libavcodec/dirac_parser.c - vendor/opensource/ffmpeg - Git at Google

 /*
  * Dirac parser
  *
  * Copyright (c) 2007-2008 Marco Gerards <marco@gnu.org>
  * Copyright (c) 2008 BBC, Anuradha Suraparaju <asuraparaju@gmail.com>
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */

 /**
  * @file libavcodec/dirac_parser.c
  * Dirac Parser
  * @author Marco Gerards <marco@gnu.org>
  */

 #include "libavutil/intreadwrite.h"
 #include "parser.h"

 #define DIRAC_PARSE_INFO_PREFIX 0x42424344

 /**
  * Finds the end of the current frame in the bitstream.
  * @return the position of the first byte of the next frame or -1
  */
 typedef struct DiracParseContext {
     int state;
     int is_synced;
     int sync_offset;
     int header_bytes_needed;
     int overread_index;
     int buffer_size;
     int index;
     uint8_t *buffer;
     int dirac_unit_size;
     uint8_t *dirac_unit;
 } DiracParseContext;

 static int find_frame_end(DiracParseContext *pc,
                           const uint8_t *buf, int buf_size)
 {
     uint32_t state = pc->state;
     int i = 0;

     if (!pc->is_synced) {
         for (i = 0; i < buf_size; i++) {
             state = (state << 8) | buf[i];
             if (state == DIRAC_PARSE_INFO_PREFIX) {
                 state                   = -1;
                 pc->is_synced           = 1;
                 pc->header_bytes_needed = 9;
                 pc->sync_offset         = i;
                 break;
             }
         }
     }

     if (pc->is_synced) {
         pc->sync_offset = 0;
         for (; i < buf_size; i++) {
             if (state == DIRAC_PARSE_INFO_PREFIX) {
                 if ((buf_size-i) >= pc->header_bytes_needed) {
                     pc->state = -1;
                     return i + pc->header_bytes_needed;
                 } else {
                     pc->header_bytes_needed = 9-(buf_size-i);
                     break;
                 }
             } else
               state = (state << 8) | buf[i];
         }
     }
     pc->state = state;
     return -1;
 }

 typedef struct DiracParseUnit
 {
     int next_pu_offset;
     int prev_pu_offset;
     uint8_t pu_type;
 } DiracParseUnit;

 static int unpack_parse_unit(DiracParseUnit *pu, DiracParseContext *pc,
                              int offset)
 {
     uint8_t *start = pc->buffer + offset;
     uint8_t *end   = pc->buffer + pc->index;
     if (start < pc->buffer || (start+13 > end))
         return 0;
     pu->pu_type = start[4];

     pu->next_pu_offset = AV_RB32(start+5);
     pu->prev_pu_offset = AV_RB32(start+9);

     if (pu->pu_type == 0x10 && pu->next_pu_offset == 0)
         pu->next_pu_offset = 13;

     return 1;
 }

 static int dirac_combine_frame(AVCodecParserContext *s, AVCodecContext *avctx,
                                int next, const uint8_t **buf, int *buf_size)
 {
     int parse_timing_info = (s->pts == AV_NOPTS_VALUE &&
                              s->dts == AV_NOPTS_VALUE);
     DiracParseContext *pc = s->priv_data;

     if (pc->overread_index) {
         memcpy(pc->buffer, pc->buffer + pc->overread_index,
                pc->index - pc->overread_index);
         pc->index -= pc->overread_index;
         pc->overread_index = 0;
         if (*buf_size == 0 && pc->buffer[4] == 0x10) {
             *buf      = pc->buffer;
             *buf_size = pc->index;
             return 0;
         }
     }

     if ( next == -1) {
         /* Found a possible frame start but not a frame end */
         void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
                                            pc->index + (*buf_size -
                                                         pc->sync_offset));
         pc->buffer = new_buffer;
         memcpy(pc->buffer+pc->index, (*buf + pc->sync_offset),
                *buf_size - pc->sync_offset);
         pc->index += *buf_size - pc->sync_offset;
         return -1;
     } else {
         /* Found a possible frame start and a  possible frame end */
         DiracParseUnit pu1, pu;
         void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
                                            pc->index + next);
         pc->buffer = new_buffer;
         memcpy(pc->buffer + pc->index, *buf, next);
         pc->index += next;

         /* Need to check if we have a valid Parse Unit. We can't go by the
          * sync pattern 'BBCD' alone because arithmetic coding of the residual
          * and motion data can cause the pattern triggering a false start of
          * frame. So check if the previous parse offset of the next parse unit
          * is equal to the next parse offset of the current parse unit then
          * we can be pretty sure that we have a valid parse unit */
         if (!unpack_parse_unit(&pu1, pc, pc->index - 13)                     ||
             !unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) ||
             pu.next_pu_offset != pu1.prev_pu_offset) {
             pc->index -= 9;
             *buf_size = next-9;
             pc->header_bytes_needed = 9;
             return -1;
         }

         /* All non-frame data must be accompanied by frame data. This is to
          * ensure that pts is set correctly. So if the current parse unit is
          * not frame data, wait for frame data to come along */

         pc->dirac_unit = pc->buffer + pc->index - 13 -
                          pu1.prev_pu_offset - pc->dirac_unit_size;

         pc->dirac_unit_size += pu.next_pu_offset;

         if ((pu.pu_type&0x08) != 0x08) {
             pc->header_bytes_needed = 9;
             *buf_size = next;
             return -1;
         }

         /* Get the picture number to set the pts and dts*/
         if (parse_timing_info) {
             uint8_t *cur_pu = pc->buffer +
                               pc->index - 13 - pu1.prev_pu_offset;
             int pts =  AV_RB32(cur_pu + 13);
             if (s->last_pts == 0 && s->last_dts == 0)
                 s->dts = pts - 1;
             else
                 s->dts = s->last_dts+1;
             s->pts = pts;
             if (!avctx->has_b_frames && (cur_pu[4] & 0x03))
                 avctx->has_b_frames = 1;
         }
         if (avctx->has_b_frames && s->pts == s->dts)
              s->pict_type = FF_B_TYPE;

         /* Finally have a complete Dirac data unit */
         *buf      = pc->dirac_unit;
         *buf_size = pc->dirac_unit_size;

         pc->dirac_unit_size     = 0;
         pc->overread_index      = pc->index-13;
         pc->header_bytes_needed = 9;
     }
     return next;
 }

 static int dirac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
                        const uint8_t **poutbuf, int *poutbuf_size,
                        const uint8_t *buf, int buf_size)
 {
     DiracParseContext *pc = s->priv_data;
     int next;

     *poutbuf = NULL;
     *poutbuf_size = 0;

     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
         next = buf_size;
         *poutbuf = buf;
         *poutbuf_size = buf_size;
         /* Assume that data has been packetized into an encapsulation unit. */
     } else {
         next = find_frame_end(pc, buf, buf_size);
         if (!pc->is_synced && next == -1) {
             /* No frame start found yet. So throw away the entire buffer. */
             return buf_size;
         }

         if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0) {
             return buf_size;
         }
     }

     *poutbuf = buf;
     *poutbuf_size = buf_size;
     return next;
 }

 static void dirac_parse_close(AVCodecParserContext *s)
 {
     DiracParseContext *pc = s->priv_data;

     if (pc->buffer_size > 0)
         av_free(pc->buffer);
 }

 AVCodecParser dirac_parser = {
     { CODEC_ID_DIRAC },
     sizeof(DiracParseContext),
     NULL,
     dirac_parse,
     dirac_parse_close,
 };
	/*
	* Dirac parser
	*
	* Copyright (c) 2007-2008 Marco Gerards <marco@gnu.org>
	* Copyright (c) 2008 BBC, Anuradha Suraparaju <asuraparaju@gmail.com>
	*
	* This file is part of FFmpeg.
	*
	* FFmpeg is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Lesser General Public
	* License as published by the Free Software Foundation; either
	* version 2.1 of the License, or (at your option) any later version.
	*
	* FFmpeg is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public
	* License along with FFmpeg; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	*/

	/**
	* @file libavcodec/dirac_parser.c
	* Dirac Parser
	* @author Marco Gerards <marco@gnu.org>
	*/

	#include "libavutil/intreadwrite.h"
	#include "parser.h"

	#define DIRAC_PARSE_INFO_PREFIX 0x42424344

	/**
	* Finds the end of the current frame in the bitstream.
	* @return the position of the first byte of the next frame or -1
	*/
	typedef struct DiracParseContext {
	int state;
	int is_synced;
	int sync_offset;
	int header_bytes_needed;
	int overread_index;
	int buffer_size;
	int index;
	uint8_t *buffer;
	int dirac_unit_size;
	uint8_t *dirac_unit;
	} DiracParseContext;

	static int find_frame_end(DiracParseContext *pc,
	const uint8_t *buf, int buf_size)
	{
	uint32_t state = pc->state;
	int i = 0;

	if (!pc->is_synced) {
	for (i = 0; i < buf_size; i++) {
	state = (state << 8) \| buf[i];
	if (state == DIRAC_PARSE_INFO_PREFIX) {
	state = -1;
	pc->is_synced = 1;
	pc->header_bytes_needed = 9;
	pc->sync_offset = i;
	break;
	}
	}
	}

	if (pc->is_synced) {
	pc->sync_offset = 0;
	for (; i < buf_size; i++) {
	if (state == DIRAC_PARSE_INFO_PREFIX) {
	if ((buf_size-i) >= pc->header_bytes_needed) {
	pc->state = -1;
	return i + pc->header_bytes_needed;
	} else {
	pc->header_bytes_needed = 9-(buf_size-i);
	break;
	}
	} else
	state = (state << 8) \| buf[i];
	}
	}
	pc->state = state;
	return -1;
	}

	typedef struct DiracParseUnit
	{
	int next_pu_offset;
	int prev_pu_offset;
	uint8_t pu_type;
	} DiracParseUnit;

	static int unpack_parse_unit(DiracParseUnit pu, DiracParseContext pc,
	int offset)
	{
	uint8_t *start = pc->buffer + offset;
	uint8_t *end = pc->buffer + pc->index;
	if (start < pc->buffer \|\| (start+13 > end))
	return 0;
	pu->pu_type = start[4];

	pu->next_pu_offset = AV_RB32(start+5);
	pu->prev_pu_offset = AV_RB32(start+9);

	if (pu->pu_type == 0x10 && pu->next_pu_offset == 0)
	pu->next_pu_offset = 13;

	return 1;
	}

	static int dirac_combine_frame(AVCodecParserContext s, AVCodecContext avctx,
	int next, const uint8_t *buf, int buf_size)
	{
	int parse_timing_info = (s->pts == AV_NOPTS_VALUE &&
	s->dts == AV_NOPTS_VALUE);
	DiracParseContext *pc = s->priv_data;

	if (pc->overread_index) {
	memcpy(pc->buffer, pc->buffer + pc->overread_index,
	pc->index - pc->overread_index);
	pc->index -= pc->overread_index;
	pc->overread_index = 0;
	if (*buf_size == 0 && pc->buffer[4] == 0x10) {
	*buf = pc->buffer;
	*buf_size = pc->index;
	return 0;
	}
	}

	if ( next == -1) {
	/* Found a possible frame start but not a frame end */
	void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
	pc->index + (*buf_size -
	pc->sync_offset));
	pc->buffer = new_buffer;
	memcpy(pc->buffer+pc->index, (*buf + pc->sync_offset),
	*buf_size - pc->sync_offset);
	pc->index += *buf_size - pc->sync_offset;
	return -1;
	} else {
	/* Found a possible frame start and a possible frame end */
	DiracParseUnit pu1, pu;
	void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
	pc->index + next);
	pc->buffer = new_buffer;
	memcpy(pc->buffer + pc->index, *buf, next);
	pc->index += next;

	/* Need to check if we have a valid Parse Unit. We can't go by the
	* sync pattern 'BBCD' alone because arithmetic coding of the residual
	* and motion data can cause the pattern triggering a false start of
	* frame. So check if the previous parse offset of the next parse unit
	* is equal to the next parse offset of the current parse unit then
	* we can be pretty sure that we have a valid parse unit */
	if (!unpack_parse_unit(&pu1, pc, pc->index - 13) \|\|
	!unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) \|\|
	pu.next_pu_offset != pu1.prev_pu_offset) {
	pc->index -= 9;
	*buf_size = next-9;
	pc->header_bytes_needed = 9;
	return -1;
	}

	/* All non-frame data must be accompanied by frame data. This is to
	* ensure that pts is set correctly. So if the current parse unit is
	* not frame data, wait for frame data to come along */

	pc->dirac_unit = pc->buffer + pc->index - 13 -
	pu1.prev_pu_offset - pc->dirac_unit_size;

	pc->dirac_unit_size += pu.next_pu_offset;

	if ((pu.pu_type&0x08) != 0x08) {
	pc->header_bytes_needed = 9;
	*buf_size = next;
	return -1;
	}

	/* Get the picture number to set the pts and dts*/
	if (parse_timing_info) {
	uint8_t *cur_pu = pc->buffer +
	pc->index - 13 - pu1.prev_pu_offset;
	int pts = AV_RB32(cur_pu + 13);
	if (s->last_pts == 0 && s->last_dts == 0)
	s->dts = pts - 1;
	else
	s->dts = s->last_dts+1;
	s->pts = pts;
	if (!avctx->has_b_frames && (cur_pu[4] & 0x03))
	avctx->has_b_frames = 1;
	}
	if (avctx->has_b_frames && s->pts == s->dts)
	s->pict_type = FF_B_TYPE;

	/* Finally have a complete Dirac data unit */
	*buf = pc->dirac_unit;
	*buf_size = pc->dirac_unit_size;

	pc->dirac_unit_size = 0;
	pc->overread_index = pc->index-13;
	pc->header_bytes_needed = 9;
	}
	return next;
	}

	static int dirac_parse(AVCodecParserContext s, AVCodecContext avctx,
	const uint8_t *poutbuf, int poutbuf_size,
	const uint8_t *buf, int buf_size)
	{
	DiracParseContext *pc = s->priv_data;
	int next;

	*poutbuf = NULL;
	*poutbuf_size = 0;

	if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
	next = buf_size;
	*poutbuf = buf;
	*poutbuf_size = buf_size;
	/* Assume that data has been packetized into an encapsulation unit. */
	} else {
	next = find_frame_end(pc, buf, buf_size);
	if (!pc->is_synced && next == -1) {
	/* No frame start found yet. So throw away the entire buffer. */
	return buf_size;
	}

	if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0) {
	return buf_size;
	}
	}

	*poutbuf = buf;
	*poutbuf_size = buf_size;
	return next;
	}

	static void dirac_parse_close(AVCodecParserContext *s)
	{
	DiracParseContext *pc = s->priv_data;

	if (pc->buffer_size > 0)
	av_free(pc->buffer);
	}

	AVCodecParser dirac_parser = {
	{ CODEC_ID_DIRAC },
	sizeof(DiracParseContext),
	NULL,
	dirac_parse,
	dirac_parse_close,
	};