/H264Dec/source/h264bsd_byte_stream.c

  1/*
  2 * Copyright (C) 2009 The Android Open Source Project
  3 *
  4 * Licensed under the Apache License, Version 2.0 (the "License");
  5 * you may not use this file except in compliance with the License.
  6 * You may obtain a copy of the License at
  7 *
  8 *      http://www.apache.org/licenses/LICENSE-2.0
  9 *
 10 * Unless required by applicable law or agreed to in writing, software
 11 * distributed under the License is distributed on an "AS IS" BASIS,
 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 13 * See the License for the specific language governing permissions and
 14 * limitations under the License.
 15 */
 16
 17/*------------------------------------------------------------------------------
 18
 19    Table of contents
 20
 21     1. Include headers
 22     2. External compiler flags
 23     3. Module defines
 24     4. Local function prototypes
 25     5. Functions
 26          ExtractNalUnit
 27
 28------------------------------------------------------------------------------*/
 29
 30/*------------------------------------------------------------------------------
 31    1. Include headers
 32------------------------------------------------------------------------------*/
 33
 34#include "h264bsd_byte_stream.h"
 35#include "h264bsd_util.h"
 36
 37/*------------------------------------------------------------------------------
 38    2. External compiler flags
 39--------------------------------------------------------------------------------
 40
 41--------------------------------------------------------------------------------
 42    3. Module defines
 43------------------------------------------------------------------------------*/
 44
 45#define BYTE_STREAM_ERROR  0xFFFFFFFF
 46
 47/*------------------------------------------------------------------------------
 48    4. Local function prototypes
 49------------------------------------------------------------------------------*/
 50
 51/*------------------------------------------------------------------------------
 52
 53    Function name: ExtractNalUnit
 54
 55        Functional description:
 56            Extracts one NAL unit from the byte stream buffer. Removes
 57            emulation prevention bytes if present. The original stream buffer
 58            is used directly and is therefore modified if emulation prevention
 59            bytes are present in the stream.
 60
 61            Stream buffer is assumed to contain either exactly one NAL unit
 62            and nothing else, or one or more NAL units embedded in byte
 63            stream format described in the Annex B of the standard. Function
 64            detects which one is used based on the first bytes in the buffer.
 65
 66        Inputs:
 67            pByteStream     pointer to byte stream buffer
 68            len             length of the stream buffer (in bytes)
 69
 70        Outputs:
 71            pStrmData       stream information is stored here
 72            readBytes       number of bytes "consumed" from the stream buffer
 73
 74        Returns:
 75            HANTRO_OK       success
 76            HANTRO_NOK      error in byte stream
 77
 78------------------------------------------------------------------------------*/
 79
 80u32 h264bsdExtractNalUnit(u8 *pByteStream, u32 len, strmData_t *pStrmData,
 81    u32 *readBytes)
 82{
 83
 84/* Variables */
 85
 86    u32 i, tmp;
 87    u32 byteCount,initByteCount;
 88    u32 zeroCount;
 89    u8  byte;
 90    u32 hasEmulation = HANTRO_FALSE;
 91    u32 invalidStream = HANTRO_FALSE;
 92    u8 *readPtr, *writePtr;
 93
 94/* Code */
 95
 96    ASSERT(pByteStream);
 97    ASSERT(len);
 98    ASSERT(len < BYTE_STREAM_ERROR);
 99    ASSERT(pStrmData);
100
101    /* byte stream format if starts with 0x000001 or 0x000000 */
102    if (len > 3 && pByteStream[0] == 0x00 && pByteStream[1] == 0x00 &&
103        (pByteStream[2]&0xFE) == 0x00)
104    {
105        /* search for NAL unit start point, i.e. point after first start code
106         * prefix in the stream */
107        zeroCount = byteCount = 2;
108        readPtr = pByteStream + 2;
109        /*lint -e(716) while(1) used consciously */
110        while (1)
111        {
112            byte = *readPtr++;
113            byteCount++;
114
115            if (byteCount == len)
116            {
117                /* no start code prefix found -> error */
118                *readBytes = len;
119                return(HANTRO_NOK);
120            }
121
122            if (!byte)
123                zeroCount++;
124            else if ((byte == 0x01) && (zeroCount >= 2))
125                break;
126            else
127                zeroCount = 0;
128        }
129
130        initByteCount = byteCount;
131
132        /* determine size of the NAL unit. Search for next start code prefix
133         * or end of stream and ignore possible trailing zero bytes */
134        zeroCount = 0;
135        /*lint -e(716) while(1) used consciously */
136        while (1)
137        {
138            byte = *readPtr++;
139            byteCount++;
140            if (!byte)
141                zeroCount++;
142
143            if ( (byte == 0x03) && (zeroCount == 2) )
144            {
145                hasEmulation = HANTRO_TRUE;
146            }
147
148            if ( (byte == 0x01) && (zeroCount >= 2 ) )
149            {
150                pStrmData->strmBuffSize =
151                    byteCount - initByteCount - zeroCount - 1;
152                zeroCount -= MIN(zeroCount, 3);
153                break;
154            }
155            else if (byte)
156            {
157                if (zeroCount >= 3)
158                    invalidStream = HANTRO_TRUE;
159                zeroCount = 0;
160            }
161
162            if (byteCount == len)
163            {
164                pStrmData->strmBuffSize = byteCount - initByteCount - zeroCount;
165                break;
166            }
167
168        }
169    }
170    /* separate NAL units as input -> just set stream params */
171    else
172    {
173        initByteCount = 0;
174        zeroCount = 0;
175        pStrmData->strmBuffSize = len;
176        hasEmulation = HANTRO_TRUE;
177    }
178
179    pStrmData->pStrmBuffStart    = pByteStream + initByteCount;
180    pStrmData->pStrmCurrPos      = pStrmData->pStrmBuffStart;
181    pStrmData->bitPosInWord      = 0;
182    pStrmData->strmBuffReadBits  = 0;
183
184    /* return number of bytes "consumed" */
185    *readBytes = pStrmData->strmBuffSize + initByteCount + zeroCount;
186
187    if (invalidStream)
188    {
189        return(HANTRO_NOK);
190    }
191
192    /* remove emulation prevention bytes before rbsp processing */
193    if (hasEmulation)
194    {
195        tmp = pStrmData->strmBuffSize;
196        readPtr = writePtr = pStrmData->pStrmBuffStart;
197        zeroCount = 0;
198        for (i = tmp; i--;)
199        {
200            if ((zeroCount == 2) && (*readPtr == 0x03))
201            {
202                /* emulation prevention byte shall be followed by one of the
203                 * following bytes: 0x00, 0x01, 0x02, 0x03. This implies that
204                 * emulation prevention 0x03 byte shall not be the last byte
205                 * of the stream. */
206                if ( (i == 0) || (*(readPtr+1) > 0x03) )
207                    return(HANTRO_NOK);
208
209                /* do not write emulation prevention byte */
210                readPtr++;
211                zeroCount = 0;
212            }
213            else
214            {
215                /* NAL unit shall not contain byte sequences 0x000000,
216                 * 0x000001 or 0x000002 */
217                if ( (zeroCount == 2) && (*readPtr <= 0x02) )
218                    return(HANTRO_NOK);
219
220                if (*readPtr == 0)
221                    zeroCount++;
222                else
223                    zeroCount = 0;
224
225                *writePtr++ = *readPtr++;
226            }
227        }
228
229        /* (readPtr - writePtr) indicates number of "removed" emulation
230         * prevention bytes -> subtract from stream buffer size */
231        pStrmData->strmBuffSize -= (u32)(readPtr - writePtr);
232    }
233
234    return(HANTRO_OK);
235
236}
237