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obs-studio/libobs/obs-video.c
jp9000 11106c2fce libobs: Redesign/optimize frame encoding handling 
Previously, the design for the interaction between the encoder thread
and the graphics thread was that the encoder thread would signal to the
graphics thread when to start drawing each frame.  The original idea
behind this was to prevent mutually cascading stalls of encoding or
graphics rendering (i.e., if rendering took too long, then encoding
would have to catch up, then rendering would have to catch up again, and
so on, cascading upon each other).  The ultimate goal was to prevent
encoding from impacting graphics and vise versa.

However, eventually it was realized that there were some fundamental
flaws with this design.

1. Stray frame duplication.  You could not guarantee that a frame would
   render on time, so sometimes frames would unintentionally be lost if
   there was any sort of minor hiccup or if the thread took too long to
   be scheduled I'm guessing.

2. Frame timing in the rendering thread was less accurate.  The only
   place where frame timing was accurate was in the encoder thread, and
   the graphics thread was at the whim of thread scheduling.  On higher
   end computers it was typically fine, but it was just generally not
   guaranteed that a frame would be rendered when it was supposed to be
   rendered.

So the solution (originally proposed by r1ch and paibox) is to instead
keep the encoding and graphics threads separate as usual, but instead of
the encoder thread controlling the graphics thread, the graphics thread
now controls the encoder thread.  The encoder thread keeps a limited
cache of frames, then the graphics thread copies frames in to the cache
and increments a semaphore to schedule the encoder thread to encode that
data.

In the cache, each frame has an encode counter.  If the frame cache is
full (e.g., the encoder taking too long to return frames), it will not
cache a new frame, but instead will just increment the counter on the
last frame in the cache to schedule that frame to encode again, ensuring
that frames are on time and reducing CPU usage by lowering video
complexity.  If the graphics thread takes too long to render a frame,
then it will add that frame with the count value set to the total amount
of frames that were missed (actual legitimately duplicated frames).

Because the cache gives many frames of breathing room for the encoder to
encode frames, this design helps improve results especially when using
encoding presets that have higher complexity and CPU usage, minimizing
the risk of needlessly skipped or duplicated frames.

I also managed to sneak in what should be a bit of an optimization to
reduce copying of frame data, though how much of an optimization it
ultimately ends up being is debatable.

So to sum it up, this commit increases accuracy of frame timing,
completely removes stray frame duplication, gives better results for
higher complexity encoding presets, and potentially optimizes the frame
pipeline a tiny bit.
2014-12-31 04:03:47 -08:00

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/******************************************************************************
Copyright (C) 2013-2014 by Hugh Bailey <obs.jim@gmail.com>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
******************************************************************************/
#include "obs.h"
#include "obs-internal.h"
#include "graphics/vec4.h"
#include "media-io/format-conversion.h"
#include "media-io/video-frame.h"
static inline void calculate_base_volume(struct obs_core_data *data,
struct obs_view *view, obs_source_t *target)
{
if (!target->activate_refs) {
target->base_volume = 0.0f;
/* only walk the tree if there are transitions active */
} else if (data->active_transitions) {
float best_vol = 0.0f;
for (size_t i = 0; i < MAX_CHANNELS; i++) {
struct obs_source *source = view->channels[i];
float vol = 0.0f;
if (!source)
continue;
vol = obs_source_get_target_volume(source, target);
if (best_vol < vol)
best_vol = vol;
}
target->base_volume = best_vol;
} else {
target->base_volume = 1.0f;
}
}
static uint64_t tick_sources(uint64_t cur_time, uint64_t last_time)
{
struct obs_core_data *data = &obs->data;
struct obs_view *view = &data->main_view;
struct obs_source *source;
uint64_t delta_time;
float seconds;
if (!last_time)
last_time = cur_time -
video_output_get_frame_time(obs->video.video);
delta_time = cur_time - last_time;
seconds = (float)((double)delta_time / 1000000000.0);
pthread_mutex_lock(&data->sources_mutex);
/* call the tick function of each source */
source = data->first_source;
while (source) {
if (source->refs)
obs_source_video_tick(source, seconds);
source = (struct obs_source*)source->context.next;
}
/* calculate source volumes */
pthread_mutex_lock(&view->channels_mutex);
source = data->first_source;
while (source) {
if (source->refs)
calculate_base_volume(data, view, source);
source = (struct obs_source*)source->context.next;
}
pthread_mutex_unlock(&view->channels_mutex);
pthread_mutex_unlock(&data->sources_mutex);
return cur_time;
}
/* in obs-display.c */
extern void render_display(struct obs_display *display);
static inline void render_displays(void)
{
struct obs_display *display;
if (!obs->data.valid)
return;
gs_enter_context(obs->video.graphics);
/* render extra displays/swaps */
pthread_mutex_lock(&obs->data.displays_mutex);
display = obs->data.first_display;
while (display) {
render_display(display);
display = display->next;
}
pthread_mutex_unlock(&obs->data.displays_mutex);
/* render main display */
render_display(&obs->video.main_display);
gs_leave_context();
}
static inline void set_render_size(uint32_t width, uint32_t height)
{
gs_enable_depth_test(false);
gs_set_cull_mode(GS_NEITHER);
gs_ortho(0.0f, (float)width, 0.0f, (float)height, -100.0f, 100.0f);
gs_set_viewport(0, 0, width, height);
}
static inline void unmap_last_surface(struct obs_core_video *video)
{
if (video->mapped_surface) {
gs_stagesurface_unmap(video->mapped_surface);
video->mapped_surface = NULL;
}
}
static inline void render_main_texture(struct obs_core_video *video,
int cur_texture)
{
struct vec4 clear_color;
vec4_set(&clear_color, 0.0f, 0.0f, 0.0f, 1.0f);
gs_set_render_target(video->render_textures[cur_texture], NULL);
gs_clear(GS_CLEAR_COLOR, &clear_color, 1.0f, 0);
set_render_size(video->base_width, video->base_height);
obs_view_render(&obs->data.main_view);
video->textures_rendered[cur_texture] = true;
}
static inline gs_effect_t *get_scale_effect_internal(
struct obs_core_video *video)
{
switch (video->scale_type) {
case OBS_SCALE_BILINEAR: return video->default_effect;
case OBS_SCALE_LANCZOS: return video->lanczos_effect;
case OBS_SCALE_BICUBIC:;
}
return video->bicubic_effect;
}
static inline bool resolution_close(struct obs_core_video *video,
uint32_t width, uint32_t height)
{
long width_cmp = (long)video->base_width - (long)width;
long height_cmp = (long)video->base_height - (long)height;
return labs(width_cmp) <= 16 && labs(height_cmp) <= 16;
}
static inline gs_effect_t *get_scale_effect(struct obs_core_video *video,
uint32_t width, uint32_t height)
{
if (resolution_close(video, width, height)) {
return video->default_effect;
} else {
/* if the scale method couldn't be loaded, use either bicubic
* or bilinear by default */
gs_effect_t *effect = get_scale_effect_internal(video);
if (!effect)
effect = !!video->bicubic_effect ?
video->bicubic_effect :
video->default_effect;
return effect;
}
}
static inline void render_output_texture(struct obs_core_video *video,
int cur_texture, int prev_texture)
{
gs_texture_t *texture = video->render_textures[prev_texture];
gs_texture_t *target = video->output_textures[cur_texture];
uint32_t width = gs_texture_get_width(target);
uint32_t height = gs_texture_get_height(target);
struct vec2 base_i;
vec2_set(&base_i,
1.0f / (float)video->base_width,
1.0f / (float)video->base_height);
gs_effect_t *effect = get_scale_effect(video, width, height);
gs_technique_t *tech = gs_effect_get_technique(effect, "DrawMatrix");
gs_eparam_t *image = gs_effect_get_param_by_name(effect, "image");
gs_eparam_t *matrix = gs_effect_get_param_by_name(effect,
"color_matrix");
gs_eparam_t *bres_i = gs_effect_get_param_by_name(effect,
"base_dimension_i");
size_t passes, i;
if (!video->textures_rendered[prev_texture])
return;
gs_set_render_target(target, NULL);
set_render_size(width, height);
if (bres_i)
gs_effect_set_vec2(bres_i, &base_i);
gs_effect_set_val(matrix, video->color_matrix, sizeof(float) * 16);
gs_effect_set_texture(image, texture);
gs_enable_blending(false);
passes = gs_technique_begin(tech);
for (i = 0; i < passes; i++) {
gs_technique_begin_pass(tech, i);
gs_draw_sprite(texture, 0, width, height);
gs_technique_end_pass(tech);
}
gs_technique_end(tech);
gs_enable_blending(true);
video->textures_output[cur_texture] = true;
}
static inline void set_eparam(gs_effect_t *effect, const char *name, float val)
{
gs_eparam_t *param = gs_effect_get_param_by_name(effect, name);
gs_effect_set_float(param, val);
}
static void render_convert_texture(struct obs_core_video *video,
int cur_texture, int prev_texture)
{
gs_texture_t *texture = video->output_textures[prev_texture];
gs_texture_t *target = video->convert_textures[cur_texture];
float fwidth = (float)video->output_width;
float fheight = (float)video->output_height;
size_t passes, i;
gs_effect_t *effect = video->conversion_effect;
gs_eparam_t *image = gs_effect_get_param_by_name(effect, "image");
gs_technique_t *tech = gs_effect_get_technique(effect,
video->conversion_tech);
if (!video->textures_output[prev_texture])
return;
set_eparam(effect, "u_plane_offset", (float)video->plane_offsets[1]);
set_eparam(effect, "v_plane_offset", (float)video->plane_offsets[2]);
set_eparam(effect, "width", fwidth);
set_eparam(effect, "height", fheight);
set_eparam(effect, "width_i", 1.0f / fwidth);
set_eparam(effect, "height_i", 1.0f / fheight);
set_eparam(effect, "width_d2", fwidth * 0.5f);
set_eparam(effect, "height_d2", fheight * 0.5f);
set_eparam(effect, "width_d2_i", 1.0f / (fwidth * 0.5f));
set_eparam(effect, "height_d2_i", 1.0f / (fheight * 0.5f));
set_eparam(effect, "input_height", (float)video->conversion_height);
gs_effect_set_texture(image, texture);
gs_set_render_target(target, NULL);
set_render_size(video->output_width, video->conversion_height);
gs_enable_blending(false);
passes = gs_technique_begin(tech);
for (i = 0; i < passes; i++) {
gs_technique_begin_pass(tech, i);
gs_draw_sprite(texture, 0, video->output_width,
video->conversion_height);
gs_technique_end_pass(tech);
}
gs_technique_end(tech);
gs_enable_blending(true);
video->textures_converted[cur_texture] = true;
}
static inline void stage_output_texture(struct obs_core_video *video,
int cur_texture, int prev_texture)
{
gs_texture_t *texture;
bool texture_ready;
gs_stagesurf_t *copy = video->copy_surfaces[cur_texture];
if (video->gpu_conversion) {
texture = video->convert_textures[prev_texture];
texture_ready = video->textures_converted[prev_texture];
} else {
texture = video->output_textures[prev_texture];
texture_ready = video->output_textures[prev_texture];
}
unmap_last_surface(video);
if (!texture_ready)
return;
gs_stage_texture(copy, texture);
video->textures_copied[cur_texture] = true;
}
static inline void render_video(struct obs_core_video *video, int cur_texture,
int prev_texture)
{
gs_begin_scene();
gs_enable_depth_test(false);
gs_set_cull_mode(GS_NEITHER);
render_main_texture(video, cur_texture);
render_output_texture(video, cur_texture, prev_texture);
if (video->gpu_conversion)
render_convert_texture(video, cur_texture, prev_texture);
stage_output_texture(video, cur_texture, prev_texture);
gs_set_render_target(NULL, NULL);
gs_enable_blending(true);
gs_end_scene();
}
static inline bool download_frame(struct obs_core_video *video,
int prev_texture, struct video_data *frame)
{
gs_stagesurf_t *surface = video->copy_surfaces[prev_texture];
if (!video->textures_copied[prev_texture])
return false;
if (!gs_stagesurface_map(surface, &frame->data[0], &frame->linesize[0]))
return false;
video->mapped_surface = surface;
return true;
}
static inline uint32_t calc_linesize(uint32_t pos, uint32_t linesize)
{
uint32_t size = pos % linesize;
return size ? size : linesize;
}
static void copy_dealign(
uint8_t *dst, uint32_t dst_pos, uint32_t dst_linesize,
const uint8_t *src, uint32_t src_pos, uint32_t src_linesize,
uint32_t remaining)
{
while (remaining) {
uint32_t src_remainder = src_pos % src_linesize;
uint32_t dst_offset = dst_linesize - src_remainder;
uint32_t src_offset = src_linesize - src_remainder;
if (remaining < dst_offset) {
memcpy(dst + dst_pos, src + src_pos, remaining);
src_pos += remaining;
dst_pos += remaining;
remaining = 0;
} else {
memcpy(dst + dst_pos, src + src_pos, dst_offset);
src_pos += src_offset;
dst_pos += dst_offset;
remaining -= dst_offset;
}
}
}
static inline uint32_t make_aligned_linesize_offset(uint32_t offset,
uint32_t dst_linesize, uint32_t src_linesize)
{
uint32_t remainder = offset % dst_linesize;
return (offset / dst_linesize) * src_linesize + remainder;
}
static void fix_gpu_converted_alignment(struct obs_core_video *video,
struct video_frame *output, const struct video_data *input)
{
uint32_t src_linesize = input->linesize[0];
uint32_t dst_linesize = output->linesize[0];
uint32_t src_pos = 0;
for (size_t i = 0; i < 3; i++) {
if (video->plane_linewidth[i] == 0)
break;
src_pos = make_aligned_linesize_offset(video->plane_offsets[i],
dst_linesize, src_linesize);
copy_dealign(output->data[i], 0, dst_linesize,
input->data[0], src_pos, src_linesize,
video->plane_sizes[i]);
}
}
static void set_gpu_converted_data(struct obs_core_video *video,
struct video_frame *output, const struct video_data *input,
const struct video_output_info *info)
{
if (input->linesize[0] == video->output_width*4) {
struct video_frame frame;
for (size_t i = 0; i < 3; i++) {
if (video->plane_linewidth[i] == 0)
break;
frame.linesize[i] = video->plane_linewidth[i];
frame.data[i] =
input->data[0] + video->plane_offsets[i];
}
video_frame_copy(output, &frame, info->format, info->height);
} else {
fix_gpu_converted_alignment(video, output, input);
}
}
static void convert_frame(
struct video_frame *output, const struct video_data *input,
const struct video_output_info *info)
{
if (info->format == VIDEO_FORMAT_I420) {
compress_uyvx_to_i420(
input->data[0], input->linesize[0],
0, info->height,
output->data, output->linesize);
} else if (info->format == VIDEO_FORMAT_NV12) {
compress_uyvx_to_nv12(
input->data[0], input->linesize[0],
0, info->height,
output->data, output->linesize);
} else {
blog(LOG_ERROR, "convert_frame: unsupported texture format");
}
}
static inline void output_video_data(struct obs_core_video *video,
struct video_data *input_frame, int count)
{
const struct video_output_info *info;
struct video_frame output_frame;
bool locked;
info = video_output_get_info(video->video);
locked = video_output_lock_frame(video->video, &output_frame, count,
input_frame->timestamp);
if (locked) {
if (video->gpu_conversion) {
set_gpu_converted_data(video, &output_frame,
input_frame, info);
} else if (format_is_yuv(info->format)) {
convert_frame(&output_frame, input_frame, info);
}
video_output_unlock_frame(video->video);
}
}
static inline void video_sleep(struct obs_core_video *video,
uint64_t *p_time, uint64_t interval_ns)
{
struct obs_vframe_info vframe_info;
uint64_t cur_time = *p_time;
uint64_t t = cur_time + interval_ns;
int count;
if (!os_sleepto_ns(t)) {
*p_time = t;
count = 1;
} else {
count = (int)((os_gettime_ns() - cur_time) / interval_ns);
*p_time = cur_time + interval_ns * count;
}
vframe_info.timestamp = cur_time;
vframe_info.count = count;
circlebuf_push_back(&video->vframe_info_buffer, &vframe_info,
sizeof(vframe_info));
}
static inline void output_frame(uint64_t *cur_time, uint64_t interval)
{
struct obs_core_video *video = &obs->video;
int cur_texture = video->cur_texture;
int prev_texture = cur_texture == 0 ? NUM_TEXTURES-1 : cur_texture-1;
struct video_data frame;
bool frame_ready;
memset(&frame, 0, sizeof(struct video_data));
gs_enter_context(video->graphics);
render_video(video, cur_texture, prev_texture);
frame_ready = download_frame(video, prev_texture, &frame);
gs_flush();
gs_leave_context();
if (frame_ready) {
struct obs_vframe_info vframe_info;
circlebuf_pop_front(&video->vframe_info_buffer, &vframe_info,
sizeof(vframe_info));
frame.timestamp = vframe_info.timestamp;
output_video_data(video, &frame, vframe_info.count);
}
if (++video->cur_texture == NUM_TEXTURES)
video->cur_texture = 0;
video_sleep(video, cur_time, interval);
}
void *obs_video_thread(void *param)
{
uint64_t last_time = 0;
uint64_t cur_time = os_gettime_ns();
uint64_t interval = video_output_get_frame_time(obs->video.video);
while (!video_output_stopped(obs->video.video)) {
last_time = tick_sources(cur_time, last_time);
render_displays();
output_frame(&cur_time, interval);
}
UNUSED_PARAMETER(param);
return NULL;
}
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