Displaying 20 results from an estimated 1100 matches similar to: "mdct question"
2000 Oct 23
4
More mdct questions
Sorry for starting another topic, this is actually a reply to Segher's post
on Sun Oct 22 on the 'mdct question' topic. I wasn't subscribed properly
and so I didn't get email confirmation and thus can't add to that thread.
So Segher, if the equation is indeed what you say it is, then replacing
mdct_backward with this version should work, but it doesn't.
Am I applying
2001 Jan 02
0
mdct explanation
...as promised.
This describes the mdct used in my d.m.l patch. I think it is the
same as the Lee fast-dct.
I typed it in a kind of pseudo-TeX, 'cause the ascii art would
kill me. Hope you can read TeX source; if not, ask someone who
can to make a .ps/.gif/.whatever of the TeX output, and put it
on a webpage or something. I'm to lazy to do it (and besides, I
don't have access to TeX,
2017 Apr 11
2
MDCT implementation and his overlapped relationship
Dear all
I'm working on the implementation of the MDCT for the processor
ARM-Cortex-M4 I'm trying to replicate the behavior of the MDCT for several
overlapped values however I realized that current implementation of the
MDCT is very close to the theory only in case in which we have and overlap
exactly equal to N/2 where N is the size of the input vector as is shown in
the examples for
2005 Jan 26
2
Butterflies in mdct.c
In mdct.c there's some functions including some-point butterfly. In 32-point and 16-point there are calling of smaller-point function everytime twice on each half of data. When I looked on it I found that's just linear algebra. So it can be rewritten to matrix multiplication. Some one can say: there's optimization on in register working. But imagine there's one calling 32-point,
2013 Jul 08
2
Request for MDCT theoretical reference
Dear Experts,
Can anybody please direct me to proper MDCT theory reference which will
help me understand the code better?
I'm trying to optimize MDCT for a embedded platform. So need good
understanding about theory behind & implementation.
Thanks in advance for your time.
Warm Regards,
Mahantesh
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2002 Mar 19
1
mdct as hardware
Hi vorbis-dev!
I'm working with Pattara in the oggonachip project, and wondering about
the implementation of mdct.c as hardware. According your recomendations
about using the floating point version, I would say, we have to implement
the integerized
version of mdct as a core, and use the fpu only to round the input
values. By doing
that, you think the result would be still acceptable?
How
2002 Mar 26
2
size of vectors to be fed to MDCT
Hi,
as we are trying to implement MDCT in hardware, we are caring now about
the "n" (size of input and output vectors to and from MDCT).
As I have looked in the code, this "n" is chosen from the Ogg/Vorbis
stream data in info.c:_vorbis_unpack_info() which means this "n" can vary
aribitrarily (as the power of 2) depending only on the value got from song
data? or is
2005 Feb 20
1
Well decomposed mdct
I did composition of butterfly8 and butterfly16 and I found, that these functions are well decomposed - decomposition doesn't lower computional speed. On the other hand the same can be done with butterfly8 - decomposition to butterfly4 (further decomposition is not possible) but there's no reason to do this. I think little improvement can be done by inlining them. Compiler and processor
2002 Aug 21
1
MDCT input and output data blocks
Hi,
I'm trying to determine how the frequency data that is passed to the
MDCT, and output time domain data obtained from the MDCT, is changed
when setting #define MDCT_INTEGERIZED
For instance, the trig array, for a size 256 window begins
1.000000
0.000000
0.998795
-0.049068
0.995185
-0.098017
if INTEGERIZED is set, then it begins
16384
0
16364
-803
16305
-1605
which is simply a left shift
2014 Feb 05
4
Make check failure on clone from 31 January
Hi,
Apologies if this is a known issue, but running make on revision e3187444692195957eb66989622c7b1ad8448b06 fails one of the tests when using fixed point configuration (floating point is ok) on my linux x86.
Note that libopus1.1, as extracted from the tar ball, is OK.
Specifically, the tests that fail are in celt/tests/test_unit_mdct:
nfft=32 inverse=0,snr = 85.341197
nfft=32 inverse=1,snr =
2003 Jul 12
1
mdct query
Hi,
I have a doubt regarding MDCT window size for OggVorbis decoder.
Can the MDCT window size vary from 64 samples to 8192 samples?
Specification says that "legal frame sizes are powers of two from
64 to 8192 samples" .
Is this same as MDCT window size?
Please help me out..
Regards,
shikha
<p>--- >8 ----
List archives: http://www.xiph.org/archives/
Ogg project homepage:
2003 May 22
5
Description of MDCT
The Vorbis audio format, uses something called the Modified
Discrete Cosine Transform (MDCT). I was interested in how this
worked, but did not know where to start. Is this the name of a
particular algorithm, or does it just mean something like a
cosine transform, but not quite right? So I asked the Vorbis
mailing list. Nobody answered.
It was not a high priority, so I did other things for
2002 Mar 14
1
mdct.c
Hi vorbis-dev,
I'm investigating the mdct* function in libvorbis and writing a small
client program to test it. I found that I have to set ARRAYSIZE when
mdct_init(lookup, ARRAYSIZE) to minimum value of 62 otherwise it will
segfault with mdct_backward.
Is there any lower limit or it is more likely that my code has bug?
Thank you very much,
Pattara
--
Please avoid sending me Word or
2002 Aug 01
2
mdct.h - PI1_8, PI2_8 etc.
In vorbis/lib/mdct.h the following are defined:
for integer:
#define TRIGBITS 14
#define cPI3_8 6270
#define cPI2_8 11585
#define cPI1_8 15137
#define FLOAT_CONV(x) ((int)((x)*(1<<TRIGBITS)+.5))
for floats:
#define cPI3_8 .38268343236508977175F
#define cPI2_8 .70710678118654752441F
#define cPI1_8 .92387953251128675613F
#define FLOAT_CONV(x) = x
Could someone explain where these values
2005 Feb 01
1
mdct.c optimization
I took function mdct_butterfly_8 and write out transformation matrix. Then I rewrote this matrix into sequence of additions and substractions (see attachement). As I suspected I got the same as in the original code but I swaped some rows to get little higher speed. I hope I'll do the same with 16 point butterfly function combined with 8 point butterflies in a month. Who still believe that this
2003 May 31
4
faster mdct's
Hello Vorbis folks,
I'm one of the FFTW authors (www.fftw.org), and a few days ago I was
playing with our codelet generator for fun and modified it to spit out
hard-coded MDCTs of small sizes. The code (at
jdj.mit.edu/~stevenj/mdct_128nr.c) for 256 samples (128 outputs) seems to
be almost twice as fast as the Vorbis MDCT code for that size on my 2.2GHz
P-IV (gcc 3.2.2 and flags "-O1
2011 Aug 01
3
formula used by R to compute the t-values in a linear regression
Hello,
I was wondering if someone knows the formula used by the function lm to compute the t-values.
I am trying to implement a linear regression myself. Assuming that I have K variables, and N observations, the formula I am using is:
For the k-th variable, t-value= b_k/sigma_k
With b_k is the coefficient for the k-th variable, and sigma_k =(t(x) x )^(-1) _kk is its standard deviation.
2008 Dec 02
1
question on lmer function
suppose something like probability(passing test) is driven by
1. fixed effects -- sex
2. district effects - district funding
3. school effects - neighborhood income, racial composition, % two parent
families, ...
4. class effects - teacher quality measurement,
5. individual random effects - IQ.
how would such a model be setup in lmer? I can't find much discussion on
the
2017 May 03
0
MDCT implementation and his overlapped relationship
Dear all
In the paper section describes how CELT and SILK had implemented a look/up
head delay of (2.5ms), (5ms) respectively , could you explain me>
1) those values are fixed.
1) how you guarantee those values independent of the architecture's
performance.
Thanks so much
On Tue, Apr 18, 2017 at 10:05 AM, Diego Alejandro Parra Guzman <
daparrag at correo.udistrital.edu.co>
2013 Jul 11
0
Request for MDCT theoretical reference
http://en.wikipedia.org/wiki/Modified_discrete_cosine_transform is an OK
place to start.
On Mon, Jul 8, 2013 at 7:33 AM, Mahantesh Belakhindi
<girishec28 at gmail.com>wrote:
> Dear Experts,
>
> Can anybody please direct me to proper MDCT theory reference which will
> help me understand the code better?
>
> I'm trying to optimize MDCT for a embedded platform. So need