cannam@86: cannam@86: cannam@86: cannam@86: libogg - Decoding cannam@86: cannam@86: cannam@86: cannam@86: cannam@86: cannam@86: cannam@86: cannam@86: cannam@86: cannam@86:

libogg documentation

libogg release 1.3.0 - 20110804

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Decoding

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Libogg contains a set of functions used in the decoding process. cannam@86:

cannam@86: All the libogg specific functions are declared in "ogg/ogg.h". cannam@86:

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Decoding is based around the ogg synchronization layer. The ogg_sync_state struct coordinates between incoming data and the decoder. We read data into the synchronization layer, submit the data to the stream, and output raw packets to the decoder. cannam@86:

Decoding through the Ogg layer follows a specific logical sequence. A read loop follows these logical steps: cannam@86:

Expose a buffer using ogg_sync_buffer(). cannam@86:
Read data into the buffer, using fread() or a similar function. cannam@86:
Call ogg_sync_wrote() to tell the synchronization layer how many bytes you wrote into the buffer. cannam@86:
Write out the data using ogg_sync_pageout. cannam@86:
Submit the completed page to the streaming layer with ogg_stream_pagein. cannam@86:
Output a packet of data to the codec-specific decoding layer using ogg_stream_packetout. cannam@86:

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In practice, streams are more complex, and Ogg also must handle headers, incomplete or dropped pages, and other errors in input. cannam@86:

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function purpose
ogg_sync_init Initializes an Ogg bitstream.
ogg_sync_clear Clears the status information from the synchronization struct. cannam@86:
ogg_sync_reset Resets the synchronization status to initial values.
ogg_sync_destroy Frees the synchronization struct.
ogg_sync_check Check for asynchronous errors.
ogg_sync_buffer Exposes a buffer from the synchronization layer in order to read data.
ogg_sync_wrote Tells the synchronization layer how many bytes were written into the buffer.
ogg_sync_pageseek Finds the borders of pages and resynchronizes the stream.
ogg_sync_pageout Outputs a page from the synchronization layer.
ogg_stream_pagein Submits a complete page to the stream layer.
ogg_stream_packetout Outputs a packet to the codec-specific decoding engine.
ogg_stream_packetpeek Provides access to the next packet in the bitstream without cannam@86: advancing decoding.
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copyright © 2000-2011 Xiph.Org	Ogg Container Format
libogg documentation	libogg release 1.3.0 - 20110804

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function	purpose
ogg_sync_init	Initializes an Ogg bitstream.
ogg_sync_clear	Clears the status information from the synchronization struct.	cannam@86:
ogg_sync_reset	Resets the synchronization status to initial values.
ogg_sync_destroy	Frees the synchronization struct.
ogg_sync_check	Check for asynchronous errors.
ogg_sync_buffer	Exposes a buffer from the synchronization layer in order to read data.
ogg_sync_wrote	Tells the synchronization layer how many bytes were written into the buffer.
ogg_sync_pageseek	Finds the borders of pages and resynchronizes the stream.
ogg_sync_pageout	Outputs a page from the synchronization layer.
ogg_stream_pagein	Submits a complete page to the stream layer.
ogg_stream_packetout	Outputs a packet to the codec-specific decoding engine.
ogg_stream_packetpeek	Provides access to the next packet in the bitstream without cannam@86: advancing decoding.