[Speex-dev] Re: Speex, ACELP, G.729
B. Mitchell Loebel
BML at techstartupconnection.org
Fri Aug 19 18:14:57 PDT 2005
Thank you Jean-Marc.
At 10:39 AM -0400 8/19/05, Jean-Marc Valin wrote:
>> I've been watching the speex development from its inception because I
>> and several Tech Startup Connection members have a very important
>> application for this voice encoding/decoding. Further, we are quite
>> familiar with ACELP as implemented in G.729. As far as I know Speex
>> is also ACELP ... yes/no?
>No. Speex is CELP (Code-excited linear prediction), but not ACELP
>(Algebraic CELP). I have nothing against ACELP, but I couldn't use it
>because of patent issues.
>> Question ... what do you see as the advantages of ACELP compared to
>> MP3? I had thought that ACELP yielded much smaller files, but now I'm
>> not sure because I've listened to what I think were 16kbps MP3 files
>> (????) with Apple's ITunes that sounded pretty good ... comparable to
>> G.729's 8kbps. I'm speaking about G.729 because I'm not up on Speex
>> attributes ... e.g. what Speex bps compares to G.729's 8kbps quality.
>I think (my opinion) Speex 11 kbps is a bit better than G.729, while
>Speex 8 kbps is a bit worse. Speex 8 kbps VBR is probably equivalent. As
>for 16 kbps, I think it's terrible, you probably had AAC, not MP3 in
>your 16 kbps test. Another thing to keep in mind is that there is more
>to coding than file size. Speex (like other speech codecs like G.729) is
>designed for real-time communications. The frame size is 20 ms, so it
>has a much lower delay than MP3. Also, the Speex encoder can run in
>real-time with little complexity (e.g. it runs real-time on ARM). The
>last thing is that Speex is designed to handle packet losses, something
>that I don't think has been done to MP3.
>Jean-Marc Valin <Jean-Marc.Valin at USherbrooke.ca>
>Université de Sherbrooke
>Speex-dev mailing list
>Speex-dev at xiph.org
B. Mitchell Loebel 408 425-9920 cell
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