Speex dev - May 2006 - question about coding

Thanks for the answer.
So data are stored in little-endian format on the WAVE file. But have I to
encode in big endian format or little endian is ok?!
Thanks


---------- Original Message ----------------------------------
From: "John Miles" <jmiles@pop.net>
Date:  Tue, 23 May 2006 12:15:05 -0700
>You are probably reading little-endian samples on a big-endian platform, and
>failing to flip the byte order.  By convention, PCM samples are generally
>little-endian words, and the effect of playing them with the wrong byte
>order is just what you describe hearing, with the expected  sound buried
>under 8 bits' worth of random-sounding noise.
>
>-- john
>
>
>>
>> Hi,
>> I'm trying to encode a raw audio file with speex. No problem if I
>> normally decode it (as done in the samplenc.c, for example).
>> But if I separate odd and even samples and I try to encode
>> separately these two files (one is [odd odd odd odd..], the other
>> [even even even even..], then when I decode and I join the
>> samples in one file [odd even odd even odd even..] I heard a
>> terrible white noise, and the voice in background very weak.
>> Does anyone know the reason?
>> Thanks
>> _______________________________________________
>> Speex-dev mailing list
>> Speex-dev@xiph.org
>> http://lists.xiph.org/mailman/listinfo/speex-dev
>>
>
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You'll definitely have to encode in little-endian form.  PCM audio is always
little-endian, to the best of my knowledge.  I have never seen any
big-endian audio data files.

The frequency-domain transforms inside Speex are written to assume that most
of the "intelligence" is carried by the MSB of a 16-bit little-endian
word.
If you submit big-endian data, Speex will think you're feeding it white
noise.

That may or may not be your actual problem, of course... just something to
watch out for.

-- jm
> -----Original Message-----
> From: speex-dev-bounces@xiph.org [mailto:speex-dev-bounces@xiph.org]On
> Behalf Of Leonardi Andrea
> Sent: Friday, May 26, 2006 10:35 AM
> To: speex-dev@xiph.org
> Subject: RE: [Speex-dev] question about coding
>
>
>
> Thanks for the answer.
> So data are stored in little-endian format on the WAVE file. But
> have I to encode in big endian format or little endian is ok?!
> Thanks
>
>

John Miles wrote:
> You'll definitely have to encode in little-endian form.  PCM audio is
always
> little-endian, to the best of my knowledge.  I have never seen any
> big-endian audio data files.
Try AIFF, AU and IFF just for starters. They are definietly not the
only ones.

Erik
-- 
+-----------------------------------------------------------+
  Erik de Castro Lopo
+-----------------------------------------------------------+
"UNIX was not designed to stop you from doing stupid things,  because
that would also stop you from doing clever things."  -- Doug Gwyn

Leonardi Andrea wrote:
> 
> Thanks for the answer.
> So data are stored in little-endian format on the WAVE file. But
> have I to encode in big endian format or little endian is ok?! 
You need to pass the data in whatever is the native endian-ness
for your platform.
> >You are probably reading little-endian samples on a big-endian
platform, and
> >failing to flip the byte order.
Using libsndfile (I am the author):

    http://www.mega-nerd.com/libsndfile/

will make you life easier.
> >By convention, PCM samples are generally
> >little-endian words,
This is not right. Some file types are little endian (WAV for example)
others are big endian (ie AIFF). There is hwoever also a big endian
WAV variant (RIFX) and some AIFF files contain little endian data.

libsndfile handles all the above variations correctly.

Erik
-- 
+-----------------------------------------------------------+
  Erik de Castro Lopo
+-----------------------------------------------------------+
"Using Java as a general purpose application development language
is like going big game hunting armed with Nerf weapons."
-- Author Unknown

True, it depends on where the "raw audio file" that he mentioned came
from.
If it came from a .WAV ('WAVE'?), it's little-endian unless the
converter
program explicitly flipped the byte order.

Either way, white noise with faint traces of the original content =mis-flipped
bytes...

-- jm
> > >By convention, PCM samples are generally
> > >little-endian words,
>
> This is not right. Some file types are little endian (WAV for example)
> others are big endian (ie AIFF). There is hwoever also a big endian
> WAV variant (RIFX) and some AIFF files contain little endian data.
>
> libsndfile handles all the above variations correctly.
>
>