video2x/src/libplacebo.cpp

#include "libplacebo.h"

#include <stdio.h>
#include <stdlib.h>

#include <spdlog/spdlog.h>

#include "fsutils.h"

int init_libplacebo(
    AVBufferRef *hw_ctx,
    AVFilterGraph **filter_graph,
    AVFilterContext **buffersrc_ctx,
    AVFilterContext **buffersink_ctx,
    AVCodecContext *dec_ctx,
    int output_width,
    int output_height,
    const std::filesystem::path &shader_path
) {
    char args[512];
    int ret;

    AVFilterGraph *graph = avfilter_graph_alloc();
    if (!graph) {
        spdlog::error("Unable to create filter graph.");
        return AVERROR(ENOMEM);
    }

    // Create buffer source
    const AVFilter *buffersrc = avfilter_get_by_name("buffer");
    snprintf(
        args,
        sizeof(args),
        "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:frame_rate=%d/%d:"
        "pixel_aspect=%d/%d:colorspace=%d:range=%d",
        dec_ctx->width,
        dec_ctx->height,
        dec_ctx->pix_fmt,
        dec_ctx->time_base.num,
        dec_ctx->time_base.den,
        dec_ctx->framerate.num,
        dec_ctx->framerate.den,
        dec_ctx->sample_aspect_ratio.num,
        dec_ctx->sample_aspect_ratio.den,
        dec_ctx->colorspace,
        dec_ctx->color_range
    );

    ret = avfilter_graph_create_filter(buffersrc_ctx, buffersrc, "in", args, NULL, graph);
    if (ret < 0) {
        spdlog::error("Cannot create buffer source.");
        avfilter_graph_free(&graph);
        return ret;
    }

    AVFilterContext *last_filter = *buffersrc_ctx;

    // Create the libplacebo filter
    const AVFilter *libplacebo_filter = avfilter_get_by_name("libplacebo");
    if (!libplacebo_filter) {
        spdlog::error("Filter 'libplacebo' not found.");
        avfilter_graph_free(&graph);
        return AVERROR_FILTER_NOT_FOUND;
    }

    // Convert the shader path to a string since filter args is const char *
    std::string shader_path_string = path_to_string(shader_path);

#ifdef _WIN32
    // libplacebo does not recognize the Windows '\\' path separator
    std::replace(shader_path_string.begin(), shader_path_string.end(), '\\', '/');
#endif

    // Prepare the filter arguments
    char filter_args[512];
    snprintf(
        filter_args,
        sizeof(filter_args),
        "w=%d:h=%d:upscaler=ewa_lanczos:custom_shader_path=%s",
        output_width,
        output_height,
        shader_path_string.c_str()
    );

    AVFilterContext *libplacebo_ctx;
    ret = avfilter_graph_create_filter(
        &libplacebo_ctx, libplacebo_filter, "libplacebo", filter_args, NULL, graph
    );
    if (ret < 0) {
        spdlog::error("Cannot create libplacebo filter.");
        avfilter_graph_free(&graph);
        return ret;
    }

    // Set the hardware device context to Vulkan
    if (hw_ctx != nullptr) {
        libplacebo_ctx->hw_device_ctx = av_buffer_ref(hw_ctx);
    }

    // Link buffersrc to libplacebo
    ret = avfilter_link(last_filter, 0, libplacebo_ctx, 0);
    if (ret < 0) {
        spdlog::error("Error connecting buffersrc to libplacebo filter.");
        avfilter_graph_free(&graph);
        return ret;
    }

    last_filter = libplacebo_ctx;

    // Create buffer sink
    const AVFilter *buffersink = avfilter_get_by_name("buffersink");
    ret = avfilter_graph_create_filter(buffersink_ctx, buffersink, "out", NULL, NULL, graph);
    if (ret < 0) {
        spdlog::error("Cannot create buffer sink.");
        avfilter_graph_free(&graph);
        return ret;
    }

    // Link libplacebo to buffersink
    ret = avfilter_link(last_filter, 0, *buffersink_ctx, 0);
    if (ret < 0) {
        spdlog::error("Error connecting libplacebo filter to buffersink.");
        avfilter_graph_free(&graph);
        return ret;
    }

    // Configure the filter graph
    ret = avfilter_graph_config(graph, NULL);
    if (ret < 0) {
        spdlog::error("Error configuring the filter graph.");
        avfilter_graph_free(&graph);
        return ret;
    }

    *filter_graph = graph;
    return 0;
}