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LibVideo: Read multiple raw bits at once to refill the range decoder
This will allow BitStream::read_bool() to read more than one bit from the range-coded bitstream at a time if needed.
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13ccde8637
commit
647472b716
1 changed files with 11 additions and 10 deletions
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@ -5,6 +5,8 @@
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/BuiltinWrappers.h>
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#include "BitStream.h"
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namespace Video::VP9 {
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@ -96,16 +98,15 @@ ErrorOr<bool> BitStream::read_bool(u8 probability)
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return_bool = true;
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}
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while (m_bool_range < 128) {
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bool new_bit;
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if (m_bool_max_bits) {
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new_bit = TRY(read_bit());
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m_bool_max_bits--;
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} else {
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new_bit = false;
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}
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m_bool_range *= 2;
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m_bool_value = (m_bool_value << 1u) + new_bit;
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if (m_bool_range < 128) {
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u8 bits_to_shift_into_range = count_leading_zeroes(m_bool_range);
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if (bits_to_shift_into_range > m_bool_max_bits)
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return Error::from_string_literal("Range decoder is out of data");
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m_bool_range <<= bits_to_shift_into_range;
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m_bool_value = (m_bool_value << bits_to_shift_into_range) | TRY(read_bits(bits_to_shift_into_range));
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m_bool_max_bits -= bits_to_shift_into_range;
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}
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return return_bool;
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