fegger
36d086af4e
Four encoder quality improvements, all sender-side: - CRF rate control (default 22, --crf to override): targets a constant visual quality level instead of a fixed bitrate. Static desktop content uses 300-800 kbps (vs. forced 4000+), and the saved bits go to sharp text and clean motion when they appear. The VBV max rate (the --bitrate value, now a cap rather than a target) bounds bursts so the receiver's UDP buffers stay safe. Round-trip test bitrate dropped from 1390 kb/s to 47 kb/s on synthetic frames — the encoder uses only what it needs. - 5-second GOP (was 1 second): 80% fewer keyframe bits freed for detail frames. Screen content changes incrementally, not wholesale; PLI feedback recovers from loss in one frame time regardless of GOP length. - faster preset (was veryfast): better sub-pixel estimation and RDO on more decisions. The desktop handles it trivially at 1080p. - Screen-content x264 tuning: aq-mode=2 (auto-variance AQ moves bits away from flat areas toward text edges) and psy-rd=1.5 (preserves texture sharpness). Combined with the earlier veryfast upgrade and sender-side downscaling, this is roughly 2x the perceived quality at the same average bandwidth compared to the original ultrafast ABR encoder. meson test 5/5 in both configurations, valgrind clean.
60 lines
1.6 KiB
C++
60 lines
1.6 KiB
C++
#pragma once
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#include "screencast/capture/capture.h"
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#include "screencast/codec/error.h"
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#include <cstdint>
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#include <memory>
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#include <string>
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#include <vector>
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namespace sc {
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struct EncodedFrame {
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uint64_t capture_timestamp_ns = 0;
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uint32_t rtp_timestamp = 0;
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bool is_keyframe = false;
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std::vector<std::byte> data; // Annex-B H.264 NAL units
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};
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struct EncoderConfig {
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std::string codec_name = "h264";
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int width = 0;
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int height = 0;
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int frame_rate_num = 30;
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int frame_rate_den = 1;
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// CRF (constant rate factor, 0-51): the target visual quality level.
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// Lower = better quality. 23 is x264's default; screen content looks
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// good at 20-24.
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int crf = 22;
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// Maximum bitrate in kbps (the VBV cap). The encoder uses fewer bits on
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// static content and more on motion, but never exceeds this.
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int bitrate_kbps = 4000;
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bool hardware_accel = false;
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};
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class Encoder {
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public:
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virtual ~Encoder() = default;
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// Encode one captured frame. Returns an empty vector if the encoder emits
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// no packet for this frame.
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virtual CodecResult<std::vector<EncodedFrame>> encode(const CapturedFrame& frame) = 0;
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// Flush the encoder and return any remaining packets.
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virtual CodecResult<std::vector<EncodedFrame>> flush() = 0;
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// Force the next output frame to be a keyframe.
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virtual void request_keyframe() = 0;
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// Codec-specific parameters required by a decoder (SPS/PPS for H.264).
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virtual std::vector<std::byte> get_extradata() const = 0;
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};
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class EncoderFactory {
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public:
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static CodecResult<std::unique_ptr<Encoder>> create(const EncoderConfig& config);
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};
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} // namespace sc
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