diff options
Diffstat (limited to 'Src/h264/annexb.c')
| -rw-r--r-- | Src/h264/annexb.c | 224 |
1 files changed, 224 insertions, 0 deletions
diff --git a/Src/h264/annexb.c b/Src/h264/annexb.c new file mode 100644 index 00000000..cc6e10e0 --- /dev/null +++ b/Src/h264/annexb.c @@ -0,0 +1,224 @@ +#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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