es_defns.h

/*
 * Datastructures for handling H.264 elementary streams.
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is the MPEG TS, PS and ES tools.
 *
 * The Initial Developer of the Original Code is Amino Communications Ltd.
 * Portions created by the Initial Developer are Copyright (C) 2008
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Amino Communications Ltd, Swavesey, Cambridge UK
 *
 * ***** END LICENSE BLOCK *****
 */

#ifndef _es_defns
#define _es_defns

#include <stdio.h>
#include "compat.h"
#include "pes_defns.h"

// ------------------------------------------------------------
// A "file" offset in an ES stream, suitable for seeking to
// For an ES based on a "bare" file, the `infile` value is all that is needed
// For an ES based on a PES, the file offset of the PES packet and the byte
// offset within that packet's ES data are needed.
struct _ES_offset
{
  offset_t  infile;   // as used by lseek
  int32_t   inpacket;
};
typedef struct _ES_offset  ES_offset;
typedef struct _ES_offset *ES_offset_p;
#define SIZEOF_ES_OFFSET sizeof(struct _ES_offset)

// The number of bytes to "read ahead" when reading directly from an
// elementary stream
#define ES_READ_AHEAD_SIZE  1000

// ------------------------------------------------------------
// A datastructure to represent our input elementary stream (ES)
// (*output* elementary streams shouldn't need any particular housekeeping)
struct elementary_stream
{
  int       reading_ES;  // TRUE if we're reading ES data direct, FALSE if PES

  // If we're reading from an elementary data stream directly, then
  // we use the input directly
  int       input;
  // And maintain a buffer of "read ahead" bytes
  byte      read_ahead[ES_READ_AHEAD_SIZE];
  offset_t  read_ahead_posn;   // location of this data in the file
  int32_t   read_ahead_len;    // actual number of bytes in the buffer
  
  // And the next byte to be read is specified by its offset in said
  // data stream. For "bare" ES data, the `infile` value is used to
  // remember the next bytes actual position in the file, and for PES
  // based ES data, the `inpacket` value is used to remember the next
  // bytes offset in the current PES packet. In both cases, the "unused"
  // quantity in the ES_offset is undefined.
  // (this is, in fact, more used by tsserve than by anything else)
  ES_offset  posn_of_next_byte;

  // If we're reading from PES packets (from either a PS or TS file),
  // then we need to remember our PES reader
  PES_reader_p  reader;

  byte      *data;               // Where we're reading our bytes from
  byte      *data_end;           // How to tell we've read them all
  byte      *data_ptr;           // And which byte we're interested in

  offset_t   last_packet_posn;   // Where the last PES packet was in the file
  int32_t    last_packet_es_data_len;  // And its number of ES bytes
  
  // Regardless, our triple byte memory is the same
  byte      cur_byte;    // The current (last read) byte
  byte      prev1_byte;  // The previous byte
  byte      prev2_byte;  // The byte before *that*
};
typedef struct elementary_stream *ES_p;
#define SIZEOF_ES sizeof(struct elementary_stream)

// ------------------------------------------------------------
// And a representation of a single unit from the elementary stream
// (whether an MPEG-2 (H.262) item, or an MPEG-4/AVC (H.264) NAL unit)
// - basically, the thing that starts with a 00 00 01 prefix, and continues
// to end of file or before the next 00 00 01 prefix (so note that it
// contains any "trailing" 00 bytes).
//
// The normal way to acquire such a datastructure is via `build_ES_unit()`,
// or `find_and_build_next_ES_unit()`. If instead you want to use the
// address of a `struct ES_unit`, it is imperative that it be set up
// correctly with `setup_ES_unit()` before it is passed to any of the
// functions that use it, otherwise the contents will not be valid (and,
// particularly, the "data" pointer will reference random memory).
struct ES_unit
{
  ES_offset start_posn;   // The start of the current data unit
  byte     *data;         // Its data, including the leading 00 00 01
  uint32_t  data_len;     // Its length
  uint32_t  data_size;    // The total buffer size

  byte      start_code;   // The byte after the 00 00 01 prefix

  // Something of a hack - if we were reading PES, did any of the PES packets
  // we read to make this ES unit contain a PTS?
  byte      PES_had_PTS;
};
typedef struct ES_unit *ES_unit_p;
#define SIZEOF_ES_UNIT sizeof(struct ES_unit)

// Start and increment sizes for the es_unit/data array.
#define ES_UNIT_DATA_START_SIZE  1000  // was 500
#define ES_UNIT_DATA_INCREMENT    500  // was 100

// ------------------------------------------------------------
// An expandable list of ES units
struct ES_unit_list
{
  struct ES_unit *array;   // The current array of ES units
  int             length;  // How many there are
  int             size;    // How big the array is
};
typedef struct ES_unit_list *ES_unit_list_p;
#define SIZEOF_ES_UNIT_LIST sizeof(struct ES_unit_list)

#define ES_UNIT_LIST_START_SIZE  20
#define ES_UNIT_LIST_INCREMENT   20

#endif // _es_defns

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