search for: codeword

...acket decode. In the spec it says that [cval] = read from packet using codebook number [so and so] in *scalar context*.(page no 43). Now please tell me the following: 1. Vorbis uses an LSB bit packer. But to decode bit-by-bit from the bitstream using the huffman decode tree we need the MSB of the codeword first. How is this issue overcome in the reference implementation? I was not able to understand what was going on from the reference implementation. 2. Currently, to keep track of unused entries and to reduce memory usage we have adopted the bitpacking scheme of vorbis. For example: ...00010110 i...

Hi, I am a bit confused on how code-words are derived from the codeword lengths. I will appreciate if someone can point me in the correct direction. I will take the example of an actual codebook that i found in a valid vorbis encoded file as shown below. [SK] +------Codebook [0] -------- [SK] Codebook Dimensions = 1 [SK] Codebook Entries = 8 [SK] Unordered [SK] 1,...

Hi, We are porting the Ogg Vorbis fixed point decoder to a 24 bit fixed point precision processor. We are trying to reduce the number of cycles for MIPS optimization. In this process we observed that most of the songs do not have "maximum codeword length" greater than 24 bits. We are planning to reduce most of the double word operations (in our case 32 bit data is stored as double word) to single word, i.e. 24 bit. I would like to know, what is the chance of getting a codeword of length greater than 24 bits in a song or for songs...

hello all, we are developing and porting vorbis1decoder on a 24 bit platform. in the process we came across somedoubts about node bytes and leaf words. from the specification we got that we are arranging the huffman codeword tree into an array. the nodebytes are the number of bytes that are required to represent a node and leafwords are the no. of bytes required to represent the leaf i.e the actual codeword. is this interpretation correct? if i am wrong please explain me what exactly the nodebytes and leafwords repr...

hello, does anybody know whether the codewords have a special meaning? whether they have a different influence like the quantization matriy in jpeg? e.g. do lower or the first entries have a greater influence than the last or higher codewords? thanks gerald

hi kuhlen, what you said is correct. i am talking about how you are going to arrange these codewords into an array, i.e. in the function _make_decode_table. there he uses node bytes and leaf words for memory management. i got a 24 bit platform. so if i assume that max. codeword length that could be possible as 24 bits can i allocate a memory of (2 * used entries - 2), to arrange the whole tree in...

I was just somewhat curious as to what lossless compression is used... is it just huffman? Tony Arcieri --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/

...is perfectly sensible (and I'll point out that the code works), but playing with VQ is new to me, so others will know better. Some background and a set of assumptions: 1) VQ and Huffman coding are just special cases of a more generic method of mapping input values (scalar or vector) to a 'codeword' then reversing the process on the other side. The process may be lossless or it may quantize (ie, the original mapping may be 1-to-1 or many-to-1); the reverse process is always 1-to-1 (every codeword has an output value). A complete collection of codewords is a codebook. 2) The codebook me...

...r should be possible. ================ 5. an encoded image decomposer, coupled to receive encoded image data file having at least one compressed image block, for breaking the encoded image data file into individual compressed image blocks, each compressed image block having at least one associated codeword, each codeword generated through selecting a block type for an original image block comprising the compressed image block, computing an analog curve for the block type, selecting a partition along the analog curve for the computed analog curve, and computing the set of codewords for the partition;...

The following has been committed to the Vorbis I spec as of r19445: Errata 20150226: Single entry codebooks A ?single-entry codebook? is a codebook with one active codeword entry. A single-entry codebook may be either a fully populated codebook with only one declared entry, or a sparse codebook with only one entry marked used. The Vorbis I spec provides no means to specify a codeword length of zero, and as a result, a single-entry codebook is inherently malformed bec...

hi, i am porting ogg vorbis decoder on to a24- bit dsp platform. i would like to know how he is arranging the binary tree into an array form. i think this process is done in _make_words in tremer code. i would be if some one could explain me the exact algorithm or where can i get it? i am attaching the code here for your reference. static int _make_words(char *l,long n,ogg_uint32_t *r,long

Hi, All help is appreciated. I am looking at the function "vorbis_staticbook_unpack" in codebook.c I guess this function just reads the codebooks in some structure (static_codebook) and does not actually map the codewords to the codevalues. Does anyone know what functions can I use in this function to actually view this mapping? I just want to display something like below: I can already decode lines beginging with "[SK]". Lookat lines begining with "[XXX]" only. [SK] +------Codebook [1]...

...te if someone can clear the following questions: 1. I guess the codebooks are derived from the actual input data. Probably the encoder may be making two passes through the input. The first pass finds out the frequency of different symbols and the second pass just replaces these symbols with the codewords. If the above is true: I wonder how vorbis encoder can be used for real-time data? Will it use some known codebooks or will it use someform of adaptive coding? Any help appreciated. Shashank

...a file so you have to read bytes instead (8 bit). As an example, the first type (if the ordered bit-flag is unset): "The decoder first reads one additional bit flag, the [sparse] flag. This flag determines whether or not the codebook contains unused entries that are not to be included in the codeword decode tree: byte 8: [ X 1 ] [sparse] flag (1 bit) The decoder now performs for each of the [codebook_entries] codebook entries: 1) if([sparse] is set){ 2) [flag] = read one bit; 3) if([flag] is set){ 4) [length] = read a five bit unsigned integer;...

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Hi, I am trying to understand the building of Huffman codes from the code lengths. In the Tremor code first I see that the codewords are being generated by the function _make_words() and then sorted. After this I see some magic code and something related to unused entries. Does the code generate code words for unused entries too? Are these unused entry code words used during the decode process? If these are used why do we...

...s in n-dimensional space, and to quantize them you carefully choose a set of code vectors to minimize the average distance from each code vector to each vector in the group of input vectors it approximates. Then you make a codebook of all the code vectors and encode each input vector by the closest codeword to it. I had thought this all occurred at encoding time, and the code vectors would be specifically chosen for each audio file, but after looking closer at the source it seems like there are static codebooks that are set at compile time. This confuses me because I thought one of the strengths of V...

...Sb/LSb, just 'first bit' and 'last bit'. The Huffman tree is traversed from 'first bit' to last bit'. This is a conceptual layer above the bitpacker; all you need to know is what order the bits come out, which happens to be LSb-first. For ex. say we have the following codewords in the codebook entry 0: codeword0 - 00 entry 2: codeword1 - 0111 entry 6: codeword2 - 111 entry 7: codeword3 - 10 Now in the bitstream if there is [codeword0] followed by [codeword3] followed by [codeword1], then will bitstream be msb lsb .... 0111 10 00 or will it be...

Hi, Does anybody know how codebooks are generated in OggVorbis encoder? We are porting oggorbis encoder on embedded platform for which VQ codebook memory is hugeeee to imagine. How can we reduce that? Can we do VQ with less codebooks and if yes how? If any help available? Parul Embedded Engineer Einfochips Ltd

During the interesting interview that binaryfreedom has made with Monty and Jack, Monty mentions cascading, a feature that will be added, quote: "Cascading is the ability to make multiple passes through the frequency spectrum, iteratively filling in more detail, like a progressive jpeg". What are the advantages of something like this - does this generally improves quality or is it used