C# - ffmpeg(FFmpeg.AutoGen)를 이용한 avio_reading.c 예제 포팅

지난 예제에 이어,

C# - ffmpeg(FFmpeg.AutoGen)를 이용한 비디오 프레임의 크기 및 포맷 변경 예제(scaling_video.c)
; https://www.sysnet.pe.kr/2/0/12961

using FFmpeg.AutoGen;
using FFmpeg.AutoGen.Example;
using System;
using System.Runtime.InteropServices;
using System.Security.Cryptography;

namespace FFmpegApp1
{
    internal unsafe class Program
    {
        [DllImport("Kernel32.dll", EntryPoint = "RtlMoveMemory", SetLastError = false)]
        static extern void MoveMemory(IntPtr dest, IntPtr src, int size);

        static unsafe int Main(string[] args)
        {
            FFmpegBinariesHelper.RegisterFFmpegBinaries();

#if DEBUG
            Console.WriteLine("Current directory: " + Environment.CurrentDirectory);
            Console.WriteLine("Running in {0}-bit mode.", Environment.Is64BitProcess ? "64" : "32");
            Console.WriteLine($"FFmpeg version info: {ffmpeg.av_version_info()}");
#endif
            Console.WriteLine();

            AVFormatContext* fmt_ctx = null;
            AVIOContext* avio_ctx = null;

            byte* buffer = null;
            byte* avio_ctx_buffer = null;
            ulong buffer_size;
            ulong avio_ctx_buffer_size = 4096;
            
            int ret = 0;
            buffer_data bd = new buffer_data();

            string input_filename = @"D:\media_sample\test.mkv";
            ret = ffmpeg.av_file_map(input_filename, &buffer, &buffer_size, 0, null);
            if (ret < 0)
            {
                return ret;
            }

            bd.ptr = buffer;
            bd.size = (int)buffer_size;

            do
            {
                fmt_ctx = ffmpeg.avformat_alloc_context();
                if (fmt_ctx == null)
                {
                    ret = ffmpeg.AVERROR(ffmpeg.ENOMEM);
                    break;
                }

                avio_ctx_buffer = (byte*)ffmpeg.av_malloc(avio_ctx_buffer_size);
                if (avio_ctx_buffer == null)
                {
                    ret = ffmpeg.AVERROR(ffmpeg.ENOMEM);
                    break;
                }

                avio_ctx = ffmpeg.avio_alloc_context(avio_ctx_buffer, (int)avio_ctx_buffer_size, 0, &bd, 
                    (avio_alloc_context_read_packet_func)read_packet, null, null);
                if (avio_ctx == null)
                {
                    ret = ffmpeg.AVERROR(ffmpeg.ENOMEM);
                    break;
                }

                fmt_ctx->pb = avio_ctx;

                ret = ffmpeg.avformat_open_input(&fmt_ctx, null, null, null);
                if (ret < 0)
                {
                    Console.WriteLine("Could not open input");
                    break;
                }

                ret = ffmpeg.avformat_find_stream_info(fmt_ctx, null);
                if (ret < 0)
                {
                    Console.WriteLine("Could not find stream information");
                    break;
                }

                ffmpeg.av_dump_format(fmt_ctx, 0, input_filename, 0);

            } while (false);

            if (fmt_ctx != null)
            {
                ffmpeg.avformat_close_input(&fmt_ctx);
            }

            if (avio_ctx != null)
            {
                ffmpeg.av_freep(&avio_ctx->buffer);
                ffmpeg.avio_context_free(&avio_ctx);
            }

            ffmpeg.av_file_unmap(buffer, buffer_size);

            return ret;
        }

        static unsafe int read_packet(void *opaque, byte* buf, int buf_size)
        {
            buffer_data* bd = (buffer_data*)opaque;
            buf_size = (int)Math.Min(buf_size, bd->size);

            if (buf_size == 0)
            {
                return ffmpeg.AVERROR_EOF;
            }

            Console.WriteLine($"ptr:{new IntPtr(bd->ptr):x} size:{bd->size}");

            MoveMemory(new IntPtr(buf), new IntPtr(bd->ptr), buf_size);
            bd->ptr += buf_size;
            bd->size -= buf_size;

            return buf_size;
        }
    }

    public unsafe struct buffer_data
    {
        public byte* ptr;
        public int size;
    }
}

ptr:1b27a880000 size:75337278
ptr:1b27a881000 size:75333182
ptr:1b27a88acff size:75292991
ptr:1b27a88bcff size:75288895
ptr:1b27a8907bb size:75269763
ptr:1b27a8917bb size:75265667

Input #0, matroska,webm, from 'D:\media_sample\test.mkv':
  Metadata:
    COMPATIBLE_BRANDS: iso6avc1mp41
    MAJOR_BRAND     : dash
    MINOR_VERSION   : 0
    ENCODER         : Lavf58.45.100
  Duration: 00:03:07.98, start: -0.007000, bitrate: N/A
  Stream #0:0: Video: h264 (High), yuv420p(tv, bt709, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 29.97 fps, 29.97 tbr, 1k tbn, 59.94 tbc (default)
    Metadata:
      HANDLER_NAME    : ISO Media file produced by Google Inc.
      DURATION        : 00:03:07.954000000
  Stream #0:1(eng): Audio: opus, 48000 Hz, stereo, fltp (default)
    Metadata:
      DURATION        : 00:03:07.981000000