video2x/src/libplacebo.cpp

#include "libplacebo.h"

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

extern "C" {
#include <libavutil/dict.h>
#include <libavutil/opt.h>
}

#include <spdlog/spdlog.h>

int init_libplacebo(
    AVFilterGraph **filter_graph,
    AVFilterContext **buffersrc_ctx,
    AVFilterContext **buffersink_ctx,
    AVCodecContext *dec_ctx,
    int out_width,
    int out_height,
    uint32_t vk_device_index,
    const std::filesystem::path &shader_path
) {
    int ret;

    // Create the Vulkan hardware device context
    AVBufferRef *vk_hw_device_ctx = nullptr;
    ret = av_hwdevice_ctx_create(
        &vk_hw_device_ctx, AV_HWDEVICE_TYPE_VULKAN, std::to_string(vk_device_index).c_str(), NULL, 0
    );
    if (ret < 0) {
        spdlog::error("Failed to create Vulkan hardware device context.");
        return 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");
    if (!buffersrc) {
        spdlog::error("Filter 'buffer' not found.");
        avfilter_graph_free(&graph);
        return AVERROR_FILTER_NOT_FOUND;
    }

    // Start building the arguments string
    std::string args = "video_size=" + std::to_string(dec_ctx->width) + "x" +
                       std::to_string(dec_ctx->height) +
                       ":pix_fmt=" + std::to_string(dec_ctx->pix_fmt) +
                       ":time_base=" + std::to_string(dec_ctx->time_base.num) + "/" +
                       std::to_string(dec_ctx->time_base.den) +
                       ":frame_rate=" + std::to_string(dec_ctx->framerate.num) + "/" +
                       std::to_string(dec_ctx->framerate.den) +
                       ":pixel_aspect=" + std::to_string(dec_ctx->sample_aspect_ratio.num) + "/" +
                       std::to_string(dec_ctx->sample_aspect_ratio.den);

    // Make a copy of the AVClass on the stack
    AVClass priv_class_copy = *buffersrc->priv_class;
    AVClass *priv_class_copy_ptr = &priv_class_copy;

    // Check if the colorspace option is supported
    if (av_opt_find(&priv_class_copy_ptr, "colorspace", NULL, 0, AV_OPT_SEARCH_FAKE_OBJ)) {
        args += ":colorspace=" + std::to_string(dec_ctx->colorspace);
    } else {
        spdlog::warn("Option 'colorspace' is not supported by the buffer filter.");
    }

    // Check if the range option is supported
    if (av_opt_find(&priv_class_copy_ptr, "range", NULL, 0, AV_OPT_SEARCH_FAKE_OBJ)) {
        args += ":range=" + std::to_string(dec_ctx->color_range);
    } else {
        spdlog::warn("Option 'range' is not supported by the buffer filter.");
    }

    spdlog::debug("Buffer source args: {}", args);
    ret = avfilter_graph_create_filter(buffersrc_ctx, buffersrc, "in", args.c_str(), 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 = shader_path.u8string();

#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
    std::string filter_args = "w=" + std::to_string(out_width) +
                              ":h=" + std::to_string(out_height) + ":custom_shader_path='" +
                              shader_path_string + "'";

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

    // Set the hardware device context to Vulkan
    libplacebo_ctx->hw_device_ctx = av_buffer_ref(vk_hw_device_ctx);
    av_buffer_unref(&vk_hw_device_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;
}