69 lines
2.1 KiB
C++
69 lines
2.1 KiB
C++
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// Copyright 2019 Google LLC. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file or at
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// https://developers.google.com/open-source/licenses/bsd
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#include "packager/media/base/video_util.h"
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#include <limits>
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namespace {
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uint64_t CalculateGCD(uint64_t a, uint64_t b) {
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while (b != 0) {
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uint64_t temp = a;
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a = b;
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b = temp % b;
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}
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return a;
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}
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void ReducePixelWidthHeight(uint64_t* pixel_width, uint64_t* pixel_height) {
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if (*pixel_width == 0 || *pixel_height == 0)
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return;
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const uint64_t kMaxUint32 = std::numeric_limits<uint32_t>::max();
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while (true) {
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uint64_t gcd = CalculateGCD(*pixel_width, *pixel_height);
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*pixel_width /= gcd;
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*pixel_height /= gcd;
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// Both width and height needs to be 32 bit or less.
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if (*pixel_width <= kMaxUint32 && *pixel_height <= kMaxUint32)
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break;
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*pixel_width >>= 1;
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*pixel_height >>= 1;
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}
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}
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} // namespace
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namespace shaka {
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namespace media {
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void DerivePixelWidthHeight(uint32_t frame_width,
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uint32_t frame_height,
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uint32_t display_width,
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uint32_t display_height,
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uint32_t* pixel_width,
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uint32_t* pixel_height) {
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// DAR = PAR * FAR => PAR = DAR / FAR.
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// Thus:
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// pixel_width display_width frame_width
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// ----------- = ------------- / -----------
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// pixel_height display_height frame_height
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// So:
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// pixel_width display_width x frame_height
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// ----------- = ------------------------------
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// pixel_height display_height x frame_width
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uint64_t pixel_width_unreduced =
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static_cast<uint64_t>(display_width) * frame_height;
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uint64_t pixel_height_unreduced =
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static_cast<uint64_t>(display_height) * frame_width;
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ReducePixelWidthHeight(&pixel_width_unreduced, &pixel_height_unreduced);
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*pixel_width = pixel_width_unreduced;
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*pixel_height = pixel_height_unreduced;
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}
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} // namespace media
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} // namespace shaka
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