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Diffstat (limited to 'media/libstagefright/codecs/on2/h264dec/source/h264bsd_byte_stream.c')
| -rwxr-xr-x | media/libstagefright/codecs/on2/h264dec/source/h264bsd_byte_stream.c | 237 |
1 files changed, 237 insertions, 0 deletions
diff --git a/media/libstagefright/codecs/on2/h264dec/source/h264bsd_byte_stream.c b/media/libstagefright/codecs/on2/h264dec/source/h264bsd_byte_stream.c new file mode 100755 index 0000000..db77f8c --- /dev/null +++ b/media/libstagefright/codecs/on2/h264dec/source/h264bsd_byte_stream.c @@ -0,0 +1,237 @@ +/* + * Copyright (C) 2009 The Android Open Source Project + * + * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +/*------------------------------------------------------------------------------ + + Table of contents + + 1. Include headers + 2. External compiler flags + 3. Module defines + 4. Local function prototypes + 5. Functions + ExtractNalUnit + +------------------------------------------------------------------------------*/ + +/*------------------------------------------------------------------------------ + 1. Include headers +------------------------------------------------------------------------------*/ + +#include "h264bsd_byte_stream.h" +#include "h264bsd_util.h" + +/*------------------------------------------------------------------------------ + 2. External compiler flags +-------------------------------------------------------------------------------- + +-------------------------------------------------------------------------------- + 3. Module defines +------------------------------------------------------------------------------*/ + +#define BYTE_STREAM_ERROR 0xFFFFFFFF + +/*------------------------------------------------------------------------------ + 4. Local function prototypes +------------------------------------------------------------------------------*/ + +/*------------------------------------------------------------------------------ + + Function name: ExtractNalUnit + + Functional description: + Extracts one NAL unit from the byte stream buffer. Removes + emulation prevention bytes if present. The original stream buffer + is used directly and is therefore modified if emulation prevention + bytes are present in the stream. + + Stream buffer is assumed to contain either exactly one NAL unit + and nothing else, or one or more NAL units embedded in byte + stream format described in the Annex B of the standard. Function + detects which one is used based on the first bytes in the buffer. + + Inputs: + pByteStream pointer to byte stream buffer + len length of the stream buffer (in bytes) + + Outputs: + pStrmData stream information is stored here + readBytes number of bytes "consumed" from the stream buffer + + Returns: + HANTRO_OK success + HANTRO_NOK error in byte stream + +------------------------------------------------------------------------------*/ + +u32 h264bsdExtractNalUnit(u8 *pByteStream, u32 len, strmData_t *pStrmData, + u32 *readBytes) +{ + +/* Variables */ + + u32 i, tmp; + u32 byteCount,initByteCount; + u32 zeroCount; + u8 byte; + u32 hasEmulation = HANTRO_FALSE; + u32 invalidStream = HANTRO_FALSE; + u8 *readPtr, *writePtr; + +/* Code */ + + ASSERT(pByteStream); + ASSERT(len); + ASSERT(len < BYTE_STREAM_ERROR); + ASSERT(pStrmData); + + /* byte stream format if starts with 0x000001 or 0x000000 */ + if (len > 3 && pByteStream[0] == 0x00 && pByteStream[1] == 0x00 && + (pByteStream[2]&0xFE) == 0x00) + { + /* search for NAL unit start point, i.e. point after first start code + * prefix in the stream */ + zeroCount = byteCount = 2; + readPtr = pByteStream + 2; + /*lint -e(716) while(1) used consciously */ + while (1) + { + byte = *readPtr++; + byteCount++; + + if (byteCount == len) + { + /* no start code prefix found -> error */ + *readBytes = len; + return(HANTRO_NOK); + } + + if (!byte) + zeroCount++; + else if ((byte == 0x01) && (zeroCount >= 2)) + break; + else + zeroCount = 0; + } + + initByteCount = byteCount; + + /* determine size of the NAL unit. Search for next start code prefix + * or end of stream and ignore possible trailing zero bytes */ + zeroCount = 0; + /*lint -e(716) while(1) used consciously */ + while (1) + { + byte = *readPtr++; + byteCount++; + if (!byte) + zeroCount++; + + if ( (byte == 0x03) && (zeroCount == 2) ) + { + hasEmulation = HANTRO_TRUE; + } + + if ( (byte == 0x01) && (zeroCount >= 2 ) ) + { + pStrmData->strmBuffSize = + byteCount - initByteCount - zeroCount - 1; + zeroCount -= MIN(zeroCount, 3); + break; + } + else if (byte) + { + if (zeroCount >= 3) + invalidStream = HANTRO_TRUE; + zeroCount = 0; + } + + if (byteCount == len) + { + pStrmData->strmBuffSize = byteCount - initByteCount - zeroCount; + break; + } + + } + } + /* separate NAL units as input -> just set stream params */ + else + { + initByteCount = 0; + zeroCount = 0; + pStrmData->strmBuffSize = len; + hasEmulation = HANTRO_TRUE; + } + + pStrmData->pStrmBuffStart = pByteStream + initByteCount; + pStrmData->pStrmCurrPos = pStrmData->pStrmBuffStart; + pStrmData->bitPosInWord = 0; + pStrmData->strmBuffReadBits = 0; + + /* return number of bytes "consumed" */ + *readBytes = pStrmData->strmBuffSize + initByteCount + zeroCount; + + if (invalidStream) + { + return(HANTRO_NOK); + } + + /* remove emulation prevention bytes before rbsp processing */ + if (hasEmulation) + { + tmp = pStrmData->strmBuffSize; + readPtr = writePtr = pStrmData->pStrmBuffStart; + zeroCount = 0; + for (i = tmp; i--;) + { + if ((zeroCount == 2) && (*readPtr == 0x03)) + { + /* emulation prevention byte shall be followed by one of the + * following bytes: 0x00, 0x01, 0x02, 0x03. This implies that + * emulation prevention 0x03 byte shall not be the last byte + * of the stream. */ + if ( (i == 0) || (*(readPtr+1) > 0x03) ) + return(HANTRO_NOK); + + /* do not write emulation prevention byte */ + readPtr++; + zeroCount = 0; + } + else + { + /* NAL unit shall not contain byte sequences 0x000000, + * 0x000001 or 0x000002 */ + if ( (zeroCount == 2) && (*readPtr <= 0x02) ) + return(HANTRO_NOK); + + if (*readPtr == 0) + zeroCount++; + else + zeroCount = 0; + + *writePtr++ = *readPtr++; + } + } + + /* (readPtr - writePtr) indicates number of "removed" emulation + * prevention bytes -> subtract from stream buffer size */ + pStrmData->strmBuffSize -= (u32)(readPtr - writePtr); + } + + return(HANTRO_OK); + +} + |