blob: 151101e42aa4f0cb7f2c2e95d7086a08647f5e91 [file] [log] [blame]
// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "media/gpu/gpu_video_encode_accelerator_helpers.h"
#include <algorithm>
#include "base/check_op.h"
namespace media {
namespace {
// The maximum size for output buffer, which is chosen empirically for
// 1080p video.
constexpr size_t kMaxBitstreamBufferSizeInBytes = 2 * 1024 * 1024; // 2MB
// The frame size for 1080p (FHD) video in pixels.
constexpr int k1080PSizeInPixels = 1920 * 1080;
// The frame size for 1440p (QHD) video in pixels.
constexpr int k1440PSizeInPixels = 2560 * 1440;
// The mapping from resolution, bitrate, framerate to the bitstream buffer size.
struct BitstreamBufferSizeInfo {
int coded_size_area;
uint32_t bitrate_in_bps;
uint32_t framerate;
uint32_t buffer_size_in_bytes;
};
// The bitstream buffer size for each resolution. The table must be sorted in
// increasing order by the resolution. The value is decided by measuring the
// biggest buffer size, and then double the size as margin. (crbug.com/889739)
constexpr BitstreamBufferSizeInfo kBitstreamBufferSizeTable[] = {
{320 * 180, 100000, 30, 15000},
{640 * 360, 500000, 30, 52000},
{1280 * 720, 1200000, 30, 110000},
{1920 * 1080, 4000000, 30, 380000},
{3840 * 2160, 20000000, 30, 970000},
};
// Use quadruple size of kMaxBitstreamBufferSizeInBytes when the input frame
// size is larger than 1440p, double if larger than 1080p. This is chosen
// empirically for some 4k encoding use cases and Android CTS VideoEncoderTest
// (crbug.com/927284).
size_t GetMaxEncodeBitstreamBufferSize(const gfx::Size& size) {
if (size.GetArea() > k1440PSizeInPixels)
return kMaxBitstreamBufferSizeInBytes * 4;
if (size.GetArea() > k1080PSizeInPixels)
return kMaxBitstreamBufferSizeInBytes * 2;
return kMaxBitstreamBufferSizeInBytes;
}
} // namespace
size_t GetEncodeBitstreamBufferSize(const gfx::Size& size,
uint32_t bitrate,
uint32_t framerate) {
DCHECK_NE(framerate, 0u);
for (auto& data : kBitstreamBufferSizeTable) {
if (size.GetArea() <= data.coded_size_area) {
// The buffer size is proportional to (bitrate / framerate), but linear
// interpolation for smaller ratio is not enough. Therefore we only use
// linear extrapolation for larger ratio.
double ratio = std::max(
1.0f * (bitrate / framerate) / (data.bitrate_in_bps / data.framerate),
1.0f);
return std::min(static_cast<size_t>(data.buffer_size_in_bytes * ratio),
GetMaxEncodeBitstreamBufferSize(size));
}
}
return GetMaxEncodeBitstreamBufferSize(size);
}
// Get the maximum output bitstream buffer size. Since we don't change the
// buffer size when we update bitrate and framerate, we have to calculate the
// buffer size for the maximum bitrate.
// However, the maximum bitrate for intel chipset is 40Mbps. The buffer size
// calculated with this bitrate is always larger than 2MB. Therefore we just
// return the value.
// TODO(crbug.com/889739): Deprecate this function after we can update the
// buffer size while requesting new bitrate and framerate.
size_t GetEncodeBitstreamBufferSize(const gfx::Size& size) {
return GetMaxEncodeBitstreamBufferSize(size);
}
} // namespace media