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VP9 decoder: Sets thread count based on resolution, reinit on change.

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Previously, number of decoder threads for VP9 were always set to 8 but
with a cap at number of cores. This was done since we "can't know" the
resolution that will be used.

With this change, we now intialize the number of threads based on
resolution given in InitDecode(). If a resolution change happens in
flight, it requires a keyframe. We therefore parse the header from
any key frame and if it has a new resolution, we re-initialize the
decoder.

The number of threads used is based on pixel count. We set one thread
as target for 1280x720, and scale up lineraly from there. The 8-thread
cap is gone, but still limit it core count.

This means for instance: 1 <= 720p, 2 for 1080p, 4 for 1440p, 9 for 4K.

Bug: webrtc:11551
Change-Id: I14c169a6c651c50bd1b870c4b22bc4495c8448fd
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/174460
Commit-Queue: Erik Språng <sprang@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31507}
This commit is contained in:
Erik Språng
2020-06-11 18:24:22 +02:00
committed by Commit Bot
parent 33c0c342f6
commit d592575698
4 changed files with 199 additions and 53 deletions
Download Patch File Download Diff File Expand all files Collapse all files

41
modules/video_coding/codecs/vp9/vp9_impl.cc
View File

@ -25,6 +25,7 @@
#include "common_video/libyuv/include/webrtc_libyuv.h"
#include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
#include "modules/video_coding/codecs/vp9/svc_rate_allocator.h"
#include "modules/video_coding/utility/vp9_uncompressed_header_parser.h"
#include "rtc_base/checks.h"
#include "rtc_base/experiments/rate_control_settings.h"
#include "rtc_base/keep_ref_until_done.h"
@ -45,8 +46,6 @@ namespace {
uint8_t kRefBufIdx[4] = {0, 0, 0, 1};
uint8_t kUpdBufIdx[4] = {0, 0, 1, 0};
int kMaxNumTiles4kVideo = 8;
// Maximum allowed PID difference for differnet per-layer frame-rate case.
const int kMaxAllowedPidDiff = 30;
@ -1659,13 +1658,18 @@ int VP9DecoderImpl::InitDecode(const VideoCodec* inst, int number_of_cores) {
// errors earlier than the multi-threads version.
// - Make peak CPU usage under control (not depending on input)
cfg.threads = 1;
(void)kMaxNumTiles4kVideo; // unused
#else
// We want to use multithreading when decoding high resolution videos. But,
// since we don't know resolution of input stream at this stage, we always
// enable it.
cfg.threads = std::min(number_of_cores, kMaxNumTiles4kVideo);
// We want to use multithreading when decoding high resolution videos. But not
// too many in order to avoid overhead when many stream are decoded
// concurrently.
// Set 1280x720 pixel count as target for one core, and then scale up linearly
// from there - but cap at physical core count.
// This results in 2 for 1080p, 4 for 1440p and 8 for 4K.
int num_threads = std::max(1, (inst->width * inst->height) / (1280 * 720));
cfg.threads = std::min(number_of_cores, num_threads);
#endif
current_codec_ = *inst;
num_cores_ = number_of_cores;
vpx_codec_flags_t flags = 0;
if (vpx_codec_dec_init(decoder_, vpx_codec_vp9_dx(), &cfg, flags)) {
@ -1696,6 +1700,29 @@ int VP9DecoderImpl::Decode(const EncodedImage& input_image,
if (decode_complete_callback_ == nullptr) {
return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
}
if (input_image._frameType == VideoFrameType::kVideoFrameKey) {
absl::optional<vp9::FrameInfo> frame_info =
vp9::ParseIntraFrameInfo(input_image.data(), input_image.size());
if (frame_info) {
if (frame_info->frame_width != current_codec_.width ||
frame_info->frame_height != current_codec_.height) {
// Resolution has changed, tear down and re-init a new decoder in
// order to get correct sizing.
Release();
current_codec_.width = frame_info->frame_width;
current_codec_.height = frame_info->frame_height;
int reinit_status = InitDecode(&current_codec_, num_cores_);
if (reinit_status != WEBRTC_VIDEO_CODEC_OK) {
RTC_LOG(LS_WARNING) << "Failed to re-init decoder.";
return reinit_status;
}
}
} else {
RTC_LOG(LS_WARNING) << "Failed to parse VP9 header from key-frame.";
}
}
// Always start with a complete key frame.
if (key_frame_required_) {
if (input_image._frameType != VideoFrameType::kVideoFrameKey)