/*
 * Copyright (c) 2017 Jun Zhao
 * Copyright (c) 2017 Kaixuan Liu
 *
 * HW Acceleration API (video decoding) decode sample
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * HW-Accelerated decoding example.
 *
 * @example hw_decode.c
 * This example shows how to do HW-accelerated decoding with output
 * frames from the HW video surfaces.
 */

#include <stdio.h>

#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavutil/pixdesc.h>
#include <libavutil/hwcontext.h>
#include <libavutil/opt.h>
#include <libavutil/avassert.h>
#include <libavutil/imgutils.h>

static AVBufferRef *hw_device_ctx = NULL;
static enum AVPixelFormat hw_pix_fmt;
static FILE *output_file = NULL;

static int hw_decoder_init(AVCodecContext *ctx, const enum AVHWDeviceType type)
{
    int err = 0;

    if ((err = av_hwdevice_ctx_create(&hw_device_ctx, type,
                                      NULL, NULL, 0)) < 0) {
        fprintf(stderr, "Failed to create specified HW device.\n");
        return err;
    }
    ctx->hw_device_ctx = av_buffer_ref(hw_device_ctx);

    return err;
}

static enum AVPixelFormat get_hw_format(AVCodecContext *ctx,
                                        const enum AVPixelFormat *pix_fmts)
{
    const enum AVPixelFormat *p;

    for (p = pix_fmts; *p != -1; p++) {
        if (*p == hw_pix_fmt)
            return *p;
    }

    fprintf(stderr, "Failed to get HW surface format.\n");
    return AV_PIX_FMT_NONE;
}

static int decode_write(AVCodecContext *avctx, AVPacket *packet)
{
    AVFrame *frame = NULL, *sw_frame = NULL;
    AVFrame *tmp_frame = NULL;
    uint8_t *buffer = NULL;
    int size;
    int ret = 0;

    ret = avcodec_send_packet(avctx, packet);
    if (ret < 0) {
        fprintf(stderr, "Error during decoding\n");
        return ret;
    }

    while (ret >= 0) {
        if (!(frame = av_frame_alloc()) || !(sw_frame = av_frame_alloc())) {
            fprintf(stderr, "Can not alloc frame\n");
            ret = AVERROR(ENOMEM);
            goto fail;
        }

        ret = avcodec_receive_frame(avctx, frame);
        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
            av_frame_free(&frame);
            av_frame_free(&sw_frame);
            return 0;
        } else if (ret < 0) {
            fprintf(stderr, "Error while decoding\n");
            goto fail;
        }

        if (frame->format == hw_pix_fmt) {
            /* retrieve data from GPU to CPU */
            if ((ret = av_hwframe_transfer_data(sw_frame, frame, 0)) < 0) {
                fprintf(stderr, "Error transferring the data to system memory\n");
                goto fail;
            }
            tmp_frame = sw_frame;
        } else
            tmp_frame = frame;

        size = av_image_get_buffer_size(tmp_frame->format, tmp_frame->width,
                                        tmp_frame->height, 1);
        buffer = av_malloc(size);
        if (!buffer) {
            fprintf(stderr, "Can not alloc buffer\n");
            ret = AVERROR(ENOMEM);
            goto fail;
        }
        ret = av_image_copy_to_buffer(buffer, size,
                                      (const uint8_t * const *)tmp_frame->data,
                                      (const int *)tmp_frame->linesize, tmp_frame->format,
                                      tmp_frame->width, tmp_frame->height, 1);
        if (ret < 0) {
            fprintf(stderr, "Can not copy image to buffer\n");
            goto fail;
        }

        if ((ret = fwrite(buffer, 1, size, output_file)) < 0) {
            fprintf(stderr, "Failed to dump raw data.\n");
            goto fail;
        }

    fail:
        av_frame_free(&frame);
        av_frame_free(&sw_frame);
        if (buffer)
            av_freep(&buffer);
        if (ret < 0)
            return ret;
    }

    return 0;
}

int main(int argc, char *argv[])
{
    AVFormatContext *input_ctx = NULL;
    int video_stream, ret;
    AVStream *video = NULL;
    AVCodecContext *decoder_ctx = NULL;
    AVCodec *decoder = NULL;
    AVPacket packet;
    enum AVHWDeviceType type;
    int i;

    if (argc < 4) {
        fprintf(stderr, "Usage: %s <device type> <input file> <output file>\n", argv[0]);
        return -1;
    }

    av_register_all();

    type = av_hwdevice_find_type_by_name(argv[1]);
    if (type == AV_HWDEVICE_TYPE_NONE) {
        fprintf(stderr, "Device type %s is not supported.\n", argv[1]);
        fprintf(stderr, "Available device types:");
        while((type = av_hwdevice_iterate_types(type)) != AV_HWDEVICE_TYPE_NONE)
            fprintf(stderr, " %s", av_hwdevice_get_type_name(type));
        fprintf(stderr, "\n");
        return -1;
    }

    /* open the input file */
    if (avformat_open_input(&input_ctx, argv[2], NULL, NULL) != 0) {
        fprintf(stderr, "Cannot open input file '%s'\n", argv[2]);
        return -1;
    }

    if (avformat_find_stream_info(input_ctx, NULL) < 0) {
        fprintf(stderr, "Cannot find input stream information.\n");
        return -1;
    }

    /* find the video stream information */
    ret = av_find_best_stream(input_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, &decoder, 0);
    if (ret < 0) {
        fprintf(stderr, "Cannot find a video stream in the input file\n");
        return -1;
    }
    video_stream = ret;

    for (i = 0;; i++) {
        const AVCodecHWConfig *config = avcodec_get_hw_config(decoder, i);
        if (!config) {
            fprintf(stderr, "Decoder %s does not support device type %s.\n",
                    decoder->name, av_hwdevice_get_type_name(type));
            return -1;
        }
        if (config->methods & AV_CODEC_HW_CONFIG_METHOD_HW_DEVICE_CTX &&
            config->device_type == type) {
            hw_pix_fmt = config->pix_fmt;
            break;
        }
    }

    if (!(decoder_ctx = avcodec_alloc_context3(decoder)))
        return AVERROR(ENOMEM);

    video = input_ctx->streams[video_stream];
    if (avcodec_parameters_to_context(decoder_ctx, video->codecpar) < 0)
        return -1;

    decoder_ctx->get_format  = get_hw_format;
    av_opt_set_int(decoder_ctx, "refcounted_frames", 1, 0);

    if (hw_decoder_init(decoder_ctx, type) < 0)
        return -1;

    if ((ret = avcodec_open2(decoder_ctx, decoder, NULL)) < 0) {
        fprintf(stderr, "Failed to open codec for stream #%u\n", video_stream);
        return -1;
    }

    /* open the file to dump raw data */
    output_file = fopen(argv[3], "w+");

    /* actual decoding and dump the raw data */
    while (ret >= 0) {
        if ((ret = av_read_frame(input_ctx, &packet)) < 0)
            break;

        if (video_stream == packet.stream_index)
            ret = decode_write(decoder_ctx, &packet);

        av_packet_unref(&packet);
    }

    /* flush the decoder */
    packet.data = NULL;
    packet.size = 0;
    ret = decode_write(decoder_ctx, &packet);
    av_packet_unref(&packet);

    if (output_file)
        fclose(output_file);
    avcodec_free_context(&decoder_ctx);
    avformat_close_input(&input_ctx);
    av_buffer_unref(&hw_device_ctx);

    return 0;
}