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#include "annexb.h"
#include <bfc/platform/types.h>
enum
{
InitialUnit = 0,
NewUnit = 1, // start finding start code during AddData
MidUnit = 2, // need to find the next start code from next AddData call to form a complete unit
UnitReady = 3, // a new unit is ready and we are waiting for a GetUnit call
};
typedef struct annex_b_demuxer
{
size_t buffer_position;
size_t number_of_zero_words; // number of zero words as identified from the first unit
size_t current_zero_words; // current zero word count, saved in case NALU crosses two AddData calls
int end_of_stream; // set to 1 when there's no more data (so we know not to look for the next start code)
int state;
size_t buffer_size;
uint8_t buffer[1]; // make sure this is last
} AnnexBDemuxer;
int AddData(const uint8_t **data, size_t *data_len); // data and length remaining are updated on exit. if data_len>0 on exit, call again after calling GetUnit
void EndOfStream();
h264_annexb_demuxer_t AnnexB_Create(int size)
{
AnnexBDemuxer *demuxer = (AnnexBDemuxer *)malloc(sizeof(AnnexBDemuxer) + size);
demuxer->buffer_size = size; // MAX_CODED_FRAME_SIZE;
demuxer->state = InitialUnit;
demuxer->buffer_position = 0;
demuxer->number_of_zero_words = 0;
demuxer->current_zero_words = 0;
demuxer->end_of_stream = 0;
return (h264_annexb_demuxer_t)demuxer;
}
static int AnnexB_GetByte(const uint8_t **data, size_t *data_len, uint8_t *data_byte)
{
if (*data_len)
{
*data_byte = **data;
*data = *data + 1;
*data_len = *data_len - 1;;
return 1;
}
else
return 0;
}
int AnnexB_AddData(h264_annexb_demuxer_t d, const void **_data, size_t *data_len)
{
AnnexBDemuxer *demuxer = (AnnexBDemuxer *)d;
if (demuxer)
{
const uint8_t **data = (const uint8_t **)_data; // cast to something easier to do pointer math with
if (demuxer->state == InitialUnit)
{
// find start code with unknown number of initial zero bytes
while(demuxer->number_of_zero_words == 0)
{
uint8_t data_byte;
if (AnnexB_GetByte(data, data_len, &data_byte))
{
if (data_byte == 0)
{
demuxer->current_zero_words++;
}
else if (data_byte == 1 && demuxer->current_zero_words >= 2)
{
demuxer->number_of_zero_words = demuxer->current_zero_words;
demuxer->current_zero_words = 0;
demuxer->state = MidUnit;
}
else
{
// re-sync
demuxer->current_zero_words = 0;
}
}
else
{
return AnnexB_NeedMoreData;
}
}
}
else if (demuxer->state == NewUnit)
{
// find start code with known number of initial zero b ytes
while (demuxer->state == NewUnit)
{
uint8_t data_byte;
if (AnnexB_GetByte(data, data_len, &data_byte))
{
if (data_byte == 0)
{
demuxer->current_zero_words++;
}
else if (data_byte == 1 && demuxer->current_zero_words >= 2) // we might get more start words than required
{
demuxer->current_zero_words = 0;
demuxer->state = MidUnit;
}
else
{
// re-sync
demuxer->current_zero_words = 0;
}
}
else
{
return AnnexB_NeedMoreData;
}
}
}
if (demuxer->state == MidUnit) // no else because we fall through during the start code scanning)
{
uint8_t data_byte;
while (AnnexB_GetByte(data, data_len, &data_byte))
{
if (data_byte == 0)
{
demuxer->current_zero_words++; // might be the next start word
/* if (demuxer->current_zero_words == 3) // 00 00 00 is also a valid sequence for end-of-nal detection.
{
demuxer->state = UnitReady;
return AnnexB_UnitAvailable;
}*/
}
else if (data_byte == 1 && demuxer->current_zero_words >= 2)
{
while (demuxer->current_zero_words > demuxer->number_of_zero_words)
{
// write trailing zero bytes to stream
if (demuxer->buffer_position >= demuxer->buffer_size)
return AnnexB_BufferFull;
demuxer->buffer[demuxer->buffer_position++] = 0;
demuxer->current_zero_words--;
}
demuxer->current_zero_words = 0;
demuxer->state = UnitReady;
return AnnexB_UnitAvailable;
}
else
{
while (demuxer->current_zero_words)
{
// write any zero bytes that we read to the stream
if (demuxer->buffer_position >= demuxer->buffer_size)
return AnnexB_BufferFull;
demuxer->buffer[demuxer->buffer_position++] = 0;
demuxer->current_zero_words--;
}
if (demuxer->buffer_position >= demuxer->buffer_size)
return AnnexB_BufferFull;
demuxer->buffer[demuxer->buffer_position++] = data_byte;
}
}
if (demuxer->end_of_stream)
{
demuxer->state = UnitReady;
}
else
{
return AnnexB_NeedMoreData;
}
}
if (demuxer->state == UnitReady)
return AnnexB_UnitAvailable;
return AnnexB_NeedMoreData; // dunno how we'd get here
}
else
return AnnexB_Error;
}
void AnnexB_EndOfStream(h264_annexb_demuxer_t d)
{
AnnexBDemuxer *demuxer = (AnnexBDemuxer *)d;
if (demuxer)
demuxer->end_of_stream = 1;
}
int AnnexB_GetUnit(h264_annexb_demuxer_t d, const void **data, size_t *data_len)
{
AnnexBDemuxer *demuxer = (AnnexBDemuxer *)d;
if (demuxer)
{
if (demuxer->state == UnitReady)
{
*data = demuxer->buffer;
*data_len = demuxer->buffer_position;
demuxer->buffer_position = 0;
// if we've found the next start code, go to MidUnit state
if (demuxer->current_zero_words == 0)
{
demuxer->state = MidUnit;
}
else // no start code, need to find it
{
demuxer->state = NewUnit;
}
return AnnexB_UnitAvailable;
}
else
{
return AnnexB_NeedMoreData;
}
}
return AnnexB_Error;
}
void AnnexB_Destroy(h264_annexb_demuxer_t d)
{
AnnexBDemuxer *demuxer = (AnnexBDemuxer *)d;
if (demuxer)
free(demuxer);
}
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