ov_read()

declared in "vorbis/vorbisfile.h";

This is the main function used to decode a Vorbis file within a loop.

This function deals with more complicated bitstream chaining issues. Up to this point, everything could more or less hide the multiple logical bitstream nature of chaining from the toplevel application if the toplevel application didn't particularly care. However, when we actually read audio back, we must be aware that multiple bitstream sections do not necessarily have to have the same number of channels or sampling rate.

ov_read() passes back the index of the sequential logical bitstream currently being decoded along with the PCM data in order that the toplevel application can take action on channel/sample rate changes. This number will be incremented at chaining boundaries even for non-seekable streams. For seekable streams, it represents the actual chaining index within the physical bitstream. ov_read() passes back the logical bitstream number currently being decoded along with the PCM data in order that the toplevel application can take action on channel/sample rate changes.

long ov_read(OggVorbis_File *vf, char *buffer, int length, int bigendianp, int word, int sgned, int *bitstream);

Parameters

vf

A pointer to the OggVorbis_File structure--this is used for ALL the externally visible vorbisfile functions.

buffer

A pointer to an output buffer. The decoded output is inserted into this buffer.

length

Number of bytes to be read into the buffer. Should be the same size as the buffer. A typical value is 4096.

bigendianp

Specifies big or little endian byte packing. 0 for little endian, 1 for big endian. Typical value is 0.

word

Specifies word size. Possible arguments are 1 for 8-bit samples, or 2 or 16-bit samples. Typical value is 2.

sgned

Signed or unsigned data. 0 for unsigned, 1 for signed. Typically 1.

bitstream

A pointer to the number of the current logical bitstream.

Return Values

OV_HOLE

indicates there was an interruption in the data.
(one of: garbage between pages, loss of sync followed by recapture, or a corrupt page)

OV_EBADLINK

indicates that an invalid stream section was supplied to libvorbisfile, or the requested link is corrupt.

0

indicates EOF

n

indicates actual number of bytes read. ov_read() will decode at most one vorbis packet per invocation, so the value returned will generally be less than length.

Notes

Typical usage:

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