GstJpegParser

Provides useful functions for parsing JPEG images

Functions

gst_jpeg_get_default_huffman_tables

void 
gst_jpeg_get_default_huffman_tables (GstJpegHuffmanTables * huff_tables)

Fills in huf_tables with the default AC/DC Huffman tables, as specified by the JPEG standard.

Parameters:

huff_tables
No description available
Returns (void )
No description available

Since : 1.6


gst_jpeg_get_default_quantization_tables

void 
gst_jpeg_get_default_quantization_tables (GstJpegQuantTables * quant_tables)

Parameters:

quant_tables
No description available
Returns (void )
No description available

gst_jpeg_parse

gboolean
gst_jpeg_parse (GstJpegSegment * seg,
                guint8* data,
                gsize size,
                guint offset)

Parses the JPEG bitstream contained in data, and returns the detected segment as a GstJpegSegment.

Note that a valid segment may be returned with a length that exceeds the available data. It is up to the caller to make sure there's enough data available when parsing the segment.

Parameters:

seg
No description available
data

The data to parse

size

The size of data

offset

The offset from which to start parsing

Returns (gboolean)

TRUE if a packet start code was found.

Since : 1.6


gst_jpeg_segment_parse_frame_header

gboolean
gst_jpeg_segment_parse_frame_header (GstJpegSegment * segment,
                                     GstJpegFrameHdr * frame_hdr)

Parses the frame_hdr JPEG frame header structure members from segment.

The caller must make sure there is enough data for the whole segment available.

Parameters:

segment

the JPEG segment

frame_hdr

The GstJpegFrameHdr structure to fill in

Returns (gboolean)

TRUE if the frame header was correctly parsed.

Since : 1.6


gst_jpeg_segment_parse_huffman_table

gboolean
gst_jpeg_segment_parse_huffman_table (GstJpegSegment * segment,
                                      GstJpegHuffmanTables * huff_tables)

Parses the JPEG Huffman table structure members from segment.

The caller must make sure there is enough data for the whole segment available.

Note: huf_tables represents the complete set of possible Huffman tables. However, the parser will only write to the Huffman table specified by the table destination identifier (Th). While doing so, the valid flag of the specified Huffman table will also be set to TRUE;

Parameters:

segment

the JPEG segment

huff_tables

The GstJpegHuffmanTables structure to fill in

Returns (gboolean)

TRUE if the Huffman table was correctly parsed.

Since : 1.6


gst_jpeg_segment_parse_quantization_table

gboolean
gst_jpeg_segment_parse_quantization_table (GstJpegSegment * segment,
                                           GstJpegQuantTables * quant_tables)

Parses the JPEG quantization table structure members from segment.

The caller must make sure there is enough data for the whole segment available.

Note: quant_tables represents the complete set of possible quantization tables. However, the parser will only write to the quantization table specified by the table destination identifier (Tq). While doing so, the valid flag of the specified quantization table will also be set to TRUE.

Parameters:

segment

the JPEG segment

quant_tables

The GstJpegQuantTables structure to fill in

Returns (gboolean)

TRUE if the quantization table was correctly parsed.

Since : 1.6


gst_jpeg_segment_parse_restart_interval

gboolean
gst_jpeg_segment_parse_restart_interval (GstJpegSegment * segment,
                                         guint* interval)

The caller must make sure there is enough data for the whole segment available.

Parameters:

segment

the JPEG segment

interval

The parsed restart interval value

Returns (gboolean)

TRUE if the restart interval value was correctly parsed.

Since : 1.6


gst_jpeg_segment_parse_scan_header

gboolean
gst_jpeg_segment_parse_scan_header (GstJpegSegment * segment,
                                    GstJpegScanHdr * scan_hdr)

Parses the scan_hdr JPEG scan header structure members from segment.

The caller must make sure there is enough data for the whole segment available.

Parameters:

segment

the JPEG segment

scan_hdr

The GstJpegScanHdr structure to fill in

Returns (gboolean)

TRUE if the scan header was correctly parsed

Since : 1.6


Structures

GstJpegFrameComponent

struct _GstJpegFrameComponent
{
  guint8 identifier;                    /* 0 .. 255     */
  guint8 horizontal_factor;             /* 1 .. 4       */
  guint8 vertical_factor;               /* 1 .. 4       */
  guint8 quant_table_selector;          /* 0 .. 3       */
};

Component-specification parameters.

Fields

identifier (guint8) –

Component identifier (Ci)

horizontal_factor (guint8) –

Horizontal sampling factor (Hi)

vertical_factor (guint8) –

Vertical sampling factor (Vi)

quant_table_selector (guint8) –

Quantization table destination selector (Tqi)

Since : 1.6


GstJpegFrameHdr

struct _GstJpegFrameHdr
{
  guint8 sample_precision;              /* 2 .. 16      */
  guint16 width;                        /* 1 .. 65535   */
  guint16 height;                       /* 0 .. 65535   */
  guint8 num_components;                /* 1 .. 255     */
  GstJpegFrameComponent components[GST_JPEG_MAX_FRAME_COMPONENTS];
};

Frame header.

Fields

sample_precision (guint8) –

Sample precision (P)

width (guint16) –

Number of samples per line (X)

height (guint16) –

Number of lines (Y)

num_components (guint8) –

Number of image components in frame (Nf)

components (GstJpegFrameComponent[256] ) –

Image components

Since : 1.6


GstJpegHuffmanTable

struct _GstJpegHuffmanTable
{
  guint8 huf_bits[16];
  guint8 huf_values[256];
  gboolean valid;
};

Huffman table.

Fields

huf_bits (guint8[16] ) –

Number of Huffman codes of length i + 1 (Li)

huf_values (guint8[256] ) –
No description available
valid (gboolean) –

If the Huffman table is valid, which means it has already been parsed

Since : 1.6


GstJpegHuffmanTables

struct _GstJpegHuffmanTables
{
  GstJpegHuffmanTable dc_tables[GST_JPEG_MAX_SCAN_COMPONENTS];
  GstJpegHuffmanTable ac_tables[GST_JPEG_MAX_SCAN_COMPONENTS];
};

Helper data structure that holds all AC/DC Huffman tables used to decode an image.

Fields

dc_tables (GstJpegHuffmanTable[4] ) –

DC Huffman tables

ac_tables (GstJpegHuffmanTable[4] ) –

AC Huffman tables

Since : 1.6


GstJpegQuantTable

struct _GstJpegQuantTable
{
  guint8 quant_precision;
  guint16 quant_table[GST_JPEG_MAX_QUANT_ELEMENTS];
  gboolean valid;
};

Quantization table.

Fields

quant_precision (guint8) –

Quantization table element precision (Pq)

quant_table (guint16[64] ) –

Quantization table elements (Qk)

valid (gboolean) –

If the quantization table is valid, which means it has already been parsed

Since : 1.6


GstJpegQuantTables

struct _GstJpegQuantTables
{
  GstJpegQuantTable quant_tables[GST_JPEG_MAX_SCAN_COMPONENTS];
};

Helper data structure that holds all quantization tables used to decode an image.

Fields

quant_tables (GstJpegQuantTable[4] ) –

All quantization tables

Since : 1.6


GstJpegScanComponent

struct _GstJpegScanComponent
{
    guint8 component_selector;          /* 0 .. 255     */
    guint8 dc_selector;                 /* 0 .. 3       */
    guint8 ac_selector;                 /* 0 .. 3       */
};

Component-specification parameters.

Fields

component_selector (guint8) –

Scan component selector (Csj)

dc_selector (guint8) –

DC entropy coding table destination selector (Tdj)

ac_selector (guint8) –

AC entropy coding table destination selector (Taj)

Since : 1.6


GstJpegScanHdr

struct _GstJpegScanHdr
{
  guint8 num_components;                /* 1 .. 4       */
  GstJpegScanComponent components[GST_JPEG_MAX_SCAN_COMPONENTS];

};

Scan header.

Fields

num_components (guint8) –

Number of image components in scan (Ns)

components (GstJpegScanComponent[4] ) –

Image components

Since : 1.6


GstJpegSegment

struct _GstJpegSegment
{
  GstJpegMarker marker;
  const guint8 *data;
  guint offset;
  gssize size;
};

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

Fields

marker (GstJpegMarker) –

The type of the segment that starts at offset

data (guint8*) –

the data containing the jpeg segment starting at offset

offset (guint) –

The offset to the segment start in bytes. This is the exact start of the segment, no marker code included

size (gssize) –

The size of the segment in bytes, or -1 if the end was not found. It is the exact size of the segment, without the sync byte and marker code but including any length bytes.

Since : 1.6


Aliases

GstJpegEntropyCodingMode

typedef enum GstJpegEntropyCodingMode GstJpegEntropyCodingMode

JPEG entropy coding mode.

Since : 1.6


GstJpegMarker

typedef enum GstJpegMarker GstJpegMarker

Indicates the type of JPEG segment.

Since : 1.6


GstJpegProfile

typedef enum GstJpegProfile GstJpegProfile

JPEG encoding processes.

Since : 1.6


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