similar to: MDCT input and output data blocks

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

Hi all, I'm attempting to convert all the pointers to arrays the mdct_backward function so it can be partitioned off for a hardware implementation. Although this code is quite short I'm finding it a little tricky. As it stands, mdct_backward is passed values by reference i.e. void mdct_backward(mdct_lookup *init, DATA_TYPE *in, DATA_TYPE *out) o my modified version starts void

As some of you know, I'm creating a hardware MDCT core. At the moment I'm working out the best way to create a lookup table for the trig values, as set up in mdct_init: /* trig lookups... */ for(i=0;i<n/4;i++){ T[i*2]=FLOAT_CONV(cos((M_PI/n)*(4*i))); T[i*2+1]=FLOAT_CONV(-sin((M_PI/n)*(4*i))); T[n2+i*2]=FLOAT_CONV(cos((M_PI/(2*n))*(2*i+1)));

Here's an updated version of the MDCT callback patch. -------------- next part --------------

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 -------------- next part -------------- An HTML attachment was scrubbed... URL:

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

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>

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

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

Hi The inverse MDCT formula seems to be missing from the vorbis specification. From reading the source code of stb_vorbis (http://nothings.org/stb_vorbis/) I've a good idea of what it might be, but cannot find the formula anywhere in the official specification (the one on http://xiph.org/vorbis/doc/Vorbis_I_spec.html ). I also understand that the formula stated in the eusipco_corrected.ps

Hi On http://www.xiph.org/ogg/vorbis/doc/vorbis-spec-intro.html there is a link to a document titled 'The use of multirate filter banks for coding of high quality digital audio' that explains window functions for iMDCT. I would very much like to read that document, but the link is broken. If someone would send me the document or a working link to it, I would be very happy. Thanks in

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:

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

Hi, Can someone tell me which MDCT and invMDCT equation uses? I implemented the invMDCT one given in eusipco.corrected.ps file (handed out by Monty way back) and it produces different time domain samples. I tried both the FFT method and the slow way directly from the equation and couldn't reproduce the results from the original code. This leads me to believe that the forward MDCT used in

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

mdct.c, lines 436 onward (part of mdct_backward) state { DATA_TYPE *oX1=out+n2+n4; DATA_TYPE *oX2=out+n2+n4; DATA_TYPE *iX =out; T =init->trig+n2; do{ oX1-=4; oX1[3] = MULT_NORM (iX[0] * T[1] - iX[1] * T[0]); oX2[0] = -MULT_NORM (iX[0] * T[0] + iX[1] * T[1]); oX1[2] = MULT_NORM (iX[2] * T[3] - iX[3] * T[2]); oX2[1] =

...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,

If You want to compile vorbis libraries under win32 environment you can experience some problems: 1) If you unzip vorbis libraries, you will have 3 directories: "libogg-1.0", "libvorbis-1.0" and "vorbis-tools-1.0". You need to rename them to "ogg", "vorbis", "vorbis-tools". Otherwise batch files or even dsp project files, won't work.

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,

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