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libav: Add a low latency encode option #751

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merged 1 commit into from
Dec 4, 2024
Merged

libav: Add a low latency encode option #751

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3 changes: 3 additions & 0 deletions core/video_options.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -158,6 +158,8 @@ struct VideoOptions : public Options
("av-sync", value<std::string>(&av_sync_)->default_value("0us"),
"Add a time offset (in microseconds if no units provided) to the audio stream, relative to the video stream. "
"The offset value can be either positive or negative.")
("low-latency", value<bool>(&low_latency)->default_value(false)->implicit_value(true),
"Enables the libav/libx264 low latncy presets for video encoding.")
#endif
;
// clang-format on
Expand Down Expand Up @@ -191,6 +193,7 @@ struct VideoOptions : public Options
uint32_t segment;
size_t circular;
uint32_t frames;
bool low_latency;

virtual bool Parse(int argc, char *argv[]) override
{
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22 changes: 17 additions & 5 deletions encoder/libav_encoder.cpp
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Expand Up @@ -80,16 +80,28 @@ void encoderOptionsH264M2M(VideoOptions const *options, AVCodecContext *codec)

void encoderOptionsLibx264(VideoOptions const *options, AVCodecContext *codec)
{
codec->max_b_frames = 1;
codec->me_range = 16;
codec->me_cmp = 1; // No chroma ME
codec->me_subpel_quality = 0;
codec->thread_count = 0;
codec->thread_type = FF_THREAD_FRAME;
codec->slices = 1;

av_opt_set(codec->priv_data, "preset", "superfast", 0);
av_opt_set(codec->priv_data, "partitions", "i8x8,i4x4", 0);
if (options->low_latency)
{
codec->thread_type = FF_THREAD_SLICE;
codec->slices = 4;
codec->refs = 1;
av_opt_set(codec->priv_data, "preset", "ultrafast", 0);
av_opt_set(codec->priv_data, "tune", "zerolatency", 0);
}
else
{
codec->thread_type = FF_THREAD_FRAME;
codec->slices = 1;
codec->max_b_frames = 1;
av_opt_set(codec->priv_data, "preset", "superfast", 0);
av_opt_set(codec->priv_data, "partitions", "i8x8,i4x4", 0);
}

av_opt_set(codec->priv_data, "weightp", "none", 0);
av_opt_set(codec->priv_data, "weightb", "0", 0);
av_opt_set(codec->priv_data, "motion-est", "dia", 0);
Expand Down