Ogg Vorbis

https://xiph.org/vorbis/doc/
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Ogg Vorbis is a free, open-source audio codec and file format for lossy audio compression, providing...
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### Encoding using average bitrate (ABR)

Source: https://xiph.org/vorbis/doc/vorbisenc/examples.html

Prepares a vorbis_info structure for encoding using an Average Bitrate (ABR) mode. Example: 44kHz stereo coupled, average 128kbps ABR.

```c
** 
   vorbis_info_init(&vi);

  /*********************************************************************
   Encoding using an average bitrate mode (ABR).
   example: 44kHz stereo coupled, average 128kbps ABR 
   *********************************************************************/
  
   ret = vorbis_encode_init(&vi,2,44100,-1,128000,-1);

  /*********************************************************************
   do not continue if setup failed; this can happen if we ask for a
   mode that libVorbis does not support (eg, too low a bitrate, etc, 
   will return 'OV_EIMPL')
   *********************************************************************/

   if(ret) exit(1);
**

```

--------------------------------

### Encoding using constant bitrate (CBR)

Source: https://xiph.org/vorbis/doc/vorbisenc/examples.html

Prepares a vorbis_info structure for encoding using a Constant Bitrate (CBR) mode. Example: 44kHz stereo coupled, average 128kbps CBR.

```c
** 
   vorbis_info_init(&vi);

  /*********************************************************************
   Encoding using a constant bitrate mode (CBR).
   example: 44kHz stereo coupled, average 128kbps CBR 
   *********************************************************************/
  
   ret = vorbis_encode_init(&vi,2,44100,128000,128000,128000);

  /*********************************************************************
   do not continue if setup failed; this can happen if we ask for a
   mode that libVorbis does not support (eg, too low a bitrate, etc, 
   will return 'OV_EIMPL')
   *********************************************************************/

   if(ret) exit(1);
**

```

--------------------------------

### vorbisfile_example.c

Source: https://xiph.org/vorbis/doc/vorbisfile/vorbisfile_example_c.html

The example program source code.

```c
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "vorbis/codec.h"
#include "vorbis/vorbisfile.h"

#ifdef _WIN32
#include <io.h>
#include <fcntl.h>
#endif

char pcmout[4096];

int main(int argc, char **argv){
  OggVorbis_File vf;
  int eof=0;
  int current_section;

#ifdef _WIN32
  _setmode( _fileno( stdin ), _O_BINARY );
  _setmode( _fileno( stdout ), _O_BINARY );
#endif

  if(ov_open_callbacks(stdin, &vf, NULL, 0, OV_CALLBACKS_NOCLOSE) < 0) {
      fprintf(stderr,"Input does not appear to be an Ogg bitstream.\n");
      exit(1);
  }

  {
    char **ptr=ov_comment(&vf,-1)->user_comments;
    vorbis_info *vi=ov_info(&vf,-1);
    while(*ptr){
      fprintf(stderr,"%s\n",*ptr);
      ++ptr;
    }
    fprintf(stderr,"\nBitstream is %d channel, %ldHz\n",vi->channels,vi->rate);
    fprintf(stderr,"Encoded by: %s\n\n",ov_comment(&vf,-1)->vendor);
  }
  
  while(!eof){
    long ret=ov_read(&vf,pcmout,sizeof(pcmout),0,2,1,&current_section);
    if (ret == 0) {
      /* EOF */
      eof=1;
    } else if (ret < 0) {
      /* error in the stream.  Not a problem, just reporting it in
	 case we (the app) cares.  In this case, we don't. */
    } else {
      /* we don't bother dealing with sample rate changes, etc, but
	 you'll have to */
      fwrite(pcmout,1,ret,stdout);
    }
  }

  ov_clear(&vf);
    
  fprintf(stderr,"Done.\n");
  return(0);
}

```

--------------------------------

### Include Headers

Source: https://xiph.org/vorbis/doc/vorbisfile/seekexample.html

Includes necessary standard and Vorbis-specific headers for the seeking example.

```c
#include <stdlib.h>
#include <stdio.h>
#include "vorbis/codec.h"
#include "vorbis/vorbisfile.h"
```

--------------------------------

### Encoding using a VBR quality mode

Source: https://xiph.org/vorbis/doc/vorbisenc/examples.html

Prepares a vorbis_info structure for encoding using a Variable Bitrate (VBR) quality mode. The usable range is -.1 (lowest quality, smallest file) to 1.0 (highest quality, largest file). Example quality mode .4: 44kHz stereo coupled, roughly 128kbps VBR.

```c
** 
   vorbis_info_init(&vi);

  /*********************************************************************
   Encoding using a VBR quality mode.  The usable range is -.1
   (lowest quality, smallest file) to 1.0 (highest quality, largest file).
   Example quality mode .4: 44kHz stereo coupled, roughly 128kbps VBR 
   *********************************************************************/
  
   ret = vorbis_encode_init_vbr(&vi,2,44100,.4);

  /*********************************************************************
   do not continue if setup failed; this can happen if we ask for a
   mode that libVorbis does not support (eg, too low a quality mode, etc, 
   will return 'OV_EIMPL')
   *********************************************************************/

   if(ret) exit(1);
**

```

--------------------------------

### Encoding using VBR selected by approximate bitrate

Source: https://xiph.org/vorbis/doc/vorbisenc/examples.html

Prepares a vorbis_info structure for encoding using a quality mode, but selects that quality mode by asking for an approximate bitrate. This is true VBR, but selected using the bitrate interface, and then turning bitrate management off.

```c
** 
   vorbis_info_init(&vi);

  /*********************************************************************
   Encode using a quality mode, but select that quality mode by asking for
   an approximate bitrate.  This is not ABR, it is true VBR, but selected
   using the bitrate interface, and then turning bitrate management off:
   *********************************************************************/

   ret = ( vorbis_encode_setup_managed(&vi,2,44100,-1,128000,-1) ||
           vorbis_encode_ctl(&vi,OV_ECTL_RATEMANAGE2_SET,NULL) ||
           vorbis_encode_setup_init(&vi));

  /*********************************************************************
   do not continue if setup failed; this can happen if we ask for a
   mode that libVorbis does not support (eg, too low a bitrate, etc, 
   will return 'OV_EIMPL')
   *********************************************************************/

   if(ret) exit(1);
**

```

--------------------------------

### Typical ov_read() usage example

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_read.html

A common example of how to call the ov_read() function in C.

```c
bytes_read = ov_read(&vf, buffer, 4096,0,2,1,&current_section)
```

--------------------------------

### Chaining Example C Program

Source: https://xiph.org/vorbis/doc/vorbisfile/chaining_example_c.html

This C program demonstrates how to open and read information from Ogg Vorbis streams provided via standard input, chaining multiple logical bitstreams if present. It uses the vorbisfile library to access stream details like sample rate, channels, bitrate, and playing time.

```c
#include <vorbis/codec.h>
#include <vorbis/vorbisfile.h>

int main(){
  OggVorbis_File ov;
  int i;

#ifdef _WIN32 /* We need to set stdin to binary mode on windows. */
  _setmode( _fileno( stdin ), _O_BINARY );
#endif

  /* open the file/pipe on stdin */
  if(ov_open_callbacks(stdin,&ov,NULL,-1,OV_CALLBACKS_NOCLOSE)<0){
    printf("Could not open input as an OggVorbis file.\n\n");
    exit(1);
  }
  
  /* print details about each logical bitstream in the input */
  if(ov_seekable(&ov)){
    printf("Input bitstream contained %ld logical bitstream section(s).\n",
           ov_streams(&ov));
    printf("Total bitstream playing time: %ld seconds\n\n",
           (long)ov_time_total(&ov,-1));

  }else{
    printf("Standard input was not seekable.\n"
           "First logical bitstream information:\n\n");
  }

  for(i=0;i<ov_streams(&ov);i++){
    vorbis_info *vi=ov_info(&ov,i);
    printf("\tlogical bitstream section %d information:\n",i+1);
    printf("\t\t%ldHz %d channels bitrate %ldkbps serial number=%ld\n",
           vi->rate,vi->channels,ov_bitrate(&ov,i)/1000,
           ov_serialnumber(&ov,i));
    printf("\t\tcompressed length: %ld bytes ",(long)(ov_raw_total(&ov,i)));
    printf(" play time: %lds\n",(long)ov_time_total(&ov,i));
  }

  ov_clear(&ov);
  return 0;
}

```

--------------------------------

### Opening the OggVorbis File

Source: https://xiph.org/vorbis/doc/vorbisfile/seekexample.html

Initializes the OggVorbis_File structure using ov_open_callbacks and checks if the input is a valid Ogg Vorbis format.

```c
  if(ov_open_callbacks(stdin,&ov,NULL,-1, OV_CALLBACKS_NOCLOSE)<0){
    printf("Could not open input as an OggVorbis file.\n\n");
    exit(1);
  }
```

--------------------------------

### Typical usage example

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_read_float.html

A typical usage example demonstrating how to call ov_read_float() to decode audio samples.

```c
float **pcm; samples_read = ov_read_float(&vf,pcm, 1024, &current_section);
```

--------------------------------

### Check Seekability and Get Stream Information

Source: https://xiph.org/vorbis/doc/vorbisfile/chainingexample.html

Check if the stream is seekable using ov_seekable(). Then, find the number of logical bitstreams using ov_streams() and the total length of the physical bitstream using ov_time_total().

```c
  if(ov_seekable(&ov)){
    printf("Input bitstream contained %ld logical bitstream section(s).\n",
	   ov_streams(&ov));
    printf("Total bitstream playing time: %ld seconds\n\n",
	   (long)ov_time_total(&ov,-1));

  }else{
    printf("Standard input was not seekable.\n"
	   "First logical bitstream information:\n\n");
  }
```

--------------------------------

### Include Headers

Source: https://xiph.org/vorbis/doc/vorbisfile/chainingexample.html

Relevant headers, including vorbis-specific "codec.h" and "vorbisfile.h", need to be included.

```c
#include "vorbis/codec.h"
#include "vorbis/vorbisfile.h"
#include "../lib/misc.h"
```

--------------------------------

### Read Loop

Source: https://xiph.org/vorbis/doc/vorbisfile/example.html

The read loop uses ov_read() to get data blocks. It checks the return value for EOF or errors and writes valid data to stdout.

```c

  while(!eof){
    long ret=ov_read(&vf,pcmout,sizeof(pcmout),0,2,1,&current_section);
    if (ret == 0) {
      /* EOF */
      eof=1;
    } else if (ret < 0) {
      /* error in the stream.  Not a problem, just reporting it in
	 case we (the app) cares.  In this case, we don't. */
    } else {
      /* we don't bother dealing with sample rate changes, etc, but
	 you'll have to*/
      fwrite(pcmout,1,ret,stdout);
    }
  }

  
```

--------------------------------

### SDP Example

Source: https://xiph.org/vorbis/doc/rfc5215.txt

An example of a Session Description Protocol (SDP) for a single Vorbis audio stream, including media type parameters mapped to SDP fields.

```sdp
c=IN IP4 192.0.2.1

m=audio RTP/AVP 98

a=rtpmap:98 vorbis/44100/2

a=fmtp:98 configuration=AAAAAZ2f4g9NAh4aAXZvcmJpcwA...;
```

--------------------------------

### Include Headers

Source: https://xiph.org/vorbis/doc/vorbisfile/example.html

Relevant headers, including vorbis-specific "vorbis/codec.h" and "vorbisfile.h", need to be included.

```c
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "vorbis/codec.h"
#include "vorbisfile.h"
```

--------------------------------

### Main Function Declaration

Source: https://xiph.org/vorbis/doc/vorbisfile/chainingexample.html

Declare the primary OggVorbis_File structure and other helpful variables to track progress within the file.

```c
int main(){
  OggVorbis_File ov;
  int i;
```

--------------------------------

### seeking_test.c

Source: https://xiph.org/vorbis/doc/vorbisfile/seeking_test_c.html

The example program source code for testing seeking functionality with Vorbisfile.

```c
#include <stdlib.h>
#include <stdio.h>
#include "vorbis/codec.h"
#include "vorbis/vorbisfile.h"

int main(){
  OggVorbis_File ov;
  int i;

#ifdef _WIN32 /* We need to set stdin to binary mode under Windows */
  _setmode( _fileno( stdin ), _O_BINARY );
#endif

  /* open the file/pipe on stdin */
  if(ov_open_callbacks(stdin,&ov,NULL,-1,OV_CALLBACKS_NOCLOSE)==-1){
    printf("Could not open input as an OggVorbis file.\n\n");
    exit(1);
  }
  
  /* print details about each logical bitstream in the input */
  if(ov_seekable(&ov)){
    double length=ov_time_total(&ov,-1);
    printf("testing seeking to random places in %g seconds....\n",length);
    for(i=0;i<100;i++){
      double val=(double)rand()/RAND_MAX*length;
      ov_time_seek(&ov,val);
      printf("\r\t%%d [%%gs]...     ",i,val); 
      fflush(stdout);
    }
    
    printf("\r                                   \nOK.\n\n");
  }else{
    printf("Standard input was not seekable.\n");
  }

  ov_clear(&ov);
  return 0;
}

```

--------------------------------

### Initialize OggVorbis_File Structure

Source: https://xiph.org/vorbis/doc/vorbisfile/chainingexample.html

Initialize the OggVorbis_File structure using ov_open_callbacks(). This also checks if the input is a Vorbis format. OV_CALLBACKS_NOCLOSE prevents stdin from being closed during cleanup.

```c
  if(ov_open_callbacks(stdin,&ov,NULL,-1,OV_CALLBACKS_NOCLOSE)<0){
    printf("Could not open input as an OggVorbis file.\n\n");
    exit(1);
  }
```

--------------------------------

### Windows Specific Includes

Source: https://xiph.org/vorbis/doc/vorbisfile/example.html

For Windows users, specific libraries must be declared to set stdin/stdout to binary mode.

```c
#ifdef _WIN32
#include <io.h>
#include <fcntl.h>
#endif
```

--------------------------------

### Windows ov_open() Substitute

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_open_callbacks.html

Example of using ov_open_callbacks as a substitute for ov_open() on Windows.

```c
`ov_open_callbacks(f, vf, initial, ibytes, OV_CALLBACKS_DEFAULT);`
```

--------------------------------

### PCM Output Buffer

Source: https://xiph.org/vorbis/doc/vorbisfile/example.html

A buffer for the PCM audio output is declared.

```c
char pcmout[4096];
```

--------------------------------

### Multiple Artist Example

Source: https://xiph.org/vorbis/doc/Vorbis_I_spec.html

Demonstrates how to handle multiple values for the same field name, such as listing multiple artists for a track.

```text
ARTIST=Dizzy Gillespie
ARTIST=Sonny Rollins
ARTIST=Sonny Stitt
```

--------------------------------

### Typical usage of ov_read_filter()

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_read_filter.html

An example demonstrating the typical way to call the ov_read_filter() function in C.

```c
bytes_read = ov_read_filter(&vf, buffer, 4096,0,2,1,&current_section, filter, (void *)filter_data_ptr)
```

--------------------------------

### Initialize OggVorbis_File Structure

Source: https://xiph.org/vorbis/doc/vorbisfile/example.html

ov_open_callbacks() initializes the OggVorbis_File structure and checks for Vorbis format. OV_CALLBACKS_NOCLOSE prevents libvorbisfile from closing stdin during cleanup.

```c
  if(ov_open_callbacks(stdin, &vf, NULL, 0, OV_CALLBACKS_NOCLOSE) < 0) {
      fprintf(stderr,"Input does not appear to be an Ogg bitstream.\n");
      exit(1);
  }
```

--------------------------------

### Set stdin to Binary Mode (Windows)

Source: https://xiph.org/vorbis/doc/vorbisfile/chainingexample.html

On Windows, stdin needs to be set to binary mode to prevent corruption of input data.

```c
#ifdef _WIN32 /* We need to set stdin to binary mode under Windows */
  _setmode( _fileno( stdin ), _O_BINARY );
#endif
```

--------------------------------

### ov_test_callbacks as ov_test() Substitute on Windows

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_test_callbacks.html

Example of using ov_test_callbacks with default callbacks to achieve the same functionality as ov_test() on Windows.

```c
`ov_test_callbacks(f, vf, initial, ibytes, OV_CALLBACKS_DEFAULT);`
```

--------------------------------

### Decoding example

Source: https://xiph.org/vorbis/doc/Vorbis_I_spec.html

Reading two, two-bit integer fields from the previously encoded bytestream.

```text
1 |
2 V
3
4 7 6 5 4 3 2 1 0
5byte 0 [1 1 1 1 1 1 0 0] <-
6byte 1 [0 1 0 0 1 0 0 0]
7byte 2 [1 1 0 0 1 1 1 0]
8byte 3 [0 0 0 0 0 1 1 0] bytestream length == 4 bytes
9
We read two, two-bit integer fields, resulting in the returned numbers ’b00’ and ’b11’. Two things are worth noting here:
  * Although these four bits were originally written as a single four-bit integer, reading some other combination of bit-widths from the bitstream is well defined. There are no artificial alignment boundaries maintained in the bitstream.
  * The second value is the two-bit-wide integer ’b11’. This value may be interpreted either as the unsigned value ’3’, or the signed value ’-1’. Signedness is dependent on decode context.
```

--------------------------------

### Cleanup and Exit

Source: https://xiph.org/vorbis/doc/vorbisfile/example.html

After processing, ov_clear() is called to clean up resources, and the program exits.

```c
  ov_clear(&vf);
    
  fprintf(stderr,"Done.\n");
  return(0);
}
```

--------------------------------

### Display File Information

Source: https://xiph.org/vorbis/doc/vorbisfile/example.html

The code retrieves and displays channel/bitrate info using ov_info(), comments using ov_comment(), total PCM samples using ov_pcm_total(), and the encoder information using ov_comment().

```c
  {
    char **ptr=ov_comment(&vf,-1)->user_comments;
    vorbis_info *vi=ov_info(&vf,-1);
    while(*ptr){
      fprintf(stderr,"%s\n",*ptr);
      ++ptr;
    }
    fprintf(stderr,"\nBitstream is %d channel, %ldHz\n",vi->channels,vi->rate);
    fprintf(stderr,"\nDecoded length: %ld samples\n",
            (long)ov_pcm_total(&vf,-1));
    fprintf(stderr,"Encoded by: %s\n\n",ov_comment(&vf,-1)->vendor);
  }
```

--------------------------------

### Main Function and Windows Binary Mode

Source: https://xiph.org/vorbis/doc/vorbisfile/example.html

Inside main(), the primary OggVorbis_File structure and other variables are declared. For Windows users, stdin and stdout are set to binary mode.

```c
int main(int argc, char **argv){
  OggVorbis_File vf;
  int eof=0;
  int current_section;

#ifdef _WIN32
  _setmode( _fileno( stdin ), _O_BINARY );
  _setmode( _fileno( stdout ), _O_BINARY );
#endif
```

--------------------------------

### Clear OggVorbis_File Structure

Source: https://xiph.org/vorbis/doc/vorbisfile/chainingexample.html

Release the bitstream resources by calling ov_clear() when done with the entire physical bitstream.

```c
  ov_clear(&ov);
  return 0;
}
```

--------------------------------

### Iterate and Print Logical Bitstream Information

Source: https://xiph.org/vorbis/doc/vorbisfile/chainingexample.html

Iterate through each logical bitstream, printing information such as rate, channels, bitrate, serial number, compressed length, and play time using ov_info(), ov_serialnumber(), ov_raw_total(), and ov_time_total().

```c
  for(i=0;i<ov_streams(&ov);i++){
    vorbis_info *vi=ov_info(&ov,i);
    printf("\tlogical bitstream section %d information:\n",i+1);
    printf("\t\t%ldHz %d channels bitrate %ldkbps serial number=%ld\n",
	   vi->rate,vi->channels,ov_bitrate(&ov,i)/1000,
	   ov_serialnumber(&ov,i));
    printf("\t\tcompressed length: %ld bytes ",(long)(ov_raw_total(&ov,i)));
    printf(" play time: %lds\n",(long)ov_time_total(&ov,i));
  }
```

--------------------------------

### Example RTP Packet with Two Vorbis Packets

Source: https://xiph.org/vorbis/doc/rfc5215.txt

This diagram shows an example RTP packet containing two Vorbis packets, illustrating the header fields and the payload data structure.

```text
       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | 2 |0|0|  0    |0|      PT     |       sequence number         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |               timestamp (in sample rate units)                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           synchronisation source (SSRC) identifier            |
      +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
      |            contributing source (CSRC) identifiers             |
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Ident                     | 0 | 0 | 2 pks |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            length             |          vorbis data         ..
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ..                        vorbis data                           |
```

--------------------------------

### Comment Vector Structure Example

Source: https://xiph.org/vorbis/doc/Vorbis_I_spec.html

Illustrates the basic structure of comment vectors, similar to Unix environment variables, with field names and values.

```text
comment[0]="ARTIST=me";
comment[1]="TITLE=the sound of Vorbis";
```

--------------------------------

### Coding a 7-bit integer

Source: https://xiph.org/vorbis/doc/Vorbis_I_spec.html

Example of coding the 7-bit integer value '17' into a bytestream.

```text
1 |
2 V
3
4 7 6 5 4 3 2 1 0
5byte 0 [1 1 1 1 1 1 0 0]
6byte 1 [0 0 0 0 1 0 0 0] <-
7byte 2 [ ]
8byte 3 [ ]
9 ...
10byte n [ ] bytestream length == 2 bytes
11 bit cursor == 6
```

--------------------------------

### Seeking to Random Positions

Source: https://xiph.org/vorbis/doc/vorbisfile/seekexample.html

Checks if the stream is seekable and then seeks to 100 random positions within the bitstream using ov_time_seek.

```c
  
  /* print details about each logical bitstream in the input */
  if(ov_seekable(&ov)){
    double length=ov_time_total(&ov,-1);
    printf("testing seeking to random places in %g seconds....\n",length);
    for(i=0;i<100;i++){
      double val=(double)rand()/RAND_MAX*length;
      ov_time_seek(&ov,val);
      printf("\r\t%d [%gs]...     ",i,val);
      fflush(stdout);
    }
    
    printf("\r                                   \nOK.\n\n");
  }else{
    printf("Standard input was not seekable.\n");
  }
  
```

--------------------------------

### Coding a 13-bit integer

Source: https://xiph.org/vorbis/doc/Vorbis_I_spec.html

Example of coding the 13-bit integer value '6969' into a bytestream.

```text
1 |
2 V
3
4 7 6 5 4 3 2 1 0
5byte 0 [1 1 1 1 1 1 0 0]
6byte 1 [0 1 0 0 1 0 0 0]
7byte 2 [1 1 0 0 1 1 1 0]
8byte 3 [0 0 0 0 0 1 1 0] <-
9 ...
10byte n [ ] bytestream length == 4 bytes
```

--------------------------------

### Packet segmentation example 1

Source: https://xiph.org/vorbis/doc/framing.html

Illustrates how a 753-byte raw packet is logically divided into segments for an Ogg page header, with lacing values indicating segment sizes.

```text
`
raw packet:
  ___________________________________________
 |______________packet data__________________|
 753 bytes

lacing values for page header segment table: 255,255,243
`
```

--------------------------------

### Coding a 3-bit integer

Source: https://xiph.org/vorbis/doc/Vorbis_I_spec.html

Example of coding the 3-bit integer value '-1' into a bytestream.

```text
1 |
2 V
3
4 7 6 5 4 3 2 1 0
5byte 0 [0 1 1 1 1 1 0 0] <-
6byte 1 [ ]
7byte 2 [ ]
8byte 3 [ ]
9 ...
10byte n [ ] bytestream length == 1 byte
```

--------------------------------

### Residue 1 Example

Source: https://xiph.org/vorbis/doc/Vorbis_I_spec.html

Illustrates how residue 1 encodes partition vector scalars in order, based on codebook dimensions for a partition vector of size eight.

```text
original residue vector: [ 0 1 2 3 4 5 6 7 ]

codebook dimensions = 8 encoded as: [ 0 1 2 3 4 5 6 7 ]

codebook dimensions = 4 encoded as: [ 0 1 2 3 ], [ 4 5 6 7 ]

codebook dimensions = 2 encoded as: [ 0 1 ], [ 2 3 ], [ 4 5 ], [ 6 7 ]

codebook dimensions = 1 encoded as: [ 0 ], [ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ], [ 6 ], [ 7 ]
```

--------------------------------

### Packet segmentation example 2

Source: https://xiph.org/vorbis/doc/framing.html

Shows how a 255-byte raw packet is represented with lacing values, where a value of 255 is followed by a 0 to indicate the end of the packet after 255 bytes.

```text
`
raw packet:
  _______________________________
 |________packet data____________|
 255 bytes

lacing values: 255, 0
`
```

--------------------------------

### Content Vector Format Example

Source: https://xiph.org/vorbis/doc/v-comment.html

Illustrates the structure of comment fields, similar to UNIX environment variables.

```plaintext
comment[0]="ARTIST=me"; 
comment[1]="TITLE=the sound of Vorbis"; 
```

--------------------------------

### Residue 0 Example

Source: https://xiph.org/vorbis/doc/Vorbis_I_spec.html

Illustrates how residue 0 interleaves VQ encoding based on codebook dimensions for a partition vector of size eight.

```text
original residue vector: [ 0 1 2 3 4 5 6 7 ]

codebook dimensions = 8 encoded as: [ 0 1 2 3 4 5 6 7 ]

codebook dimensions = 4 encoded as: [ 0 2 4 6 ], [ 1 3 5 7 ]

codebook dimensions = 2 encoded as: [ 0 4 ], [ 1 5 ], [ 2 6 ], [ 3 7 ]

codebook dimensions = 1 encoded as: [ 0 ], [ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ], [ 6 ], [ 7 ]
```

--------------------------------

### Multiple ARTIST fields

Source: https://xiph.org/vorbis/doc/v-comment.html

Example showing that field names are not required to be unique within a comment header, allowing for multiple entries for the same field.

```text
ARTIST=Dizzy Gillespie 
ARTIST=Sonny Rollins 
ARTIST=Sonny Stitt 

```

--------------------------------

### RTP Header Example

Source: https://xiph.org/vorbis/doc/rfc5215.txt

A standard RTP header format, showing Version (V), Padding (P), Extension (X), CSRC count (CC), Marker bit (M), Payload Type (PT), and Sequence Number fields.

```text
0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
|V=2|P|X|  CC   |M|     PT      |             xxxx              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
|                             xxxxx                             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
|           synchronization source (SSRC) identifier            |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=
|            contributing source (CSRC) identifiers             |
|                              ...                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

```

--------------------------------

### Packed Headers Detail

Source: https://xiph.org/vorbis/doc/rfc5215.txt

A detailed bit-level diagram of the packed headers, showing fields like Ident, length, number of headers, and the structure for Identification, Comment, and Setup Headers.

```text
0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
|                   Ident                       |    length    ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
..              | n. of headers |    length1    |    length2   ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
..              |             Identification Header            ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
.................................................................
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
..              |         Comment Header                       ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
.................................................................
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
..                        Comment Header                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
|                          Setup Header                        ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
.................................................................
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
..                         Setup Header                         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

```

--------------------------------

### Example Fragmented Packet (Packet 2)

Source: https://xiph.org/vorbis/doc/rfc5215.txt

Illustrates the structure of a fragmented Vorbis packet, specifically Packet 2, showing the 'Ident', 'Fragment type', 'number of packets', 'length', and 'vorbis data' fields.

```text
|            contributing source (CSRC) identifiers             |
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Ident                   | 2 | 0 |      0|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             length            |          vorbis data         ..
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ..                        vorbis data                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
```

--------------------------------

### Function Signature

Source: https://xiph.org/vorbis/doc/vorbisenc/vorbis_encode_setup_init.html

The C function signature for vorbis_encode_setup_init.

```c
extern int vorbis_encode_setup_init(vorbis_info *vi);
```

--------------------------------

### Coding a 4-bit integer

Source: https://xiph.org/vorbis/doc/Vorbis_I_spec.html

Example of coding the 4-bit integer value '12' into a bytestream.

```text
1 |
2 V
3
4 7 6 5 4 3 2 1 0
5byte 0 [0 0 0 0 1 1 0 0] <-
6byte 1 [ ]
7byte 2 [ ]
8byte 3 [ ]
9 ...
10byte n [ ] bytestream length == 1 byte
```

--------------------------------

### vorbis_info_init declaration

Source: https://xiph.org/vorbis/doc/libvorbis/vorbis_info_init.html

This function initializes a vorbis_info structure and allocates its internal storage.

```c
extern void     vorbis_info_init(vorbis_info *vi);
```

--------------------------------

### vorbis_packet_blocksize function declaration

Source: https://xiph.org/vorbis/doc/libvorbis/vorbis_packet_blocksize.html

This function gets the size of the block that would result from decoding a Vorbis packet but does not actually decode the packet.

```c
**
extern long     vorbis_packet_blocksize(vorbis_info *vi,ogg_packet *op);
**
```

--------------------------------

### Function Signature

Source: https://xiph.org/vorbis/doc/libvorbis/vorbis_synthesis_init.html

The function signature for vorbis_synthesis_init.

```c
extern int      vorbis_synthesis_init(vorbis_dsp_state *v,vorbis_info *vi);
```

--------------------------------

### vorbis_analysis_init function declaration

Source: https://xiph.org/vorbis/doc/libvorbis/vorbis_analysis_init.html

The function declaration for vorbis_analysis_init.

```c
extern int      vorbis_analysis_init(vorbis_dsp_state *v,vorbis_info *vi);
```

--------------------------------

### Function Signature

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_bitrate_instant.html

The C function signature for ov_bitrate_instant.

```c
long ov_bitrate_instant(OggVorbis_File *vf);
```

--------------------------------

### vorbis_block_init function declaration

Source: https://xiph.org/vorbis/doc/libvorbis/vorbis_block_init.html

The function declaration for vorbis_block_init.

```c
**
extern int      vorbis_block_init(vorbis_dsp_state *v, vorbis_block *vb);
**
```

--------------------------------

### ov_open function signature

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_open.html

The function signature for ov_open, showing its parameters and return type.

```c
**
int ov_open(FILE *f,OggVorbis_File *vf,char *initial,long ibytes);
**
```

--------------------------------

### vorbis_encode_init function signature

Source: https://xiph.org/vorbis/doc/vorbisenc/vorbis_encode_init.html

The function signature for vorbis_encode_init, which sets up managed bitrate modes for Vorbis encoding.

```c
**
extern int vorbis_encode_init(vorbis_info *vi,
			      long channels,
			      long rate,
			      
			      long max_bitrate,
			      long nominal_bitrate,
			      long min_bitrate);

**
```

--------------------------------

### Function Signature

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_fopen.html

The C function signature for ov_fopen.

```c
int ov_fopen(const char *path,OggVorbis_File *vf);
```

--------------------------------

### Function Signature

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_raw_total.html

The C function signature for ov_raw_total.

```c
ogg_int64_t ov_raw_total(OggVorbis_File *vf,int i);
```

--------------------------------

### ov_test_open function declaration

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_test_open.html

The function declaration for ov_test_open.

```c
int ov_test_open(OggVorbis_File *vf);
```

--------------------------------

### Example Fragmented Vorbis Packet (Packet 2)

Source: https://xiph.org/vorbis/doc/rfc5215.txt

Diagram showing the second RTP payload of a fragmented Vorbis packet, maintaining the same timestamp as the first fragment.

```text
0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V=2|P|X|  CC   |M|     PT      |           1001                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                             12345                             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|           synchronization source (SSRC) identifier            |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
```

--------------------------------

### Example Fragmented Vorbis Packet (Packet 1)

Source: https://xiph.org/vorbis/doc/rfc5215.txt

Diagram showing the first RTP payload of a fragmented Vorbis packet, including RTP headers and Vorbis data.

```text
0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V=2|P|X|  CC   |M|     PT      |           1000                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                            12345                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|           synchronization source (SSRC) identifier            |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
|            contributing source (CSRC) identifiers             |
|                              ...                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       Ident                   | 1 | 0 |      0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|             length            |            vorbis data       ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
..                        vorbis data                           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
```

--------------------------------

### vorbis_encode_init_vbr function signature

Source: https://xiph.org/vorbis/doc/vorbisenc/vorbis_encode_init_vbr.html

The function signature for vorbis_encode_init_vbr, used for setting up variable bitrate encoding.

```c
**
extern int vorbis_encode_init_vbr(vorbis_info *vi,
			      long channels,
			      long rate,
			      
			      float base_quality);

**
```

--------------------------------

### ov_bitrate function signature

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_bitrate.html

The function signature for ov_bitrate.

```c
long ov_bitrate(OggVorbis_File *vf,int i);
```

--------------------------------

### Example Fragmented Packet (Packet 3)

Source: https://xiph.org/vorbis/doc/rfc5215.txt

Shows the structure of the final fragmented Vorbis packet, Packet 3, including RTP header fields and Vorbis-specific fields like 'Ident', 'Fragment type', and 'number of packets'.

```text
       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |V=2|P|X|  CC   |M|     PT      |           1002                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             12345                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           synchronization source (SSRC) identifier            |
      +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
      |            contributing source (CSRC) identifiers             |
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Ident                    | 3 | 0 |      0|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             length            |          vorbis data         ..
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ..                        vorbis data                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
```

--------------------------------

### Floor 1 Configuration Decode Steps

Source: https://xiph.org/vorbis/doc/Vorbis_I_spec.html

A step-by-step breakdown of how to read and interpret the floor 1 configuration from a Vorbis packet header.

```pseudocode
1) [floor1_partitions] = read 5 bits as unsigned integer
2) [maximum_class] = -1
3) iterate [i] over the range 0 ... [floor1_partitions]-1 {
  4) vector [floor1_partition_class_list] element [i] = read 4 bits as unsigned integer
}
5) [maximum_class] = largest integer scalar value in vector [floor1_partition_class_list]
6) iterate [i] over the range 0 ... [maximum_class] {
  7) vector [floor1_class_dimensions] element [i] = read 3 bits as unsigned integer and add 1
  8) vector [floor1_class_subclasses] element [i] = read 2 bits as unsigned integer
  9) if ( vector [floor1_class_subclasses] element [i] is nonzero ) {
    10) vector [floor1_class_masterbooks] element [i] = read 8 bits as unsigned integer
  }
  11) iterate [j] over the range 0 ... (2 exponent [floor1_class_subclasses] element [i]) - 1 {
    12) array [floor1_subclass_books] element [i],[j] = read 8 bits as unsigned integer and subtract one
  }
}
13) [floor1_multiplier] = read 2 bits as unsigned integer and add one
14) [rangebits] = read 4 bits as unsigned integer
15) vector [floor1_X_list] element [0] = 0
16) vector [floor1_X_list] element [1] = 2 exponent [rangebits]
17) [floor1_values] = 2
18) iterate [i] over the range 0 ... [floor1_partitions]-1 {
  19) [current_class_number] = vector [floor1_partition_class_list] element [i]
  20) iterate [j] over the range 0 ... ([floor1_class_dimensions] element [current_class_number])-1 {
    21) vector [floor1_X_list] element ([floor1_values]) = read [rangebits] bits as unsigned integer
    22) increment [floor1_values] by one
  }
}
23) done
```

--------------------------------

### vorbis_comment_init function declaration

Source: https://xiph.org/vorbis/doc/libvorbis/vorbis_comment_init.html

The C declaration for the vorbis_comment_init function.

```c
**
extern void     vorbis_comment_init(vorbis_comment *vc);
**
```

--------------------------------

### Function Signature

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_open_callbacks.html

The C function signature for ov_open_callbacks.

```c
int ov_open_callbacks(void *datasource, OggVorbis_File *vf, char *initial, long ibytes, ov_callbacks callbacks);
```

--------------------------------

### render_line Algorithm

Source: https://xiph.org/vorbis/doc/Vorbis_I_spec.html

Integer line drawing algorithm for constructing an integer floor curve for contiguous piecewise line segments, using integer division that rounds toward zero.

```Pseudocode
render_line(x0, y0, x1, y1, v)
1) [dy] = [y1] - [y0]
2) [adx] = [x1] - [x0]
3) [ady] = absolute value of [dy]
4) [base] = [dy] / [adx] using integer division
5) [x] = [x0]
6) [y] = [y0]
7) [err] = 0
8) if ( [dy] is less than 0 ) {
9) [sy] = [base] - 1
} else {
10) [sy] = [base] + 1
}
11) [ady] = [ady] - (absolute value of [base]) * [adx]
12) vector [v] element [x] = [y]
13) iterate [x] over the range [x0]+1 ... [x1]-1 {
14) [err] = [err] + [ady]
15) if ( [err] >= [adx] ) {
16) [err] = [err] - [adx]
17) [y] = [y] + [sy]
} else {
18) [y] = [y] + [base]
}
19) vector [v] element [x] = [y]
}
```

--------------------------------

### Function Signature

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_raw_seek_lap.html

The function signature for ov_raw_seek_lap.

```c
int ov_raw_seek_lap(OggVorbis_File *vf,long pos);
```

--------------------------------

### Function Signature

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_time_tell.html

The function signature for ov_time_tell.

```c
double ov_time_tell(OggVorbis_File *vf);
```

--------------------------------

### Function Declaration

Source: https://xiph.org/vorbis/doc/libvorbis/vorbis_bitrate_addblock.html

The C declaration for the vorbis_bitrate_addblock function.

```c
**
extern int      vorbis_bitrate_addblock(vorbis_block *vb);
**
```

--------------------------------

### Residue Decode Header - Step 1-5

Source: https://xiph.org/vorbis/doc/Vorbis_I_spec.html

Reads the initial header information for residue decoding, including begin, end, partition size, classifications, and classbook.

```pseudocode
1 1) [residue_begin] = read 24 bits as unsigned integer  
2 2) [residue_end] = read 24 bits as unsigned integer   
3 3) [residue_partition_size] = read 24 bits as unsigned integer and add one   
4 4) [residue_classifications] = read 6 bits as unsigned integer and add one  
5 5) [residue_classbook] = read 8 bits as unsigned integer
```

--------------------------------

### Step 2: Curve Synthesis

Source: https://xiph.org/vorbis/doc/Vorbis_I_spec.html

Algorithm for generating the final floor curve using synthesized amplitude values and step flags.

```pseudocode
1 1) [hx] = 0  
2 2) [lx] = 0  
3 3) [ly] = vector [floor1_final_Y]’ element [0] * [floor1_multiplier]   
4 4) iterate [i] over the range 1 ... [floor1_values]-1 {  
5  
6 5) if ( [floor1_step2_flag]’ element [i] is set ) {  
7   
8 6) [hy] = [floor1_final_Y]’ element [i] * [floor1_multiplier]  
9 7) [hx] = [floor1_X_list]’ element [i]   
10 8) render_line( [lx], [ly], [hx], [hy], [floor] )  
11 9) [lx] = [hx]  

```

--------------------------------

### ov_test function signature

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_test.html

The function signature for ov_test.

```c
#
int ov_test(FILE *f,OggVorbis_File *vf,char *initial,long ibytes);
#
```

--------------------------------

### ov_info function signature

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_info.html

The C function signature for ov_info.

```c
**
vorbis_info *ov_info(OggVorbis_File *vf,int link);
**
```

--------------------------------

### Function Declaration

Source: https://xiph.org/vorbis/doc/libvorbis/vorbis_info_blocksize.html

The C function declaration for vorbis_info_blocksize.

```c
**
extern int      vorbis_info_blocksize(vorbis_info *vi,int zo);
**
```

--------------------------------

### vorbis_bitrate_flushpacket declaration

Source: https://xiph.org/vorbis/doc/libvorbis/vorbis_bitrate_flushpacket.html

The C declaration for the vorbis_bitrate_flushpacket function.

```c
**
extern int      vorbis_bitrate_flushpacket(vorbis_dsp_state *vd,
                                           ogg_packet *op);
**
```

--------------------------------

### Function Signature

Source: https://xiph.org/vorbis/doc/vorbisfile/ov_clear.html

The C function signature for ov_clear.

```c
#
int ov_clear(OggVorbis_File *vf);
#
```

--------------------------------

### Packet Decode Steps

Source: https://xiph.org/vorbis/doc/Vorbis_I_spec.html

Step-by-step process for decoding a floor 0 curve from an audio packet.

```pseudocode
1 1) [amplitude] = read an unsigned integer of [floor0_amplitude_bits] bits  
2 2) if ( [amplitude] is greater than zero ) {   
3 3) [coefficients] is an empty, zero length vector  
4 4) [booknumber] = read an unsigned integer of ilog( [floor0_number_of_books] ) bits   
5 5) if ( [booknumber] is greater than the highest number decode codebook ) then packet is undecodable  
6 6) [last] = zero;   
7 7) vector [temp_vector] = read vector from bitstream using codebook number [floor0_book_list] element [booknumber] in VQ context.   
8 8) add the scalar value [last] to each scalar in vector [temp_vector]  
9 9) [last] = the value of the last scalar in vector [temp_vector]   
10 10) concatenate [temp_vector] onto the end of the [coefficients] vector   
11 11) if (length of vector [coefficients] is less than [floor0_order], continue at step 6  
12  
13 }  
14  
15 12) done.
```
Tokens:
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