Subject: [AVT] Requesting feedback on new CELT codec

From: Jean-Marc Valin <[email-masked]>
Date: Mon, 21 Jul 2008 23:54:48 -0400

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
_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www.ietf.org/mailman/listinfo/avt

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From: "Christian Hoene" <[email-masked]>
Date: Sat, 26 Jul 2008 19:51:14 +0200

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: [email-masked] [mailto:[email-masked]] 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
>

---

From: "Even, Roni" <[email-masked]>
Date: Sat, 26 Jul 2008 21:07:35 +0300

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

Roni Even

> Sent: Saturday, July 26, 2008 8:51 PM
> To: 'Jean-Marc Valin'
> Cc: [email-masked]
> Subject: Re: [AVT] Requesting feedback on new CELT codec
> 
> Hello Jean-Marc,
> 
> Great work!
> 
> > I have been working on a new codec called CELT. It is not a
successor
> > to

---

From: "Christian Hoene" <[email-masked]>
Date: Sat, 26 Jul 2008 20:51:23 +0200

Hello Roni,

isn't the G.719 covered by patents? (Ericsson patents as far as I know.)
I believe that we need more open-source and free codecs. 

Nowadays, you can make telephone calls for free but must pay for the
telephone codec? Is this the right way to go?

With best regards,
 
Christian

> From: Even, Roni [mailto:[email-masked]]
> Sent: Saturday, July 26, 2008 8:08 PM
> To: Christian Hoene; Jean-Marc Valin
> Cc: [email-masked]
> Subject: RE: [AVT] Requesting feedback on new CELT codec
> 
> Jean-Marc,

---

From: Jean-Marc Valin <[email-masked]>
Date: Sat, 26 Jul 2008 15:48:22 -0400

> 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/

> performances) to higher delays (e.g., 40ms if the is beneficial for the

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.

> 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

---

From: Steve Underwood <[email-masked]>
Date: Sun, 27 Jul 2008 10:24:54 +0800

Hi,

So far Polycom has managed to get each of its codecs into an ITU spec - 
G.722.1, G.722.1C and G.719. However, I've only ever seen these things 
supported by Polycom products. That is in spite of the patents on 
G.722.1C being offered  royalty free. An ITU spec is no guarantee of 
anything happening in the real world.

The only codec beyond 8k samples/second to get any traction in the 
marketplace so far is AMR-WB, because its in the 3G standards. I'd say 
the world is still wide open for wider band codecs over IP, and the 
opportunity to avoid the destructive lock-in G.729 has achieved in 8k 
VoIP - and if you don't think its destructive, look at all the things 
you can't do because you'd need to give away the software to make them 
viable, and the need to support G.729 for interoperability stops you.

Steve

Jean-Marc Valin wrote:
>>> 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
>>     
>>>> From: [email-masked] [mailto:[email-masked]] On Behalf
>>>>         
>> Of
>>     
>>>> Jean-Marc Valin
>>>> 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.
>>>