question about IMA ADPCM

[L Hao]

Hi, I am a newbie on this subject. Can someone tell me or point me to a
right place on what the difference is between IMA ADPCM and G.726?

I have downloaded G.726 recommandation. However, I cannot find IMA ADPCM
spec. I heard that it is not free. I know they are similar, and G.726 is
more complicated and results better qaulity. But I want to know the detailed
difference on implementation level.

Thanks.

[Steve Underwood]

G.726 isn't really any higher quality. Its substantial extra complexity
is to get tones, especially DTMF ones, through without serious
degradation, and to avoid repeated degradations in tandem operation.

For something that doesn't need these qualities, most reasonable forms
of ADPCM do a similar quality job.

That said, I've no idea where to get the IMA ADPCM spec.

Regards,
Steve

[Phil Frisbie, Jr.]

I don't know the difference, but I do know Intel/DVI ADPCM is free.

--
Phil Frisbie, Jr.
Hawk Software
http://www.hawksoft.com

[L Hao]

Steve, thanks for the reply. So if I have a file encoded in G.726(32kbps),
should an IMA ADPCM codec be able to decode and play it?
"Steve Underwood" <ste...@dis.org> wrote in message
news:b5v0mq$iau$1...@hfc.pacific.net.hk...

[Erik de Castro Lopo]

L Hao wrote:
>
> Steve, thanks for the reply. So if I have a file encoded in G.726(32kbps),
> should an IMA ADPCM codec be able to decode and play it?

No. Altought the algorithms may be vaguely similar, the way the
ADPCM data is encoded in the file is WAY different.

Erik
--
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Erik de Castro Lopo nos...@mega-nerd.com (Yes it's valid)
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The word "Windows" is a word out of an old dialect of the
Apaches. It means: "White man staring through glass-screen
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[Erik de Castro Lopo]

Erik de Castro Lopo wrote:
>
> L Hao wrote:
> >
> > Steve, thanks for the reply. So if I have a file encoded in G.726(32kbps),
> > should an IMA ADPCM codec be able to decode and play it?
>
> No. Altought the algorithms may be vaguely similar, the way the
> ADPCM data is encoded in the file is WAY different.

As a further example, I know the MS ADPCM cannot be decoded with an
IMA ADPCM decoder (and vice versa). I also know that G.721 and G.732
decoders cannot decode IMA or MD ADPCM.

Erik
--
+-----------------------------------------------------------+
Erik de Castro Lopo nos...@mega-nerd.com (Yes it's valid)
+-----------------------------------------------------------+

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[Deepak]

"L Hao" <hao...@yahoo.com> wrote in message news:<FNxga.228506$3D1.73365@sccrnsc01>...

Hi,

For IMA ADPCM, please check out Microchip website. They have an
application note on it.

Hope it helps.

Regards
Deepak

[Vladimir Vassilevsky]

Hello Mr. Hao,

G.726 makes use of 6-th order backward adaptive predictor as well as
adaptive differential coding. IMA ADPCM does not have the adaptive
predictor. That makes much simpler algorithm, although the quality
suffers especially on the stationary signal.
You can find an appnote with IMA ADPCM description at the microchip web
site.

Vladimir Vassilevsky
DSP consultant

[L Hao]

Thank you all very much for the information. It has been very helpful to me.

"L Hao" <hao...@yahoo.com> wrote in message
news:FNxga.228506$3D1.73365@sccrnsc01...

[L Hao]

Thank you all for the replies. Those were good and helpful information.

"L Hao" <hao...@yahoo.com> wrote in message
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