marc,
I looked at your web site. Note that the ITU-T approved G.719 which is a
low complexity full band codec (40kHz) at rates from 32 - 128 kbit/s
It seems to me like G.719 is basically a further extension on the
G.722.1 and G.722.1C codecs. From what I could read, it has an
algorithmic delay of 40ms, whereas CELT's delay is tunable between 2ms
and 15ms. In terms of quality, I also did some listening tests and CELT
with 8.7ms delay came up ahead of G.722.1C despite having less than 1/4
of the delay. The comparison with AAC-LD closer, but CELT still had an
edge at 48 kbit/s, again with 1/4 of the delay. The rest results are at:
http://www.celt-codec.org/comparison/
Christian Hoene a écrit :
I would suggest you to support multiple coding rates (from 16 to 200) and
various coding delays ranging from 2ms (for interactive ensemble
performances) to higher delays (e.g., 40ms if the is beneficial for the
audio quality).
Actually, this is pretty much already supported. The bit-rate starts at
around 24 kbit/s (to have vaguely decent quality) and can currently go
up to ~128 kbit/s/channel. The delay can be tuned from 2ms to 15ms. It's
even possible to go below 2ms, but performance suffers a lot. I don't
think going above 15ms is really worth it for CELT.
Then, various application scenarios and the use of CELT over congestion
aware transport protocols like DCCP or TCP would make sense.
Note that the bit-rate can vary on-the-fly, but the delay (linked to the
frame size) has to be constant throughout the session. Is there any
other important feature to have?
Cheers,
Jean-Marc
Roni Even
-----Original Message-----
From: avt-bounces at ietf.org [mailto:avt-bounces at ietf.org] On Behalf Of
Christian Hoene
Sent: Saturday, July 26, 2008 8:51 PM
To: 'Jean-Marc Valin'
Cc: avt at ietf.org
Subject: Re: [AVT] Requesting feedback on new CELT codec
Hello Jean-Marc,
Great work!
I would suggest you to support multiple coding rates (from 16 to 200)
and
various coding delays ranging from 2ms (for interactive ensemble
performances) to higher delays (e.g., 40ms if the is beneficial for
the
audio quality).
Then, various application scenarios and the use of CELT over
congestion
aware transport protocols like DCCP or TCP would make sense.
With best regards,
Christian Hoene
-----Original Message-----
From: avt-bounces at ietf.org [mailto:avt-bounces at ietf.org] On Behalf
Of
Jean-Marc Valin
Sent: Tuesday, July 22, 2008 5:55 AM
To: IETF AVT WG
Subject: [AVT] Requesting feedback on new CELT codec
Hi everyone (bit of background, I'm the author of the Speex speech
codec),
I have been working on a new codec called CELT. It is not a
successor
to
Speex, but a much higher quality codec (44.1/48 kHz) with very low
delay
(<10 ms) and rates in the 32-200 kbps range. The bit-stream isn't
frozen
yet and before I freeze it, I would be very interested in feedback.
Is
there anything I could add (or remove) to make everyone's life
easier.
Any application I'm not considering?
The website is http://www.celt-codec.org/ and it includes some
comparisons and audio samples. Like Speex, CELT is completely open.
Cheers,
Jean-Marc