## mpeg4parser mpeg4parser — Convenience library for parsing mpeg4 part 2 video bitstream. |

## Synopsis

    #include <gst/codecparsers/gstmpeg4parser.h>

    enum                GstMpeg4StartCode;
    enum                GstMpeg4VisualObjectType;
    enum                GstMpeg4AspectRatioInfo;
    enum                GstMpeg4ParseResult;
    enum                GstMpeg4VideoObjectCodingType;
    enum                GstMpeg4ChromaFormat;
    enum                GstMpeg4VideoObjectLayerShape;
    enum                GstMpeg4SpriteEnable;
    enum                GstMpeg4Profile;
    enum                GstMpeg4Level;
    struct              GstMpeg4VisualObjectSequence;
    struct              GstMpeg4VisualObject;
    struct              GstMpeg4VideoSignalType;
    struct              GstMpeg4VideoPlaneShortHdr;
    struct              GstMpeg4VideoObjectLayer;
    struct              GstMpeg4SpriteTrajectory;
    struct              GstMpeg4GroupOfVOP;
    struct              GstMpeg4VideoObjectPlane;
    struct              GstMpeg4Packet;
    struct              GstMpeg4VideoPacketHdr;
    GstMpeg4ParseResult gst_mpeg4_parse                     (GstMpeg4Packet *packet,
                                                             gboolean skip_user_data,
                                                             GstMpeg4VideoObjectPlane *vop,
                                                             const guint8 *data,
                                                             guint offset,
                                                             gsize size);
    GstMpeg4ParseResult gst_mpeg4_parse_video_object_plane  (GstMpeg4VideoObjectPlane *vop,
                                                             GstMpeg4SpriteTrajectory *sprite_trajectory,
                                                             GstMpeg4VideoObjectLayer *vol,
                                                             const guint8 *data,
                                                             gsize size);
    GstMpeg4ParseResult gst_mpeg4_parse_group_of_vop        (GstMpeg4GroupOfVOP *gov,
                                                             const guint8 *data,
                                                             gsize size);
    GstMpeg4ParseResult gst_mpeg4_parse_video_object_layer  (GstMpeg4VideoObjectLayer *vol,
                                                             GstMpeg4VisualObject *vo,
                                                             const guint8 *data,
                                                             gsize size);
    GstMpeg4ParseResult gst_mpeg4_parse_visual_object       (GstMpeg4VisualObject *vo,
                                                             GstMpeg4VideoSignalType *signal_type,
                                                             const guint8 *data,
                                                             gsize size);
    GstMpeg4ParseResult gst_mpeg4_parse_visual_object_sequence
                                                            (GstMpeg4VisualObjectSequence *vos,
                                                             const guint8 *data,
                                                             gsize size);
    GstMpeg4ParseResult gst_mpeg4_parse_video_packet_header (GstMpeg4VideoPacketHdr *videopackethdr,
                                                             GstMpeg4VideoObjectLayer *vol,
                                                             GstMpeg4VideoObjectPlane *vop,
                                                             GstMpeg4SpriteTrajectory *sprite_trajectory,
                                                             const guint8 *data,
                                                             gsize size);

## Description

For more details about the structures, you can refer to the specifications: ISO-IEC-14496-2_2004_MPEG4_VISUAL.pdf

## Details

### enum GstMpeg4StartCode

    typedef enum {
      GST_MPEG4_VIDEO_OBJ_FIRST      = 0x00,
      GST_MPEG4_VIDEO_OBJ_LAST       = 0x1f,
      GST_MPEG4_VIDEO_LAYER_FIRST    = 0x20,
      GST_MPEG4_VIDEO_LAYER_LAST     = 0x2f,
      GST_MPEG4_VISUAL_OBJ_SEQ_START = 0xb0,
      GST_MPEG4_VISUAL_OBJ_SEQ_END   = 0xb1,
      GST_MPEG4_USER_DATA            = 0xb2,
      GST_MPEG4_GROUP_OF_VOP         = 0xb3,
      GST_MPEG4_VIDEO_SESSION_ERR    = 0xb4,
      GST_MPEG4_VISUAL_OBJ           = 0xb5,
      GST_MPEG4_VIDEO_OBJ_PLANE      = 0xb6,
      GST_MPEG4_FBA                  = 0xba,
      GST_MPEG4_FBA_PLAN             = 0xbb,
      GST_MPEG4_MESH                 = 0xbc,
      GST_MPEG4_MESH_PLAN            = 0xbd,
      GST_MPEG4_STILL_TEXTURE_OBJ    = 0xbe,
      GST_MPEG4_TEXTURE_SPATIAL      = 0xbf,
      GST_MPEG4_TEXTURE_SNR_LAYER    = 0xc0,
      GST_MPEG4_TEXTURE_TILE         = 0xc1,
      GST_MPEG4_SHAPE_LAYER          = 0xc2,
      GST_MPEG4_STUFFING             = 0xc3,
      GST_MPEG4_SYSTEM_FIRST         = 0xc6,
      GST_MPEG4_SYSTEM_LAST          = 0xff,
      GST_MPEG4_RESYNC               = 0xfff
    } GstMpeg4StartCode;

Defines the different startcodes present in the bitstream as defined in: Table 6-3 — Start code values

### enum GstMpeg4VisualObjectType

    typedef enum {
      GST_MPEG4_VIDEO_ID         = 0x01,
      GST_MPEG4_STILL_TEXTURE_ID = 0x02,
      GST_MPEG4_STILL_MESH_ID    = 0x03,
      GST_MPEG4_STILL_FBA_ID     = 0x04,
      GST_MPEG4_STILL_3D_MESH_ID = 0x05,
      /*... reserved */
    } GstMpeg4VisualObjectType;

Defines the different visual object types as defined in: Table 6-5 -- Meaning of visual object type

### enum GstMpeg4AspectRatioInfo

    typedef enum {
      GST_MPEG4_SQUARE        = 0x01,
      GST_MPEG4_625_TYPE_4_3  = 0x02,
      GST_MPEG4_525_TYPE_4_3  = 0x03,
      GST_MPEG4_625_TYPE_16_9 = 0x04,
      GST_MPEG4_525_TYPE_16_9 = 0x05,
      GST_MPEG4_EXTENDED_PAR  = 0x0f,
    } GstMpeg4AspectRatioInfo;

Defines the different pixel aspect ratios as defined in: Table 6-12 -- Meaning of pixel aspect ratio

`GST_MPEG4_SQUARE` | 1:1 square
`GST_MPEG4_625_TYPE_4_3` | 12:11 (625-type for 4:3 picture)
`GST_MPEG4_525_TYPE_4_3` | 10:11 (525-type for 4:3 picture)
`GST_MPEG4_625_TYPE_16_9` | 16:11 (625-type stretched for 16:9 picture)
`GST_MPEG4_525_TYPE_16_9` | 40:33 (525-type stretched for 16:9 picture)
`GST_MPEG4_EXTENDED_PAR` | Extended par

### enum GstMpeg4ParseResult

    typedef enum {
      GST_MPEG4_PARSER_OK,
      GST_MPEG4_PARSER_BROKEN_DATA,
      GST_MPEG4_PARSER_NO_PACKET,
      GST_MPEG4_PARSER_NO_PACKET_END,
      GST_MPEG4_PARSER_ERROR,
    } GstMpeg4ParseResult;

Result type of any parsing function.

`GST_MPEG4_PARSER_OK` | The parsing went well
`GST_MPEG4_PARSER_BROKEN_DATA` | The bitstream was broken
`GST_MPEG4_PARSER_NO_PACKET` | There was no packet in the buffer
`GST_MPEG4_PARSER_NO_PACKET_END` | There was no packet end in the buffer
`GST_MPEG4_PARSER_ERROR` |

### enum GstMpeg4VideoObjectCodingType

    typedef enum {
      GST_MPEG4_I_VOP = 0x0,
      GST_MPEG4_P_VOP = 0x1,
      GST_MPEG4_B_VOP = 0x2,
      GST_MPEG4_S_VOP = 0x3
    } GstMpeg4VideoObjectCodingType;

The vop coding types as defined in: Table 6-20 -- Meaning of vop_coding_type

`GST_MPEG4_I_VOP` | intra-coded (I)
`GST_MPEG4_P_VOP` | predictive-coded (P)
`GST_MPEG4_B_VOP` | bidirectionally-predictive-coded (B)
`GST_MPEG4_S_VOP` | sprite (S)

### enum GstMpeg4ChromaFormat

    typedef enum {
      /* Other value are reserved */
      GST_MPEG4_CHROMA_4_2_0 = 0x01
    } GstMpeg4ChromaFormat;

The chroma format in use as defined in: Table 6-13 -- Meaning of chroma_format

### enum GstMpeg4VideoObjectLayerShape

    typedef enum {
      GST_MPEG4_RECTANGULAR,
      GST_MPEG4_BINARY,
      GST_MPEG4_BINARY_ONLY,
      GST_MPEG4_GRAYSCALE
    } GstMpeg4VideoObjectLayerShape;

The different video object layer shapes as defined in: Table 6-16 — Video Object Layer shape type

### enum GstMpeg4SpriteEnable

    typedef enum {
      GST_MPEG4_SPRITE_UNUSED,
      GST_MPEG4_SPRITE_STATIC,
      GST_MPEG4_SPRITE_GMG
    } GstMpeg4SpriteEnable;

Indicates the usage of static sprite coding or global motion compensation (GMC) as defined in: Table V2 - 2 -- Meaning of sprite_enable codewords

### enum GstMpeg4Profile

    typedef enum {
      GST_MPEG4_PROFILE_CORE,
      GST_MPEG4_PROFILE_MAIN,
      GST_MPEG4_PROFILE_N_BIT,
      GST_MPEG4_PROFILE_SIMPLE,
      GST_MPEG4_PROFILE_HYBRID,
      GST_MPEG4_PROFILE_RESERVED,
      GST_MPEG4_PROFILE_SIMPLE_FBA,
      GST_MPEG4_PROFILE_CORE_STUDIO,
      GST_MPEG4_PROFILE_SIMPLE_STUDIO,
      GST_MPEG4_PROFILE_CORE_SCALABLE,
      GST_MPEG4_PROFILE_ADVANCED_CORE,
      GST_MPEG4_PROFILE_ADVANCED_SIMPLE,
      GST_MPEG4_PROFILE_SIMPLE_SCALABLE,
      GST_MPEG4_PROFILE_SCALABLE_TEXTURE,
      GST_MPEG4_PROFILE_SIMPLE_FACE_ANIMATION,
      GST_MPEG4_PROFILE_BASIC_ANIMATED_TEXTURE,
      GST_MPEG4_PROFILE_ADVANCED_REALTIME_SIMPLE,
      GST_MPEG4_PROFILE_ADVANCED_SCALABLE_TEXTURE,
      GST_MPEG4_PROFILE_FINE_GRANULARITY_SCALABLE,
      GST_MPEG4_PROFILE_ADVANCED_CODING_EFFICIENCY
    } GstMpeg4Profile;

Different defined profiles as defined in: 9- Profiles and levels

It is computed using: Table G.1 — FLC table for profile_and_level_indication

### enum GstMpeg4Level

    typedef enum {
      GST_MPEG4_LEVEL0,
      GST_MPEG4_LEVEL1,
      GST_MPEG4_LEVEL2,
      GST_MPEG4_LEVEL3,
      GST_MPEG4_LEVEL3b,
      GST_MPEG4_LEVEL4,
      GST_MPEG4_LEVEL5,
      GST_MPEG4_LEVEL_RESERVED
    } GstMpeg4Level;

Different levels as defined in: 9- Profiles and levels

It is computed using: Table G.1 — FLC table for profile_and_level_indication

### struct GstMpeg4VisualObjectSequence

    struct GstMpeg4VisualObjectSequence {
      guint8 profile_and_level_indication;

      /* Computed according to:
       * Table G.1 — FLC table for profile_and_level_indication */
      GstMpeg4Level level;
      GstMpeg4Profile profile;
    };

The visual object sequence structure as defined in: 6.2.2 Visual Object Sequence and Visual Object

### struct GstMpeg4VisualObject

    struct GstMpeg4VisualObject {
      guint8 is_identifier;
      /* If is_identifier */
      guint8 verid;
      guint8 priority;

      GstMpeg4VisualObjectType type;
    };

### struct GstMpeg4VideoSignalType

    struct GstMpeg4VideoSignalType {
      guint8 type;

      guint8 format;
      guint8 range;
      guint8 color_description;
      guint8 color_primaries;
      guint8 transfer_characteristics;
      guint8 matrix_coefficients;
    };

The video signal type structure as defined in: 6.2.2 Visual Object Sequence and Visual Object.

### struct GstMpeg4VideoPlaneShortHdr

    struct GstMpeg4VideoPlaneShortHdr {
      guint8 temporal_reference;
      guint8 split_screen_indicator;
      guint8 document_camera_indicator;
      guint8 full_picture_freeze_release;
      guint8 source_format;
      guint8 picture_coding_type;
      guint8 vop_quant;
      guint8 pei;
      guint8 psupp;

      /*  Gob layer specific fields */
      guint8 gob_header_empty;
      guint8 gob_number;
      guint8 gob_frame_id;
      guint8 quant_scale;

      /* Computed
       * If all the values are set to 0, then it is reserved
       * Table 6-25 -- Parameters Defined by source_format Field
       */
      guint16 vop_width;
      guint16 vop_height;
      guint16 num_macroblocks_in_gob;
      guint8 num_gobs_in_vop;

      /* The size in bits */
      guint size;
    };

The video plane short header structure as defined in: 6.2.5.2 Video Plane with Short Header

### struct GstMpeg4VideoObjectLayer

    struct GstMpeg4VideoObjectLayer {
      guint8 random_accessible_vol;
      guint8 video_object_type_indication;

      guint8 is_object_layer_identifier;
      /* if is_object_layer_identifier */
      guint8 verid;
      guint8 priority;

      GstMpeg4AspectRatioInfo aspect_ratio_info;
      guint8 par_width;
      guint8 par_height;

      guint8 control_parameters;
      /* if control_parameters */
      GstMpeg4ChromaFormat chroma_format;
      guint8 low_delay;
      guint8 vbv_parameters;
      /* if vbv_parameters */
      guint16 first_half_bitrate;
      guint16 latter_half_bitrate;
      guint16 first_half_vbv_buffer_size;
      guint16 latter_half_vbv_buffer_size;
      guint16 first_half_vbv_occupancy;
      guint16 latter_half_vbv_occupancy;

      /* Computed values */
      guint32 bit_rate;
      guint32 vbv_buffer_size;

      GstMpeg4VideoObjectLayerShape shape;
      /* if shape == GST_MPEG4_GRAYSCALE && verid =! 1 */
      guint8 shape_extension;

      guint16 vop_time_increment_resolution;
      guint8 vop_time_increment_bits;
      guint8 fixed_vop_rate;
      /* if fixed_vop_rate */
      guint16 fixed_vop_time_increment;

      guint16 width;
      guint16 height;
      guint8 interlaced;
      guint8 obmc_disable;

      GstMpeg4SpriteEnable sprite_enable;
      /* if vol->sprite_enable == SPRITE_GMG or SPRITE_STATIC*/
      /* if vol->sprite_enable != GST_MPEG4_SPRITE_GMG */
      guint16 sprite_width;
      guint16 sprite_height;
      guint16 sprite_left_coordinate;
      guint16 sprite_top_coordinate;

      guint8 no_of_sprite_warping_points;
      guint8 sprite_warping_accuracy;
      guint8 sprite_brightness_change;
      /* if vol->sprite_enable != GST_MPEG4_SPRITE_GMG */
      guint8 low_latency_sprite_enable;

      /* if shape != GST_MPEG4_RECTANGULAR */
      guint8 sadct_disable;

      guint8 not_8_bit;

      /* if no_8_bit */
      guint8 quant_precision;
      guint8 bits_per_pixel;

      /* if shape == GRAYSCALE */
      guint8 no_gray_quant_update;
      guint8 composition_method;
      guint8 linear_composition;

      guint8 quant_type;
      /* if quant_type */
      guint8 load_intra_quant_mat;
      guint8 intra_quant_mat[64];
      guint8 load_non_intra_quant_mat;
      guint8 non_intra_quant_mat[64];

      guint8 quarter_sample;
      guint8 complexity_estimation_disable;
      guint8 resync_marker_disable;
      guint8 data_partitioned;
      guint8 reversible_vlc;
      guint8 newpred_enable;
      guint8 reduced_resolution_vop_enable;
      guint8 scalability;
      guint8 enhancement_type;

      GstMpeg4VideoPlaneShortHdr short_hdr;
    };

The video object layer structure as defined in: 6.2.3 Video Object Layer

### struct GstMpeg4SpriteTrajectory

    struct GstMpeg4SpriteTrajectory {
      guint16 vop_ref_points[63]; /* Defined as "du" in 6.2.5.4 */
      guint16 sprite_ref_points[63]; /* Defined as "dv" in 6.2.5.4 */
    };

The sprite trajectory structure as defined in: 7.8.4 Sprite reference point decoding and 6.2.5.4 Sprite coding

### struct GstMpeg4GroupOfVOP

    struct GstMpeg4GroupOfVOP {
      guint8 hours;
      guint8 minutes;
      guint8 seconds;

      guint8 closed;
      guint8 broken_link;
    };

The group of video object plane structure as defined in: 6.2.4 Group of Video Object Plane

### struct GstMpeg4VideoObjectPlane

    struct GstMpeg4VideoObjectPlane {
      GstMpeg4VideoObjectCodingType coding_type;

      guint8  modulo_time_base;
      guint16 time_increment;

      guint8  coded;
      /* if newpred_enable */
      guint16 id;
      guint8  id_for_prediction_indication;
      guint16 id_for_prediction;

      guint16 width;
      guint16 height;
      guint16 horizontal_mc_spatial_ref;
      guint16 vertical_mc_spatial_ref;

      guint8  rounding_type;
      /*if vol->shape != GST_MPEG4_RECTANGULAR */
      guint8  background_composition;
      guint8  change_conv_ratio_disable;
      guint8  constant_alpha;
      guint8  constant_alpha_value;
      guint8  reduced_resolution;

      guint8  intra_dc_vlc_thr;

      guint8  top_field_first;
      guint8  alternate_vertical_scan_flag;

      guint16 quant;

      guint8  fcode_forward;
      guint8  fcode_backward;

      guint8  shape_coding_type;
      guint8  load_backward_shape;
      guint8  ref_select_code;

      /* Computed macroblock informations */
      guint16 mb_height;
      guint16 mb_width;
      guint mb_num;

      /* The size of the header */
      guint    size;
    };

The Video object plane structure as defined in: 6.2.5 Video Object Plane and Video Plane with Short Header

### struct GstMpeg4Packet

    struct GstMpeg4Packet {
      const guint8     *data;
      guint             offset;
      gsize             size;
      guint             marker_size;

      GstMpeg4StartCode type;
    };

A structure that contains the type of a packet, its offset and its size

const guint8 *`data`; | the data of the packet, statring at `offset`
guint `offset`; | offset of the start of the packet (without the 3 bytes startcode), but including the GstMpeg4StartCode byte.
gsize `size`; | The size in bytes of the packet or `G_MAXUINT` if the end wasn't found.
guint `marker_size`; | The size in bit of the resync marker.
GstMpeg4StartCode `type`; | the type of the packet that start at `offset`

### struct GstMpeg4VideoPacketHdr

    struct GstMpeg4VideoPacketHdr {
      guint8  header_extension_code;
      guint16 macroblock_number;
      guint16 quant_scale;
      guint   size;
    };

The video packet header structure as defined in: 6.2.5.2 Video Plane with Short Header

guint8 `header_extension_code`; |
guint16 `macroblock_number`; |
guint16 `quant_scale`; |
guint `size`; | Size of the header in bit.

### gst_mpeg4_parse ()

    GstMpeg4ParseResult gst_mpeg4_parse                     (GstMpeg4Packet *packet,
                                                             gboolean skip_user_data,
                                                             GstMpeg4VideoObjectPlane *vop,
                                                             const guint8 *data,
                                                             guint offset,
                                                             gsize size);

Parses `data` and fills `packet` with the information of the next packet found.

`packet` : | The GstMpeg4Packet to fill
`skip_user_data` : | `TRUE` to skip user data packet `FALSE` otherwize
`vop` : | The last parsed GstMpeg4VideoObjectPlane or `NULL` if you do not need to detect the resync codes.
`offset` : | offset from which to start the parsing
`data` : | The data to parse
`size` : | The size of the `data` to parse
Returns : | a GstMpeg4ParseResult

### gst_mpeg4_parse_video_object_plane ()

    GstMpeg4ParseResult gst_mpeg4_parse_video_object_plane  (GstMpeg4VideoObjectPlane *vop,
                                                             GstMpeg4SpriteTrajectory *sprite_trajectory,
                                                             GstMpeg4VideoObjectLayer *vol,
                                                             const guint8 *data,
                                                             gsize size);

Parses `data` containing the video object plane packet, and fills the `vol` structure.

`vop` : | The GstMpeg4VideoObjectPlane currently being parsed
`sprite_trajectory` : | A GstMpeg4SpriteTrajectory to fill or `NULL`
`vol` : | The GstMpeg4VideoObjectLayer structure to fill
`data` : | The data to parse
`size` : | The size of the `data` to parse
Returns : | a GstMpeg4ParseResult

### gst_mpeg4_parse_group_of_vop ()

    GstMpeg4ParseResult gst_mpeg4_parse_group_of_vop        (GstMpeg4GroupOfVOP *gov,
                                                             const guint8 *data,
                                                             gsize size);

Parses `data` containing the group of video object plane packet, and fills the `gov` structure.

`gov` : | The GstMpeg4GroupOfVOP structure to fill
`data` : | The data to parse
`size` : | The size of the `data` to parse
Returns : | a GstMpeg4ParseResult

### gst_mpeg4_parse_video_object_layer ()

    GstMpeg4ParseResult gst_mpeg4_parse_video_object_layer  (GstMpeg4VideoObjectLayer *vol,
                                                             GstMpeg4VisualObject *vo,
                                                             const guint8 *data,
                                                             gsize size);

Parses `data` containing the video object layer packet, and fills the `vol` structure.

`vol` : | The GstMpeg4VideoObjectLayer structure to fill
`vo` : | The GstMpeg4VisualObject currently being parsed or `NULL`
`data` : | The data to parse
`size` : | The size of the `data` to parse
Returns : | a GstMpeg4ParseResult

### gst_mpeg4_parse_visual_object ()

    GstMpeg4ParseResult gst_mpeg4_parse_visual_object       (GstMpeg4VisualObject *vo,
                                                             GstMpeg4VideoSignalType *signal_type,
                                                             const guint8 *data,
                                                             gsize size);

Parses `data` containing the visual object packet, and fills the `vo` structure.

`vo` : | The GstMpeg4VisualObject structure to fill
`signal_type` : | The GstMpeg4VideoSignalType to fill or `NULL`
`data` : | The data to parse, should contain the vo_start_code but not the start code prefix
`size` : | The size of the `data` to parse
Returns : | a GstMpeg4ParseResult

### gst_mpeg4_parse_visual_object_sequence ()

    GstMpeg4ParseResult gst_mpeg4_parse_visual_object_sequence
                                                            (GstMpeg4VisualObjectSequence *vos,
                                                             const guint8 *data,
                                                             gsize size);

Parses `data` containing the visual object sequence packet, and fills the `vos` structure.

`vos` : | The GstMpeg4VisualObjectSequence structure to fill
`data` : | The data to parse, should contain the visual_object_sequence_start_code but not the start code prefix
`size` : | The size of the `data` to parse
Returns : | a GstMpeg4ParseResult

### gst_mpeg4_parse_video_packet_header ()

    GstMpeg4ParseResult gst_mpeg4_parse_video_packet_header (GstMpeg4VideoPacketHdr *videopackethdr,
                                                             GstMpeg4VideoObjectLayer *vol,
                                                             GstMpeg4VideoObjectPlane *vop,
                                                             GstMpeg4SpriteTrajectory *sprite_trajectory,
                                                             const guint8 *data,
                                                             gsize size);

Parsers `data` containing the video packet header and fills the `videopackethdr` structure

`videopackethdr` : | The GstMpeg4VideoPacketHdr structure to fill
`vol` : | The last parsed GstMpeg4VideoObjectLayer, will be updated with the informations found during the parsing
`vop` : | The last parsed GstMpeg4VideoObjectPlane, will be updated with the informations found during the parsing
`sprite_trajectory` : | A GstMpeg4SpriteTrajectory to fill or `NULL` with the informations found during the parsing
`data` : | The data to parse, should be set after the resync marker.
`size` : | The size of the data to parse