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encoders/codecs/h264: Basic support for parsing NALs
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@ -20,3 +20,68 @@
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// SOFTWARE.
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#include "h264.hpp"
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uint8_t* is_nal_start(uint8_t* ptr, uint8_t* end_ptr, size_t& size)
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{
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// Ensure that the remaining space actually can contain a prefix and NAL header.
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if ((ptr + (3 + 1)) >= end_ptr)
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return nullptr;
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if (*ptr != 0x0)
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return nullptr;
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if (*(ptr + 1) != 0x0)
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return nullptr;
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// 3-Byte NAL prefix.
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if (*(ptr + 2) == 0x1) {
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size = 3;
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return ptr + 3;
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}
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// 4-Byte NAL Prefix
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if ((ptr + (4 + 1)) >= end_ptr)
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return nullptr;
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if (*(ptr + 2) != 0x0)
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return nullptr;
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if (*(ptr + 3) != 0x01)
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return nullptr;
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size = 4;
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return ptr + 4;
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}
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uint8_t* streamfx::encoder::codec::h264::find_closest_nal(uint8_t* ptr, uint8_t* end_ptr, size_t& size)
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{
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for (uint8_t* seek_ptr = ptr; seek_ptr < end_ptr; seek_ptr++) {
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if (auto nal_ptr = is_nal_start(seek_ptr, end_ptr, size); nal_ptr != nullptr)
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return nal_ptr;
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}
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return nullptr;
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}
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uint32_t streamfx::encoder::codec::h264::get_packet_reference_count(uint8_t* ptr, uint8_t* end_ptr)
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{
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size_t nal_ptr_prefix = 0;
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uint8_t* nal_ptr = find_closest_nal(ptr, end_ptr, nal_ptr_prefix);
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while ((nal_ptr != nullptr) && (nal_ptr < end_ptr)) {
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// Try and figure out the actual size of the NAL.
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size_t nal_end_ptr_prefix = 0;
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uint8_t* nal_end_ptr = find_closest_nal(nal_ptr, end_ptr, nal_end_ptr_prefix);
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size_t nal_size = (nal_end_ptr ? nal_end_ptr : end_ptr) - nal_ptr - nal_end_ptr_prefix;
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// Try and figure out the ideal priority.
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switch (static_cast<nal_unit_type>((*nal_ptr) & 0x5)) {
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case nal_unit_type::CODED_SLICE_NONIDR:
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return (*nal_ptr >> 5) & 0x2;
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case nal_unit_type::CODED_SLICE_IDR:
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return (*nal_ptr >> 5) & 0x2;
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default:
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break;
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}
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// Update our NAL pointer.
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nal_ptr = nal_end_ptr;
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}
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return std::numeric_limits<uint32_t>::max();
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}
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@ -60,4 +60,40 @@ namespace streamfx::encoder::codec::h264 {
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L6_2,
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UNKNOWN = -1,
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};
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// See ITU-T H.264
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enum class nal_unit_type : uint8_t {
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UNSPECIFIED = 0,
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CODED_SLICE_NONIDR = 1,
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CODED_SLICE_DATA_PARTITION_A = 2,
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CODED_SLICE_DATA_PARTITION_B = 3,
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CODED_SLICE_DATA_PARTITION_C = 4,
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CODED_SLICE_IDR = 5,
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SUPPLEMENTAL_ENHANCEMENT_INFORMATION = 6,
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SEQUENCE_PARAMETER_SET = 7,
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PICTURE_PARAMETER_SET = 8,
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ACCESS_UNIT_DELIMITER = 9,
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END_OF_SEQUENCE = 10,
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END_OF_STREAM = 11,
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FILLER_DATA = 12,
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SEQUENCE_PARAMETER_SET_EXTENSION = 13,
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PREFIX_NAL_UNIT = 14,
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SUBSET_SEQUENCE_PARAMETER_SET = 15,
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DEPTH_PARAMETER_SET = 16,
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CODED_SLICE_AUXILIARY_PICTURE = 19,
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CODED_SLICE_EXTENSION = 20,
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CODED_SLICE_EXTENSION_DEPTH_VIEW = 21,
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};
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/** Search for the closest NAL unit.
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*
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* \param ptr Beginning of the search range.
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* \param endptr End of the search range (exclusive).
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*
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* \return A valid pointer if a NAL was found, otherwise \ref nullptr.
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*/
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uint8_t* find_closest_nal(uint8_t* ptr, uint8_t* endptr, size_t& size);
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uint32_t get_packet_reference_count(uint8_t* ptr, uint8_t* endptr);
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} // namespace streamfx::encoder::codec::h264
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