Compressed stream support

Compressed stream support. More...

Data Structures
struct	gavl_compression_info_t
	Compression format. More...
struct	gavl_packet_t
	Packet structure. More...
Defines
#define	GAVL_COMPRESSION_HAS_P_FRAMES   (1<<0)
	Not all frames are keyframes.
#define	GAVL_COMPRESSION_HAS_B_FRAMES   (1<<1)
	Frames don't appear in presentation order.
#define	GAVL_COMPRESSION_HAS_FIELD_PICTURES   (1<<2)
	Packets can consist of 2 consecutive fields.
#define	GAVL_COMPRESSION_SBR   (1<<3)
	Samplerate got doubled by decoder, format and sample counts are for the upsampled rate.
#define	GAVL_PACKET_TYPE_I   'I'
	Packet is an I-frame.
#define	GAVL_PACKET_TYPE_P   'P'
	Packet is a P-frame.
#define	GAVL_PACKET_TYPE_B   'B'
	Packet is a B-frame.
#define	GAVL_PACKET_TYPE_MASK   0xff
	Mask for frame type.
#define	GAVL_PACKET_KEYFRAME   (1<<8)
	Packet is a keyframe.
#define	GAVL_PACKET_LAST   (1<<9)
	Packet is the last in the stream (only Xiph codecs need this flag).
Enumerations
enum	gavl_codec_id_t {   GAVL_CODEC_ID_NONE = 0,   GAVL_CODEC_ID_ALAW = 1,   GAVL_CODEC_ID_ULAW,   GAVL_CODEC_ID_MP2,   GAVL_CODEC_ID_MP3,   GAVL_CODEC_ID_AC3,   GAVL_CODEC_ID_AAC,   GAVL_CODEC_ID_VORBIS,   GAVL_CODEC_ID_FLAC,   GAVL_CODEC_ID_JPEG = 0x10000,   GAVL_CODEC_ID_PNG,   GAVL_CODEC_ID_TIFF,   GAVL_CODEC_ID_TGA,   GAVL_CODEC_ID_MPEG1,   GAVL_CODEC_ID_MPEG2,   GAVL_CODEC_ID_MPEG4_ASP,   GAVL_CODEC_ID_H264,   GAVL_CODEC_ID_THEORA,   GAVL_CODEC_ID_DIRAC,   GAVL_CODEC_ID_DV }
	Codec ID. More...
Functions
GAVL_PUBLIC void	gavl_compression_info_free (gavl_compression_info_t *info)
	Free all dynamically allocated memory of a compression info.
GAVL_PUBLIC void	gavl_compression_info_dump (const gavl_compression_info_t *info)
	Dump a compression info to stderr.
GAVL_PUBLIC void	gavl_compression_info_copy (gavl_compression_info_t *dst, const gavl_compression_info_t *src)
	Copy a compression info.
GAVL_PUBLIC const char *	gavl_compression_get_extension (gavl_codec_id_t id, int *separate)
	Get the file extension of the corresponding raw format.
GAVL_PUBLIC int	gavl_compression_need_pixelformat (gavl_codec_id_t id)
	Check if the compression supports multiple pixelformats.
GAVL_PUBLIC int	gavl_compression_constant_frame_samples (gavl_codec_id_t id)
	Check if an audio compression constant frame samples.
GAVL_PUBLIC void	gavl_packet_alloc (gavl_packet_t *p, int len)
	Allocate memory for a packet.
GAVL_PUBLIC void	gavl_packet_free (gavl_packet_t *p)
	Free memory of a packet.
GAVL_PUBLIC void	gavl_packet_dump (const gavl_packet_t *p)
	Dump a packet to stderr.

---

Detailed Description

Compressed stream support.

gavl provides some structures and functions for handling compressed data packets. It is a completely independent API layer and has nothing to do with the uncompressed video and audio API. In particular the conversion between compressed and uncompressed data (i.e. codecs) are outside the scope of gavl. These are implemented in gmerlin-avdecoder and gmerlin encoding plugins.

---

Define Documentation

#define GAVL_COMPRESSION_HAS_P_FRAMES   (1<<0)

Not all frames are keyframes.

#define GAVL_COMPRESSION_HAS_B_FRAMES   (1<<1)

Frames don't appear in presentation order.

#define GAVL_COMPRESSION_HAS_FIELD_PICTURES   (1<<2)

Packets can consist of 2 consecutive fields.

#define GAVL_COMPRESSION_SBR   (1<<3)

Samplerate got doubled by decoder, format and sample counts are for the upsampled rate.

#define GAVL_PACKET_TYPE_I   'I'

Packet is an I-frame.

#define GAVL_PACKET_TYPE_P   'P'

Packet is a P-frame.

#define GAVL_PACKET_TYPE_B   'B'

Packet is a B-frame.

#define GAVL_PACKET_TYPE_MASK   0xff

Mask for frame type.

#define GAVL_PACKET_KEYFRAME   (1<<8)

Packet is a keyframe.

#define GAVL_PACKET_LAST   (1<<9)

Packet is the last in the stream (only Xiph codecs need this flag).

---

Enumeration Type Documentation

enum gavl_codec_id_t

Codec ID.

These are used as identifiers for the type of compression

Enumerator:

GAVL_CODEC_ID_NONE	Unknown/unsupported compression format.
GAVL_CODEC_ID_ALAW	alaw 2:1
GAVL_CODEC_ID_ULAW	mu-law 2:1
GAVL_CODEC_ID_MP2	MPEG-1 audio layer II.
GAVL_CODEC_ID_MP3	MPEG-1/2 audio layer 3 CBR/VBR.
GAVL_CODEC_ID_AC3	AC3.
GAVL_CODEC_ID_AAC	AAC as stored in quicktime/mp4.
GAVL_CODEC_ID_VORBIS	Vorbis (segmented extradata and packets).
GAVL_CODEC_ID_FLAC	Flac (extradata contain a file header without comment and seektable).
GAVL_CODEC_ID_JPEG	JPEG image.
GAVL_CODEC_ID_PNG	PNG image.
GAVL_CODEC_ID_TIFF	TIFF image.
GAVL_CODEC_ID_TGA	TGA image.
GAVL_CODEC_ID_MPEG1	MPEG-1 video.
GAVL_CODEC_ID_MPEG2	MPEG-2 video.
GAVL_CODEC_ID_MPEG4_ASP	MPEG-4 ASP (a.k.a. Divx4).
GAVL_CODEC_ID_H264	H.264 (Annex B).
GAVL_CODEC_ID_THEORA	Theora (segmented extradata).
GAVL_CODEC_ID_DIRAC	Complete DIRAC frames, sequence end code appended to last packet.
GAVL_CODEC_ID_DV	DV (several variants).

---

Function Documentation

GAVL_PUBLIC void gavl_compression_info_free

(

gavl_compression_info_t *

info

)

Free all dynamically allocated memory of a compression info.

Parameters:

info

A compression info

GAVL_PUBLIC void gavl_compression_info_dump

(

const gavl_compression_info_t *

info

)

Dump a compression info to stderr.

Parameters:

info

A compression info

Use this for debugging

GAVL_PUBLIC void gavl_compression_info_copy	(	gavl_compression_info_t *	dst,
		const gavl_compression_info_t *	src
	)

Copy a compression info.

Parameters:

	dst	Destination
	src	Source

GAVL_PUBLIC const char* gavl_compression_get_extension	(	gavl_codec_id_t	id,
		int *	separate
	)

Get the file extension of the corresponding raw format.

Parameters:

	id	A codec ID
	separate	If non-null returns 1 if each packet should be in a separate file

Returns:

The file extension of the raw file or NULL

This function can be used for writing elementary streams to files. It returns a suitable file extension. If separate is 1, each packet should be written to a separate file. This basically means, that the codec corresponds to an image format.

Not all compression formats have a suitable elementary stream format, in this case NULL is returned for the extension. Most prominent examples are Vorbis and Theora, which can hardly exist outside an OGG container.

GAVL_PUBLIC int gavl_compression_need_pixelformat

(

gavl_codec_id_t

id

)

Check if the compression supports multiple pixelformats.

Parameters:

id

A codec ID

Returns:

1 if the compression ID must be associated with a pixelformat, 0 else

This function can be used by decoding libraries to check if the compresison ID is sufficient or if the pixelformat must be valid in the associated video format.

GAVL_PUBLIC int gavl_compression_constant_frame_samples

(

gavl_codec_id_t

id

)

Check if an audio compression constant frame samples.

Parameters:

id

A codec ID

Returns:

1 if the compression has the same number of samples in each frame, 0 else

GAVL_PUBLIC void gavl_packet_alloc	(	gavl_packet_t *	p,
		int	len
	)

Allocate memory for a packet.

Parameters:

	p	A packet
	len	Number of bytes you want to store in the packet

This function uses realloc(), which means that it preserves the data already contained in the packet.

GAVL_PUBLIC void gavl_packet_free

(

gavl_packet_t *

p

)

Free memory of a packet.

Parameters:

p

A packet

GAVL_PUBLIC void gavl_packet_dump

(

const gavl_packet_t *

p

)

Dump a packet to stderr.

Parameters:

p

A packet

Use this for debugging